Serum Folate in Relation to Lipid Abnormalities in Community-Dwelling Adults: A Population-Based Cross-Sectional Study in Zhejiang Province, China

Objectives: This study aimed to examine the cross-sectional associations between serum folate concentrations and four lipid abnormality subtypes among community-dwelling adults in Zhejiang Province, China. Methods: This population-based cross-sectional study included 3254 adults from Zhejiang Province, China. Serum folate concentrations were analyzed both as quartiles and per 1-standard deviation (SD) increments. Multivariable logistic regression models were used to evaluate the associations of serum folate with hypercholesterolemia, hypertriglyceridemia, high low-density lipoprotein cholesterol (LDL-C), and low high-density lipoprotein cholesterol (HDL-C). Restricted cubic spline (RCS) regression models were further applied to assess dose–response patterns. Additional RCS analyses using continuous lipid parameters were also performed. False discovery rate (FDR) correction, exploratory subgroup analyses, and sensitivity analyses were additionally conducted. Results: The prevalences of hypercholesterolemia, hypertriglyceridemia, high LDL-C, and low HDL-C were 7.87%, 17.12%, 4.30%, and 4.46%, respectively. In the fully adjusted model, each 1-SD increment in serum folate was associated with lower odds of hypertriglyceridemia (OR = 0.82, 95% CI: 0.73–0.92) and low HDL-C (OR = 0.63, 95% CI: 0.49–0.81). Compared with the lowest quartile, participants in the highest serum folate quartile had lower odds of hypertriglyceridemia (OR = 0.62, 95% CI: 0.46–0.82) and low HDL-C (OR = 0.38, 95% CI: 0.22–0.64), with significant trends across quartiles (both p for trend < 0.001). No significant associations were observed for hypercholesterolemia or high LDL-C. These findings remained significant after FDR correction. RCS analyses suggested an overall inverse association between serum folate and hypertriglyceridemia, with no evidence of nonlinearity (p for overall = 0.001; p for nonlinearity = 0.212), whereas the association with low HDL-C showed evidence of nonlinearity (p for overall < 0.001; p for nonlinearity = 0.009). Additional RCS analyses using continuous lipid parameters showed broadly consistent findings for TG and HDL-C. Exploratory subgroup and sensitivity analyses showed generally similar results. Conclusions: Higher serum folate concentrations were cross-sectionally associated with lower odds of hypertriglyceridemia and low HDL-C among community-dwelling adults in Zhejiang Province, China, whereas no significant associations were observed for hypercholesterolemia or high LDL-C. Further prospective cohort studies are warranted to verify these cross-sectional findings and to explore underlying mechanisms.