Climate Change and Cardiovascular Health: A Systematic Review

Abstract

Importance: Climate change may increase the risk of adverse cardiovascular outcomes by causing direct physiologic changes, psychological distress, and disruption of health-related infrastructure. Yet, the association between numerous climate change-related environmental stressors and the incidence of adverse cardiovascular events has not been systematically reviewed.

Objective: To review the current evidence on the association between climate change-related environmental stressors and adverse cardiovascular outcomes.

Evidence review: PubMed, Embase, Web of Science, and Cochrane Library were searched to identify peer-reviewed publications from January 1, 1970, through November 15, 2023, that evaluated associations between environmental exposures and cardiovascular mortality, acute cardiovascular events, and related health care utilization. Studies that examined only nonwildfire-sourced particulate air pollution were excluded. Two investigators independently screened 20 798 articles and selected 2564 for full-text review. Study quality was assessed using the Navigation Guide framework. Findings were qualitatively synthesized as substantial differences in study design precluded quantitative meta-analysis.

Findings: Of 492 observational studies that met inclusion criteria, 182 examined extreme temperature, 210 ground-level ozone, 45 wildfire smoke, and 63 extreme weather events, such as hurricanes, dust storms, and droughts. These studies presented findings from 30 high-income countries, 17 middle-income countries, and 1 low-income country. The strength of evidence was rated as sufficient for extreme temperature; ground-level ozone; tropical storms, hurricanes, and cyclones; and dust storms. Evidence was limited for wildfire smoke and inadequate for drought and mudslides. Exposure to extreme temperature was associated with increased cardiovascular mortality and morbidity, but the magnitude varied with temperature and duration of exposure. Ground-level ozone amplified the risk associated with higher temperatures and vice versa. Extreme weather events, such as hurricanes, were associated with increased cardiovascular risk that persisted for many months after the initial event. Some studies noted a small increase in cardiovascular mortality, out-of-hospital cardiac arrests, and hospitalizations for ischemic heart disease after exposure to wildfire smoke, while others found no association. Older adults, racial and ethnic minoritized populations, and lower-wealth communities were disproportionately affected.

Conclusions and relevance: Several environmental stressors that are predicted to increase in frequency and intensity with climate change are associated with increased cardiovascular risk, but data on outcomes in low-income countries are lacking. Urgent action is needed to mitigate climate change-associated cardiovascular risk, particularly in vulnerable populations.

Figure 1.. Global Temperature Trends 1881–2024.

The figure shows negative (blue) and positive (red) deviations from the average 20^th century land temperature from 1850 to 2023. Despite year-on-year variability, a clear trend of warming temperatures is noted. All 10 of the warmest years on record have occurred in the past decade, and 2023 was the warmest year on record since record-keeping began in 1850. Data from the National Centers for Environmental Information at the National Oceanic and Atmospheric Administration.

Figure 2.. Climate Change and Cardiovascular Health.

Climate change may adversely affect cardiovascular health through several pathways, including direct effects on physical and mental health and indirect effects from disruption of healthcare delivery or worsening social determinants of health. The relative importance of each of these mechanisms may vary by community and over time, but collectively they have the potential to undermine the substantial gains in cardiovascular health achieved globally in recent decades.

Figure 3.. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) flow diagram.

We searched PubMed, Embase, Web of Science, and Cochrane Library databases for relevant publications from 1970 to 2023. Two investigators independently screened the titles and abstracts of 20,798 articles, of which 2,564 were considered for full-text review. A total of 492 studies were included in the final analysis. *Six studies assessed both extreme temperature and ground-level ozone, 1 study assessed both extreme tmpereature and wildfires, and 1 study assessed both wildfires and extreme weather(dust storms)

Figure 4.. Countries with Studies Examining the Association Between Climate Change and Cardiovascular Health.

The 492 studies that met inclusion criteria for this systematic review reported data from 30 high-income, 13 upper-middle income, 4 lower-middle income countries, and one low-income countries. Numbers indicate the number of included studies from each country. Several studies included data from more than one country. The dearth of studies from low- and middle-income countries is problematic both because of the large number of people at risk and because of the greater expected impact of climate change in these countries.