Plasma folate levels in relation to cognitive impairment: a community-based cohort of older adults in China.

Purpose: Lower plasma level of folate has been associated with an increased risk of age-related cognitive impairment. However, studies that examined this relation have yielded mixed results. We aimed to examine the prospective association of plasma folate level with risk of cognitive impairment in a community-based prospective cohort of older adults in China.

Methods: This study included 615 participants (mean age: 76.3 years) without baseline cognitive impairment from the Rugao Longevity and Ageing Study (RuLAS). We used logistic regression to examine the prospective association between baseline plasma folate and risk of cognitive impairment in the next two years. Fasting blood samples were collected and assayed for plasma folate level at baseline. Cognitive impairment was defined as Hasegawa Dementia Scale (HDS) score ≤ 21.5 points.

Results: During two years' follow-up, 20.7% of the participants developed cognitive impairment. After controlled for age, gender, and plasma homocysteine, a higher level of plasma folate was associated with lower odds of cognitive impairment. The corresponding odds ratio (OR) with 95% confidence interval was 0.41 (0.19-0.89) comparing participants at extreme quintiles of plasma folate (median level 17.2 vs. 6.3 nmol/L). The associations were similar after further adjustment for major demographic and lifestyle factors (OR = 0.42, 0.18-0.98). Moreover, the inverse association was particularly stronger among males (OR = 0.12, 0.03-0.52) but was non-significant among females.

Conclusion: Our findings support a potential beneficial role of higher plasma folate levels in cognitive function in older Chinese adults, particularly among males. Future studies with larger sample size and longer follow-up are warranted to confirm these findings and to identify the optimal plasma folate level for cognitive function.