Time-dependent impact of diabetes on mortality in patients after major lower extremity amputation: survival in a population-based 5-year cohort in Germany.

Abstract

To estimate the impact of diabetes on mortality in patients after first major lower extremity amputation (LEA). 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. 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. 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.