Risk differences and underlying factors of cardiovascular events and mortality in patients with type 2 diabetes versus type 1 diabetes: a longitudinal cohort study of Swedish nationwide register data.

BACKGROUND

Despite improvements in diabetes care and risk factor management, the residual risk for cardiovascular disease and premature death remains substantially elevated in people both with type 1 and type 2 diabetes. This study aimed to compare the risk of cardiovascular disease and mortality, as well as the contibution of underlying risk factors, between type 1 and type 2 diabetes.

METHODS

In this nationwide, population-based cohort study, all living people with diabetes aged 18-84 years reported in the Swedish National Diabetes Register (NDR) by Jan 1, 2016, were followed-up over a period of 5 years until Dec 31, 2020. Data from the National Patient Register, including all inpatient and outpatient hospital visits, were used to compare the incidence of major cardiovascular disease events (myocardial infarction, heart failure onset or exacerbation, stroke, and cardiovascular death) and all-cause death, also in different age groups. Baseline data were collected from NDR and other national registers. Cox regression analyses, adjusted for age and sex, as well as for multiple cardiovascular risk factors were performed. In addition, the type 1 diabetes and type 2 diabetes cohorts were compared with matched control groups with no diabetes.

FINDINGS

404 026 adults with type 1 diabetes (38 351 [9·5%]) or type 2 diabetes (365 675 [90·5%]) were included. Individuals with type 2 diabetes had a higher risk than individuals with type 1 diabetes for the composite endpoint of any cardiovascular disease event (HR 1·23, 95% CI 1·07-1·41) at ages younger than 50 years but a lower risk at ages older than 60 years (0·87, 0·82-0·92). A similar pattern was observed for myocardial infarction (0·67, 0·61-0·73) and all-cause mortality (0·89, 0·84-0·95) in ages older than 60 years. However, the risk for stroke was overall lower in type 2 diabetes (0·91, 0·84-0·98, all ages combined), whereas for heart failure it was higher at ages younger than 50 years (1·60, 1·15-2·21). Among people with previous cardiovascular disease, those with type 2 diabetes overall had a lower risk versus type 1 diabetes for all cardiovascular disease (0·76, 0·70-0·81), for myocardial infarction (0·62, 0·56-0·70), cardiovascular mortality (0·68, 0·61-0·75) and all-cause mortality (0·71, 0·66-0·77). In analyses adjusting for multiple cardiovascular risk factors, the whole cohort with type 2 diabetes had a greater risk for incident cardiovascular disease and mortality compared with type 1 diabetes. However, when diabetes duration was excluded from the model, type 1 diabetes was associated with higher risk. Compared with matched controls, both diabetes types were associated with greater risk for the studied outcomes, but this was most marked for type 1 diabetes.

INTERPRETATION

In this study, type 1 diabetes was associated with higher overall risk for cardiovascular disease events and all-cause mortality than type 2 diabetes, particularly at ages older than 60 years for the studied outcomes. Longer diabetes duration seems to be a main contributing factor for higher risk found in people with type 1 diabetes versus those with type 2 diabetes in this age group. Enhanced management of all modifiable risk factors could help prevent cardiovascular disease and premature death in both type 1 and type 2 diabetes.

FUNDING

Swedish Heart and Lung Foundation, Swedish Research Council, and ALF grants at the Uppsala University Hospital.