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

1 July 2008 | Volume 149 Issue 1 | Pages 11-19

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 A_1c [HbA_1c] level of 7.0) versus moderate glucose control (HbA_1c 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.

Editors' Notes Context Whether tight glucose control benefits elderly patients with type 2 diabetes is subject to debate because some studies show adverse outcomes with tight control. Contribution This computer model estimated the net benefits of treating to a hemoglobin A1c level of 7% versus 7.9% among individuals 60 to 80 years of age with various life expectancies and suggests modest benefits of tight control, ranging from 51 to 116 additional quality-adjusted days. Benefits decreased as age increased and life expectancy decreased, supporting a relaxation of hemoglobin A1c targets for elderly people with comorbid illness. Caution The mortality index that the investigators used to predict life expectancy in the model is not appropriate for predicting an individual patient's life expectancy. —The Editors

 

Author and Article Information

From the University of Chicago, Chicago, Illinois; Old Dominion University, Norfolk, Virginia; and Boston University School of Medicine, Boston, Massachusetts.

Acknowledgment: The authors thank Priya John, MPH, for her assistance in preparing this manuscript.

Grant Support: By a National Institute on Aging Career Development Award (K23 AG021963 [Dr. Huang]), a National Institute of Diabetes and Digestive and Kidney Diseases Diabetes Research and Training Center (P60 DK20595 [Drs. Huang, Zhang, Chin, and Meltzer]), the Chicago Center of Excellence in Health Promotion Economics (Drs. Huang, Chin, and Meltzer), a National Institute of Child Health and Human Development Small Grant (R03 HD056073 [Dr. Zhang]), and a National Institute of Diabetes and Digestive and Kidney Diseases Midcareer Investigator Award in Patient-Oriented Research (K24 DK071933 [Dr. Chin]).

Potential Financial Conflicts of Interest: None disclosed.

Reproducible Research Statement: Study protocol: Not available. Statistical code: Readers with questions about the simulation model used in this analysis may contact Dr. Huang (ehuang{at}medicine.bsd.uchicago.edu). The model is not available without establishing written agreements with the authors. Data set: Not available.

Requests for Single Reprints: Elbert S. Huang, MD, MPH, The University of Chicago, 5841 South Maryland Avenue, MC 2007, Chicago, IL 60637; e-mail, ehuang{at}medicine.bsd.uchicago.edu.

Current Author Addresses: Drs. Huang, Chin, and Meltzer: The University of Chicago, 5841 South Maryland Avenue, MC 2007, Chicago, IL 60637.

Dr. Zhang: 3138 Health Sciences Building, School of Community and Environmental Health, Old Dominion University, Norfolk, VA 23529.

Mr. Gandra: 10 Buick Street, Box 8298, Boston, MA 02215.

Author Contributions: Conception and design: E.S. Huang, Q. Zhang, M.H. Chin, D.O. Meltzer.

Analysis and interpretation of the data: E.S. Huang, Q. Zhang, N. Gandra, D.O. Meltzer.

Drafting of the article: E.S. Huang.

Critical revision of the article for important intellectual content: E.S. Huang, Q. Zhang, M.H. Chin, D.O. Meltzer.

Final approval of the article: E.S. Huang, Q. Zhang, N. Gandra, M.H. Chin, D.O. Meltzer.

Provision of study materials or patients: D.O. Meltzer.

Statistical expertise: E.S. Huang, Q. Zhang.

Obtaining of funding: E.S. Huang.

Administrative, technical, or logistic support: N. Gandra.

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Letter to the Editor

Thomas E. Finucane

Annals Online, 14 Jul 2008 [Full text]