Vitamin D and the Risk of Dementia: The Rotterdam Study

Background: Vitamin D has gained interest as a potentially modifiable risk factor for dementia because of its putative neuroprotective effects. However, longitudinal studies examining the association between Vitamin D and dementia have provided inconsistent results.
Objective: To determine the relationship of serum Vitamin D with prevalent and incident dementia in the general population.
Methods: Within the prospective Rotterdam Study, we measured serum 25-hydroxyVitamin D concentrations between 1997 and 2001 using electrochemiluminescence-immunoassay in 6220 participants 55 years or older. We assessed dementia at baseline and continuously during follow-up until 1 January 2015. We used appropriate regression models to determine the relationship of Vitamin D with prevalent and incident dementia, including Alzheimer's disease (AD). We adjusted models for age, sex, and season of blood collection. Additionally, we adjusted for ethnicity, education, cardiovascular risk factors, serum calcium, kidney function, depression, outdoor-activity and APOE 4 carriership. Results: At baseline, 127 of 6,220 participants had dementia, of whom 97 had AD. Lower Vitamin D concentrations were associated with a non-significantly higher prevalence of dementia, but not with AD. Among 6,087 non-demented participants with 68,884 person-years of follow-up, 795 participants developed dementia, of whom 641 had AD. Lower Vitamin D concentrations were associated with higher risk of dementia and AD.
Conclusion: Lower serum Vitamin D concentrations are associated with a higher incidence of dementia.