Type 1 Diabetes Diagnosed in Adulthood Heightens Cardiovascular Risk

Type 1 diabetes (T1D) development in adulthood was linked to an elevated risk of cardiovascular disease (CVD) and death, with diagnosis at age ≥40 years not related to an improved long-term prognosis compared with those diagnosed earlier.1

The registry-based study, using nationwide Swedish data from 2001 to 2022, identified more than 10,000 people diagnosed with T1D in adulthood between 2001 and 2020 in the National Diabetes Register (NDR), and compared them with approximately 509,000 matched individuals in the control cohort.

“The main reasons for the poor prognosis are smoking, overweight/obesity, and poor glucose control. We found that they were less likely to use assistive devices, such as insulin pumps,” said Yuxia Wei, a postdoctoral fellow at the institute of environmental medicine at Karolinska Institute and first author of the study.

Investigations into the prognosis of T1D are limited, and evidence is often extrapolated from research in type 2 diabetes (T2D) or the general population. For those with adult-onset T1D, available data typically stems from diagnosis during childhood or adolescence, while prognostic factors are less understood for T1D diagnosed in later life.

For this study, Wei and colleagues measured the prognosis of adult-onset T1D, notably those diagnosed at age ≥40 years, to determine the risk factors leading to poor prognosis. All-cause mortality, cause-specific mortality, and incident CVD were all compared with adult-onset T1D, T2D, and population controls using the nationwide Swedish data.

The population included 10,184 people diagnosed with adult-onset T1D, 375,523 diagnosed with T2D, and 509,172 population controls from the Total Population Register. Participants were followed until the date of the outcome occurrence, death, emigration, diabetes diagnosis (for controls), or end of follow-up: June 2022 for all-cause mortality, June 2021 for cause-specific mortality, and December 2021 for major adverse cardiovascular events (MACE).

For the analysis, hazard ratios (HRs) were estimated for all-cause mortality and MACE for each factor using the first measurement since cohort entry: smoking, physical activity, body mass index (BMI), hemoglobin A1c (HbA1c), blood pressure, triglycerides, estimated glomerular filtration rate (eGFR), and albuminuria.

Approximately 40% of the cohort (n = 4113) were diagnosed with T1D at ages 18 to 29, compared with approximately 38% (n = 3899) at age ≥40. Those diagnosed at ≥40 years were more likely to be female, smokers, with higher blood pressure, triglycerides, and HbA1c, as well as worse kidney function and more severe insulin resistance.

Individuals with T1D experienced a higher incidence of all-cause mortality (HR, 1.71; 95% CI, 1.60–1.84), MACE (HR, 1.30; 95% CI, 1.17–1.45), and mortality from CVD or non-CVD-related diseases, cancer, or infection, compared with controls. Mortality risk from diabetic coma or ketoacidosis was nearly sevenfold higher in T1D than T2D (HR, 7.04; 95% CI, 4.54–10.9), across all age and sex cohorts.

Those with T1D diagnosed at age ≥40 years exhibited a slight superiority in rates of all-cause mortality, non-cardiovascular death, cancer death, and death from infection versus T2D, particularly in men. Smoking (10.7%) and HbA1c ≥53 mmol/mol (10.4%) accounted for most deaths, while overweight or obesity (19.8%), smoking (8.4%), and above-target HbA1c (8.8%) accounted for most MACE events in T1D.

Wei and colleagues identified a dose-response relationship between the number of risk factors and an excess risk of all-cause mortality, cardiovascular death, non-cardiovascular death, and MACE in people with T1D, compared with controls. The team found results similar for T1D diagnosed at age ≥40, despite this population reporting lower insulin pump usage and higher HbA1c.

“We show that the prognosis can be significantly improved by preventing smoking and obesity and improving glucose control, not least in people diagnosed at older ages,” said Sofia Carlsson, a senior lecturer and associate professor at Karolinska Institutet and senior author of the study. “We hope to shed light on these issues in the coming years.”

References

1. Wei Y, Andersson T, Tuomi T, Nystrom T, Carlsson S. Adult-onset type 1 diabetes: predictors of major cardiovascular events and mortality . European Heart Journal. May 14, 2025. Accessed May 14, 2025. https://academic.oup.com/eurheartj/advance-article/doi/10.1093/eurheartj/ehaf304/8127980.

2. Karolinskainst. Adult-onset type 1 diabetes increases risk of cardiovascular disease and death. EurekAlert! May 14, 2025. Accessed May 14, 2025. https://www.eurekalert.org/news-releases/1083515.

3. de Ferranti SD, de Boer IH, Fonseca V, et al. Type 1 diabetes mellitus and cardiovascular disease: a scientific statement from the American Heart Association and American Diabetes Association. Circulation. 2014;130(13):1110-1130. doi:10.1161/CIR.0000000000000034