Vitamin D has been linked to brain function. To date, there have been limited studies investigating vitamin D receptor (VDR) genetic polymorphisms and cognition. The objective of this study was, therefore, to examine whether any relationships exist between VDR polymorphisms and cognitive decline in an elderly population.
Six hundred and fifty participants aged ≥ 65 years were recruited from the Central Coast, New South Wales, Australia, and were genotyped for 8 VDR polymorphisms (VDR-ApaI, VDR-BsmI, VDR-TaqI, VDR-FokI, VDR-Tru91, VDR-Cdx2, VDR-A1012G, and VDR-NIaIII). Gene variants were identified using polymerase chain reaction, followed by restriction fragment length polymorphism analysis and gel electrophoresis. Cognitive decline was measured using the mini-mental state examination (MMSE), while a self-administered food frequency questionnaire was used to estimate participants’ dietary intake of vitamin D.
Odds ratio (OR) analysis found that VDR-BsmI and VDR-TaqI polymorphic alleles were both associated with increased risk of cognitive decline (OR = 1.55 and OR = 1.49, respectively). VDR-TaqI was also found to be significantly associated with MMSE score, following adjustment for age and sex (p = 0.0005). Examination of the distribution of VDR-TaqI genotypes showed that a greater proportion of participants with the homozygous recessive tt genotype had some degree of cognitive decline (24%). As might be predicted, a significant association was also observed between age and MMSE score (p = 0.015). When examined by sex, a significant relationship was found between age and MMSE for females (p ≤ 0.0001) but no relationship was observed in males. Dietary intake of vitamin D did not influence MMSE outcomes in this cohort.
The VDR-BsmI and VDR-TaqI genetic polymorphisms are associated with cognitive decline in an elderly population.
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