Survival, disabilities in activities of daily living, and physical and cognitive functioning among the oldest-old in China: a cohort study

Background The oldest-old (those aged >= 80 years) are the most rapidly growing age group globally, and are most in need of health care and assistance. We aimed to assess changes in mortality, disability in activities of daily living, and physical and cognitive functioning among oldest-old individuals between 1998 and 2008. Methods We used data from the Chinese Longitudinal Healthy Longevity Study. Three pairs of cohorts aged 80-89 years, 90-99 years, and 100-105 years (in total, 19 528 oldest-old participants) were examined; the two cohorts in each pair were born 10 years apart, with the same age at the time of the assessment in the 1998 and 2008 surveys. Four health outcomes were investigated: annual death rate, Activities of Daily Living (ADL), physical performance in three tests and cognitive function measured by Mini-Mental State Examination (MMSE). We used different tests and multivariate regression analyses to examine the cohort differences. Findings Controlling for various confounding factors, we noted that annual mortality among oldest-old individuals was substantially reduced between 0.2% and 1.3% in 1998-2008 compared with individuals of the same age born 10 years previously, and that disability according to activities of daily living had significantly reduced annually between 0.8% and 2.8%. However, cognitive impairment in the later cohorts increased annually between 0.7% and 2.2% and objective physical performance capacity (standing up from a chair, picking up a book from the floor, and turning around 360 degrees) decreased anually between 0.4% and 3.8%. We also noted that female mortality was substantially lower than male mortality among the oldest-old, but that women's functional capacities in activities of daily living, cognition, and physical performance were worse than their male counterparts. Interpretation Advances in medications, lifestyle, and socioeconomics might compress activities of daily living disability, that is, benefits of success, but lifespan extension might expand disability of physical and cognitive functioning as more frail, elderly individuals survive with health problems, that is, costs of success.