ArticleBMC geriatrics2025
Exploring effects of greenness and extreme heat exposure on hypertension incidence in elderly Chinese: a national cohort study.
Article in BMC geriatrics, 2025. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Not yet cited in PubMed.
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Abstract
backgroundHypertension poses a significant health challenge, particularly within aging populations, yet the health effects of modifiable environmental factors remain insufficiently understood. This study aims to examine the association between greenness and hypertension among older adults in China, and to determine whether the association is modified by extreme heat exposure.
methodsWe selected 7,726 participants aged ≥ 65 without hypertension at baseline from the Chinese Longitudinal Healthy Longevity Survey (CLHLS), recruited during the 2000, 2002, and 2005 waves, and followed up through the 2018 survey. Greenness and extreme heat exposure during the inter-hypertension interval in each participant’s city of residence were quantified as the average Normalized Difference Vegetation Index (NDVI) and the total number of days with daily mean temperature exceeding the T-year return level, based on Extreme Value Theory (EVT), respectively. Cox proportional hazards models were employed to assess the association between greenness and hypertension, incorporating interaction terms to evaluate extreme heat exposure modifications.
resultsEach 0.1-unit increase in NDVI was associated with a 9.6% lower risk of developing hypertension (HR = 0.904; 95% CI: 0.859–0.952), after adjusting for demographic, lifestyle, and physical health variables, as well as extreme heat exposure at the 20-year return level and its interaction with NDVI. The exposure-response curve revealed an inverted V-shaped pattern, with risk decreasing up to an NDVI of around 0.65 before plateauing or reversing. Consistent significant negative interaction was found between NDVI and extreme heat exposure across various T-year return levels, with the most pronounced one at the largest 20-year return level, suggesting that greenness may mitigate the incidence of hypertension during intense heat periods. Stratified analyses showed stronger protective associations in rural or town residents, single or divorced individuals, and those with limited gardening activity (all p-interaction < 0.05), with consistent protective effects observed across both low and high NDVI exposure levels.
conclusionGreen space mitigated the incidence of hypertension in older adults, particularly during extreme heat events. Urban greening could serve as a dual adaptation strategy against climate change and population aging.
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