The Effect of Comorbid Illness and Functional Status on the Expected Benefits of Intensive Glucose Control in Older Patients with Type 2 Diabetes: A Decision Analysis

Abstract

BACKGROUND: Physicians are uncertain about when to pursue intensive glucose control among older patients with diabetes. OBJECTIVE: To assess the effect of comorbid illnesses and functional status, mediated through background mortality, on the expected benefits of intensive glucose control. DESIGN: Decision analysis. DATA SOURCES: Major clinical studies in diabetes and geriatrics. TARGET POPULATION: Patients 60 to 80 years of age who have type 2 diabetes and varied life expectancies estimated from a mortality index that was validated at the population level. TIME HORIZON: Patient lifetime. PERSPECTIVE: Health care system. INTERVENTION: Intensive glucose control (hemoglobin A1c [HbA1c] level of 7.0) versus moderate glucose control (HbA1c level of 7.9). OUTCOME MEASURES: Lifetime differences in incidence of complications and average quality-adjusted days. RESULTS OF BASE-CASE ANALYSIS: Healthy older patients of different age groups had expected benefits of intensive glucose control ranging from 51 to 116 quality-adjusted days. Within each age group, the expected benefits of intensive control steadily declined as the level of comorbid illness and functional impairment increased (mortality index score, 1 to 26 points). For patients 60 to 64 years of age with new-onset diabetes, the benefits declined from 106 days at baseline good health (life expectancy, 14.6 years) to 44 days with 3 additional index points (life expectancy, 9.7 years) and 8 days with 7 additional index points (life expectancy, 4.8 years). A similar decline in benefits occurred among patients with prolonged duration of diabetes. RESULTS OF SENSITIVITY ANALYSIS: With alternative model assumptions (such as Framingham models), expected benefits of intensive control declined as mortality index scores increased. LIMITATIONS: Diabetes clinical trial data were lacking for frail, older patients. The mortality index was not validated for use in predicting individual-level life expectancies. Adverse effects of intensive control were not taken into account. CONCLUSION: Among older diabetic patients, the presence of multiple comorbid illnesses or functional impairments is a more important predictor of limited life expectancy and diminishing expected benefits of intensive glucose control than is age alone.