Association between serum folate and sleep duration in American adults: A cross-sectional analysis of the National Health and Nutrition Examination Survey 2005 to 2010

Folate is a vitamin that is exclusively derived from diet sources. Low folate levels are typically associated with cardiovascular disease, cognitive impairment, and cancer risk. However, few studies have examined the direct relationship between serum folate levels and sleep duration. Accordingly, we aimed to examine the relationship between serum folate levels and sleep duration. Using data from the National Health and Nutrition Examination Survey (NHANES), we examined the association between serum folate levels and sleep duration. We used laboratory data to obtain independent serum folate, and covariate data, including total cholesterol, high-density lipoprotein, blood glucose, and glycated hemoglobin; dependent variable sleep duration and covariate data including race, family income, marital status, education, and country of birth from questionnaire data; and other covariate data such as systolic blood pressure, diastolic blood pressure, waist circumference, and body mass index data from the measured data. Data was primarily analyzed using multiple regression analysis, stratified analysis with interactions, restricted cubic splines (RCS), and threshold effect analysis. A total of 14,072 participants over 19 years of age were enrolled, comprising 6923 (49.2%) males and 7149 (50.8%) females, with a median age of 48 years. The association between serum folate levels and sleep duration exhibited an inverted L-shaped curve (P = .033) in RCS. In the threshold analysis, for participants with serum folate of <32.208 nmol/L (β = 0.608, 95% CI: (0.275, 0.942), P < .001), the sleep duration was significantly increased by 0.608 minutes, with every 1 nmol/L in serum folate increased. At serum folate of ≥32.208 nmol/L, no significant association between serum folate and sleep duration was detected [β = 5.686, 95% CI: (-1.508, 12.88), P = .118]. Our findings revealed an inverted L-shaped relationship and saturation effects between serum folate levels and sleep duration in adults in the United States.