Epidemiological aspects of cardiovascular morbidity and mortality among individuals with diabetes: the relative importance of cardiovascular risk factors

Abstract

Background: Long-term trends of cardiovascular complications and death among patients with diabetes have not been studied extensively. In addition, we aimed to examine the effect of multifactorial risk factor control, as well as optimal levels- and relative importance of cardiovascular risk factors, in patients with type 1 diabetes and type 2 diabetes. The analyses for patients with diabetes were compared to the general population. Method: We used data from the National Diabetes Register along with other Swedish health registries and applied different statistical methods such as survival analysis and different machine learning models to study our research questions. We have focused on the following outcomes: all-cause mortality, acute myocardial infarction, coronary heart disease, cardiovascular disease, stroke and heart failure. Results: During the period 1998-2014, patients with type 1 diabetes experienced approximately 40% greater relative risk reduction for cardiovascular complications, compared to matched controls, while patients with type 2 diabetes experienced roughly 20% greater risk reduction than their matched controls. A paradoxical finding was the lower relative risk reduction of fatal outcomes in patients with diabetes. Nevertheless, death and complications have decreased substantially during the last two decades. Multifactorial risk factor control is associated with significant risk reduction for patients with diabetes. Still, patients with type 1 diabetes display 82% and 97% elevated risk for myocardial infarction and heart failure, respectively. For type 2 diabetes, we observed marginally increased risk of death and cardiovascular complications in patients with all risk factor at target level. Moreover, there is a monotone relationship between number of risk factor at target level and excess risk of outcomes in patients with diabetes. Patients with type 2 diabetes and all risk factors at target level had 16% lower relative risk for myocardial infarction, compared to the general population. The most important risk factors for cardiovascular complications were glycated hemoglobin, physical activity level, systolic blood pressure, low-density lipoprotein cholesterol, albuminuria, as well as risk factors that in some form denote exposure time to the disease (e.g. age, duration of diabetes and age at onset of disease). Lower levels for glycated hemoglobin, systolic blood pressure and low-density lipoprotein cholesterol is associated with reduced risk for cardiovascular complications, compared to matched controls. The relative importance analyses suggest that risk factors contribute differently between outcomes and type of diabetes. Conclusion: Morbidity and mortality have decreased significantly among individuals with diabetes. Multifactorial risk factor control is associated with significant risk reduction and could perhaps even eliminate the excess risk for cardiovascular disease. Lower levels for selected risk factors than recommended target levels is associated with lower risk for complications. Heart failure is an emerging diabetes-related complication and young individuals with diabetes are at the highest risk of complications.