Glycaemic control and excess risk of ischaemic and haemorrhagic stroke in patients with type 1 diabetes: a cohort study of 33 453 patients.

ABSTRACT

OBJECTIVE: To estimate the excess risk of stroke in relation to glycaemic control in patients with type 1 diabetes. METHODS: In this prospective, matched cohort study, we identified patients with type 1 diabetes, aged ≥18 years, who were registered in the Swedish National Diabetes Register from 1998-2011 and five control subjects for each case from the general population, matched for age, sex and county of residence. The risks of all strokes, ischaemic stroke and haemorrhagic stroke were estimated using Cox hazard regression. RESULTS: Of 33 453 type 1 diabetes patients [mean age, 35.5 (SD 14.4) years; mean follow-up, 7.9 (SD 4.3) years; and mean diabetes duration, 20.2 years (SD 14.6)], 762 (2.3%) were diagnosed with stroke compared with 1122 (0.7%) of 159 924 control subjects [mean follow-up, 8.2 (SD 4.3) years]. The overall multiple-adjusted hazard ratios (HRs) for type 1 diabetes patients versus control subjects were 3.29 (95% CI 2.96-3.66) and 2.49 (95% CI 1.96-3.16) for ischaemic and haemorrhagic stroke, respectively. The risk of ischaemic and haemorrhagic stroke incrementally increased with increasing HbA1c; the risk of ischaemic stroke was significantly increased with HbA1c within target [≤6.9% (≤52 mmol mol-1 )] [multiple-adjusted HR 1.89 (95% CI 1.44-2.47)]. For HbA1c ≥9.7% (≥83 mmol mol-1 ), there was a markedly increased risk of both ischaemic and haemorrhagic stroke, with multiple-adjusted HRs of 7.94 (95% CI 6.29-10.03) and 8.17 (95% CI 5.00-13.35), respectively. CONCLUSIONS: Individuals with type 1 diabetes have an increased risk of ischaemic and haemorrhagic stroke, increasing markedly with poor glycaemic control.