YBRBI 2502
No. of Pages 5, Model 5G
12 December 2014 Brain, Behavior, and Immunity xxx (2014) xxx–xxx 1
Contents lists available at ScienceDirect
Brain, Behavior, and Immunity journal homepage: www.elsevier.com/locate/ybrbi
2
Short Communication
6 4 7
Immediate rather than delayed memory impairment in older adults with latent toxoplasmosis
5 8 9 10 11 12 13 14 15 1 1 7 3 18 19 20 21 22 23 24 25 26 27 28 29 30
Q1
Angelico Mendy a,⇑, Edgar R. Vieira b, Ahmed N. Albatineh c, Janvier Gasana d a
Department of Epidemiology, College of Public Health, University of Iowa, S161 CPHB 105 River Street, Iowa City, IA 52242, USA Department of Physical Therapy, Florida International University, 11200 SW 8th St, Miami, FL 33199, USA c Department of Biostatistics, Robert Stempel School of Public Health and Social Work, Florida International University, 11200 SW 8th St, Miami, FL 33199, USA d Department of Occupational and Environmental Health, Robert Stempel School of Public Health and Social Work, Florida International University, 11200 SW 8th St, Miami, FL 33199, USA b
a r t i c l e
i n f o
Article history: Received 11 August 2014 Received in revised form 25 November 2014 Accepted 4 December 2014 Available online xxxx Keywords: Toxoplasma gondii Toxoplasmosis Memory Cognition Older age Aging
a b s t r a c t The neurotropic parasite Toxoplasma gondii infects one third of the world population, but its effect on memory remains ambiguous. To examine a potential relationship of the infection with immediate and delayed memory, a population-based study was conducted in 4485 participants of the Third National Health and Nutrition Examination Survey aged 60 years and older. Serum anti-Toxoplasma IgG antibodies were measured by enzyme immune assay and verbal memory was assessed using the Mini-Mental State Examination and the East Boston Memory Test. The prevalence of latent toxoplasmosis was 41%; in one way analysis of variance, anti-Toxoplasma IgG antibody levels significantly differed across tertiles for immediate (P = 0.006) but not delayed memory scores (P = 0.22). In multinomial logistic regression adjusting for covariates, Toxoplasma seropositivity was associated with lower immediate memory performance (OR: 0.65, 95% CI: 0.44, 0.97 for medium tertile and OR: 0.61, 95% CI: 0.37, 0.98 for highest tertile in reference to the lowest tertile), especially in non-Hispanic Whites (OR: 0.56, 95% CI: 0.36, 0.88 for medium tertile and OR: 0.51, 95% CI: 0.30, 0.87 for highest tertile in reference to the lowest tertile). However, no relationship with delayed memory was observed. In conclusion, latent toxoplasmosis is widespread in older adults and may primarily affect immediate rather than delayed memory, particularly in White Americans. Ó 2014 Published by Elsevier Inc.
32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49
50 51
1. Introduction
52
Toxoplasma gondii is an intracellular parasitic protozoan infecting more than 30% of the world population (Pappas et al., 2009). Cats are the only definitive host and T. gondii is transmitted to humans via contaminated food or water, vertically from mother to child, and through organ transplantation (Jones et al., 2009). After infection, Toxoplasma antibodies remain detectable in one’s serum for life with dormant cysts located in brain cells (astrocytes and neurons), often establishing latent toxoplasmosis (Prandovszky et al., 2011). The infection is believed to be asymptomatic in immunocompetent people, but possible link with psychiatric and cognitive disorders have been reported due to the parasite’s ability to induce neuronal cell death, cytokines’ release,
53 54 55 56 57 58 59 60 61 62 63
⇑ Corresponding author. Tel.: +1 (319) 384 1500; fax: +1 954 524 3162.
or neurochemical changes via its genome which encodes aromatic amino acid hydroxylases (Kusbeci et al., 2011; Stock et al., 2013). Yet, it is only recently that latent toxoplasmosis has been reported for the first time to significantly impair episodic and working memory in older adults in an epidemiologic report. This study included 84 participants, some of whom had hypertension, hypo or hyperthyroidism and/or hypercholesterolemia, all known to impair memory (Gajewski et al., 2014). The authors adjusted Q2 for medication use for these conditions, but not for their presence. Pearce et al., for their part, examined the relationship between Toxoplasma and cognitive functions including short term memory assessed by the serial-digit learning test in a large but younger population sample of adults aged 20–59 years (Pearce et al., 2014). Therefore, we propose to investigate the relationship between latent toxoplasmosis and both immediate and delayed verbal memory in a large sample, representative of the US older adult population, adjusting for a wide range of covariates missing in previous research.
