Annals of Otology, Rhinology & Laryngology 122(11):701-706. © 2013 Annals Publishing Company. All rights reserved.
Association Between Tinnitus and Sleep Disorders in the General Japanese Population Keiichi Izuhara, MD; Keiko Wada, MD, PhD; Kozue Nakamura, MD, PhD; Yuya Tamai, MD, PhD; Michiko Tsuji, PhD; Yatsuji Ito, MD, PhD; Chisato Nagata, MD, PhD Objectives: There are few studies about the association between tinnitus and sleep disorders in the general population worldwide. This study assessed this association in a Japanese community. Methods: A total of 14,027 participants 45 to 79 years of age who were in the Takayama Study responded to a self-administered questionnaire about tinnitus and sleep disorders. Results: Of this population, 13.3% of men and 10.6% of women had current tinnitus. The percentages of insomnia, respectively, among individuals with and without tinnitus were 28.1% in men and 36.1% in women and 18.8% in men and 21.5% in women. There were 1.7-fold (95% confidence interval [CI], 1.4 to 2.1) and 1.8-fold (95% CI, 1.5 to 2.2) increases in the odds ratios (ORs) of insomnia for those with tinnitus compared with those without tinnitus in men and women, respectively. Loud or very loud tinnitus was associated with 2.8-fold (95% CI, 1.8 to 4.3) and 3.3-fold (95% CI, 1.9 to 5.6) increases in the OR of insomnia in men and women, respectively. Even low (ie, quiet) or moderate tinnitus was significantly associated with insomnia. Difficulty initiating sleep, difficulty maintaining sleep, and a poor perceived quality of sleep were also significantly associated with tinnitus. Conclusions: Insomnia and other sleep disorders were significantly associated with tinnitus in Japanese adults. Key Words: epidemiology, insomnia, Japan, population-based study, sleep disorder, tinnitus.
tinnitus and sleep disorders among the general Japanese population. Our study examined this association among the participants in the Takayama Study.
INTRODUCTION
Various tinnitus-related complaints, such as sleep disorders, have been described as disrupting daily life.1-7 Since many reports only give the prevalence of sleep disorders among patients who sought treatment for severe tinnitus, it is highly likely that there are also many untreated individuals with tinnitus and sleep disorders who do not seek treatment. The reported prevalences of sleep disorders among tinnitus patients who sought treatment have ranged from 15%3 to 77%,2 although these studies varied in terms of patient characteristics such as age and in the definitions of tinnitus and sleep disorders. The prevalence of sleep disorders among individuals with tinnitus in the general population may be less than that among patients with tinnitus who seek treatment. The prevalence of tinnitus in a Japanese cohort 45 to 79 years of age was 11.9%.8 In addition, sleep symptoms should be compared between individuals with and without tinnitus in assessing the sleep disorders associated with tinnitus. There have been only a handful of such studies worldwide.9,10 There has been no study on the relationship between
MATERIALS AND METHODS
Study Population. The Takayama Study was a population-based cohort study initiated in 1992, and its design and methodology has been described elsewhere.11,12 All non-hospitalized residents in Takayama City, Gifu, who were at least 35 years of age were invited to participate in the study. A total of 31,552 individuals, yielding a participation rate of 85.3%, completed a baseline questionnaire that included questions on demographic characteristics, smoking and drinking habits, diet, exercise, occupation, and medical and reproductive histories. In July 2002, we sent a questionnaire inquiring about tinnitus, sleep disorders, smoking status, medication use, and medical histories to the participants. In this 2002 survey, the target population was restricted to respondents whose current age was between 45 and 79 years. After exclusion of those who had died, were physically unable to complete the questionnaire, or had moved,
From the Departments of Otolaryngology (Izuhara, Ito) and Epidemiology and Preventive Medicine (Wada, Nakamura, Tamai, Tsuji, Nagata), Gifu University Graduate School of Medicine, Gifu, Japan. This study was supported in part by a grant from the Ministry of Education, Culture, Sports, Science and Technology of Japan. Correspondence: Keiichi Izuhara, MD, Dept of Otolaryngology, Gifu University Graduate School of Medicine, 1-1 Yanagido, Gifu City 501-1193, Japan.
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Izuhara et al, Tinnitus & Sleep Disorders Table 1. Questions for evaluation of four types of sleep disorders, selected from Pittsburgh Sleep Quality Index
Type
DIS DMS PQS HMU
Question
During the past month, how often have you had trouble sleeping because you cannot get to sleep within 30 minutes? During the past month, how often have you had trouble sleeping because you wake up in the middle of the night or early morning? During the past month, how would you rate your sleep quality overall? During the past month, how often have you taken medicine (prescribed or “over the counter”) to help you sleep?
Responses
Not during the past month, less than once a week, once or twice a week, three or more times a week Not during the past month, less than once a week, once or twice a week, three or more times a week Very good, fairly good, fairly bad, very bad Not during the past month, less than once a week, once or twice a week, three or more times a week
Questions were selected on basis of study by Doi et al.17 DIS — difficulty initiating sleep; DMS — difficulty maintaining sleep; PQS — poor perceived quality of sleep; HMU — hypnotic medication use.
