Nonoptimal Temperature and Cardiovascular Health: A Scientific Statement From the American Heart Association

Ambient temperature is a key environmental driver of cardiovascular health. With rising global temperatures and increasing frequency, intensity, and duration of extreme temperature events, understanding the cardiovascular impacts of nonoptimal temperature is more urgent than ever. Short-term exposures to both heat and cold increase the risk of cardiovascular events, including myocardial infarction, stroke, heart failure decompensation, arrhythmias, and sudden cardiac death. Climate, built environment, socioeconomic variables, physiological vulnerability, and systemic inequities exacerbate these risks. There is also a growing appreciation of the importance of contextual factors such as geographic location, housing, occupation, and individual-level exposure. A range of biological mechanisms, including autonomic and neurohormonal activation, endothelial dysfunction, inflammation, hemoconcentration, and impaired thermoregulation, mediate temperature-related cardiovascular risk. Nonoptimal temperatures affect not only the incidence of cardiovascular disease but also health care access and delivery. They can increase demand for emergency care, disrupt operations, and pose challenges to the resilience and sustainability of health systems. Meanwhile, cardiovascular care contributes significantly to health care-related greenhouse gas emissions, highlighting a paradox in which efforts to protect cardiovascular health can indirectly contribute to climate-driven risks. This scientific statement synthesizes current knowledge of the relationship between nonoptimal temperature and cardiovascular health, highlights inequalities in exposure and outcomes, and identifies actionable strategies at the individual, community, health system, and public policy levels. Last, this scientific statement outlines significant research gaps and future priorities, including the need for improved exposure assessment, better understanding and measurement of the impact of long-term exposures, interactions with medications and coexposures, and identification of risk modifiers. Coordinated action is needed in research, clinical practice, and policy to mitigate the rising risks of nonoptimal temperatures on cardiovascular health in a changing climate.