Multimorbidity redefined: Prospective health outcomes and the cumulative effect of co-occurring conditions

Introduction Multimorbidity is common among middle-aged and older adults; however the prospective effects of multimorbidity on health outcomes (health status, major health decline, and mortality) have not been fully explored. This study addresses this gap in the literature. Methods We used self-reported data from the 2008 and 2010 Health and Retirement Study. Our study population included 13,232 adults aged 50 or older. Our measure of baseline multimorbidity in 2008 was based on the occurrence or co-occurrence of chronic conditions, functional limitations, and/or geriatric syndromes, as follows: MM0, no chronic conditions, functional limitations, or geriatric syndromes; MM1, occurrence (but no co-occurrence) of chronic conditions, functional limitations, or geriatric syndromes; MM2, co-occurrence of any 2 of chronic conditions, functional limitations, or geriatric syndromes; and MM3, co-occurrence of all 3 of chronic conditions, functional limitations, and geriatric syndromes. Outcomes in 2010 included fair or poor health status, major health decline, and mortality. Results All 3 outcomes were significantly associated with multimorbidity. Compared with MM0 (respectively for fair or poor health and major health decline), the adjusted odds ratios (AORs) and 95% confidence intervals were as follows: 2.61 (1.79-3.78) and 2.20 (1.42-3.41) for MM1; 7.49 (5.20-10.77) and 3.70 (2.40-5.71) for MM2; and 22.66 (15.64-32.83) and 4.72 (3.03-7.37) for MM3. Multimorbidity was also associated with mortality: an adult classified as MM3 was nearly 12 times (AOR, 11.87 [5.72-24.62]) as likely as an adult classified as MM0 to die within 2 years. Conclusion Given the strong and significant association between multimorbidity and prospective health status, major health decline, and mortality, multimorbidity may be used - both in clinical practice and in research - to identify older adults with heightened vulnerability for adverse outcomes.