Adults with type 1 diabetes who had on-target glycemic control still showed twice the risk of death from any cause and death from cardiovascular causes as did the general population, according to findings from a Swedish study involving virtually every affected patient in that country that was reported online Nov. 20.
The excess mortality despite good glycemic control was attributed almost entirely to diabetes itself (ketoacidosis or hypoglycemia) or to cardiovascular disease (CVD), which is particularly puzzling because adults with type 1 diabetes “generally do not have excess rates of obesity, hypertension, or hypercholesterolemia.” Moreover, the diabetes patients in this study were four to five times more likely than controls to be taking cardioprotective drugs such as statins or renin-angiotensin-aldosterone system inhibitors, said Dr. Marcus Lind of Uddevalla Hospital and the University of Gothenburg in Sweden, and his associates.
The investigators assessed mortality risks in patients who had varying degrees of glycemic control using data from the Swedish National Diabetes Register and national mortality databases during a 14-year period. They matched 33,915 patients for age, sex, and region of residence with 169,249 adults in the general population. The mean duration of diabetes was 20 years, and the mean glycosylated hemoglobin level at baseline was 8.2%.
Overall mortality for patients with type 1 diabetes was 8% (9.97 per 1,000 observation-years), compared with 2.9% (3.45 per 1,000 observation-years) for controls. After the data were adjusted to account for education level and other possible confounding factors, hazard ratios for patients vs. controls were still high at 3.52 for death from any cause and 4.60 for death from CVD causes, the investigators said (N. Engl. J. Med. 2014 November 20 [ doi:10.1056/NEJMoa1408214 ]).
Even patients who had good glycemic control, with a mean glycosylated hemoglobin level of 6.9% or lower, had an hazard ratio for death from any cause of 2.36 and an HR for cardiovascular death of 2.92, in relation to controls. Mortality increased as mean glycosylated hemoglobin level increased, so that patients with a mean glycosylated hemoglobin level of 9.7% or higher were 8 times more likely to die from any cause and 10 times more likely to die from cardiovascular causes, in relation to controls.