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Focus should shift to multiple diseases contributing to deaths among older adults

The concept of multiple diseases and conditions contributing to death may be more appropriate than the common method of identifying one underlying cause in older adults, according to recent study results.

Researchers examined data from the Medicare Current Beneficiary Survey to conduct a longitudinal, national study that included 22,890 beneficiaries, aged 65 years and older, enrolled from 2002 to 2006. Reviewing Medicare claims, researchers collected information on chronic and acute diseases among this cohort of which 2,445 participants died.

During a median follow-up of 15 months, investigators used regression models to empirically identify 39 chronic diseases (accounting for 52% of deaths) with frequencies of 1% or more that contributed to death and bivariate hazard ratios for death of greater than one. They included cancers of the lung (HR=7.5; 95% CI, 6.2-9.0), and liver and pancreas (HR=7.2; 95% CI, 5.5-9.5); heart failure (HR=5.1; 95% CI, 4.7-5.5); and dementia (HR=4.1; 95% CI, 3.7-4.6). Twenty-four acute diseases (15% of deaths) showed significant associations with death, including septicemia (HR=13.8; 95% CI, 12.2-15.6), acute kidney injury (HR=9.4; 95% CI, 8.2-10.7), myocardial infarction (HR=8.3; 95% CI, 7.1-9.8), and pneumonia (HR=8.1; 95% CI, 7.3-9.1).

Upon empirical examination, the additive contributions of 15 of these acute diseases and events were then calculated with a longitudinal extension of the average attributable fraction. They significantly contributed to 67.6% of all deaths after adjusting for coexisting diseases. The major contributors to death included heart failure (20.0%; 95% CI, 17.9-22.2), dementia (13.6%; 95% CI, 12.1-15.2), chronic lower respiratory disease (12.4%; 95% CI, 10.4-14.9), and pneumonia (5.3%; 95% CI, 4.5-6.3).

“Death in older adults results from the accumulated effect of coexisting diseases, a fact that current methods do not accurately reflect,” the researchers said. “The contribution of some diseases may be overestimated, and others underestimated. An accurate, empirical method … is needed to measure the burden of disease and establish public health, clinical, and research priorities for an aging population.”