E-mail address: [email protected] (A. Mendy). http://dx.doi.org/10.1016/j.bbi.2014.12.006 0889-1591/Ó 2014 Published by Elsevier Inc.
Please cite this article in press as: Mendy, A., et al. Immediate rather than delayed memory impairment in older adults with latent toxoplasmosis. Brain Behav. Immun. (2014), http://dx.doi.org/10.1016/j.bbi.2014.12.006
64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81
YBRBI 2502
No. of Pages 5, Model 5G
12 December 2014 2
A. Mendy et al. / Brain, Behavior, and Immunity xxx (2014) xxx–xxx
82
2. Materials and methods
83
2.1. Data source and study design
84
98
We used data from the Third National Health and Nutrition Examination Survey (NHANES III) conducted from 1988 to 1994 by the National Center for Health Statistics (NCHS) of the Centers for Disease Control and Prevention (CDC) (Centers for Disease Control and Prevention (CDC), National Center for Health Statistics (NCHS)). The NHANES is an ongoing cross-sectional survey of the US non-institutionalized civilian population selected using a complex multistage sampling design to derive a representative sample of the US population. T. gondii antibodies and memory test scores were available in 4654 adults aged 60 years and older. After excluding participants with missing data, the final sample size included 4485 participants. NHANES protocols were approved by the institutional review boards of the NCHS and CDC and informed consent was obtained from all participants.
99
2.2. T. gondii infection
85 86 87 88 89 90 91 92 93 94 95 96 97
114
Serum T. gondii IgG antibodies were measured using the Patelia Toxo-G immunoglobulin G enzyme immunoassay (Sanofi Diagnostics Pasteur, BioRad, Hercules, California). The Patelia Toxo-G kit was beforehand evaluated in comparison with various titers in the CDC Toxoplasma immunofluorescence assay-immunoglobulin G test and dye test (Dr. Jack Remington, Palo Alto, California); both specificity and sensitivity were 100%. Results were reported in International Units (IU) and, as per the instructions of the manufacturer, samples with titer of lower than 6 IU/mL were considered seronegative, while those with results of 6 IU/mL and higher, seropositive. In the present study we were also interested in differentiating participants on the basis of serointensity and thus considered antibody titer in our analyses. Null values were indicative of no exposure to Toxoplasma and higher titer suggested higher intensity.
115
2.3. Memory function assessment
116
134
Immediate and delayed verbal memory were assessed using object recall tests from the Mini-Mental State Examination and story recall tests from the East Boston Memory Test. In the object recall test, participants were asked to repeat the words ‘‘apple,’’ ‘‘table,’’ and ‘‘penny’’ up to three times until they have been successfully learned and were scored from 1 to 3 on the first trial (immediate recall). After a short delay, they were asked to repeat the objects (delayed recall) (Folstein et al., 1975). In the story recall participants were asked to repeat a narrative (‘‘Three children were alone at home and the house caught on fire. A brave fireman managed to climb in a back window and carry them to safety. Aside from minor cuts and bruises, all were well’’) immediately after it was read (immediate recall) and then after answering unrelated questions (delayed recall) (Gfeller and Horn, 1996). Participants were scored from 1 to 6 for recall of each of the six following ideas ‘‘three children’’, ‘‘house on fire’’, ‘‘fireman climbed in’’, ‘‘children rescued’’, ‘‘minor injuries’’, and ‘‘everyone well’’. Total immediate and delayed memory scores (from 0 to 9) were obtained after summing object and story recall tests scores.
135
2.4. Covariates
136
Data on age, gender, race/ethnicity, family income, level of education smoking, alcohol consumption, medication use, and medical conditions were collected during the NHANES using
100 101 102 103 104 105 106 107 108 109 110 111 112 113
117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133
137 138
questionnaires. Family income to poverty ratio was calculated using guidelines and adjustment for family size, year and state. Participants’ weight and height were measured and body mass index (BMI) was calculated as weight in kilograms divided by height in meters squared. Diabetes was defined by self-report, serum glucose P 200 mg/dL, or glycohemoglobin P 6.5%. Hypertension was defined by self-report or mean systolic blood pressure > 140 mmHg on up to 4 measurements on 2 separate occasions. HDL cholesterol and triglycerides were quantitatively measured by peroxidase-catalyzed reaction. Other infection was dichotomized into presence of any positive serum antibody testing against Hepatitis B or C, Herpes simplex virus (HSV) 1 or 2 determined using immunodot assay (HSV) or enzyme linked immunosorbent assay (hepatitis) or their absence.
