Contribution of individual diseases to death in older adults with multiple diseases.

OBJECTIVES

To determine empirically the diseases contributing most commonly and strongly to death in older adults, accounting for coexisting diseases.

DESIGN

Longitudinal.

SETTING

United States.

PARTICIPANTS

Twenty-two thousand eight hundred ninety Medicare Current Beneficiary Survey participants, a national representative sample of Medicare beneficiaries, enrolled during 2002 to 2006.

MEASUREMENTS

Information on chronic and acute diseases was ascertained from Medicare claims data. Diseases contributing to death during follow-up were identified empirically using regression models for all diseases with a frequency of 1% or greater and hazard ratio for death of greater than 1. The additive contributions of these diseases, adjusting for coexisting diseases, were calculated using a longitudinal extension of average attributable fraction; 95% confidence intervals were estimated from bootstrapping.

RESULTS

Fifteen diseases and acute events contributed significantly to death, together accounting for nearly 70% of death. Heart failure (20.0%), dementia (13.6%), chronic lower respiratory disease (12.4%), and pneumonia (5.3%) made the largest contributions to death. Cancer, including lung, colorectal, lymphoma, and head and neck, together contributed to 5.6% of death. Other diseases and events included acute kidney injury, stroke, septicemia, liver disease, myocardial infarction, and unintentional injuries.

CONCLUSION

The use of methods that focus on determining a single underlying cause may lead to underestimation of the extent of the contribution of some diseases such as dementia and respiratory disease to death in older adults and overestimation of the contribution of other diseases. Current conceptualization of a single underlying cause may not account adequately for the contribution to death of coexisting diseases that older adults experience.