The Non-High-Density Lipoprotein Cholesterol to High-Density Lipoprotein Cholesterol Ratio (NHHR) as a Predictor of All-Cause and Cardiovascular Mortality in US Adults with Diabetes or Prediabetes: NHANES 1998-2018

Background The non-high-density lipoprotein cholesterol to high-density lipoprotein cholesterol ratio (NHHR) serves as a novel composite lipid indicator for atherosclerosis. However, the association between the NHHR and mortality in patients with diabetes or prediabetes remains unclear. Therefore, the present study aimed to examine the correlation between the NHHR and both all-cause and cardiovascular mortality in U.S. adults with diabetes or prediabetes. Methods This study enrolled a total of 12,578 adult participants with diabetes or prediabetes from the National Health and Nutrition Examination Survey in the US (1998–2018). The mortality outcomes were ascertained through linkage with the National Death Index (NDI) records available until December 31, 2019. We employed weighted multivariate Cox proportional hazards models to estimate the associations between the NHHR and both all-cause and cardiovascular mortality. Restricted cubic splines (RCS) were employed to evaluate nonlinear correlations. Moreover, a segmented Cox proportional hazards model was utilized to assess the associations between the NHHR and mortality on both sides of the inflection point. Results During a median follow-up period of 8.08 years, 2403 participants experienced all-cause mortality, with 662 of them specifically succumbing to cardiovascular mortality. The RCS revealed a U-shaped association between the NHHR and all-cause mortality in participants with diabetes or prediabetes, while an L-shaped association was observed for cardiovascular mortality. The analysis of threshold effects revealed that the inflection points for the NHHR and all-cause and cardiovascular mortality were 2.71 and 2.85, respectively. Specifically, when the baseline NHHR was below the inflection points, a negative correlation was observed between the NHHR and both all-cause mortality (HR: 0.80, 95% CI: 0.73–0.88) and cardiovascular mortality (HR: 0.78, 95% CI: 0.67–0.92). Conversely, when the baseline NHHR exceeded the inflection points, a positive correlation was observed between the NHHR and all-cause mortality (HR: 1.07, 95% CI: 1.03–1.11). Conclusions In U.S. adults with diabetes or prediabetes, a U-shaped correlation was observed between the NHHR and all-cause mortality, whereas an L-shaped correlation was identified with cardiovascular mortality. The inflection points for all-cause and cardiovascular mortality were 2.71 and 2.85, respectively.