Type 1 diabetes and risk factors associated with COVID-19 mortality

Previous studies have identified an increased risk of death from COVID-19 infection in people with diabetes. These two studies, conducted by NHS England, have shed more light on this topic by assessing the increased risk according to diabetes type, and by evaluating the associations between various risk factors in people with type 1 and type 2 diabetes.

The first study¹ evaluated all in-hospital deaths with COVID-19 that occurred in England between 1 March and 11 May. Over that period, 23 698 people with COVID-19 died in hospital, and a third of these deaths occurred in those with diabetes. Overall, 1.5% of the deaths occurred in those with type 1 diabetes, despite people with this condition making up only 0.4% of the general population. The relative risk of death was higher in those with type 1 than type 2 diabetes.

After adjustment for age, sex, socioeconomic deprivation, ethnicity and region, the odds ratio (OR) for death in people with type 1 diabetes was 3.51 (95% confidence interval [CI], 3.16–3.90) compared with the general population. After further adjustment for the presence of cardiovascular comorbidities, the association was weakened slightly but the risk remained significantly greater (OR, 2.86; 95% CI, 2.58–3.18).

Although the relative risk of death in people aged under 70 years was much higher in those with type 1 diabetes than in the general population (OR, 6.39; 95% CI, 5.40–7.56), the absolute risk in the lower age groups was small.

This study was limited by a lack of data on other risk factors for COVID-related death, including BMI, hypertension and glycaemic control. However, the second study² was able to evaluate the effects of these factors in people with type 1 and type 2 diabetes, by linking National Diabetes Audit data with Office for National Statistics mortality numbers.

Compared with an HbA_1c of 48–53 mmol/mol (6.5–7.0%), the risk of COVID-related death increased with rising HbA_1c; however, in people with type 1 diabetes the difference was significant only in those with an HbA_1c ≥86 mmol/mol (10.0%; hazard ratio [HR], 2.23; 95% CI, 1.50–3.30).

BMI showed a U-shaped association with mortality, with those in the overweight category faring best. People of Asian and black ethnicity had a 57% and 77% greater risk of death, respectively. Reduced kidney function had a linear association with mortality, with an HR of 2.46 in those with an eGFR ≤30 mL/min/1.73 m², rising to 8.35 in those with an eGFR under 15. Hypertension, antihypertensive treatment and cholesterol levels were not significantly associated with mortality risk.

The authors point out that many of the risk factors identified here are not modifiable; however, obesity and glycaemic control can be improved through lifestyle and medical interventions, and these findings demonstrate a great need to support people with diabetes to achieve and sustain effective self-management of their condition.

1. Barron E, Bakhai C, Kar P et al (2020) Associations of type 1 and type 2 diabetes with COVID-19-related mortality in England: a whole-population study. Lancet Diabetes Endocrinol 8: 813–22. Click here to access

2. Holman N, Knighton P, Kar P et al (2020) Risk factors for COVID-19-related mortality in people with type 1 and type 2 diabetes in England: a population-based cohort study. Lancet Diabetes Endocrinol 8: 823–33. Click here to access

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