Abstract
OBJECTIVES: To determine the extent to which disease-related symptoms and impairments, which constitute measures of disease severity or targets of therapy, account for the associations between chronic diseases and universal health outcomes. DESIGN: Cross-sectional. SETTING: The Cardiovascular Health Study (CHS) and the Health, Aging and Body Composition Study (Health ABC). PARTICIPANTS: Five thousand six hundred fifty-four CHS members and 2,706 Health ABC members. MEASUREMENTS: Diseases included heart failure (HF), chronic obstructive pulmonary disease (COPD), osteoarthritis, and cognitive impairment. The universal health outcomes included self-rated health, basic and instrumental activities of daily living (ADLs and IADLs), and death. Disease-related symptoms and impairments included HF symptoms and ejection fraction (EF) for HF, Dyspnea Scale and forced expiratory volume in 1 second for COPD, joint pain for osteoarthritis, and executive function for cognitive impairment. RESULTS: The diseases were associated with the universal health outcomes (P<.001) except osteoarthritis with death (both cohorts) and cognitive impairment with self-rated health (Health ABC). Symptoms and impairments accounted for 30% or more of each disease's effect on the universal health outcomes. In CHS, for example, HF was associated with one fewer (0.918) ADL and IADL performed without difficulty than no HF; HF symptoms accounted for 27% of this effect and EF for only 5%. The hazard ratio for death with HF was 6.5 (95% confidence interval=4.7-8.9) with EF accounting for 40% and HF symptoms for only 14%. CONCLUSION: Disease-related symptoms and impairments accounted for much of the significant associations between the four chronic diseases and the universal health outcomes. Results support considering universal health outcomes as common metrics across diseases in clinical decision-making, perhaps by targeting the disease-related symptoms and impairments that contribute most strongly to the effect of the disease on the universal health outcomes.