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Vitamin D Status Linked to Cognitive Function in Older Men Print E-mail
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อาทิตย์, 07 มิถุนายน 2009

        June 2, 2009 — Lower 25-hydroxyvitamin D [25(OH)D] levels in older men are associated with slower psychomotor processing speed, according to the results of a population-based, cross-sectional study reported in the May 21 Online First issue of the Journal of Neurology, Neurosurgery & Psychiatry.

"Although there is evidence that vitamin D inadequacy may be linked to adverse cognitive outcomes, results from studies on this topic have been inconsistent," write David M. Lee, from the University of Manchester in Manchester, United Kingdom, and colleagues. "The aim of our trial was to examine the association between...25(OH)D levels and cognitive performance in middle-aged and older European men."At 8 centers taking part in the European Male Ageing Study, 3369 men, ranging in age from 40 to 79 years, underwent evaluation of cognitive performance and measurement of serum 25(OH)D levels by radioimmunoassay. Psychological testing included the Rey-Osterrieth Complex Figure (ROCF) test, the Camden Topographical Recognition Memory (CTRM) test, and the Digit Symbol Substitution Test (DSST). Physical activity, functional performance, and mood/depression were also evaluated. Locally weighted and linear regression models were used to explore associations between cognitive function and 25(OH)D levels.The analysis included 3133 men, mean age 60 ± 11 years, and mean 25(OH)D concentration 63 ± 31 nmol/L. Age-adjusted linear regressions showed that high levels of 25(OH)D were associated with high scores on the copy component of the ROCF test (β per 10 nmol/L, 0.096; 95% confidence interval [CI], 0.049 - 0.144), the CTRM test (β per 10 nmol/L, 0.075; 95% CI, 0.026 - 0.124), and the DSST (β per 10 nmol/L, 0.318; 95% CI, 0.235 - 0.401).When adjustments were made for other potentially confounding variables, only the association of 25(OH)D levels with DSST score remained significant (β per 10 nmol/L, 0.152; 95% CI, 0.051 - 0.253). At 25(OH)D concentrations less than 35 nmol/L, the relationship between 25(OH)D concentration and cognitive function was most pronounced, according to the results of locally weighted and spline regressions."In this study, lower 25(OH)D levels were associated with poorer performance on the DSST," the study authors write. "Further research is warranted to determine whether vitamin D sufficiency might have a role in preserving cognitive function in older adults."Limitations of this study include cross-sectional design, preventing determination of causality; overall response rate for participation in the study of only 41%; predominantly Caucasian European population; and analysis restricted to vision-based tests of cognitive function. Low serum 25(OH)D concentration may merely be a "risk marker," and some of the findings may be the result of unmeasured factors and/or residual confounding. Furthermore, the single serum 25(OH)D measurement performed in this study may not accurately reflect each participant's long-term vitamin D status."The magnitude of the association between 25(OH)D concentration and processing speed was comparatively small; however, if cognitive function could be improved by a simple intervention such as vitamin D supplementation, our results would have potentially important implications for population health," the study authors write. "In light of our findings, and the fact that vitamin D inadequacy is common among adults, further prospective studies are warranted to determine whether vitamin D supplementation could aid in minimising ageing-related declines in specific cognitive domains."The Commission of the European Communities Fifth Framework Program "Quality of Life and Management of Living Resources" Grant and the Arthritis Research Campaign (United Kingdom) supported this study. The study authors have disclosed no relevant financial relationships. J Neurol Neurosurg Psychiatry. Published online May 21, 2009.
Clinical Context
Vitamin D is crucial for maintaining bone health and regulating calcium metabolism and also plays some role in other physiologic outcomes. Some evidence to date suggests that vitamin D deficiency may adversely affect cognitive or behavioral function, but findings have been inconclusive.In 2 recent observational studies, low serum 25(OH)D levels were associated with cognitive impairment in patients with mild Alzheimer's disease, and a retrospective study of older adults seen at a memory assessment clinic showed that 25(OH)D levels were associated with scores on the Mini-Mental State Examination. However, survey data from the Third National Health and Nutrition Examination Survey did not support an association between low 25(OH)D levels and impaired neurocognitive performance.
Study Highlights
  • The objective of the study was to evaluate the association between vitamin D levels and cognition in older men.
  • This cross-sectional analysis used baseline data from the European Male Ageing Study, an ongoing, large, population-based study of aging in middle-aged and older men.
  • Measurements obtained in the European Male Ageing Study include standardized measurements of cognitive function and comprehensive lifestyle and functional assessments, allowing adjustment for a wide range of possible confounders.
  • The study sample consisted of 3369 men, ranging in age from 40 to 79 years, from 8 centers taking part in the European Male Ageing Study.
  • Measurement of serum 25(OH)D levels was done by radioimmunoassay.
  • Psychological testing included the ROCF test, the CTRM test, and the DSST.
  • Other measurements included assessment of physical activity, functional performance, and mood/depression.
  • Locally weighted and linear regression models were used to examine associations between cognitive test scores and 25(OH)D levels.
  • The sample used for analysis was 3133 men, mean age 60 ± 11 years, and mean 25(OH)D concentration 63 ± 31 nmol/L.
  • Based on age-adjusted linear regressions, high levels of 25(OH)D were associated with high scores on the copy component of the ROCF test, the CTRM test, and the DSST.
  • There was an inverse association between 25(OH)D levels and the Beck Depression Inventory score.
  • Only the association of 25(OH)D levels with DSST score remained significant after adjustment for other potentially confounding variables.
  • The magnitude of the association between 25(OH)D concentration and processing speed was relatively small.
  • The relationship between 25(OH)D concentration and cognitive function was most pronounced at 25(OH)D concentrations of less than 35 nmol/L, based on locally weighted and spline regressions.
  • When regression analyses were stratified by age decade, the association between increased 25(OH)D concentration and a higher DSST score was only significant in the older men (aged 60 - 69 years and aged 70 - 79 years).
  • The investigators concluded that lower 25(OH)D levels were associated with poorer performance on the DSST but that further research is needed to evaluate whether vitamin D sufficiency might help preserve cognitive function in older adults.
  • Limitations of the study include cross-sectional design, 41% response rate, mostly Caucasian European population, use of only vision-based tests of cognitive function, and unmeasured factors and/or residual confounding.
Clinical Implications
  • In a population-based study of European men 40 years or older, lower levels of 25(OH)D were associated with slower psychomotor processing speed as indicated by poor performance on the DSST, after adjustment for potential confounders.
  • This association between DSST score and serum 25(OH)D levels was most pronounced in men with a 25(OH)D level of less than 35 nmol/L and in men 60 years or older.
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