Joint 30-year HbA1c and lipid trajectories and mortality in type 1 diabetes

Higher HbA1c has been associated with dyslipidemia in type 1 diabetes, but it is unknown whether there is heterogeneity in this association. Thus we assessed the longitudinal association between HbA1c and lipids over 30 years in a type 1 diabetes cohort and examined whether variation in such longitudinal patterns was associated with total and cause-specific mortality.

Data were from the Pittsburgh Epidemiology of Diabetes Complications study (n = 581 with ≥2 visits, 51% male, baseline mean age 27, diabetes duration 19 years). Longitudinal associations between HbA1c and lipids were assessed in mixed models. Group-based multi-trajectory models identified simultaneous trajectories of HbA1c and lipids.

Longitudinal HbA1c was associated with Non-HDLc (p < 0.0001) and triglycerides (p < 0.0001), but not HDLc (men: p = 0.72, women: p = 0.76). There was heterogeneity in the HbA1c-Non-HDLc association only, with five HbA1c-Non-HDLc groups identified. One group (20%) had an unexpected combination of high HbA1c but normal Non-HDLc and had only moderately increased cardiovascular mortality (rate ratio [RR] = 2.80, 95% CI 1.31-6.00) and kidney disease mortality (RR = 2.30, 95% CI 0.97-5.50) compared to Low HbA1c-Normal Non-HDLc.

These results suggest there is a subgroup with type 1 diabetes who, despite poor glycemic control, has a relatively good prognosis, perhaps related to good Non-HDLc.