Serum Homocysteine Levels and All-Cause and Cause-Specific Mortality in Korean Adult Men: A Cohort Study.

Background: Hyperhomocysteinemia can increase the risk of cardiovascular disease (CVD), cancer, and neurological disorders; however, hypohomocysteinemia is generally not considered harmful. This study aimed to evaluate the relationship between all levels of homocysteine, both low and high homocysteine levels, and the risk of all-cause and cause-specific mortality in adult Korean men. Methods: Adult Korean men (n = 221,356) were categorized into quintiles based on their homocysteine levels. The primary endpoints were all-cause, CVD, cancer, and dementia mortality. Hazard ratios were calculated using Cox proportional hazards models, and the dose–response relationship between homocysteine levels and mortality risk was further explored using restricted cubic spline models. Results: Compared with the reference category (Q2, 8.8–9.9 µmol/L), there was a significant increase in all-cause mortality associated with both low and high levels after multivariable adjustment (P_interaction = 0.002). Additionally, in spline regression, a U-shaped association between homocysteine levels and all-cause and CVD mortality was observed (inflection point = 9.1 µmol/L). This association was not observed in the vitamin supplementation subgroup. Conclusion: Among Korean adult men, both low and high homocysteine levels increased the risk of all-cause and CVD mortality, indicating a U-shaped relationship. However, this relationship was not statistically significant with vitamin supplementation, suggesting a potential protective role for vitamins. [ABSTRACT FROM AUTHOR]