Time-dependent impact of diabetes on mortality in patients with stroke: survival up to 5 years in a health insurance population cohort in Germany

Abstract

Objective: To estimate the impact of diabetes on mortality in patients after first stroke event.

Research design and methods: Using claims data from a nationwide statutory health insurance fund (Gmünder ErsatzKasse), we assessed all deaths in a cohort of 5,757 patients with a first stroke between 2005 and 2007 (69.3% male, mean age 68.1 years, 32.2% with diabetes) up to 2009. By use of Cox regression, we estimated time-dependent hazard ratios (HRs) to compare patients with and without diabetes stratified by sex.

Results: The cumulative 5-year mortality was 40.0 and 54.2% in diabetic men and women, and 32.3 and 38.1% in their nondiabetic counterparts, respectively. In males, mortality was significantly lower in diabetic compared with nondiabetic patients in the first 30 days (multiple-adjusted HR 0.67 [95% CI 0.53-0.84]). After approximately a quarter of a year, the diabetes risk increased, yielding crossed survival curves. Later on, mortality risk tended to be similar in diabetic and nondiabetic men (1-2 years: 1.42 [1.09-1.85]; 3-5 years: 1.00 [0.67-1.41]; time dependency of diabetes, P = 0.008). In women, the pattern was similar; however, time dependency was not statistically significant (P = 0.89). Increasing age, hemorrhagic stroke, renal failure (only in men), levels of care dependency, and number of prescribed medications were significantly associated with mortality.

Conclusions: We found a time-dependent mortality risk of diabetes after first stroke in men. Possible explanations may be type of stroke or earlier and more intensive treatment of risk factors in diabetic patients.

Figure 1

A: Kaplan-Meier estimates of crude survival after first incident stroke for male GEK insurants, Germany, 2005–2007. B: Kaplan-Meier estimates of crude survival after first incident stroke for female GEK insurants, Germany, 2005–2007. C: Crude log-log survival curves after first incident stroke for male GEK insurants, Germany, 2005–2007. D: Crude log-log survival curves after first incident stroke for female GEK insurants, Germany, 2005–2007. SDF, survival distribution function.