Is Neighborhood Green Space Associated With Less Frailty? Evidence From the Mr. and Ms. Os (Hong Kong) Study

Abstract

Objectives: To examine whether neighborhood green space was related to frailty risk longitudinally and to examine the relative contributions of green space, physical activity, and individual health conditions to the frailty transitions.

Design, setting, and participants: Four thousand community-dwelling Chinese adults aged ≥65 years participating in the Mr. and Ms. Os (Hong Kong) study in 2001-2003 were followed up for 2 years.

Methods: The percentage of green space within a 300-meter radial buffer around the participants' place of residence was derived for each participant at baseline based on the normalized difference vegetation index. Frailty status was classified according to the Fried criteria at baseline and after 2 years. Ordinal logistic regression and path analysis were used to examine associations between green space and the frailty transitions, adjusting for demographics, socioeconomic status, lifestyle factors, health conditions, and baseline frailty status.

Results: At baseline, 53.5% of the participants met the criterion for robust, 41.5% were classified as prefrailty, and 5.0% were frail. After 2 years, 3240 participants completed all the measurements. Among these, 18.6% of prefrail or frail participants improved, 66% remained in their frailty state, and 26.8% of robust or prefrail participants progressed in frailty status. In multivariable models, the frailty status of participants living in neighborhoods with more than 34.1% green space (the highest quartile) at baseline was more likely to improve at the 2-year follow-up than it was for those living in neighborhoods with 0 to 4.5% (the lowest quartile) [odds ratio (OR): 1.29, 95% confidence interval (CI): 1.04-1.60; P for trend: 0.022]. When men and women were analyzed separately, the association between green space and frailty remained significant in men (OR: 1.40, 95% CI: 1.03-1.90) but not in women. Path analysis showed that green space directly affects frailty transitions (β = 0.041, P < .05) and also exerts an effect through physical activity (β = 0.034, P < .05). Physical activity directly affects frailty (β = 0.134, P < .05), and also indirectly affects frailty through health conditions including number of diseases (β = -0.057, P < .05) and cognitive functions (β = 0.041, P < .05). The magnitude of the direct effect of green space on the 2-year frailty transitions is comparable to those of the indirect effect through physical activity.

Conclusion: Older people living in neighborhoods with a higher percentage of green space were associated with improvement in frailty status, independent of a wide range of individual characteristics.

Keywords: Neighborhood; frailty; green space; normalized difference vegetation index; older adults; path analysis; physical activity; transitions.