the study population consisted of 22,392 individuals, of whom 14,975 responded to the questionnaire. Information on deaths and relocations between 1992 and 2002 was obtained from the residential registry. The response rate was 66.9%. We excluded 948 individuals who did not respond to the questions about tinnitus or sleep disorders from our analysis. Thus, the analysis population included 14,027 individuals (6,309 men and 7,718 women) 45 to 79 years of age. Informed consent was obtained from each subject, and the study was approved by the ethical board of the Gifu University Graduate School of Medicine. Measurements. The questionnaire item “Have you ever had tinnitus lasting longer than 5 minutes? Do not include when this happened immediately after hearing very loud sounds” was used to identify tinnitus cases based on the criterion proposed by Coles.13 The participants were asked to choose from 3 responses: “I have never had tinnitus,” “I have tinnitus,” or “I have had tinnitus.” Those who reported “I have tinnitus,” were included for the count of tinnitus cases. They were also asked about the loudness and the regularity of tinnitus, which were assessed by the questions “How is the loudness of your tinnitus usually?” (asked to choose low, moderate, loud, or very loud) and “How often do you notice tinnitus during your waking hours?” (asked to choose rare, sometimes, often, or always). These questions were based on those used in studies by Coles13 and Erlandsson et al.14 The study questionnaire included some questions from the Japanese version of the Pittsburgh Sleep Quality Index (PSQI).15,16 The PSQI assesses the sleep duration, sleep latency, and frequency and severity of specific sleep-related problems of the previous month. On the basis of the study by Doi et al,17 4 items from the PSQI were included in the questionnaire: difficulty initiating sleep (DIS), difficulty maintaining sleep (DMS), poor perceived quality of sleep (PQS), and hypnotic medication use (HMU). The details of the questions on sleep disorders are
shown in Table 1.17 Those who responded “three or more times a week” to questions for DIS, DMS, and HMU were counted in the category of DIS, DMS, and HMU cases, and those who chose “fairly bad” or “very bad” to questions for PQS were counted in the category of PQS cases. Insomnia was defined as DIS and/or DMS that has occurred 3 or more times per week during the past month, as proposed by Doi et al.17
Data Analysis. The data were analyzed with the SAS statistical software package v9.2 (SAS Institute, Inc, Cary, North Carolina). Logistic regression models were used to assess the associations between the tinnitus status and the indices for sleep disorders. Odds ratios (ORs) and 95% confidence intervals (CIs) for insomnia, DIS, DMS, PQS, and HMU according to tinnitus status were estimated after we controlled for age and potential confounders such as a medical history of diabetes, hypertension, ischemic heart disease, or asthma; steroid use; and occupational histories that were associated with tinnitus in either men or women in our previous study8: metal production or processing; mine quarrying, rock crushing, or cement manufacturing (men only); cotton, wool, or textile processing; and chemical work. Information from the 1992 questionnaire was used only for occupational histories. RESULTS
The status of tinnitus and sleep disorders among study subjects is shown in Table 2; 11.8% of all subjects (13.3% of men and 10.6% of women) were classified as having tinnitus, and 21.7% (20.1% of men and 23.0% of women) were classified as having insomnia.
Table 3 shows the crude and multiple-adjusted ORs for insomnia related to tinnitus. Adjustment for covariates did not have a significant impact on the association between insomnia and tinnitus. The percentages of insomnia among individuals with and without tinnitus were 28.1% in men and 36.1% in
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Izuhara et al, Tinnitus & Sleep Disorders Table 2. Status of tinnitus and sleep disorders among study subjects
Men Characteristic No. % Age (y) 45-49 595 9.4 50-59 1,998 31.7 60-69 2,158 34.2 1,558 24.7 70-79 Tinnitus Never 5,276 83.6 Past tinnitus 196 3.1 Current tinnitus 837 13.3 Loudness of current tinnitus 417 49.8 Low Moderate 272 32.5 90 10.8 Loud Very loud 26 3.1 Missing value 32 3.8 Regularity of current tinnitus Rare 297 35.5 Sometimes 102 12.2 169 20.2 Often Always 233 27.9 36 4.3 Missing value Insomnia (defined as DIS and/or DMS) Without insomnia 5,044 79.9 With insomnia 1,265 20.1 0 0 Missing value DIS Without DIS 5,603 88.8 With DIS 644 10.2 62 1.0 Missing value DMS Without DMS 4,964 78.7 With DMS 1,028 16.3 Missing value 317 5.0 PQS Without PQS 5,175 82.0 With PQS 1,070 17.0 Missing value 64 1.0 HMU Without HMU 5,791 91.8 With HMU 458 7.3 Missing value 60 1.0
Women No. %
830 2,572 2,594 1,722
10.8 33.3 33.6 22.3
6,513 84.4 386 5.0 819 10.6 442 54.0 230 28.1 73 8.9 10 1.2 64 7.8 346 102 133 179 59
42.2 12.5 16.2 21.9 7.2
5,939 77.0 1,779 23.0 0 0 6,324 81.9 1,299 16.8 95 1.2 5,958 77.2 1,235 16.0 525 6.8 5,798 75.1 1,768 22.9 152 2.0 6,772 87.7 867 11.2 79 1.0
DIS — difficulty initiating sleep; DMS — difficulty maintaining sleep; PQS — poor perceived quality of sleep; HMU — hypnotic medication use.
women and 18.8% in men and 21.5% in women, respectively. There was a 1.7-fold increase in the OR of insomnia in men with tinnitus compared with those without tinnitus. A similar increase in the OR of insomnia was also observed among women with tinnitus (1.8-fold). All loudness levels of tinnitus, including low and moderate, were significantly associated with insomnia; loud or very loud tinnitus was
associated with a more than 2-fold increase in the OR of insomnia in men and a more than 3-fold increase in women. Subjects who chose either “often” or “always” for the question about the frequency of tinnitus had a more than 2-fold increase in the OR of insomnia, whereas less-frequent tinnitus (“rare” or “sometimes”) was not significantly associated with insomnia. Table 4 shows the relationship between tinnitus and each sleep disorder index. We found that DIS, DMS, and PQS in both men and women and HMU in women were significantly associated with the tinnitus status.
