The avalanche hypothesis and compression of morbidity: Testing assumptions through cohort-sequential analysis

Abstract

Background: The compression of morbidity model posits a breakpoint in the adult lifespan that separates an initial period of relative health from a subsequent period of ever increasing morbidity. Researchers often assume that such a breakpoint exists; however, this assumption is hitherto untested. Purpose: To test the assumption that a breakpoint exists - which we term a morbidity tipping point - separating a period of relative health from a subsequent deterioration in health status. An analogous tipping point for healthcare costs was also investigated. Methods: Four years of adults' (N = 55,550) morbidity and costs data were retrospectively analyzed. Data were collected in Pittsburgh, PA between 2006 and 2009; analyses were performed in Rochester, NY and Ann Arbor, MI in 2012 and 2013. Cohort-sequential and hockey stick regression models were used to characterize long-term trajectories and tipping points, respectively, for both morbidity and costs. Results: Morbidity increased exponentially with age (P