Background and Objective: The combined effect of insulin resistance (IR) and total plasma homocysteine (tHcy) levels on the risk of mortality in nondiabetic populations has rarely been studied. We aimed to examine the association of tHcy levels and IR with the risk of mortality in nondiabetic populations. Methods: This observational cohort study was based on data from the Third National Health and Nutrition Examination Survey (NHANES III) database (1999-2002). A generalized additive model based on the Cox proportional hazards models was applied to estimate the relationship of tHcy levels with all-cause and cardiovascular disease (CVD) mortality. Smooth curve fitting was used to analyze their dose-dependent relationship. Results: During 5.7 years of follow-up, a total of 146 (5.8%) deaths occurred, including 65 deaths from CVD among 2053 individuals aged 40-80 years. In the multivariable adjusted model, every 1-μM increment of the tHcy level was associated with a 15% increase in risk of all-cause mortality and 20% increase in risk of CVD mortality among participants with IR (adjusted HR [95% CI]: 1.15 [1.06-1.24] and 1.20 [1.04-1.38]). However, among participants without IR, an increase of 1 μM in the tHcy level was associated with a 6% increase in risk of all-cause mortality and 3% increase in risk of CVD mortality (adjusted HR [95% CI]: 1.06 [1.00-1.13] and 1.03 [0.92-1.16]). Conclusions: Homocysteine levels were associated with higher risk of all-cause and CVD mortality among individuals with IR than among those without IR in a nondiabetic population aged 40-80 years.
Keywords: cardiovascular disease; homocysteine; insulin resistance; mortality.