纪思翰及其合作者最新研究发现改善绿地环境可能是应对气候变化带来的健康风险的有效措施之一

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图片来自https://www.gov.uk

第26届联合国气候变化大会（COP26）将于10月31日至11月12日在格拉斯哥举行，与会者将就发展新能源等进一步削减温室气体排放的问题进行磋商，减缓气候变化措施是决策制定和执行的重点。

气候行动的倡导者也建议通过对气候变化采取适应行动，如提供防洪专项资金、建立弹性基础设施、设置极端天气预警系统，提升社会对全球变暖的抵御能力。其中一项适应措施提到增加绿地。

清华大学万科公共卫生与健康学院纪思翰（John S. Ji）与其合作者最近发表在《环境污染》（Environmental Pollution）杂志上的研究“Effect of heatwaves and greenness on mortality among Chinese older adults”发现，绿地可以抵御热浪持时间及其对死亡率的影响。

极端天气事件与热浪会对生态系统、国民经济及人类健康造成不利影响，导致生产力损失、经济产出下跌、学习能力下降等诸多问题。相关研究表明，高温热浪暴露会带来过早死亡的健康风险，心血管疾病、呼吸系统疾病、肾脏疾病高发的老年人群体对这一风险更为敏感。但是，热浪与其他环境因素的互作关系并不明确，例如居住环境的绿地条件。

研究发现

研究人员发现，改善居住地周围的绿地环境可能是应对气候变化、气温上升健康风险的有效措施之一。绿地的正面健康效应包括死亡率下降、心理健康提高等，且绿地环境更优的居民能够享有更多的运动机会与社交互动，并暴露于更少的空气污染及噪音污染中。

研究发现

研究人员利用大规模队列研究发现，对于生活在绿地水平较低的老年人来说，死亡前一年每多经历3天热浪，死亡风险会增加7%；而对于生活在绿地水平中等或较高的老年人来说，这一风险则分别增加3%和4%。

此外，亚组分析还发现，城市居民对热浪的健康风险更为敏感，但绿地改善带来的边际效益也会更高。对于城市居民来说，每多经历3天热浪，死亡风险会增加6%，而农村居民为3%；绿地水平（NDVI，归一化植被指数）每下降0.1个单位，城市居民的死亡风险会增加8%，而农村居民则为4%。这说明绿地能够减少热浪带来的死亡风险，而热浪也会影响绿地的健康效应。

Abstract 

Heatwaves and greenness have been shown to affect health, but the evidence on their joint effects is limited. We aim to assess the associations of the combined exposure to greenness and heatwaves. We utilized five waves (February 2000–October 2014) of the Chinese Longitudinal Healthy Longevity Survey (CLHLS), a prospective cohort of older adults aged 65. We defined heatwaves as the daily maximum temperature ≥92.5th percentile with duration ≥3 days. We calculated the number of heatwave days in one year before death to and cumulative Normalized Difference Vegetation Index (NDVI) during follow-up to assess individual long-term exposure to heatwaves and greenness. Cox proportional hazards models were used to assess the effects of greenness, heatwaves, and their interaction on mortality, adjusted for covariates. We conducted subgroup analyses by residence, gender, and age. There were 20,758 participants in our study, totaling 67,312 person-years of follow-up. The mean NDVI was 0·41 (SD 0.13), and the mean number of heatwave days was 8.92 (2.04). In the adjusted model, the mortality hazard ratio (HR) for each 3-day increase in heatwave days was 1.04 (95% CI 1.04, 1.05), each 0.1-unit decrease in cumulative NDVI was 1.06 (1.05, 1.07). In the adjusted model with an interaction term, the HR for the interaction term was 1.01 (1.01, 1.02) with a p-value less than 0.001. In our subgroup analyses, the HR for each 3-day increase in heatwave days was higher in urban areas than in rural areas (1.06 vs. 1.03), and the HR for 0.1-unit decrease in NDVI was higher in urban areas than in rural areas (1.08 vs. 1.04). Greenness can protect against the effect of heatwaves on mortality, and heatwaves affect the health effects of greenness. Urban dwellers have a higher response to the detrimental effect of heatwaves and a higher marginal benefit from greenness exposure.

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教授简介

John S. Ji 纪思翰

■ 清华万科卫健学院副教授

■ 研究方向：环境流行病学，神经流行病学，老龄化，长寿，环境基因交互，植被，空气污染，重金属，气候变化

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