The associations were not substantially affected by additional adjustments for body mass index, years of education, smoking, and alcohol intake. Further comparative analysis, stratified by age, between younger (45 to 59 years) and older (60 to 79 years) age groups revealed similar magnitudes of association of tinnitus and sleep disorders in the groups (ORs, 1.68 for younger men, 1.70 for older men, 2.10 for younger women, and 1.66 for older women). DISCUSSION
To the best of our knowledge, this is the first study to assess the relationship between tinnitus and sleep disorders in a Japanese population. A significant association between insomnia and tinnitus in men (OR, 1.70) and women (OR, 1.82) was observed, even in those with low or moderate tinnitus loudness. The observed OR of insomnia appeared to be modest (less than 2.0) for low or moderate tinnitus loudness. However, considering that poor sleep is an important health issue, this association should not be ignored. The potential mechanism by which tinnitus could cause sleep disorders is most likely the commonly expected relationship between disturbing noise and sleep. For example, residence in noisy areas is an important predictor of the occurrence of difficulties with falling asleep (OR, 2.7; 95% CI, 1.3 to 5.8), difficulties with falling back to sleep (OR, 1.9; 95% CI, 1.0 to 3.4), and poor sleep quality (OR, 3.0; 95% CI, 1.1 to 7.9).18 It is also likely that tinnitus is more noticeable and bothersome in quiet circumstances at bedtime. In fact, quiet environments evoke tinnitus perception.19 At bedtime, there is also a lack of the activities such as work, conversations, and watching television that can reduce awareness of tinnitus. Two cross-sectional studies9,10 evaluated the association between tinnitus and sleep disorders in a general population. The study by Asplund9 evaluated
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Izuhara et al, Tinnitus & Sleep Disorders TABLE 3. ODDS RATIOS FOR INSOMNIA ACCORDING TO TINNITUS STATUS
Men Women Multiple- Multiple Insomnia % With Crude OR Adjusted* Insomnia % With Crude OR Adjusted* (+/–) Insomnia (95% CI) OR (95% CI) (+/–) Insomnia (95% CI) OR (95% CI) Presence of tinnitus Without tinnitus 1,030/4,442 18.8 1 1 1,483/5,416 21.5 1 1 With tinnitus 235/602 28.1 1.68 (1.43 to 1.99) 1.70 (1.39 to 2.07) 296/523 36.1 2.07 (1.77 to 2.41) 1.82 (1.51 to 2.21) Loudness of tinnitus No tinnitus 1,030/4,442 18.8 1 1 1,483/5,416 21.5 1 1 Low 104/313 24.9 1.43 (1.14 to 1.81) 1.47 (1.12 to 1.92) 149/293 33.7 1.86 (1.51 to 2.28) 1.58 (1.22 to 2.04) Moderate 77/195 28.3 1.70 (1.30 to 2.24) 1.62 (1.17 to 2.25) 80/150 34.8 1.95 (1.48 to 2.57) 1.80 (1.28 to 2.51) Loud or very loud 44/72 37.9 2.64 (1.80 to 3.86) 2.76 (1.75 to 4.34) 41/42 49.4 3.57 (2.31 to 5.50) 3.28 (1.92 to 5.61) Regularity of tinnitus No tinnitus 1,030/4,442 18.8 1 1 1,483/5,416 21.5 1 1 Rare 69/228 23.2 1.31 (0.99 to 1.72) 1.35 (0.97 to 1.87) 111/235 32.1 1.73 (1.37 to 2.18) 1.38 (1.03 to 1.84) Sometimes 23/79 22.5 1.26 (0.79 to 2.01) 1.05 (0.60 to 1.85) 29/73 28.4 1.45 (0.94 to 2.24) 0.99 (0.55 to 1.77) Often 51/118 30.2 1.86 (1.33 to 2.61) 2.12 (1.44 to 3.12) 56/77 42.1 2.66 (1.87 to 3.77) 2.62 (1.71 to 4.02) Always 79/154 33.9 2.21 (1.67 to 2.93) 2.25 (1.61 to 3.14) 81/98 45.3 3.02 (2.24 to 4.07) 2.90 (2.01 to 4.19) Items with OR of 1 are reference items. *Adjusted for the following: age; medical history of diabetes, hypertension, ischemic heart disease, or asthma; steroid use; and certain occupa tional histories (metal production or processing; mine quarrying, rock crushing, or cement manufacturing [men only]; cotton, wool, or textile processing; and chemical work).
6,103 elderly persons in Sweden (mean ages, 73.0 ± 6.0 years in men and 72.6 ± 6.7 years in women) and found that the percentages of individuals with poor sleep were approximately 18.2% and 13.8% in men with and without tinnitus, respectively, and 35.5% and 26.9% in women with and without tinnitus, respectively (estimated from a graph presented by Asplund9). Poor sleep (OR, 1.4; 95% CI, 1.0 to 2.0) and frequent waking (OR, 1.4; 95% CI, 1.1 to 1.9) were also significantly associated with tinnitus. Tinnitus was defined by the statement “often troubled by disturbing sounds in my head,” whereas poor sleep was identified from the response to “I don’t have a good night’s sleep.” No international standard questionnaire such as the PSQI was used to assess sleep disorders in that study. The Ibadan Study of Aging in Nigeria10 of elderly subjects (at least 65
years of age; mean age not indicated) reported that insomnia was significantly more common among the elderly subjects with tinnitus (51.9%) than in those without tinnitus (33.8%); the crude OR of tinnitus-associated insomnia was estimated to be 2.11. Tinnitus was defined as a sensation of noise in the ear in the absence of an external sound source. Insomnia was defined as difficulty falling asleep, difficulty maintaining sleep, early morning wakefulness, daytime sleepiness, or non-restorative sleep. Neither the Swedish study nor the Nigerian study inquired about details of tinnitus such as its severity. Three additional studies13,20,21 surveyed the tinnitus status of a general population, but described the percentage of sleep disorders only for those with tinnitus. The percentages of sleep disorders in individu-
Table 4. Odds ratios for each sleep disorder indicator according to tinnitus status DIS
DMS
PQS
HMU
Multiple- Multiple- Multiple- Multiple Adjusted* Adjusted* Adjusted* Adjusted* No. OR 95% CI OR 95% CI OR 95% CI OR 95% CI Men Without tinnitus 5,472 1 1 1 1 With tinnitus 837 1.69 1.31 to 2.17 1.68 1.36 to 2.07 1.82 1.49 to 2.24 1.34 0.98 to 1.84 Women Without tinnitus 6,899 1 1 1 1 With tinnitus 819 1.89 1.53 to 2.32 1.88 1.52 to 2.32 1.76 1.45 to 2.13 1.78 1.39 to 2.27 Items with OR of 1 are reference items. DIS — difficulty initiating sleep; DMS — difficulty maintaining sleep; PQS — poor perceived quality of sleep; HMU — hypnotic medication use. *Adjusted for the following: age; medical history of diabetes, hypertension, ischemic heart disease, or asthma; steroid use; and certain occupa tional histories (metal production or processing; mine quarrying, rock crushing, or cement manufacturing [men only]; cotton, wool, or textile processing; and chemical work).
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als with tinnitus were variously reported as ranging from 5.6%13 to 51.9%10 in these studies, whereas the percentage of insomnia in individuals with tinnitus was 28.1% in men and 36.1% in women in our study. The prevalence of sleep disorders associated with tinnitus probably varies among studies according to the definition of tinnitus and sleep disorders. Therefore, it is difficult to generalize our results on the prevalence of sleep disorders to other populations. However, the magnitude of the association between tinnitus and insomnia (OR, 1.70 in men and 1.82 in women) did not differ greatly from those of two previous reports9,10 and might be generalized to other populations. This result may interest primary care physicians. When physicians encounter persons with tinnitus in daily clinical practice, even if tinnitus is not their chief complaint, the physicians should be aware of the possibility of sleep disorders. On the other hand, when patients complain of sleep disorders, they should be asked whether they suffer from tinnitus.
