Introduction: heat, aging, and the silent risk
As the climate heats up, an overlooked public health crisis is unfolding at the intersection of aging and extreme heat. A recent narrative review published in the Journal of Applied Physiology synthesizes for the first time how aging magnifies the cardiovascular stress of high ambient temperatures. The result is a sobering portrait: older adults are disproportionately exposed to heat-related cardiovascular disease (CVD) hospitalizations and deaths as heat waves become longer, more intense, and more frequent.
Why heat hits older adults hardest
Thermoregulation is a complex, energy-demanding process. When temperatures rise, the body must increase cardiac output to supply skin with blood for cooling via sweating. In younger adults, this rise can be robust, but aging blunts this cardiovascular response. The review highlights that older individuals often achieve a lower peak cardiac output during heat exposure—roughly 7 L/min compared with about 11 L/min in younger adults. The consequence is greater cardiac strain, especially for those with preexisting heart conditions.
Beyond flow, older adults also struggle to boost skin blood flow due to reduced nitric oxide availability and heightened oxidative stress. This limitation impairs vasodilation, hampering the body’s ability to dissipate heat. The result is a higher internal heat burden and more pronounced cardiovascular strain, increasing the likelihood of events such as heart failure, ischemia, and stroke during heat exposure.
Evidence from epidemiology: the aging population at risk
Data from around the world point to a clear pattern: people over 65 have the highest rates of heat-related hospitalizations and mortality, and cardiovascular disease is a leading cause of these deaths in heat waves. Regional studies show that even a modest 1°C rise in temperature is associated with about a 2% increase in CVD mortality, with sharper increases as heatwave intensity grows. Across the United States, each additional extreme heat day per month from 2008 to 2017 translated into thousands of extra cardiovascular deaths among older adults.
The review projects a stark future: a roughly 187% increase in heat-related cardiovascular deaths could occur between 2036 and 2065 if current climate trends continue. Importantly, these projections are driven by recent data and emphasize the growing relevance of heat as a cardiovascular risk factor across diverse regions, including areas not traditionally accustomed to extreme heat.
Age-related physiological responses and what they mean for risk
Several age-related physiological shifts drive the heightened risk. The aging heart has diminished stroke volume and reduced heart rate reserve, making it harder to sustain the increased cardiac output needed for cooling. Even when older adults maintain stroke volume, they may rely more on contractility and operate closer to their maximal heart rate, elevating the risk of myocardial stress and ischemia, particularly in those with existing coronary disease.
Another key factor is reduced peripheral blood flow during heating, limiting heat loss through the skin. This is compounded by metabolic and vascular changes that alter heat storage within the body. Together, these changes mean that older bodies accumulate heat faster and experience greater cardiovascular strain during heat events than younger ones.
Environmental thresholds and prevention implications
Researchers have begun defining “critical environmental limits”—the temperature-humidity combinations that trigger rapid cardiovascular drift and strain. For older adults performing light daily tasks, cardiovascular strain can begin around 35°C with high humidity in warm-humid settings, or near 41°C in hot-dry environments. Notably, older women may reach these limits at lower thresholds than men, signaling a need for tailored public health guidance.
The concept of cardiovascular drift—an ongoing rise in heart rate during sustained heat exposure—offers a practical early-warning signal. Recognizing these thresholds could underpin early-warning systems, as well as policy measures such as heat alert programs, cooling centers, and guidance for safer daily activity during heat waves.
What is needed next: translating science into protection
The authors urge more ecologically valid studies that reflect real-world exposure, beyond laboratory heating suits, to better quantify risk and refine prevention strategies. They also emphasize translating findings into actionable guidelines for clinicians, caregivers, and communities to reduce heat-related cardiovascular events among older adults. Public health planning must increasingly incorporate the realities of aging populations facing hotter climates, ensuring infrastructure, social support, and clinical care are aligned to protect heart health in a warming world.
Conclusion: a mounting challenge with clear paths forward
Heat-related mortality and morbidity disproportionately affect older adults, with cardiovascular disease as a central driver. As climate change accelerates and aging populations grow, the convergence of these trends will shape global health for decades. While scientific work continues to pinpoint precise environmental triggers, immediate steps—early warnings, cooling access, targeted guidance for older adults, and cardiovascular-focused care during heat events—offer a practical path to reduce the burden on the world’s growing elderly population.
