J Chron Dis 1977, Vol. 30, pp. 599-611. Pergamon Press. Printed in Great Britain
THE RELATIONSHIP OF SOCIO-ENVIRONMENTAL FACTORS TO THE PREVALENCE OF OBSTRUCTIVE LUNG DISEASES AND OTHER CHRONIC CONDITIONS* MICHAEL
D. LEBOWITZ
Arizona Medical Center, College of Medicine, (Westend Research Laboratory), Division of Respiratory Sciences, Tucson. AZ 85724. U.S.A. (Rrceiced
in recisedform
21 January 1977)
Abstract-Socio-environmental factors have been studied in relation to the prevalence of obstructive lung problems and other chronic conditions. The primary findings are that education and income were inversely related to these conditions, even after controlling for sex, age, and smoking. In addition, marital status had a complex relationship with these chronic diseases. Social mobility, residential mobility, crowding, and other housing factors had inconsistent and usually non-significant associations with lung problems.
INTRODUCTION
long been recognized that social factors are strongly related to the incidence, prevalence and mortality of various diseases [l-S]. Such factors are thought to play a large role in the etiology and natural history of obstructive lung disorders [9-131. Socio-economic status (SES), one of the major social variables, appears to have a general influence on health and its perceptions, and the receipt of medical care. Specific components of SES, such as education, income and occupation, are thought to have independent influences [l-6], and may differ in the nature of their influences. Other social variables which have been shown to be related to chronic diseases include: areas of residence, status inconsistency (differences in status using different measures), residential mobility, social mobility (inter- and intra-generational), marital status, family size, and various aspects of housing [8-201. It is the purpose of this paper to test in a general population sample the various hypothetical relationships between the social variables mentioned above and respiratory symptomatology, reported diagnoses, and lung function. IT HAS
METHODOLOGY
The Tucson Epidemiologic Study of Obstructive Lung Diseases has been described in detail elsewhere [21]. Briefly, it is a multi-stage stratified cluster sample *Presented at the Ninth Annual Meeting of the Society for Epidemiologic 1976. This work was supported by NHLBI SCOR Grant No. HL 14136. 599
Research, Toronto, June.
MICHAEI. D. LEEKIWITZ
600
of Anglo-white households in the Tucson area. Stratification was based on SES and age of head-of-household. The study’s major purposes are to determine the etiology and natural history of obstructive lung diseases. A pilot study of 50 households was used to complete training and to test all instruments. In the first year of the study (1971-1972). 3800 individuals from 1655 households were enrolled: to be representative this was 75”,, of those eligible. Analysis showed participants of the total target population. Of these, 3485 were Anglo-whites, which represents the population analyzed. These individuals were interviewed and examined by nurse-interviewers who went through rigorous survey interview training, and were assigned randomly to the enrollment and examination processes. Tests of interobserver variability conducted throughout the year showed no significant observer differences. The first year’s data. on which this report is based. includes questionnaire information on demographic characteristics, social variables. respiratory history. other chronic disease history, smoking. migration, residential mobility. housing characteristics. and objective tests of lung function. Only reports of present disease were utilized herein. A dichotomous SES scale was developed using variables of income, education, and occupation. Income itself was represented by an interval scale of family incomes, education by the number of years of completed education, and occupation by the two-digit Bureau of the Census Occupational Category. Status inconsistency values were differences scores between those three values. Intra-generational occupational mobility was the difference between usual and first occupation. using the first digit of the occupational code. Inter-generational occupational mobility was the difference between usual occupation and father’s occupation when the individual was a teenager, using the first digit of the codes. Inter-generational educational mobility was the difference between the individual’s educational attainment (grouped) and the educational attainment of his/her parent of the same sex (grouped). All other variables were either multiple choice, scaled, or continuous fill-in responses. Age, sex, and smoking history were used as controlling (specific or adjusted) variables in this report; their relation to symptomatology and diagnoses has been explored previously [21]. General tabular analysis, utilizing Chi square, contingency coefficients, and other nonparametric methods, were utihzed for data analysis. In addition, multivariate statistical techniques, specifically regression analyses, principal components analyses and cluster analyses, were also utilized. In addition to examining the Tucson data, replications of other studies [l@- 131 were conducted using the Tucson data. RESULTS Socio-econonzic