For tinnitus patients, comprehensive tinnitus management programs involving tinnitus evaluations, education, counseling, stress reduction, and the use of therapeutic sounds from recordings, sound machines, or sound pillows has been recommended.22-24 Folmer22 reported that this comprehensive tinnitus management program reduced sleep disturbances due to tinnitus. Relaxation therapy,25 cognitive-behavioral therapy,25 yoga,26 meditation,27 and occasional use of over-the-counter or prescription medications28 may also be helpful. The advantages of the present study were the rel-
atively large size of the study population in comparison with previous studies, the use of the PSQI, which is an internationally standardized questionnaire, and the taking into account of numerous potential confounders.
Several limitations of the present study are noteworthy. We utilized the follow-up data from the Takayama Study. Thus, we could not include individuals 80 or more years of age, who were excluded from the follow-up survey because of their potential high dropout rate. The present study also did not include a young population (less than 45 years of age), as participation in the Takayama cohort study was restricted to those at least 35 years of age at baseline. Because this was a nested cross-sectional study, we cannot determine whether tinnitus or insomnia was any patient’s primary condition. The study did not obtain information on personality patterns or other psychological conditions, which may influence sleep disorders. Hearing loss is often associated with tinnitus and may influence sleep29; however, we did not obtain information on the hearing thresholds of the subjects. CONCLUSIONS
Insomnia and other sleep disorders were significantly associated with tinnitus in Japanese adults. Even low (quiet) or moderate tinnitus was significantly associated with insomnia. Our results can be used as reference data for the management of tinnitus and sleep disorders. They highlight the need to better understand, as well as prevent, sleep disorders among individuals with tinnitus.
REFERENCES
1. Tyler RS, Baker LJ. Difficulties experienced by tinnitus sufferers. J Speech Hear Disord 1983;48:150-4.
2. Alster J, Shemesh Z, Ornan M, Attias J. Sleep disturbance associated with chronic tinnitus. Biol Psychiatry 1993;34:8490.
3. Sanchez L, Stephens D. A tinnitus problem questionnaire in a clinic population. Ear Hear 1997;18:210-7.
4. Folmer RL, Griest SE. Tinnitus and insomnia. Am J Otolaryngol 2000;21:287-93.
5. McKenna L, Daniel HC. Tinnitus-related insomnia treatment. In: Tyler RS, ed. Tinnitus treatment: clinical protocols. New York, NY: Thieme Medical Publishers, 2006:81-95.
6. Hébert S, Carrier J. Sleep complaints in elderly tinnitus patients: a controlled study. Ear Hear 2007;28:649-55. 7. Ferreira LM, Ramos Júnior AN, Mendes EP. Characterization of tinnitus in the elderly and its possible related disorders. Braz J Otorhinolaryngol 2009;75:249-55.
8. Fujii K, Nagata C, Nakamura K, et al. Prevalence of tinnitus in community-dwelling Japanese adults. J Epidemiol 2011;21:299-304.
9. Asplund R. Sleepiness and sleep in elderly persons with tinnitus. Arch Gerontol Geriatr 2003;37:139-45.
10. Lasisi AO, Gureje O. Prevalence of insomnia and impact on quality of life among community elderly subjects with tinnitus. Ann Otol Rhinol Laryngol 2011;120:226-30.
11. Shimizu H. The basic report on Takayama Study. Gifu, Japan: Department of Public Health, Gifu University School of Medicine, 1996. 12. Nagata C, Takatsuka N, Shimizu H. Soy and fish oil intake and mortality in a Japanese community. Am J Epidemiol 2002;156:824-31. 13. Coles RR. Epidemiology of tinnitus: (1) prevalence. J Laryngol Otol Suppl 1984;9:7-15. 14. Erlandsson SI, Hallberg LR, Axelsson A. Psychological and audiological correlates of perceived tinnitus severity. Audiology 1992;31:168-79. 15. Buysse DJ, Reynolds CF III, Monk TH, Berman SR, Kupfer DJ. The Pittsburgh Sleep Quality Index: a new instrument for psychiatric practice and research. Psychiatry Res 1989; 28:193-213. 16. Doi Y, Minowa M, Okawa M, Uchiyama M. Develop-
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ment of the Japanese version of the Pittsburgh Sleep Quality Index [in Japanese]. Jpn J Psychiatry Treat (Seishinka Chiryogaku) 1998;13:755-63.
17. Doi Y, Minowa M, Okawa M, Uchiyama M. Prevalence of sleep disturbance and hypnotic medication use in relation to sociodemographic factors in the general Japanese adult population. J Epidemiol 2000;10:79-86. 18. Jakovljević B, Belojević G, Paunović K, Stojanov V. Road traffic noise and sleep disturbances in an urban population: cross-sectional study. Croat Med J 2006;47:125-33.
19. Heller MF, Bergman M. Tinnitus aurium in normally hearing persons. Ann Otol Rhinol Laryngol 1953;62:73-83. 20. Axelsson A, Ringdahl A. Tinnitus — a study of its prevalence and characteristics. Br J Audiol 1989;23:53-62.
21. Khedr EM, Ahmed MA, Shawky OA, Mohamed ES, El Attar GS, Mohammad KA. Epidemiological study of chronic tinnitus in Assiut, Egypt. Neuroepidemiology 2010;35:45-52. 22. Folmer RL. Long-term reductions in tinnitus severity. BMC Ear Nose Throat Disord 2002;2:3.
23. Tyler RS, Gogel SA, Gehringer AK. Tinnitus activities
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treatment. Prog Brain Res 2007;166:425-34.
24. Henry JA, Zaugg TL, Myers PJ, Schechter MA. Using therapeutic sound with progressive audiologic tinnitus management. Trends Amplif 2008;12:188-209.
25. Andersson G. Psychological aspects of tinnitus and the application of cognitive-behavioral therapy. Clin Psychol Rev 2002;22:977-90.
26. Kröner-Herwig B, Hebing G, van Rijn-Kalkmann U, Frenzel A, Schilkowsky G, Esser G. The management of chronic tinnitus — comparison of a cognitive-behavioural group training with yoga. J Psychosom Res 1995;39:153-65. 27. Sadlier M, Stephens SD, Kennedy V. Tinnitus rehabilitation: a mindfulness meditation cognitive behavioural therapy approach. J Laryngol Otol 2008;122:31-7.
28. Elgoyhen AB, Langguth B. Pharmacological approaches to tinnitus treatment. In: Møller AR, Langguth B, De Ridder D, Kleinjung T, eds. Textbook of tinnitus. New York, NY: Springer-Verlag, 2011:625-37. 29. Test T, Canfi A, Eyal A, Shoam-Vardi I, Sheiner EK. The influence of hearing impairment on sleep quality among workers exposed to harmful noise. Sleep 2011;34:25-30.
