About the Discussion

@NEJM Ask the Authors & Experts: Mortality and Cardiovascular Disease in Type 1 and Type 2 Diabetes

BACKGROUND

Long-term trends in excess risk of mortality and cardiovascular outcomes have not been extensively studied in type 1 diabetes and type 2 diabetes.

METHODS

We included patients registered in the Swedish National Diabetes Register from 1998–2014. Trends in mortality and cardiovascular events were estimated with Cox regression and standardized incidence rates. For each patient, age-, sex- and county-matched controls were randomly selected from the general population.

RESULTS

Among patients with type 1 diabetes, incidence rates (per 10,000 person-years) for sentinel outcomes changed as follows: mortality -31.4 (95% confidence interval [CI], -56.1 to -6.7), fatal cardiovascular disease -26.0 (95% CI, -42.6 to -9.4), fatal coronary heart disease -21.7 (95% CI, -37.1 to -6.4) and hospitalization for cardiovascular disease -45.7 (95% CI, -71.4 to -20.1). Absolute changes for patients with type 2 diabetes were as follows: mortality -69.6 (95% CI, -95.9 to -43.2), fatal cardiovascular disease -110.0 (95% CI, -128.9 to -91.1), fatal coronary heart disease -91.9 (95% CI, -108.9 to -75.0) and hospitalization for cardiovascular disease -203.6 (95% CI, -230.9 to -176.3). Compared to controls cardiovascular Cardiovascular outcomes declined by roughly 40% and 20% in type 1 diabetes and type 2 diabetes, respectively. Reductions in fatal outcomes were similar for patients with type 1 diabetes and controls, whereas, individuals with type 2 diabetes had smaller reductions in fatal outcomes compared with controls.

CONCLUSION

Mortality and cardiovascular disease have declined substantially for individuals with diabetes, although fatal outcomes have improved less in patients with type 2 diabetes.

Diabetes mellitus is a complex and heterogeneous group of chronic metabolic diseases characterized by hyperglycemia. Type 1 diabetes occurs predominantly in young people and is generally thought to be precipitated by an immune-associated destruction of insulin-producing pancreatic β-cells, leading to insulin deficiency and an immediate need for exogenous insulin replacement.1 Type 2 diabetes is a progressive metabolic disease characterized by insulin resistance and eventual pancreatic β-cell failure.2 The prevalence of type 2 diabetes has been increasing dramatically over the past few decades,3 with projections of an even greater growth over coming decades.4

Landmark studies such as the Diabetes Control and Complications Trial (DCCT), United Kingdom Prospective Diabetes Study (UKPDS), Collaborative Atorvastatin Diabetes Study (CARDS), and several others have demonstrated the importance of intensive glucose-lowering therapy, statin use, blood pressure control and multifactorial intervention in reducing the risk of cardiovascular outcomes in diabetes.5-10,11-14,15-18 These trial results and the clinical application of their findings, along with lifestyle interventions (including smoking cessation), have likely improved outcomes in patients with diabetes over the past two decades.

We set out to evaluate the influence of this evolution of clinical care for patients with diabetes on key clinical outcomes of patients with diabetes by investigating the long-term trends (1998-2014) for all-cause mortality and major diabetes-related cardiovascular complications, compared with contemporary trends in the general population.