Low Vitamin D and Its Association with Cognitive Impairment and Dementia

Table 3

Summary of findings of vitamin D supplementation and its effect on cognition.

Author, year	Study design	Sample size	Study period	Population characteristics	Intervention	Outcome measures	Findings
Przybelski et al., 2008 [39]	Prospective; Pre-post interventional study	63	4 weeks	USA-nursing home residents; Intervention groups N = 25; Mean age = 86.2 females 68%; Deficiency defined as 25(OH)D ˂25 ng/mL; Comparison group N = 38; Mean age = 87.4, female 78.9%; Serum 25(OH)D ˂25 ng/mL	Unblinded study Intervention group 50,000 IU of Vit D2, 3 times per week for duration of 4 weeks; Comparison group; No placebo; No supplementation	Cognitive test; Clock drawing test; Semantic fluency test	No significant difference in cognitive outcome measures, although significant change () in serum 25(OH)D levels from 17.3 to 63.8 ng/mL
Stein, et al., 2011 [36]	Randomized controlled trial	32	6 weeks	Australia- community dwellers with mild-to-moderate dementia; High dose group N = 16; Low dose group N = 16; Mean age 79; Females = 50%	First 1,000 IU Vit D2 daily for 8 weeks; Then, 6,000 IU Vit D2 daily for 8; Intranasal insulin (60 IU/4 times/day) and 50% randomized to placebo; Comparison group 1,000 IU Vit D2 daily for 16 weeks; Finally, 50% randomized to Intranasal insulin (60 IU4 times/day) and 50% randomized to placebo for 2 days	Alzheimer assessment scale-cognitive subscale (ADAS memory scale-revised logical memory (WSM- RLM)	Minitab release 13.1 used to calculate CI. Significant median increase in serum 25(OH)D concentrations in the high dose group (187 nM); No significant differences () on any of the outcome measures) between groups. ADAS-Cog (95% CI-5 to 3); WSM-RLM (95% CI −1 to 3)
Annweiler, et al., 2012 [40]	Prospective; Pre-post interventiona l study	44	16 months	France-outpatient from memory clinic; Intervention group N = 20; Mean age 81.9 females = 55%; Comparison group N = 24; Mean age 75.; Females = 54.2%	Unblinded; Unrandomized intervention group = 800 IU/day or 1,000,000 IU of Vit D3/month comparison group = no placebo	MMSE; Frontal assessment battery; Cognitive assessment battery	Over the 3-year period, MMSE scores increased in both groups (), although change over time was not significantly different between the groups
Owusu et al., 2018 [37]	Randomized controlled trial	390	3 years	USA-healthy African-American postmenopausal women; Intervention group N = 130; Mean age 67.8; Control group N = 130	Double-blind randomized placebo-controlled trial; Intervention Vit D3 (2,400 IU–3,600 IU or 4,800 IU/day) which maintained 25(OH)D level of 30 ng/mL; Control group Placebo follow-up of 3 years	MMSE; Every 6 months ˂ 27; Considered as mild MCI	No difference in cognition over time between older African-American women with serum concentrations of 25(OH)D of 30 ng/mL and greater than those taking placebo
Petterson Trial, 2017 [38]	Randomized controlled trial	82	18 weeks	Canada-healthy adults; High dose group N = 42; Mean age = 56.7; Low dose group N = 40; Mean age = 52.6; Females = 65%	Randomized and blinded to high dose; High dose group Vit D3 4,000 IU/day; Low; Dose group Vit D3 400 IU/day	Pattern recognition memory task; Paired associate learning task	Visual memory benefit with high dose () in those who are insufficient (<75 nmol/L); No change in verbal memory