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Association Between Tinnitus and Sleep Disorders in the General Japanese Population Keiichi Izuhara, MD; Keiko Wada, MD, PhD; Kozue Nakamura, MD, PhD; Yuya Tamai, MD, PhD; Michiko Tsuji, PhD; Yatsuji Ito, MD, PhD; Chisato Nagata, MD, PhD Objectives: There are few studies about the association between tinnitus and sleep disorders in the general population worldwide. This study assessed this association in a Japanese community. Methods: A total of 14,027 participants 45 to 79 years of age who were in the Takayama Study responded to a self-administered questionnaire about tinnitus and sleep disorders. Results: Of this population, 13.3% of men and 10.6% of women had current tinnitus. The percentages of insomnia, respectively, among individuals with and without tinnitus were 28.1% in men and 36.1% in women and 18.8% in men and 21.5% in women. There were 1.7-fold (95% confidence interval [CI], 1.4 to 2.1) and 1.8-fold (95% CI, 1.5 to 2.2) increases in the odds ratios (ORs) of insomnia for those with tinnitus compared with those without tinnitus in men and women, respectively. Loud or very loud tinnitus was associated with 2.8-fold (95% CI, 1.8 to 4.3) and 3.3-fold (95% CI, 1.9 to 5.6) increases in the OR of insomnia in men and women, respectively. Even low (ie, quiet) or moderate tinnitus was significantly associated with insomnia. Difficulty initiating sleep, difficulty maintaining sleep, and a poor perceived quality of sleep were also significantly associated with tinnitus. Conclusions: Insomnia and other sleep disorders were significantly associated with tinnitus in Japanese adults. Key Words: epidemiology, insomnia, Japan, population-based study, sleep disorder, tinnitus.
tinnitus and sleep disorders among the general Japanese population. Our study examined this association among the participants in the Takayama Study.
INTRODUCTION
Various tinnitus-related complaints, such as sleep disorders, have been described as disrupting daily life.1-7 Since many reports only give the prevalence of sleep disorders among patients who sought treatment for severe tinnitus, it is highly likely that there are also many untreated individuals with tinnitus and sleep disorders who do not seek treatment. The reported prevalences of sleep disorders among tinnitus patients who sought treatment have ranged from 15%3 to 77%,2 although these studies varied in terms of patient characteristics such as age and in the definitions of tinnitus and sleep disorders. The prevalence of sleep disorders among individuals with tinnitus in the general population may be less than that among patients with tinnitus who seek treatment. The prevalence of tinnitus in a Japanese cohort 45 to 79 years of age was 11.9%.8 In addition, sleep symptoms should be compared between individuals with and without tinnitus in assessing the sleep disorders associated with tinnitus. There have been only a handful of such studies worldwide.9,10 There has been no study on the relationship between
MATERIALS AND METHODS
Study Population. The Takayama Study was a population-based cohort study initiated in 1992, and its design and methodology has been described elsewhere.11,12 All non-hospitalized residents in Takayama City, Gifu, who were at least 35 years of age were invited to participate in the study. A total of 31,552 individuals, yielding a participation rate of 85.3%, completed a baseline questionnaire that included questions on demographic characteristics, smoking and drinking habits, diet, exercise, occupation, and medical and reproductive histories. In July 2002, we sent a questionnaire inquiring about tinnitus, sleep disorders, smoking status, medication use, and medical histories to the participants. In this 2002 survey, the target population was restricted to respondents whose current age was between 45 and 79 years. After exclusion of those who had died, were physically unable to complete the questionnaire, or had moved,
From the Departments of Otolaryngology (Izuhara, Ito) and Epidemiology and Preventive Medicine (Wada, Nakamura, Tamai, Tsuji, Nagata), Gifu University Graduate School of Medicine, Gifu, Japan. This study was supported in part by a grant from the Ministry of Education, Culture, Sports, Science and Technology of Japan. Correspondence: Keiichi Izuhara, MD, Dept of Otolaryngology, Gifu University Graduate School of Medicine, 1-1 Yanagido, Gifu City 501-1193, Japan.
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Izuhara et al, Tinnitus & Sleep Disorders Table 1. Questions for evaluation of four types of sleep disorders, selected from Pittsburgh Sleep Quality Index
Type
DIS DMS PQS HMU
Question
During the past month, how often have you had trouble sleeping because you cannot get to sleep within 30 minutes? During the past month, how often have you had trouble sleeping because you wake up in the middle of the night or early morning? During the past month, how would you rate your sleep quality overall? During the past month, how often have you taken medicine (prescribed or “over the counter”) to help you sleep?
Responses
Not during the past month, less than once a week, once or twice a week, three or more times a week Not during the past month, less than once a week, once or twice a week, three or more times a week Very good, fairly good, fairly bad, very bad Not during the past month, less than once a week, once or twice a week, three or more times a week
Questions were selected on basis of study by Doi et al.17 DIS — difficulty initiating sleep; DMS — difficulty maintaining sleep; PQS — poor perceived quality of sleep; HMU — hypnotic medication use.
