Selected red blood cell folate measures are associated with lower odds of insufficient sleep in United States adults.

Insufficient sleep has been linked to diet, but its relation to longer term folate status is unclear. We hypothesized that red blood cell (RBC) folate measures would be inversely associated with insufficient sleep. We analyzed 4224 adults aged ≥20 years from the National Health and Nutrition Examination Survey 2021-2023, including 836 with insufficient sleep. Insufficient sleep was defined as a weekday/weekend weighted mean sleep duration <7 h/night. Survey-weighted logistic regression accounted for the complex sampling design. The weighted prevalence of insufficient sleep was 19.2%. In the primary model, each 1-standard deviation higher concentration was associated with lower odds of insufficient sleep for conventional RBC folate (odds ratio, 0.865; 95% confidence interval, 0.777-0.963), total washed RBC folate (0.847; 0.746-0.962), washed RBC 5-methyltetrahydrofolate (0.853; 0.764-0.953), and MeFox (0.842; 0.761-0.930); THF and 5,10-methenylTHF were not associated with the outcome. Estimates changed little after adjustment for day 1 energy intake, dietary folate equivalents, and supplement use. Restricted cubic spline models showed no evidence of nonlinearity. Model-standardized prevalence was 20.3% in the lowest and 15.2% in the highest quartile of total washed RBC folate. Results were similar in sensitivity analyses, including additional adjustment for serum cotinine. These cross-sectional findings are consistent with inverse associations for selected RBC folate measures but do not establish temporal direction or a benefit of folate supplementation.