139
2.5. Statistical analysis
153
Descriptive analyses were performed and P-values for differences in proportions or means by Toxoplasma seropositivity status were calculated using chi-square test for categorical variables and student t-test for continuous ones. Memory scores were disproportionately distributed, therefore we chose to divide them into tertiles (frequency distribution for memory scores and results from analyses for undivided outcomes are displayed in the Supplementary materials). Given the positive skewness of the data, anti-T. gondii IgG antibody levels were log-transformed to improve normality; geometric means were obtained by exponentiation of the log-transformed data arithmetic mean and one way Analysis of Variance (ANOVA) allowed comparing means over immediate and delayed memory score tertiles. Multinomial logistic regression models with the lowest tertile memory scores as reference were constructed to examine associations of Toxoplasma seropositivity and serointensity (log-transformed anti-T. gondii IgG antibodies) with immediate or delayed recall adjusting for age, gender, race/ ethnicity, family income to poverty ratio, years of education, smoking, diabetes, hypertension, stroke, cancer, other infections, medication use, BMI, daily alcohol consumption, serum HDL cholesterol, serum Triglycerides, thyroid stimulating hormone. Memory score tertiles were automatically generated by the analysis software. Effect modification by covariates was investigated by including an interaction or product term between the Toxoplasma seropositivity or serointensity and the variable of interest in the models. All analyses were performed in STATA (Version 11, STATA Corporation, College Station, TX, USA). NHANES sampling weights and STATA survey commands taking into account the multistage and complex survey design were used in all statistical procedures to adjust for unequal selection probabilities, non-responses, oversampling, post-stratification, and sampling errors, so that estimates were nationally representative. P-values
No. of Pages 5, Model 5G
12 December 2014 Brain, Behavior, and Immunity xxx (2014) xxx–xxx 1
Contents lists available at ScienceDirect
Brain, Behavior, and Immunity journal homepage: www.elsevier.com/locate/ybrbi
2
Short Communication
6 4 7
Immediate rather than delayed memory impairment in older adults with latent toxoplasmosis
5 8 9 10 11 12 13 14 15 1 1 7 3 18 19 20 21 22 23 24 25 26 27 28 29 30
Q1
Angelico Mendy a,⇑, Edgar R. Vieira b, Ahmed N. Albatineh c, Janvier Gasana d a
Department of Epidemiology, College of Public Health, University of Iowa, S161 CPHB 105 River Street, Iowa City, IA 52242, USA Department of Physical Therapy, Florida International University, 11200 SW 8th St, Miami, FL 33199, USA c Department of Biostatistics, Robert Stempel School of Public Health and Social Work, Florida International University, 11200 SW 8th St, Miami, FL 33199, USA d Department of Occupational and Environmental Health, Robert Stempel School of Public Health and Social Work, Florida International University, 11200 SW 8th St, Miami, FL 33199, USA b
a r t i c l e
i n f o
Article history: Received 11 August 2014 Received in revised form 25 November 2014 Accepted 4 December 2014 Available online xxxx Keywords: Toxoplasma gondii Toxoplasmosis Memory Cognition Older age Aging
a b s t r a c t The neurotropic parasite Toxoplasma gondii infects one third of the world population, but its effect on memory remains ambiguous. To examine a potential relationship of the infection with immediate and delayed memory, a population-based study was conducted in 4485 participants of the Third National Health and Nutrition Examination Survey aged 60 years and older. Serum anti-Toxoplasma IgG antibodies were measured by enzyme immune assay and verbal memory was assessed using the Mini-Mental State Examination and the East Boston Memory Test. The prevalence of latent toxoplasmosis was 41%; in one way analysis of variance, anti-Toxoplasma IgG antibody levels significantly differed across tertiles for immediate (P = 0.006) but not delayed memory scores (P = 0.22). In multinomial logistic regression adjusting for covariates, Toxoplasma seropositivity was associated with lower immediate memory performance (OR: 0.65, 95% CI: 0.44, 0.97 for medium tertile and OR: 0.61, 95% CI: 0.37, 0.98 for highest tertile in reference to the lowest tertile), especially in non-Hispanic Whites (OR: 0.56, 95% CI: 0.36, 0.88 for medium tertile and OR: 0.51, 95% CI: 0.30, 0.87 for highest tertile in reference to the lowest tertile). However, no relationship with delayed memory was observed. In conclusion, latent toxoplasmosis is widespread in older adults and may primarily affect immediate rather than delayed memory, particularly in White Americans. Ó 2014 Published by Elsevier Inc.