stufus
(SES)
There was no significant correlation between prevalence rates of various symptoms or reported diagnoses with the dichotomous SES index, where smoking, age, and sex were controlled. Analysis of variance for inter-group differences did not demonstrate statistically significant differences. However, when symptoms and diagnoses were examined by income, education, and occupation separately, significant correlations were found. There was an inverse relationship between education
Prevalence
of Obstructke
Lung
Diseases
6Cll
and almost all respiratory problems. as well as other chronic conditions. Education was not found to be related to tuberculosis, coccidioidomycosis. acute respiratory illnesses or diffuse bronchial trouble. Income was inversely related to most symptoms and diseases, although not significantly related to asthma. ulcers, or productive cough. There were age, sex, and smoking habit differentials in symptoms rates. Also, smoking showed a slight association with income (a direct relationship) and with education level. with eight or less years and 16 or mol-e years having slightly fewer present smokers. Therefore, it was decided to examine associations of disease rate with social status variables after age, sex, and smoking adjustment of those rates for the adults (Table 1) and to examine age- and sex-adjusted rates within smoking groups (Tables 2, 3). Education was inversely related to chronic obstructive lung disease (AOD) prevalence. as well as pneumonia and severe productive cough prevalence. It was directly related to respiratory troubles before age 16. These inverse associations were strong within present smokers (Table 2). The association with emphysema, chronic bronchitis. and early respiratory trouble persisted in ex-smokers and never smokers, but the relation of education to respiratory symptoms was not as evident in these groups. Fathers’ education and mothers’ education. which were highly correlated with the individuals’ education, had similar but weaker relations to symptomatology. The same overall associations were seen between income and the respiratory disease prevalence rates, although in some cases the association was not as strong (Table I). Within smoking categories. the same trends were generally found (Table 3). Occupational status had a weaker relation with these respiratory prevalences than either income or education (Table 1). Neither productive cough. pneumonia, nor abnormal lung function had clear inverse trends with occupation. and the AOD inverse associations with occupation were much weaker. Within the different smoking groups, the associations diminished. Age- and sex-adjusted prevalence rates of arthritis and ulcers were also inversely related to education. This association of arthritis with education was seen in all smoking groups. while the ulcers’ association was its strong only in present smokers. Age- and sex-adjusted prevalence rates of heart trouble or high blood pressure did not appear to be related to educational level. nor did hardening of arteries. diabetes. bowel trouble. kidney trouble. or liver trouble. Arthritis, heart trouble, and high blood pressure were inversely related to income. but ulcers was not (Table I ). The association of income with heart trouble persisted in all smoking groups, while the association of income with arthritis was strong only in present smokers. The association of high blood pressure was strong only in never smokers (Table 3). The other chronic conditions were not related to income, except fol a slight association of bowel trouble and income. Occupational status did not appear to be strongly related to any of these chronic conditions (Table I). Although physician-confirmed asthma in adults was inversely related to family income (see above), in children under 15 ye- of age, there were no significant differences in asthma prevalence rates between income groups. In adults. age- and sexspecific allergic rhinitis was not significantly related to income or education. In
10.3 9.0 11.9 13.6
Prof. & Semi-Prof. Mgr, Prof, Cler, Sals Skilled & Semi-Skil. Unskilled & Dom. 20.2 17.1 15.9 13.5
10.4 14.5 18.7 17.2 f
15.4 15.9 13.6 16.4 22.1 t
Resp. ills cl6 yr
3.3 4.2 4.6 5.4
t
5.1 5.3 3.9 4.5 2.2 t
Occupation 4.4 6.1 1.1 8.4
t 9.1 6.7 1.3 6.3
1.4 6.4 6.8 5.0
11.6 8.9 5.3 7.0 4.4 t
Asthma
present
Education 9.2 8.0 5.1 6.2 5.0 f Family income 6.6 8.2 5.6 6.5 4.3 7.0 1.7 3.6
MD confirmed Chr. Emph. branch.
*Note total population by age and sex used as standard population. tsignificant differences by x2 and x2 for trend. P < 0.05. IPersistent cough and phlegm, both morning and at other times of day/night.
