A higher exposure to greenery might prolong the life of the elderly, according to a study led by scientists from Duke Kunshan University and Duke University.
The findings, published in the January issue of The Lancet Planetary Health, provide evidence to urban planners and health policymakers of the role of greenery in prolonging life, as China undergoes urbanization in an unprecedented rate.
The research, with a 14-year follow-up, is believed to be the first study of its kind in the Chinese mainland, and even among middle-income countries. The sample size consisted of 23,754 people aged 80 years or older living in a wide range of geographies in China.
Four of the co-authors are from Duke Kunshan, including John Ji, Anna Zhu, Lijing Yan, and Shenglan Tang. The other four co-authors are from Peking University, Renmin University of China, Cheng Kung University of Taiwan, and Harvard Medical School.
Although previous studies have reported the beneficial effects of exposure to greenery, the published studies have been done in regions of the world that have a high human development index and high per capita incomes. The positive effect of exposure to greenery on the oldest (those aged over 80) among a primarily rural population had not been studied.
“Few studies of the effects of greenery have focused on Asia, and, to the best of our knowledge, no study has assessed the effect on the vulnerable oldest population. With an ageing population and rapid urbanization in China, this is an important evidence gap,” said John Ji, assistant professor of Environmental Health Science at Duke Kunshan.
“Our research suggests that proximity to more green space is associated with increased longevity, which has policy implications for the national blueprint for an ecological civilization and preparation for an ageing society in China,” said Ji.
As part of China’s reform program, urbanization continues to make gradual progress. The country's leadership has set a target rate of 60 percent in 2020.The study found that elders living in the highest quintile of greenness had 27 percent lower mortality than did elders living in the lowest quintile.
“This study led by Professor John Ji was not only innovative in revealing exciting new results on the health impacts of greenness but also pointed to new directions and more in-depth analyses for future research,” said Lijing Yan, head of Non-communicable Chronic Diseases Research at the Global Health Research Center of Duke Kunshan.
This study also involved participation of many Duke Kunshan undergraduate and graduate students.
“It took our team about three months to complete geocoding residential addresses and measuring green space using NASA satellite images. Advancements in remote sensing technology have been a great tool for environmental exposure assessment. Multidisciplinary collaboration made this environmental health study possible,” said Anna Zhu, research assistant for Environmental Health at Duke Kunshan.
This work will be continued. The authors caution that physical, mental, and immune-system factors could affect the association between greenery and later mortality. For example, the study found those who exercised also tended to live longer than those who did not.
The authors suggest there might be a correlation as more green spaces might provide greater opportunities and inclination for physical activities, which are known to help to reduce the incidence of non-communicable diseases such as diabetes and cardiovascular diseases, leading to decreased mortality. The mechanisms need to be elucidated further.
"Our study of greenness might contribute to the assessment of China's burden of disease from environmental causes," Ji said.
China now faces a populace demanding better environmental and health protections and the concept of “ecological civilization” has been enshrined in the Constitution. A major reorganization ministry responsibilities was announced last year to help consolidate environmental protection and natural resources management.
These moves all suggested that China is on track to achieve “ecological rejuvenation”.