Residential greenness and activities of daily living in the Chinese elderly: a prospective cohort study

Background Activities of daily living (ADL) is a measurement of the ability to care for one's self and body, including personal care, mobility, and eating. Greenness in the built environment has been shown to improve physical health and mental wellbeing. We hypothesise that greenness could delay declines in activities of daily living. Methods Using the prospective cohort of the China Longitudinal Healthy Longevity Survey (CLHLS) between 2000 and 2014, we explored the association between ADL and greenness in the oldest-old (people aged ≥80 years). We assessed exposure using satellite-derived Normalized Difference Vegetation Index (NDVI) in the 250 m radius around each participant's residential address and then categorised them into quartiles. Our study outcome was self-care capacity, measured by a six-item ADL survey (eating, bathing, dressing, toileting, transferring, and continence). We stratified our analysis of participants with complete independence at baseline (ADL score 0 out of 6). Both NDVI values and ADL scores were repeatedly measured in 2000, 2002, 2005, 2008, 2011, and 2014. We used mixed-effects logistic regression, adjusted for age, sex, ethnicity, marital status, childhood and adult socioeconomic status, smoking status, alcohol consumption, exercise, Mini-Mental State Examination scores, and time since study entry. Findings Among 3044 elderly participants at baseline, the mean age was 91 years (SD 7·1). 837 (27·5%) became dependent and needed assistance in performing any one of the ADL functions during follow-up. Participants who became dependent in ADL were more likely to be older, female, Han Chinese, and poor cognitive function at baseline. Participants in the highest quartile of greenness had an odds ratio of 0·54 (95% CI 0·43–0·68) of becoming dependent in ADL, compared with the lowest quartile. Interpretation The ageing of China's population is an irreversible trend, and poses a challenge to the care givers who care for the elderly. Our findings suggest that increasing green space, if properly introduced into city planning, might reduce the burden of long-term care for the Chinese elderly. Funding None