the study population consisted of 22,392 individuals, of whom 14,975 responded to the questionnaire. Information on deaths and relocations between 1992 and 2002 was obtained from the residential registry. The response rate was 66.9%. We excluded 948 individuals who did not respond to the questions about tinnitus or sleep disorders from our analysis. Thus, the analysis population included 14,027 individuals (6,309 men and 7,718 women) 45 to 79 years of age. Informed consent was obtained from each subject, and the study was approved by the ethical board of the Gifu University Graduate School of Medicine. Measurements. The questionnaire item “Have you ever had tinnitus lasting longer than 5 minutes? Do not include when this happened immediately after hearing very loud sounds” was used to identify tinnitus cases based on the criterion proposed by Coles.13 The participants were asked to choose from 3 responses: “I have never had tinnitus,” “I have tinnitus,” or “I have had tinnitus.” Those who reported “I have tinnitus,” were included for the count of tinnitus cases. They were also asked about the loudness and the regularity of tinnitus, which were assessed by the questions “How is the loudness of your tinnitus usually?” (asked to choose low, moderate, loud, or very loud) and “How often do you notice tinnitus during your waking hours?” (asked to choose rare, sometimes, often, or always). These questions were based on those used in studies by Coles13 and Erlandsson et al.14 The study questionnaire included some questions from the Japanese version of the Pittsburgh Sleep Quality Index (PSQI).15,16 The PSQI assesses the sleep duration, sleep latency, and frequency and severity of specific sleep-related problems of the previous month. On the basis of the study by Doi et al,17 4 items from the PSQI were included in the questionnaire: difficulty initiating sleep (DIS), difficulty maintaining sleep (DMS), poor perceived quality of sleep (PQS), and hypnotic medication use (HMU). The details of the questions on sleep disorders are
shown in Table 1.17 Those who responded “three or more times a week” to questions for DIS, DMS, and HMU were counted in the category of DIS, DMS, and HMU cases, and those who chose “fairly bad” or “very bad” to questions for PQS were counted in the category of PQS cases. Insomnia was defined as DIS and/or DMS that has occurred 3 or more times per week during the past month, as proposed by Doi et al.17
Data Analysis. The data were analyzed with the SAS statistical software package v9.2 (SAS Institute, Inc, Cary, North Carolina). Logistic regression models were used to assess the associations between the tinnitus status and the indices for sleep disorders. Odds ratios (ORs) and 95% confidence intervals (CIs) for insomnia, DIS, DMS, PQS, and HMU according to tinnitus status were estimated after we controlled for age and potential confounders such as a medical history of diabetes, hypertension, ischemic heart disease, or asthma; steroid use; and occupational histories that were associated with tinnitus in either men or women in our previous study8: metal production or processing; mine quarrying, rock crushing, or cement manufacturing (men only); cotton, wool, or textile processing; and chemical work. Information from the 1992 questionnaire was used only for occupational histories. RESULTS
The status of tinnitus and sleep disorders among study subjects is shown in Table 2; 11.8% of all subjects (13.3% of men and 10.6% of women) were classified as having tinnitus, and 21.7% (20.1% of men and 23.0% of women) were classified as having insomnia.
Table 3 shows the crude and multiple-adjusted ORs for insomnia related to tinnitus. Adjustment for covariates did not have a significant impact on the association between insomnia and tinnitus. The percentages of insomnia among individuals with and without tinnitus were 28.1% in men and 36.1% in
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Izuhara et al, Tinnitus & Sleep Disorders Table 2. Status of tinnitus and sleep disorders among study subjects
Men Characteristic No. % Age (y) 45-49 595 9.4 50-59 1,998 31.7 60-69 2,158 34.2 1,558 24.7 70-79 Tinnitus Never 5,276 83.6 Past tinnitus 196 3.1 Current tinnitus 837 13.3 Loudness of current tinnitus 417 49.8 Low Moderate 272 32.5 90 10.8 Loud Very loud 26 3.1 Missing value 32 3.8 Regularity of current tinnitus Rare 297 35.5 Sometimes 102 12.2 169 20.2 Often Always 233 27.9 36 4.3 Missing value Insomnia (defined as DIS and/or DMS) Without insomnia 5,044 79.9 With insomnia 1,265 20.1 0 0 Missing value DIS Without DIS 5,603 88.8 With DIS 644 10.2 62 1.0 Missing value DMS Without DMS 4,964 78.7 With DMS 1,028 16.3 Missing value 317 5.0 PQS Without PQS 5,175 82.0 With PQS 1,070 17.0 Missing value 64 1.0 HMU Without HMU 5,791 91.8 With HMU 458 7.3 Missing value 60 1.0
Women No. %
830 2,572 2,594 1,722
10.8 33.3 33.6 22.3
6,513 84.4 386 5.0 819 10.6 442 54.0 230 28.1 73 8.9 10 1.2 64 7.8 346 102 133 179 59
42.2 12.5 16.2 21.9 7.2
5,939 77.0 1,779 23.0 0 0 6,324 81.9 1,299 16.8 95 1.2 5,958 77.2 1,235 16.0 525 6.8 5,798 75.1 1,768 22.9 152 2.0 6,772 87.7 867 11.2 79 1.0
DIS — difficulty initiating sleep; DMS — difficulty maintaining sleep; PQS — poor perceived quality of sleep; HMU — hypnotic medication use.
women and 18.8% in men and 21.5% in women, respectively. There was a 1.7-fold increase in the OR of insomnia in men with tinnitus compared with those without tinnitus. A similar increase in the OR of insomnia was also observed among women with tinnitus (1.8-fold). All loudness levels of tinnitus, including low and moderate, were significantly associated with insomnia; loud or very loud tinnitus was
associated with a more than 2-fold increase in the OR of insomnia in men and a more than 3-fold increase in women. Subjects who chose either “often” or “always” for the question about the frequency of tinnitus had a more than 2-fold increase in the OR of insomnia, whereas less-frequent tinnitus (“rare” or “sometimes”) was not significantly associated with insomnia. Table 4 shows the relationship between tinnitus and each sleep disorder index. We found that DIS, DMS, and PQS in both men and women and HMU in women were significantly associated with the tinnitus status.
