Table 2.

Summary characteristics of studies included in the analysis of vitamin D deficiency and risk of dementia

References	Year	Country	Study type	Participants	Average age (years)	OR	95 % CI	25(OH)D (nmol/L)	Adjustment
Littlejohns [9]	2014	UK	Prospective cohort	1547	73.6 ± 4.5	2.25	1.23–4.13	<25	Age, season of vitamin D collection, education, sex, BMI, smoking, alcohol consumption, and depressive symptoms
Littlejohns [9]	2014	UK	Prospective cohort	1547	73.6 ± 4.5	1.53	1.06–2.21	25–50	Age, season of vitamin D collection, education, sex, BMI, smoking, alcohol consumption, and depressive symptoms
Buell [12]	2010	USA	Cross-sectional	318	73.5 ± 8.1	2.21	1.13–4.32	≤50	Age, race, sex, body mass index, and education, kidney function, multivitamin use, season, diabetes, hypertension, plasma homocysteine, and ApoE allele status
Annweiler [13]	2011	France	Cross-sectional	288	86.0 ± 0.4	2.57	1.05–6.27	<25	Fully adjusted but without detailed information
Nagel [14]	2015	Germany	Cross-sectional	1373	75.6 ± 6.57	1.08	0.60–1.92	≤50	Adjusted for age, sex, school education, smoking status, season, alcohol consumption, BMI, and history of depression