The relationship between serum HDL-cholesterol, cardiovascular disease and mortality in community-based people with type 2 diabetes: the Fremantle Diabetes Study phase 2

BACKGROUND: Older general population-based studies found an inverse association between serum HDL-cholesterol and both cardiovascular disease (CVD) events and mortality, but more recent data have suggested a U-shaped relationship. Whether this applies to type 2 diabetes is uncertain. The aim of this study was to assess the prognostic significance of serum HDL-cholesterol concentrations in representative, community-based participants from the Fremantle Diabetes Study Phase II (FDS2). METHODS: We followed 1,479 FDS2 participants with confirmed type 2 diabetes (713 females, mean age 65.6 years; 763 males, mean age 65.9 years) from entry (2008-2011) to death/end-2021. Major adverse cardiovascular events (non-fatal myocardial infarction (MI), non-fatal stroke, cardiovascular death; 3-point MACE), and all-cause mortality were ascertained from prospectively collected data and validated administrative databases. Independent associates of 3-point MACE by sex, excluding participants with prior MI/stroke, were assessed using Cox and competing risk models with sex-specific quintiles of HDL-cholesterol added to the most parsimonious models. Predictors of all-cause mortality were identified using Cox proportional hazards modelling. RESULTS: In females, with baseline serum HDL-cholesterol quintile 2 (1.04-1.22 mmol/L) as reference, both quintiles 1 (< 1.04 mmol/L) and 5 (> 1.59 mmol/L) were significant independent predictors of 3-point MACE (P < 0.027) and all-cause death (P < 0.019) after adjustment for a full range of demographic, clinical and laboratory variables. In males, serum HDL-cholesterol quintile did not add to the most parsimonious model for 3-point MACE, but quintile 1 (< 0.90 mmol/L) was a significant predictor of death (P = 0.026 versus quintile 4 (1.15-1.31 mmol/L) as reference) after adjustment. Competing risk analyses for 3-point MACE showed similar results to the Cox models for both sexes. CONCLUSION: There was a significant U-shaped relationship between serum HDL-cholesterol and both 3-point MACE and all-cause death in females with type 2 diabetes after adjustment for confounders. There was no such relationship for 3-point MACE in males but a low HDL-cholesterol was associated with all-cause mortality. These data have sex-specific implications for assessment of serum lipid profiles in the clinical management of type 2 diabetes.