Impact of comorbidities on mortality in managed care patients with CKD.

BACKGROUND: Our previous work showed that patients with chronic kidney disease (CKD) were 10 times more likely to die than progress to end-stage renal disease. This study examines the impact of comorbidities on mortality risk in a cohort with CKD at 3 levels of progression and a sex- and age-matched comparison group. METHODS: In a historical, prospective, cohort study, we selected electronic medical record data for health maintenance organization (HMO) members with an index and repeated glomerular filtration rate (GFR) in the range of 15 to 90 mL/min/1.73 m(2) (0.25 to 1.50 mL/s/1.73 m(2)) in 1996 who were followed up for at least 54 months or died during this period. These were matched for birth year and sex with HMO members not meeting GFR criteria, but with the same follow-up criteria. Major comorbid chronic conditions also were identified based on International Classification of Diseases, Ninth Revision, diagnostic codes in the electronic medical record. Conditional logistic regression was used to estimate the relative risk for mortality versus comparison subjects as a function of GFR, age, and other chronic conditions. RESULTS: In the final sample of 19,945 pairs, we found that risk for mortality increases as GFR decreases, but also that both age and other chronic conditions are significant risk factors for mortality. CONCLUSION: Baseline levels of estimated GFR and other major chronic disorders all contributed negatively to survival. The relative impact of these comorbidities was greatest among younger (<60 years) patients with CKD, and their relative effect diminished with age.