A matched cohort study evaluating the risks of infections in people with type 1 diabetes and their associations with glycated haemoglobin

Aims: People with type 1 diabetes (T1D) have raised infection rates compared to those without, but how these risks vary by age, sex and ethnicity, or by glycated haemoglobin (HbA1c), remain uncertain.

Methods: 33,829 patients with T1D in Clinical Practice Research Datalink on 01/01/2015 were age-sex-ethnicity matched to two non-diabetes patients. Infections were collated from primary care and linked hospitalisation records during 2015-2019, and incidence rate ratios (IRRs) were estimated versus non-diabetes. For 26,096 people with T1D, with ≥3 HbA1c measurements in 2012-2014, mean and coefficient of variation were estimated, and compared across percentiles.

Results: People with T1D had increased risk for infections presenting in primary care (IRR = 1.81, 95%CI 1.77-1.85) and hospitalisations (IRR = 3.37, 3.21-3.53) compared to non-diabetes, slightly attenuated after further adjustment. Younger ages and non-White ethnicities had greater relative risks, potentially explained by higher HbA1c mean and variability amongst people with T1D within these sub-groups. Both mean HbA1c and greater variability were strongly associated with infection risks, but the greatest associations were at the highest mean levels (hospitalisations IRR = 4.09, 3.64-4.59) for >97 versus ≤53 mmol/mol.

Conclusions: Infections are a significant health burden in T1D. Improved glycaemic control may reduce infection risks, while prompter infection treatments may reduce hospital admissions.