32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49
50 51
1. Introduction
52
Toxoplasma gondii is an intracellular parasitic protozoan infecting more than 30% of the world population (Pappas et al., 2009). Cats are the only definitive host and T. gondii is transmitted to humans via contaminated food or water, vertically from mother to child, and through organ transplantation (Jones et al., 2009). After infection, Toxoplasma antibodies remain detectable in one’s serum for life with dormant cysts located in brain cells (astrocytes and neurons), often establishing latent toxoplasmosis (Prandovszky et al., 2011). The infection is believed to be asymptomatic in immunocompetent people, but possible link with psychiatric and cognitive disorders have been reported due to the parasite’s ability to induce neuronal cell death, cytokines’ release,
53 54 55 56 57 58 59 60 61 62 63
⇑ Corresponding author. Tel.: +1 (319) 384 1500; fax: +1 954 524 3162.
or neurochemical changes via its genome which encodes aromatic amino acid hydroxylases (Kusbeci et al., 2011; Stock et al., 2013). Yet, it is only recently that latent toxoplasmosis has been reported for the first time to significantly impair episodic and working memory in older adults in an epidemiologic report. This study included 84 participants, some of whom had hypertension, hypo or hyperthyroidism and/or hypercholesterolemia, all known to impair memory (Gajewski et al., 2014). The authors adjusted Q2 for medication use for these conditions, but not for their presence. Pearce et al., for their part, examined the relationship between Toxoplasma and cognitive functions including short term memory assessed by the serial-digit learning test in a large but younger population sample of adults aged 20–59 years (Pearce et al., 2014). Therefore, we propose to investigate the relationship between latent toxoplasmosis and both immediate and delayed verbal memory in a large sample, representative of the US older adult population, adjusting for a wide range of covariates missing in previous research.
E-mail address: [email protected] (A. Mendy). http://dx.doi.org/10.1016/j.bbi.2014.12.006 0889-1591/Ó 2014 Published by Elsevier Inc.
Please cite this article in press as: Mendy, A., et al. Immediate rather than delayed memory impairment in older adults with latent toxoplasmosis. Brain Behav. Immun. (2014), http://dx.doi.org/10.1016/j.bbi.2014.12.006
64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81
YBRBI 2502
No. of Pages 5, Model 5G
12 December 2014 2
A. Mendy et al. / Brain, Behavior, and Immunity xxx (2014) xxx–xxx
82
2. Materials and methods
83
2.1. Data source and study design
84
98
We used data from the Third National Health and Nutrition Examination Survey (NHANES III) conducted from 1988 to 1994 by the National Center for Health Statistics (NCHS) of the Centers for Disease Control and Prevention (CDC) (Centers for Disease Control and Prevention (CDC), National Center for Health Statistics (NCHS)). The NHANES is an ongoing cross-sectional survey of the US non-institutionalized civilian population selected using a complex multistage sampling design to derive a representative sample of the US population. T. gondii antibodies and memory test scores were available in 4654 adults aged 60 years and older. After excluding participants with missing data, the final sample size included 4485 participants. NHANES protocols were approved by the institutional review boards of the NCHS and CDC and informed consent was obtained from all participants.
99
2.2. T. gondii infection
85 86 87 88 89 90 91 92 93 94 95 96 97
114
Serum T. gondii IgG antibodies were measured using the Patelia Toxo-G immunoglobulin G enzyme immunoassay (Sanofi Diagnostics Pasteur, BioRad, Hercules, California). The Patelia Toxo-G kit was beforehand evaluated in comparison with various titers in the CDC Toxoplasma immunofluorescence assay-immunoglobulin G test and dye test (Dr. Jack Remington, Palo Alto, California); both specificity and sensitivity were 100%. Results were reported in International Units (IU) and, as per the instructions of the manufacturer, samples with titer of lower than 6 IU/mL were considered seronegative, while those with results of 6 IU/mL and higher, seropositive. In the present study we were also interested in differentiating participants on the basis of serointensity and thus considered antibody titer in our analyses. Null values were indicative of no exposure to Toxoplasma and higher titer suggested higher intensity.