41,999 g-14,999 15.000+
yr
14.0 12.6 10.8 10.2 4.0 t
13.0 12.2 9.0 1.2
-c$4OOO/yr
9-11 12 13-15 16+ yr
THE RELATIONSHIP OF SOCIO-ENVIRONMENTAL FACTORS TO THE PREVALENCE OF OBSTRUCTIVE LUNG DISEASES AND OTHER CHRONIC CONDITIONS* MICHAEL
D. LEBOWITZ
Arizona Medical Center, College of Medicine, (Westend Research Laboratory), Division of Respiratory Sciences, Tucson. AZ 85724. U.S.A. (Rrceiced
in recisedform
21 January 1977)
Abstract-Socio-environmental factors have been studied in relation to the prevalence of obstructive lung problems and other chronic conditions. The primary findings are that education and income were inversely related to these conditions, even after controlling for sex, age, and smoking. In addition, marital status had a complex relationship with these chronic diseases. Social mobility, residential mobility, crowding, and other housing factors had inconsistent and usually non-significant associations with lung problems.
INTRODUCTION
long been recognized that social factors are strongly related to the incidence, prevalence and mortality of various diseases [l-S]. Such factors are thought to play a large role in the etiology and natural history of obstructive lung disorders [9-131. Socio-economic status (SES), one of the major social variables, appears to have a general influence on health and its perceptions, and the receipt of medical care. Specific components of SES, such as education, income and occupation, are thought to have independent influences [l-6], and may differ in the nature of their influences. Other social variables which have been shown to be related to chronic diseases include: areas of residence, status inconsistency (differences in status using different measures), residential mobility, social mobility (inter- and intra-generational), marital status, family size, and various aspects of housing [8-201. It is the purpose of this paper to test in a general population sample the various hypothetical relationships between the social variables mentioned above and respiratory symptomatology, reported diagnoses, and lung function. IT HAS
METHODOLOGY
The Tucson Epidemiologic Study of Obstructive Lung Diseases has been described in detail elsewhere [21]. Briefly, it is a multi-stage stratified cluster sample *Presented at the Ninth Annual Meeting of the Society for Epidemiologic 1976. This work was supported by NHLBI SCOR Grant No. HL 14136. 599
Research, Toronto, June.
MICHAEI. D. LEEKIWITZ
600
of Anglo-white households in the Tucson area. Stratification was based on SES and age of head-of-household. The study’s major purposes are to determine the etiology and natural history of obstructive lung diseases. A pilot study of 50 households was used to complete training and to test all instruments. In the first year of the study (1971-1972). 3800 individuals from 1655 households were enrolled: to be representative this was 75”,, of those eligible. Analysis showed participants of the total target population. Of these, 3485 were Anglo-whites, which represents the population analyzed. These individuals were interviewed and examined by nurse-interviewers who went through rigorous survey interview training, and were assigned randomly to the enrollment and examination processes. Tests of interobserver variability conducted throughout the year showed no significant observer differences. The first year’s data. on which this report is based. includes questionnaire information on demographic characteristics, social variables. respiratory history. other chronic disease history, smoking. migration, residential mobility. housing characteristics. and objective tests of lung function. Only reports of present disease were utilized herein. A dichotomous SES scale was developed using variables of income, education, and occupation. Income itself was represented by an interval scale of family incomes, education by the number of years of completed education, and occupation by the two-digit Bureau of the Census Occupational Category. Status inconsistency values were differences scores between those three values. Intra-generational occupational mobility was the difference between usual and first occupation. using the first digit of the occupational code. Inter-generational occupational mobility was the difference between usual occupation and father’s occupation when the individual was a teenager, using the first digit of the codes. Inter-generational educational mobility was the difference between the individual’s educational attainment (grouped) and the educational attainment of his/her parent of the same sex (grouped). All other variables were either multiple choice, scaled, or continuous fill-in responses. Age, sex, and smoking history were used as controlling (specific or adjusted) variables in this report; their relation to symptomatology and diagnoses has been explored previously [21]. General tabular analysis, utilizing Chi square, contingency coefficients, and other nonparametric methods, were utihzed for data analysis. In addition, multivariate statistical techniques, specifically regression analyses, principal components analyses and cluster analyses, were also utilized. In addition to examining the Tucson data, replications of other studies [l@- 131 were conducted using the Tucson data. RESULTS Socio-econonzic
