Causes of excess mortality in diabetes patients without coronary artery disease

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Abstract Background Diabetes (DM) patients without coronary artery disease (CAD) by coronary angiography have a similar risk of myocardial infarction and cardiac death as non-DM patients without CAD. Yet, even with absence of CAD, patients with DM have higher mortality compared to non-DM patients. Aims To examine the underlying causes of death in patients undergoing coronary angiography depending on DM and CAD. Methods We included every patient with no previous history of CAD who underwent coronary angiography in Western Denmark between 2003–2016. Patients were stratified by DM and CAD and followed for a maximum of 10 years. We estimated the 10-year cumulative risk of all-cause death and cause-specific death. Causes of death were categorized as “cardiovascular”, “pulmonary”, “cancer”, “renal”, “bleeding-related”, and “other” based on ICD-10 codes listed as underlying causes of death obtained from death certificates. Deaths where DM was listed as the underlying cause of death (i.e. ICD-10 code DE1) were included in the category “other”. Results We included 132,432 patients, of whom 33% had neither DM nor CAD, 5% had DM only, 51% had CAD only, and 11% had both DM and CAD. Mean age was 64 years. Median follow-up was 6.3 year (inter-quartile range 3.8–10.0). During follow-up, 35,036 (26.5%) patients died. Patients with both DM and CAD had the highest 10-year mortality (47.4%, 95% CI 46.3–48.4), followed by CAD only (33.3%, 95% CI 32.8–33.7), DM only (30.7%, 95% CI 29.3–32.2), and patients with neither DM nor CAD (21.6%, 95% CI 21.1–22.1). The proportion of cardiovascular deaths were similar in patients with DM only (29.2%, 95% CI 27.0–31.5, Figure) and patients with neither DM nor CAD (29.7%, 95% CI 28.8–30.7). Patients with DM were more likely to die from causes categorized as “other” compared to patients with neither DM nor CAD [38.4% (95% CI 36.0–40.9) versus 30.2% (95% CI 29.3–31.2)]. Among patients with DM only, 43.7% of deaths classified as “other” were attributable to DM-related complications such as ketoacidosis and diabetic nephropathy. Conclusion Despite absence of CAD, DM remained associated with increased mortality. Excess mortality was primarily driven by patients dying of DM-related microvascular complications and ketoacidosis. Thus, despite absence of CAD, patients with DM require continued preventative measures to reduce DM-related mortality. Funding Acknowledgement Type of funding sources: Public hospital(s). Main funding source(s): Aarhus University Hospital