The associations were not substantially affected by additional adjustments for body mass index, years of education, smoking, and alcohol intake. Further comparative analysis, stratified by age, between younger (45 to 59 years) and older (60 to 79 years) age groups revealed similar magnitudes of association of tinnitus and sleep disorders in the groups (ORs, 1.68 for younger men, 1.70 for older men, 2.10 for younger women, and 1.66 for older women). DISCUSSION
To the best of our knowledge, this is the first study to assess the relationship between tinnitus and sleep disorders in a Japanese population. A significant association between insomnia and tinnitus in men (OR, 1.70) and women (OR, 1.82) was observed, even in those with low or moderate tinnitus loudness. The observed OR of insomnia appeared to be modest (less than 2.0) for low or moderate tinnitus loudness. However, considering that poor sleep is an important health issue, this association should not be ignored. The potential mechanism by which tinnitus could cause sleep disorders is most likely the commonly expected relationship between disturbing noise and sleep. For example, residence in noisy areas is an important predictor of the occurrence of difficulties with falling asleep (OR, 2.7; 95% CI, 1.3 to 5.8), difficulties with falling back to sleep (OR, 1.9; 95% CI, 1.0 to 3.4), and poor sleep quality (OR, 3.0; 95% CI, 1.1 to 7.9).18 It is also likely that tinnitus is more noticeable and bothersome in quiet circumstances at bedtime. In fact, quiet environments evoke tinnitus perception.19 At bedtime, there is also a lack of the activities such as work, conversations, and watching television that can reduce awareness of tinnitus. Two cross-sectional studies9,10 evaluated the association between tinnitus and sleep disorders in a general population. The study by Asplund9 evaluated
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Izuhara et al, Tinnitus & Sleep Disorders TABLE 3. ODDS RATIOS FOR INSOMNIA ACCORDING TO TINNITUS STATUS
Men Women Multiple- Multiple Insomnia % With Crude OR Adjusted* Insomnia % With Crude OR Adjusted* (+/–) Insomnia (95% CI) OR (95% CI) (+/–) Insomnia (95% CI) OR (95% CI) Presence of tinnitus Without tinnitus 1,030/4,442 18.8 1 1 1,483/5,416 21.5 1 1 With tinnitus 235/602 28.1 1.68 (1.43 to 1.99) 1.70 (1.39 to 2.07) 296/523 36.1 2.07 (1.77 to 2.41) 1.82 (1.51 to 2.21) Loudness of tinnitus No tinnitus 1,030/4,442 18.8 1 1 1,483/5,416 21.5 1 1 Low 104/313 24.9 1.43 (1.14 to 1.81) 1.47 (1.12 to 1.92) 149/293 33.7 1.86 (1.51 to 2.28) 1.58 (1.22 to 2.04) Moderate 77/195 28.3 1.70 (1.30 to 2.24) 1.62 (1.17 to 2.25) 80/150 34.8 1.95 (1.48 to 2.57) 1.80 (1.28 to 2.51) Loud or very loud 44/72 37.9 2.64 (1.80 to 3.86) 2.76 (1.75 to 4.34) 41/42 49.4 3.57 (2.31 to 5.50) 3.28 (1.92 to 5.61) Regularity of tinnitus No tinnitus 1,030/4,442 18.8 1 1 1,483/5,416 21.5 1 1 Rare 69/228 23.2 1.31 (0.99 to 1.72) 1.35 (0.97 to 1.87) 111/235 32.1 1.73 (1.37 to 2.18) 1.38 (1.03 to 1.84) Sometimes 23/79 22.5 1.26 (0.79 to 2.01) 1.05 (0.60 to 1.85) 29/73 28.4 1.45 (0.94 to 2.24) 0.99 (0.55 to 1.77) Often 51/118 30.2 1.86 (1.33 to 2.61) 2.12 (1.44 to 3.12) 56/77 42.1 2.66 (1.87 to 3.77) 2.62 (1.71 to 4.02) Always 79/154 33.9 2.21 (1.67 to 2.93) 2.25 (1.61 to 3.14) 81/98 45.3 3.02 (2.24 to 4.07) 2.90 (2.01 to 4.19) Items with OR of 1 are reference items. *Adjusted for the following: age; medical history of diabetes, hypertension, ischemic heart disease, or asthma; steroid use; and certain occupa tional histories (metal production or processing; mine quarrying, rock crushing, or cement manufacturing [men only]; cotton, wool, or textile processing; and chemical work).
6,103 elderly persons in Sweden (mean ages, 73.0 ± 6.0 years in men and 72.6 ± 6.7 years in women) and found that the percentages of individuals with poor sleep were approximately 18.2% and 13.8% in men with and without tinnitus, respectively, and 35.5% and 26.9% in women with and without tinnitus, respectively (estimated from a graph presented by Asplund9). Poor sleep (OR, 1.4; 95% CI, 1.0 to 2.0) and frequent waking (OR, 1.4; 95% CI, 1.1 to 1.9) were also significantly associated with tinnitus. Tinnitus was defined by the statement “often troubled by disturbing sounds in my head,” whereas poor sleep was identified from the response to “I don’t have a good night’s sleep.” No international standard questionnaire such as the PSQI was used to assess sleep disorders in that study. The Ibadan Study of Aging in Nigeria10 of elderly subjects (at least 65
years of age; mean age not indicated) reported that insomnia was significantly more common among the elderly subjects with tinnitus (51.9%) than in those without tinnitus (33.8%); the crude OR of tinnitus-associated insomnia was estimated to be 2.11. Tinnitus was defined as a sensation of noise in the ear in the absence of an external sound source. Insomnia was defined as difficulty falling asleep, difficulty maintaining sleep, early morning wakefulness, daytime sleepiness, or non-restorative sleep. Neither the Swedish study nor the Nigerian study inquired about details of tinnitus such as its severity. Three additional studies13,20,21 surveyed the tinnitus status of a general population, but described the percentage of sleep disorders only for those with tinnitus. The percentages of sleep disorders in individu-
Table 4. Odds ratios for each sleep disorder indicator according to tinnitus status DIS
DMS
PQS
HMU
Multiple- Multiple- Multiple- Multiple Adjusted* Adjusted* Adjusted* Adjusted* No. OR 95% CI OR 95% CI OR 95% CI OR 95% CI Men Without tinnitus 5,472 1 1 1 1 With tinnitus 837 1.69 1.31 to 2.17 1.68 1.36 to 2.07 1.82 1.49 to 2.24 1.34 0.98 to 1.84 Women Without tinnitus 6,899 1 1 1 1 With tinnitus 819 1.89 1.53 to 2.32 1.88 1.52 to 2.32 1.76 1.45 to 2.13 1.78 1.39 to 2.27 Items with OR of 1 are reference items. DIS — difficulty initiating sleep; DMS — difficulty maintaining sleep; PQS — poor perceived quality of sleep; HMU — hypnotic medication use. *Adjusted for the following: age; medical history of diabetes, hypertension, ischemic heart disease, or asthma; steroid use; and certain occupa tional histories (metal production or processing; mine quarrying, rock crushing, or cement manufacturing [men only]; cotton, wool, or textile processing; and chemical work).
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als with tinnitus were variously reported as ranging from 5.6%13 to 51.9%10 in these studies, whereas the percentage of insomnia in individuals with tinnitus was 28.1% in men and 36.1% in women in our study. The prevalence of sleep disorders associated with tinnitus probably varies among studies according to the definition of tinnitus and sleep disorders. Therefore, it is difficult to generalize our results on the prevalence of sleep disorders to other populations. However, the magnitude of the association between tinnitus and insomnia (OR, 1.70 in men and 1.82 in women) did not differ greatly from those of two previous reports9,10 and might be generalized to other populations. This result may interest primary care physicians. When physicians encounter persons with tinnitus in daily clinical practice, even if tinnitus is not their chief complaint, the physicians should be aware of the possibility of sleep disorders. On the other hand, when patients complain of sleep disorders, they should be asked whether they suffer from tinnitus.
For tinnitus patients, comprehensive tinnitus management programs involving tinnitus evaluations, education, counseling, stress reduction, and the use of therapeutic sounds from recordings, sound machines, or sound pillows has been recommended.22-24 Folmer22 reported that this comprehensive tinnitus management program reduced sleep disturbances due to tinnitus. Relaxation therapy,25 cognitive-behavioral therapy,25 yoga,26 meditation,27 and occasional use of over-the-counter or prescription medications28 may also be helpful. The advantages of the present study were the rel-
atively large size of the study population in comparison with previous studies, the use of the PSQI, which is an internationally standardized questionnaire, and the taking into account of numerous potential confounders.
