A new study reveals a link between extreme weather and cardiovascular disease risk in middle-aged and older adults in 157 cities in China. Depending on the city’s climate and location, exposure to extreme heat, cold, and precipitation each increase the risk of heart disease. The research results in American Journal of Preventive MedicineThis paper, published by Elsevier, provides evidence to help policy makers in different regions develop targeted strategies to protect vulnerable populations during extreme climate change.
As climate change accelerates, extreme weather events (ECEs) are intensifying globally, posing an unprecedented threat to public health. China’s population is aging rapidly, with the number of people aged 60 and over expected to reach 400 million by 2035, reflecting a growing population with increased vulnerability. Cardiovascular disease (CVD), the leading cause of death in China, is particularly prevalent among the elderly. Previous studies have linked CVD to extreme temperatures.
Principal Investigator Ya “By integrating macro (city-level) and micro (individual-level) evidence with advanced spatial and causal analysis techniques, our study has painted a more complete picture of how extreme climate threatens heart health,” said Fang, MD, Ph.D. We focus on CVD in middle-aged and older adults, a high-risk age group, to identify actionable subgroups and thereby provide the basis for adaptive urban-rural planning and clinical interventions, filling critical gaps in climate and health policy.”
Using longitudinal data (2015-2020) from the China Health and Retirement Longitudinal Study (CHARLS) and the China Longitudinal Aging Society Survey (CLASS), researchers from the School of Public Health at Xiamen University in China used spatial econometric methods to examine the impact of extreme weather events on city-level CVD prevalence among middle-aged and elderly people in China.
They used a dual machine learning approach to examine the association between individuals’ ECE exposure and CVD risk.
The main results are:
- Extreme heat (above 38°C) increased CVD prevalence at the city level and weakened the east-west collision gradient. For each increase in ECE heat, there was an increase of 1,128 CVD cases per 100,000 people.
- Extreme cold (below -10 °C) weakened the west-to-east influence gradient and increased CVD prevalence at the city level. Each additional day of cold ECE was associated with 391 additional CVD cases per 100,000 people.
- Causal inference analysis revealed that hot ECE days increased an individual’s CVD risk by 3.044%, cold ECE days by 0.110%, and wet ECE days by 1.620%.
Heterogeneity analysis identified high-risk subgroups.
- Heat ECE affected pre-retirees, smokers, and residents of high ozone (O3) areas (higher BMI reduces risk).
- Cold ECE affected those before retirement, those with higher BMI, and those with higher O3.
- Precipitation ECE had the strongest impact on older people, rural residents, pre-retirees, and unmarried people.
The researchers explained that BMI-related risks depend on the intensity of the temperature. Above 38 °C, the physics of heat exchange are reversed and heat flows from the environment into the body instead of escaping. In this scenario, body fat acts as a physical protective barrier, blocking external heat and reducing cardiovascular strain. In contrast, below -10 °C, the mild insulation of body fat is overwhelmed by the cardiovascular risks of higher body weight. In people with a high BMI, cold-induced stress (which increases blood pressure and increases blood viscosity) is greatly amplified, increasing cardiovascular risk despite its insulating effects.
Researchers were surprised by the little-studied effects of extreme precipitation. Unlike temperature extremes, precipitation extremes did not show a continuous and regular spatial pattern at the regional level, but still showed a significant negative effect on CVD at the individual level.
This discrepancy may be due to the fact that multiscale geographic analyzes emphasize average regional effects, whereas the health effects of extreme precipitation are diluted by differences in individual exposure and regional protective measures, such as urban-rural differences in drainage infrastructure and accessibility to health care. Unlike the cumulative effects of temperature extremes, precipitation ECE is mainly associated with a single short-term event (short-term heavy rainfall) with a scattered spatial distribution. The observed CVD risk can be attributed to rapid changes in temperature and humidity caused by heavy precipitation. ”
Liangwen Zhang, Co-investigator, Xiamen University
Researchers stress that further research is needed to understand the effects of extreme precipitation events on heart health.
This study highlights the following strategies for policymakers to protect vulnerable populations during extreme climate change:
- Prioritize areas vulnerable to climate change by linking weather alerts to health networks, alerting high-risk groups, and proactively deploying resources.
- Provide weight management, air purification support, and simplified health education to high-risk subgroups.
- Establish partnerships to share resources across high-capacity areas and hotspots, and prioritize CVD prevention funding in rapidly urbanizing regions.
- Expansion of green space and improvement of heating and cooling infrastructure.
- Track climate and CVD data to dynamically adjust policies.
“Climate change is not just an environmental problem. It is an important factor affecting public health, and this requires urgent multidisciplinary action,” concluded co-author Dr Linjiang Wei. “Older people are more vulnerable due to age-related declines in physiological function and underlying health conditions.”
