Serum folate, vitamin B12 and cognitive impairment in Chilean older adults

Objective: To analyse the relationship between serum folate (SF), vitamin B-12 and impaired cognitive function in the Chilean elderly. Design: We analysed the relationships between impaired cognitive function and age, SF (mu g/l) and vitamin B-12 (pg/ml) with Student's t test, as well as between impaired cognitive function and gender, educational level, residence area, diabetes and hypertension with the chi(2) test. Multiple logistic regressions with interactions were estimated to assess the impact of SF on impaired cognitive function according to these methods. Setting: Chile. Subjects: Older adults (>65 years, n 1051), drawn from representative households of a national prevalence study, assessed using the Modified Mini Mental Status Examination (MMMSE). Individuals with altered MMMSE scores (<= 13 points) were sequentially assessed using the Pfeffer Functional Activities Questionnaire (PFAQ). Results: Multivariate models using the MMMSE demonstrated an increased risk of impaired cognitive function for seniors who had hypertension, diabetes and higher vitamin B-12 levels. SF and its square (SF2) were statistically significant, indicating that this predictor of impaired cognitive function displays a U-shaped distribution. The interaction between SF and vitamin B-12 was not statistically significant. Models using the MMMSE plus PFAQ suggested that urban residence decreased the risk of impaired cognitive function, whereas male gender, older age, vitamin B-12 levels and hypertension increased this risk. The variables SF and SF2 and the SF x vitamin B-12 interaction were statistically significant (P<0.05). The risk of impaired cognitive function depended on different combinations of SF and vitamin B-12 levels. When SF was low, a one-unit increase in SF (1 mu g/l) diminished the risk. When SF was elevated, a further increase in SF raised the risk, especially at low vitamin B-12 levels. Conclusions: The relationship between folate, vitamin B-12 and impaired cognitive function warrants further study.