Long-term glycemic exposure remains central to complication risk in people with type 2 diabetes mellitus (T2DM). A retrospective analysis published in Diabetes, Obesity and Metabolism evaluated the relationship between hemoglobin A1c (HbA1c) levels and vascular outcomes and cardiovascular death.

Data were derived from the Swedish National Diabetes Registry and linked national registers between January 1, 1998, and December 31, 2019. The cohort comprised patients with T2DM; 57.2% were male, and the median age was 60 years. Incidence rates (IRs) per 100 patient-years were reported for the overall population. The IR of any microvascular complication remained relatively stable over time (8.75 in 2005; 10.95 in 2014; 8.71 in 2019), whereas cardiovascular death increased from 0.12 in 2005 to 0.46 in 2018.

Hazard ratios (HRs) for outcomes were compared across HbA1c ranges, using 6.0% to <7.0% as reference. The incidence of any macrovascular complication increased at HbA1c 7.0% to <8.0% (HR 1.08; 95% confidence interval [CI] 1.05-1.11) and 8.0% to <9.0% (HR 1.16; 95% CI 1.12-1.20). Early glycemic control was also evaluated 18 months after diagnosis. Compared with no early tight control (HbA1c >6.5%), early tight control (HbA1c ≤6.5%) was associated with lower rates of any microvascular complication (HR 0.84; 95% CI 0.80-0.89), any macrovascular complication (HR 0.86; 95% CI 0.79-0.93), and cardiovascular death (HR 0.60; 95% CI 0.46-0.79). Similar results were observed when compared with early adverse control (HbA1c >7%).

These findings indicate that higher HbA1c levels were associated with increased long-term vascular complications and cardiovascular death, while early tight HbA1c control corresponded to lower event rates in patients with T2DM.