Risk of first stroke in people with type 2 diabetes and its relation to glycaemic control: A nationwide observational study

Aims To compare stroke incidence in people with type 2 diabetes (T2D) with that in a matched control group, and to investigate whether glucose exposure in people with T2D can predict a first-time stroke event and mortality. Material and methods In a nationwide observational cohort study, individuals with T2D were linked in the Swedish National Diabetes Register and matched with five individual population-based control subjects. We calculated crude incidence rates and 95% confidence intervals (CIs), and used Cox regression and multivariable hazard ratios (HRs), to estimate the risk of stroke and mortality in relation to glycated haemoglobin (HbA1c) levels. Results A total of 406 271 people with T2D (age 64.1 ± 12.4 years, 45.7% women) and 2086 440 control subjects (age 64.0 ± 12.4 years, 45.7% women) were included. During a median follow-up of 7.3 years, 26 380 people with T2D (6.5%) versus 92 375 control subjects (4.4%) were diagnosed with a stroke. The incidence rate was 10.12 events per 1000 person-years versus 7.26 events per 1000 person-years (HR 1.54, 95% CI 1.52-1.56). In the T2D group after multivariable adjustments, the HRs for stroke stratified by HbA1c level were: 54-64 mmol/mol: 1.27 (95% CI 1.22-1.32); 65-75 mmol/mol: 1.68 (95% CI 1.60-1.76); 76-86 mmol/mol: 1.89 (95% CI, 1.75-2.05); and > 87 mmol/mol: 2.14 (95% CI 1.90-2.42), respectively, compared with the reference category of HbA1c ≤53 mmol/mol. There was a stepwise increased risk of death after stroke, for every 10-mmol/mol categorical increment of HbA1c (HR 1.71; 95% CI 1.47-2.00) for the highest HbA1c category. Conclusions An increased risk of stroke and death was associated with poor glycaemic control in people with T2D.