Is vitamin D status associated with dementia risk? Original paper

In this prospective cohort study, insufficient or deficient serum vitamin D levels were associated with an increased risk of dementia.

The association between serum vitamin D status or supplemental vitamin D use with (i) dementia risk, (ii) Alzheimer’s disease risk, and (iii) vascular dementia risk.

A total of 269,229 participants (ages 55–69; 52% women, 48% men) from across the United Kingdom, 7,087 of whom developed dementia during the study.

Data were used from the UK Biobank study,^[1] which is a prospective cohort study with a median follow-up of 13.6 years. At baseline, the participants’ serum vitamin D level was assessed, and the participants were asked whether they used vitamin D supplements, either vitamin D alone or as part of a multivitamin.

For the analyses, the participants were categorized according to whether they used vitamin D supplements or multivitamin supplements. They were also categorized according to their vitamin D status: vitamin D deficiency (<30 nmol/L or <12 ng/mL), vitamin D insufficiency (30–49 nmol/L or 12–19 ng/mL), or vitamin D sufficiency (≥50 nmol/L or ≥20 ng/mL).

The analyses were adjusted for a variety of confounders, including APOE ɛ4 status, age, sex, socioeconomic status, smoking, alcohol consumption, physical activity, diet quality, time spent outdoors, BMI, disease status, and cardiometabolic biomarkers.

Compared to the participants with vitamin D sufficiency, the following associations were found:

• The risk of dementia was 11% and 25% higher in the participants with vitamin D insufficiency and vitamin D deficiency, respectively.
• The risk of Alzheimer’s disease was 10% and 19% higher in the participants with vitamin D insufficiency and vitamin D deficiency, respectively.
• The risk of vascular dementia was 15% and 24% higher in the participants with vitamin D insufficiency and vitamin D deficiency, respectively.

Compared to the participants who did not supplement with vitamin D, the following associations were found:

• The risk of Alzheimer’s disease was 17% lower in vitamin D users.
• The risk of vascular dementia was 14% lower in multivitamin users.

Some potential limitations of this study: (i) there was a lack of information on the dose of vitamin D taken among supplement users and (ii) supplement use was only assessed at baseline, so changes in supplementation practices could have occurred during the study that were not considered.