Endogenous hormones, androgen receptor CAG repeat length and fluid cognition in middle-aged and older men: results from the European Male Ageing Study.

OBJECTIVE: Data remain divergent regarding the activational effects of endogenous hormones on adult cognitive function. We examined the association between cognition, hormones and androgen receptor (AR) CAG repeat length in a large cohort of men. DESIGN: Community-based, cross-sectional study of 3369 men aged 40-79 years. METHODS: Cognition tests were the Rey-Osterrieth Complex Figure, Camden Topographical Recognition Memory and Digit-Symbol Substitution. A fluid cognition (FC) z-score was computed from the individual tests. Testosterone, oestradiol (OE(2)) and 5alpha-dihydrotestosterone were measured by gas chromatography-mass spectrometry; DHEAS, LH, FSH and sex hormone-binding globulin (SHBG) by electrochemiluminescence. Free testosterone and OE(2) were calculated from total hormone, SHBG and albumin. CAG repeat lengths were assayed by PCR genotyping. RESULTS: Total testosterone and free testosterone were associated with higher FC z-scores, LH and FSH with lower FC z-scores in age-adjusted linear regressions. After adjusting for health, lifestyle and centre, a modest association was only observed between DHEAS and a lower FC z-score (beta=-0.011, P=0.02), although this was driven by subjects with DHEAS levels >10 micromol/l. Locally weighted plots revealed no threshold effects between hormones and FC. There was no association between CAG repeat length and FC z-score after adjustment for age and centre (beta=-0.007, P=0.06), nor any interaction effect between CAG repeat length and hormones. CONCLUSION: Our results suggest that endogenous hormones are not associated with a vision-based measure of FC among healthy, community-dwelling men. Further studies are warranted to determine whether 'high' DHEAS levels are associated with poorer performance on a broader range of neuropsychological tests.

Association between 25-hydroxyvitamin D levels and cognitive performance in middle-aged and older European men.

BACKGROUND: Although there is evidence that vitamin D inadequacy may be linked to adverse cognitive outcomes, results from studies on this topic have been inconsistent. The aim of this trial was to examine the association between 25-hydroxyvitamin D (25(OH)D) levels and cognitive performance in middle-aged and older European men. METHODS: This population-based cross-sectional study included 3,369 men aged 40-79 years from eight centres enrolled in the European Male Ageing Study. Cognitive function was assessed using the Rey-Osterrieth Complex Figure (ROCF) test, the Camden Topographical Recognition Memory (CTRM) test and the Digit Symbol Substitution Test (DSST). Serum 25(OH)D levels were measured by radioimmunoassay. Additional assessments included measurement of physical activity, functional performance and mood/depression. Associations between cognitive function and 25(OH)D levels were explored using locally weighted and linear regression models. RESULTS: In total, 3,133 men (mean (+/-SD) age 60+/-11 years) were included in the analysis. The mean (+/-SD) 25(OH)D concentration was 63+/-31 nmol/l. In age-adjusted linear regressions, high levels of 25(OH)D were associated with high scores on the copy component of the ROCF test (beta per 10 nmol/l = 0.096; 95% CI 0.049 to 0.144), the CTRM test (beta per 10 nmol/l = 0.075; 95% CI 0.026 to 0.124) and the DSST (beta per 10 nmol/l = 0.318; 95% CI 0.235 to 0.401). After adjusting for additional confounders, 25(OH)D levels were associated with only score on the DSST (beta per 10 nmol/l = 0.152; 95% CI 0.051 to 0.253). Locally weighted and spline regressions suggested the relationship between 25(OH)D concentration and cognitive function was most pronounced at 25(OH)D concentrations below 35 nmol/l. CONCLUSION: In this study, lower 25(OH)D levels were associated with poorer performance on the DSST. Further research is warranted to determine whether vitamin D sufficiency might have a role in preserving cognitive function in older adults.

The association between different cognitive domains and age in a multi-centre study of middle-aged and older European men.

OBJECTIVES: We determined levels of cognitive functioning in community dwelling men aged 40-79 (n = 3265) from eight European centres and investigated to what extent cognitive performance varied between centres, the association between different cognitive domains and age, educational level, co-morbidity and lifestyle factors and the respective contributions of centre and individual factors to cognitive performance. METHODS: Cognitive domains assessed were visuo-constructional ability and visual memory (Rey-Osterrieth Complex Figure test, ROCF), topographical memory (Camden Topographical Recognition Memory test, CTRM) and processing speed (Digit-Symbol Substitution test, DSST). RESULTS: There were significant between-centre differences in all four cognitive test scores. Using multilevel linear regression analysis (MLRA), age, education, depression, physical performance and smoking were independent predictors of cognitive function and these variables explained 10-13% of the variation in cognitive scores between centres and 17-36% of the variation in scores between individuals within centres. CONCLUSION: Our data suggest that although a proportion of the variance in cognitive function among European men is explained by individual level differences, a significant proportion is due to contextual phenomenon. Such contextual factors need to be considered when analysing multi-centre data and European men should not be treated as homogeneous when assessing cognitive performance using existing instruments.