Association of serum total folate and serum vitamin D concentrations with W-shape in depressed older adults with cognitive dysfunction: A cross-sectional observational study.

BACKGROUND

Depression and cognitive dysfunction are prevalent in the elderly population and have a serious impact on patients' quality of life and social functioning. Nutritional factors play a key role in the prevention and management of these disorders, particularly folate and vitamin D. The aim of this study was to elucidate the association between serum total folate and serum vitamin D concentrations and depressive symptoms and cognitive dysfunction in older adults.

METHODS

Using data from the National Health and Nutrition Examination Survey (NHANES) 2011-2014, 2042 participants aged 60 years and older were analyzed. Depressive symptoms were assessed by the Patient Health Questionnaire (PHQ-9) and cognitive function was assessed by the Consortium to Establish a Registry for Alzheimer's Disease (CERAD) Animal Fluency test and the Digit Symbol Substitution Test (DSST). Associations between serum total folate and vitamin D concentrations and depression with cognitive dysfunction were analyzed using multivariate logistic regression models, incorporating stratification and sensitivity analyses.

RESULTS

For every 1 nmol/L increase in serum vitamin D concentration, there was a 1 % reduction in the risk of depression in older adults (OR = 0.99 95 % CI 0.98-0.99). Serum total folate showed a significant W-shaped association with depression with cognitive dysfunction: when serum total folate concentration was below 33.00 nmol/L, the risk of depression was reduced by 7.6 % for every 1 nmol/L increase in its concentration (OR = 0.924 95 % CI 0.89-0.959); this association was not significant when the concentration was above 33.00 nmol/L (OR = 1.006 95 % CI 0.998-1.013).

CONCLUSIONS

Adequate levels of vitamin D and folate may help prevent and manage depression and cognitive dysfunction in older adults. The W-shaped association between serum total folate and these conditions suggests that folic acid supplementation could be effective within a specific range, warranting further exploration and validation through clinical studies.