Time-Dependent Impact of Diabetes on Mortality in Patients After Major Lower Extremity Amputation

Abstract

OBJECTIVE To estimate the impact of diabetes on mortality in patients after first major lower extremity amputation (LEA). RESEARCH DESIGN AND METHODS Using claims data of a nationwide statutory health insurance, we assessed all deaths in a cohort of all 444 patients with a first major LEA since 2005 (71.8% male; mean age 69.1 years; 58.3% diabetic; 43% with amputation above the knee) up to 2009. Using Cox regression, we estimated the time-dependent hazard ratios to compare patients with and without diabetes. RESULTS The cumulative 5-year mortality was 68% in diabetic and 59% in nondiabetic individuals. In the first course, mortality was lower in diabetic compared with nondiabetic patients. Later, the diabetes risk increased yielding crossed survival curves after 2 to 3 years (time dependency of diabetes; P = 0.003). Age- and sex-adjusted hazard ratios for diabetes were as follows: 0–30 days: 0.50 [95% CI 0.31–0.84]; 31–60 days: 0.60 [0.25–1.41]; 61 days to 6 months: 0.75 [0.38–1.48]; >6–12 months: 1.27 [0.63–2.53]; >12–24 months: 1.65 [0.88–3.08]; >24–36 months: 2.02 [0.80–5.09]; and >36–60 months: 1.91 [0.70–5.21]. The pattern was similar in both sexes. In the full model, significant risk factors for mortality were age (1.05; 1.03–1.06), amputation above the knee (1.50; 1.16–1.94), and quartile category 3 or 4 of the number of prescribed medications (1.64; 1.12–2.40 and 1.76; 1.20–2.59). Further adjustment for comorbidity did not alter the results. CONCLUSIONS In this population-based study, we found a time-dependent mortality risk of diabetes following first major LEA, which may be in part a result of a healthier lifestyle in diabetic patients or the access to specific treatment structures in diabetic individuals.