Non-Linear Relationship Between Serum Vitamin A and Cardiovascular Diseases: A Cross-Sectional Study Based on NHANES 1999-2002

Objective To investigate the association between serum vitamin A levels and cerebrovascular disease (CVD), given the unclear relationship between vitamin A and cardiovascular health despite CVD being a leading global cause of death. Methods This cross-sectional study analyzed data from 3,552 participants in the National Health and Nutrition Examination Survey (NHANES) 1999–2002. Serum vitamin A levels were measured as the exposure variable, with cerebrovascular disease as the outcome. Multiple confounders including demographic, lifestyle, and clinical factors were adjusted in the analysis. Results A nonlinear relationship was identified with a threshold at 1.15 µmol/L. Below this threshold, serum vitamin A showed a protective effect against cerebrovascular disease (OR = 0.083, 95% CI: 0.011–0.662, P = 0.0187), while above it, a trend toward increased risk was observed but not statistically significant (OR = 1.226, 95% CI: 0.973–1.546, P = 0.0842). Conclusion Serum vitamin A levels demonstrate a threshold effect on cerebrovascular disease risk, suggesting different roles at varying concentrations. Further longitudinal studies are needed to confirm these findings and establish optimal vitamin A ranges for cardiovascular health.