stufus
(SES)
There was no significant correlation between prevalence rates of various symptoms or reported diagnoses with the dichotomous SES index, where smoking, age, and sex were controlled. Analysis of variance for inter-group differences did not demonstrate statistically significant differences. However, when symptoms and diagnoses were examined by income, education, and occupation separately, significant correlations were found. There was an inverse relationship between education
Prevalence
of Obstructke
Lung
Diseases
6Cll
and almost all respiratory problems. as well as other chronic conditions. Education was not found to be related to tuberculosis, coccidioidomycosis. acute respiratory illnesses or diffuse bronchial trouble. Income was inversely related to most symptoms and diseases, although not significantly related to asthma. ulcers, or productive cough. There were age, sex, and smoking habit differentials in symptoms rates. Also, smoking showed a slight association with income (a direct relationship) and with education level. with eight or less years and 16 or mol-e years having slightly fewer present smokers. Therefore, it was decided to examine associations of disease rate with social status variables after age, sex, and smoking adjustment of those rates for the adults (Table 1) and to examine age- and sex-adjusted rates within smoking groups (Tables 2, 3). Education was inversely related to chronic obstructive lung disease (AOD) prevalence. as well as pneumonia and severe productive cough prevalence. It was directly related to respiratory troubles before age 16. These inverse associations were strong within present smokers (Table 2). The association with emphysema, chronic bronchitis. and early respiratory trouble persisted in ex-smokers and never smokers, but the relation of education to respiratory symptoms was not as evident in these groups. Fathers’ education and mothers’ education. which were highly correlated with the individuals’ education, had similar but weaker relations to symptomatology. The same overall associations were seen between income and the respiratory disease prevalence rates, although in some cases the association was not as strong (Table I). Within smoking categories. the same trends were generally found (Table 3). Occupational status had a weaker relation with these respiratory prevalences than either income or education (Table 1). Neither productive cough. pneumonia, nor abnormal lung function had clear inverse trends with occupation. and the AOD inverse associations with occupation were much weaker. Within the different smoking groups, the associations diminished. Age- and sex-adjusted prevalence rates of arthritis and ulcers were also inversely related to education. This association of arthritis with education was seen in all smoking groups. while the ulcers’ association was its strong only in present smokers. Age- and sex-adjusted prevalence rates of heart trouble or high blood pressure did not appear to be related to educational level. nor did hardening of arteries. diabetes. bowel trouble. kidney trouble. or liver trouble. Arthritis, heart trouble, and high blood pressure were inversely related to income. but ulcers was not (Table I ). The association of income with heart trouble persisted in all smoking groups, while the association of income with arthritis was strong only in present smokers. The association of high blood pressure was strong only in never smokers (Table 3). The other chronic conditions were not related to income, except fol a slight association of bowel trouble and income. Occupational status did not appear to be strongly related to any of these chronic conditions (Table I). Although physician-confirmed asthma in adults was inversely related to family income (see above), in children under 15 ye- of age, there were no significant differences in asthma prevalence rates between income groups. In adults. age- and sexspecific allergic rhinitis was not significantly related to income or education. In
10.3 9.0 11.9 13.6
Prof. & Semi-Prof. Mgr, Prof, Cler, Sals Skilled & Semi-Skil. Unskilled & Dom. 20.2 17.1 15.9 13.5
10.4 14.5 18.7 17.2 f
15.4 15.9 13.6 16.4 22.1 t
Resp. ills cl6 yr
3.3 4.2 4.6 5.4
t
5.1 5.3 3.9 4.5 2.2 t
Occupation 4.4 6.1 1.1 8.4
t 9.1 6.7 1.3 6.3
1.4 6.4 6.8 5.0
11.6 8.9 5.3 7.0 4.4 t
Asthma
present
Education 9.2 8.0 5.1 6.2 5.0 f Family income 6.6 8.2 5.6 6.5 4.3 7.0 1.7 3.6
MD confirmed Chr. Emph. branch.
*Note total population by age and sex used as standard population. tsignificant differences by x2 and x2 for trend. P < 0.05. IPersistent cough and phlegm, both morning and at other times of day/night.
41,999 g-14,999 15.000+
yr
14.0 12.6 10.8 10.2 4.0 t
13.0 12.2 9.0 1.2
-c$4OOO/yr
9-11 12 13-15 16+ yr