115
2.3. Memory function assessment
116
134
Immediate and delayed verbal memory were assessed using object recall tests from the Mini-Mental State Examination and story recall tests from the East Boston Memory Test. In the object recall test, participants were asked to repeat the words ‘‘apple,’’ ‘‘table,’’ and ‘‘penny’’ up to three times until they have been successfully learned and were scored from 1 to 3 on the first trial (immediate recall). After a short delay, they were asked to repeat the objects (delayed recall) (Folstein et al., 1975). In the story recall participants were asked to repeat a narrative (‘‘Three children were alone at home and the house caught on fire. A brave fireman managed to climb in a back window and carry them to safety. Aside from minor cuts and bruises, all were well’’) immediately after it was read (immediate recall) and then after answering unrelated questions (delayed recall) (Gfeller and Horn, 1996). Participants were scored from 1 to 6 for recall of each of the six following ideas ‘‘three children’’, ‘‘house on fire’’, ‘‘fireman climbed in’’, ‘‘children rescued’’, ‘‘minor injuries’’, and ‘‘everyone well’’. Total immediate and delayed memory scores (from 0 to 9) were obtained after summing object and story recall tests scores.
135
2.4. Covariates
136
Data on age, gender, race/ethnicity, family income, level of education smoking, alcohol consumption, medication use, and medical conditions were collected during the NHANES using
100 101 102 103 104 105 106 107 108 109 110 111 112 113
117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133
137 138
questionnaires. Family income to poverty ratio was calculated using guidelines and adjustment for family size, year and state. Participants’ weight and height were measured and body mass index (BMI) was calculated as weight in kilograms divided by height in meters squared. Diabetes was defined by self-report, serum glucose P 200 mg/dL, or glycohemoglobin P 6.5%. Hypertension was defined by self-report or mean systolic blood pressure > 140 mmHg on up to 4 measurements on 2 separate occasions. HDL cholesterol and triglycerides were quantitatively measured by peroxidase-catalyzed reaction. Other infection was dichotomized into presence of any positive serum antibody testing against Hepatitis B or C, Herpes simplex virus (HSV) 1 or 2 determined using immunodot assay (HSV) or enzyme linked immunosorbent assay (hepatitis) or their absence.
139
2.5. Statistical analysis
153
Descriptive analyses were performed and P-values for differences in proportions or means by Toxoplasma seropositivity status were calculated using chi-square test for categorical variables and student t-test for continuous ones. Memory scores were disproportionately distributed, therefore we chose to divide them into tertiles (frequency distribution for memory scores and results from analyses for undivided outcomes are displayed in the Supplementary materials). Given the positive skewness of the data, anti-T. gondii IgG antibody levels were log-transformed to improve normality; geometric means were obtained by exponentiation of the log-transformed data arithmetic mean and one way Analysis of Variance (ANOVA) allowed comparing means over immediate and delayed memory score tertiles. Multinomial logistic regression models with the lowest tertile memory scores as reference were constructed to examine associations of Toxoplasma seropositivity and serointensity (log-transformed anti-T. gondii IgG antibodies) with immediate or delayed recall adjusting for age, gender, race/ ethnicity, family income to poverty ratio, years of education, smoking, diabetes, hypertension, stroke, cancer, other infections, medication use, BMI, daily alcohol consumption, serum HDL cholesterol, serum Triglycerides, thyroid stimulating hormone. Memory score tertiles were automatically generated by the analysis software. Effect modification by covariates was investigated by including an interaction or product term between the Toxoplasma seropositivity or serointensity and the variable of interest in the models. All analyses were performed in STATA (Version 11, STATA Corporation, College Station, TX, USA). NHANES sampling weights and STATA survey commands taking into account the multistage and complex survey design were used in all statistical procedures to adjust for unequal selection probabilities, non-responses, oversampling, post-stratification, and sampling errors, so that estimates were nationally representative. P-values