Several limitations of the present study are noteworthy. We utilized the follow-up data from the Takayama Study. Thus, we could not include individuals 80 or more years of age, who were excluded from the follow-up survey because of their potential high dropout rate. The present study also did not include a young population (less than 45 years of age), as participation in the Takayama cohort study was restricted to those at least 35 years of age at baseline. Because this was a nested cross-sectional study, we cannot determine whether tinnitus or insomnia was any patient’s primary condition. The study did not obtain information on personality patterns or other psychological conditions, which may influence sleep disorders. Hearing loss is often associated with tinnitus and may influence sleep29; however, we did not obtain information on the hearing thresholds of the subjects. CONCLUSIONS
Insomnia and other sleep disorders were significantly associated with tinnitus in Japanese adults. Even low (quiet) or moderate tinnitus was significantly associated with insomnia. Our results can be used as reference data for the management of tinnitus and sleep disorders. They highlight the need to better understand, as well as prevent, sleep disorders among individuals with tinnitus.
REFERENCES
1. Tyler RS, Baker LJ. Difficulties experienced by tinnitus sufferers. J Speech Hear Disord 1983;48:150-4.
2. Alster J, Shemesh Z, Ornan M, Attias J. Sleep disturbance associated with chronic tinnitus. Biol Psychiatry 1993;34:8490.
3. Sanchez L, Stephens D. A tinnitus problem questionnaire in a clinic population. Ear Hear 1997;18:210-7.
4. Folmer RL, Griest SE. Tinnitus and insomnia. Am J Otolaryngol 2000;21:287-93.
5. McKenna L, Daniel HC. Tinnitus-related insomnia treatment. In: Tyler RS, ed. Tinnitus treatment: clinical protocols. New York, NY: Thieme Medical Publishers, 2006:81-95.
6. Hébert S, Carrier J. Sleep complaints in elderly tinnitus patients: a controlled study. Ear Hear 2007;28:649-55. 7. Ferreira LM, Ramos Júnior AN, Mendes EP. Characterization of tinnitus in the elderly and its possible related disorders. Braz J Otorhinolaryngol 2009;75:249-55.
8. Fujii K, Nagata C, Nakamura K, et al. Prevalence of tinnitus in community-dwelling Japanese adults. J Epidemiol 2011;21:299-304.
9. Asplund R. Sleepiness and sleep in elderly persons with tinnitus. Arch Gerontol Geriatr 2003;37:139-45.
10. Lasisi AO, Gureje O. Prevalence of insomnia and impact on quality of life among community elderly subjects with tinnitus. Ann Otol Rhinol Laryngol 2011;120:226-30.
11. Shimizu H. The basic report on Takayama Study. Gifu, Japan: Department of Public Health, Gifu University School of Medicine, 1996. 12. Nagata C, Takatsuka N, Shimizu H. Soy and fish oil intake and mortality in a Japanese community. Am J Epidemiol 2002;156:824-31. 13. Coles RR. Epidemiology of tinnitus: (1) prevalence. J Laryngol Otol Suppl 1984;9:7-15. 14. Erlandsson SI, Hallberg LR, Axelsson A. Psychological and audiological correlates of perceived tinnitus severity. Audiology 1992;31:168-79. 15. Buysse DJ, Reynolds CF III, Monk TH, Berman SR, Kupfer DJ. The Pittsburgh Sleep Quality Index: a new instrument for psychiatric practice and research. Psychiatry Res 1989; 28:193-213. 16. Doi Y, Minowa M, Okawa M, Uchiyama M. Develop-
Downloaded from aor.sagepub.com at Purdue University Libraries on June 20, 2015
706
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ment of the Japanese version of the Pittsburgh Sleep Quality Index [in Japanese]. Jpn J Psychiatry Treat (Seishinka Chiryogaku) 1998;13:755-63.
17. Doi Y, Minowa M, Okawa M, Uchiyama M. Prevalence of sleep disturbance and hypnotic medication use in relation to sociodemographic factors in the general Japanese adult population. J Epidemiol 2000;10:79-86. 18. Jakovljević B, Belojević G, Paunović K, Stojanov V. Road traffic noise and sleep disturbances in an urban population: cross-sectional study. Croat Med J 2006;47:125-33.
19. Heller MF, Bergman M. Tinnitus aurium in normally hearing persons. Ann Otol Rhinol Laryngol 1953;62:73-83. 20. Axelsson A, Ringdahl A. Tinnitus — a study of its prevalence and characteristics. Br J Audiol 1989;23:53-62.
21. Khedr EM, Ahmed MA, Shawky OA, Mohamed ES, El Attar GS, Mohammad KA. Epidemiological study of chronic tinnitus in Assiut, Egypt. Neuroepidemiology 2010;35:45-52. 22. Folmer RL. Long-term reductions in tinnitus severity. BMC Ear Nose Throat Disord 2002;2:3.
23. Tyler RS, Gogel SA, Gehringer AK. Tinnitus activities
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treatment. Prog Brain Res 2007;166:425-34.
24. Henry JA, Zaugg TL, Myers PJ, Schechter MA. Using therapeutic sound with progressive audiologic tinnitus management. Trends Amplif 2008;12:188-209.
25. Andersson G. Psychological aspects of tinnitus and the application of cognitive-behavioral therapy. Clin Psychol Rev 2002;22:977-90.
26. Kröner-Herwig B, Hebing G, van Rijn-Kalkmann U, Frenzel A, Schilkowsky G, Esser G. The management of chronic tinnitus — comparison of a cognitive-behavioural group training with yoga. J Psychosom Res 1995;39:153-65. 27. Sadlier M, Stephens SD, Kennedy V. Tinnitus rehabilitation: a mindfulness meditation cognitive behavioural therapy approach. J Laryngol Otol 2008;122:31-7.
28. Elgoyhen AB, Langguth B. Pharmacological approaches to tinnitus treatment. In: Møller AR, Langguth B, De Ridder D, Kleinjung T, eds. Textbook of tinnitus. New York, NY: Springer-Verlag, 2011:625-37. 29. Test T, Canfi A, Eyal A, Shoam-Vardi I, Sheiner EK. The influence of hearing impairment on sleep quality among workers exposed to harmful noise. Sleep 2011;34:25-30.
Downloaded from aor.sagepub.com at Purdue University Libraries on June 20, 2015
