Overview: Heat, aging, and heart health
As climate change pushes global temperatures higher and heat waves become more frequent, a silent crisis is unfolding at the intersection of aging and the cardiovascular system. A recent narrative review in the Journal of Applied Physiology synthesizes evidence from the past decade showing that older adults face disproportionate cardiovascular risks when exposed to extreme heat. The findings underscore the urgent need for adaptive health strategies as populations age and heat events intensify.
Key findings from the review
The authors examine how aging alters the body’s response to heat stress, influencing cardiovascular outcomes such as heart failure, ischemic heart disease, and stroke. They highlight that even modest increases in ambient temperature can translate into higher cardiovascular mortality among seniors, and that heatwaves – longer, more severe events – elevate risk across countries and climates.
Evidence of heightened vulnerability
Across epidemiological studies, adults over age 65 show the highest rates of heat-related hospitalizations and deaths, with cardiovascular disease accounting for a large share. In New York City, for example, roughly 580 summer deaths are heat-related each year, and about 62% involve pre-existing cardiovascular disease. A 1°C rise in temperature is linked to a roughly 2% uptick in cardiovascular mortality, while each intensifying heatwave can push deaths higher by an even larger margin. In the United States, each extra extreme heat day per month from 2008–2017 correlated with thousands more cardiovascular deaths among older adults.
Projections are sobering: estimates suggest a 187% increase in heat-related cardiovascular deaths between 2036 and 2065 if current warming trends continue. Importantly, these figures reflect recent research and indicate that regions unaccustomed to extreme heat may experience sharp health impacts as temperatures rise.
Physiological mechanisms in aging hearts
Heat exposure demands a substantial rise in cardiac output to support skin blood flow and sweating. However, aging blunts this response. Younger adults can often double cardiac output during passive heating, reaching about 11 L/min, while older adults may reach only around 7 L/min due to limited stroke volume and reduced heart rate reserve. This constraint increases cardiac strain and the risk of ischemia in those with pre-existing heart disease.
Older individuals also show diminished ability to increase skin blood flow during heat exposure. Factors like reduced nitric oxide availability, oxidative stress, and weaker neural control of blood vessels hinder vasodilation, making heat dissipation less efficient. The result is greater internal heat storage and heightened cardiovascular strain.
Another age-related pattern is the redistribution of blood away from visceral organs toward the skin to facilitate cooling. In older adults, this diversion is roughly 30% less effective, further elevating internal heat load and cardiovascular risk during heat stress.
Environmental thresholds and early warning
Researchers identify “critical environmental limits” where cardiovascular strain climbs sharply. For older adults doing light daily tasks in warm-humid conditions, strain tends to rise around 35°C with 53% relative humidity. In hot-dry environments, thresholds are around 41°C with 24% humidity. Notably, older women may reach these limits at lower temperature-humidity combinations than men, suggesting gender differences in vulnerability that warrant targeted precautions.
The review also discusses cardiovascular drift — a rising heart rate over sustained heat exposure — as an early warning sign before thermal imbalance occurs. Recognizing these signals is essential for public health planning, early warning systems, and guidance to protect older populations during heat events.
Public health implications and actions
With aging populations and increasingly frequent heat waves, protecting cardiovascular health requires a multi-pronged approach. Public health measures could include heat-health advisories tailored to older adults, improved access to cooling resources, and neighborhood-scale strategies to reduce heat exposure. Clinicians can incorporate heat-stress risk into cardiovascular risk assessments and management plans for seniors, emphasizing hydration, medication review (where certain drugs affect thermoregulation or fluid balance), and signs of heat-related cardiac strain.
Future research should prioritize ecologically valid studies that mimic real-world exposures, helping translate laboratory results into practical prevention strategies. By refining our understanding of environmental thresholds and vulnerable subgroups, researchers can inform targeted interventions and policies to reduce heat-related cardiovascular deaths globally.
Conclusion
Heat-related mortality and morbidity disproportionately affect older adults, with cardiovascular complications driving many of these outcomes. As heat waves become more severe and time-extended, the overlap between aging and rising temperatures poses a significant global health challenge. Ongoing research and proactive public health strategies are essential to safeguard older hearts from the growing heat threat.
