A groundbreaking study by the University of Southern California has found that prolonged exposure to extreme heat may silently accelerate cellular aging. Unlike visible signs such as wrinkles or grey hair, this hidden biological ageing affects the molecular systems that maintain cell health, increasing vulnerability to chronic diseases, declining organ function, and premature physical deterioration. The research indicates that heat is more than a short-term environmental nuisance; it can have lasting effects on the body’s internal systems. Individuals living in hotter climates may therefore experience faster internal ageing, even if they appear healthy externally. These findings highlight the critical role of temperature in influencing long-term human health at a microscopic scale.
Heat risk in popular US retirement states linked to accelerated aging
In recent years, many Americans have relocated to states such as Florida, Texas, and North Carolina, drawn by attractive tax policies and warm climates. These areas have become popular retirement destinations. However, according to the study, these regions are now emerging as “danger zones” for heat-induced biological wear and tear. Long-term residents in these areas may experience faster internal ageing due to consistent exposure to high temperatures, even if they feel healthy on the surface. Dr Eun Young Choi and her team analysed data from 3,686 Americans aged 56 and older, collected between 2010 and 2016. Their research, published in Science Advances, demonstrated a clear correlation between ambient temperature and accelerated biological ageing.The hotter the state, the faster residents age at the cellular level. Dr Choi explained that while the study does not yet offer the same causal certainty as research on smoking or alcohol, it highlights that chronic heat exposure is a serious, long-term health risk.
Understanding biological aging and its impact on health
Biological aging is distinct from chronological age. While chronological age simply counts the years a person has lived, biological aging measures how well the body functions on a cellular and molecular level. It indicates susceptibility to disease, organ function efficiency, and overall vitality.The USC study used three advanced ageing clocks: PCPhenoAge, PCGrimAge, and DunedinPACE to quantify biological ageing. PCPhenoAge predicts future health deterioration, PCGrimAge estimates mortality risk, and DunedinPACE tracks the pace of cellular decay in real time. Individuals experiencing more than 140 days of extreme heat in a single year showed biological ages up to 14 months older than their actual age. Over the six-year study period, residents in “extreme caution” zones with temperatures ranging from 90°F to 103°F exhibited an average accelerated ageing of 2.88 years.
Extreme heat increases cardiovascular and cognitive disease risk
Accelerated biological ageing is not just a numerical concept but it has tangible health consequences. Dr Choi noted that cumulative cellular stress increases the likelihood of cardiovascular disease, metabolic disorders, cognitive decline, and early mortality. This makes sustained exposure to high temperatures a public health concern, particularly for older adults and individuals with pre-existing conditions.While extreme heat impacts were observed across the United States, southern states bore the greatest burden. Residents of Louisiana and Mississippi endured conditions equivalent to over three years of accelerated biological aging, with temperatures reaching 103°F to 124°F. Texas, Alabama, and Arkansas also faced significant risks, demonstrating how climate extremes are unevenly distributed geographically.
How personal habits and access to cooling affect cellular aging
Dr Choi emphasised that heat exposure is influenced not only by geography but also by lifestyle and infrastructure. Access to air conditioning, cooling centres, shaded areas, and indoor environments plays a crucial role in mitigating risk. She explained that two individuals living on the same street could have vastly different experiences depending on whether they work outdoors or have reliable cooling access. Therefore, personal and community-level strategies are essential for protection.Interestingly, Dr Choi noted that not all heat exposure is harmful. Controlled short-term exposure, such as using a sauna or taking hot showers, may offer cardiovascular benefits and improve circulation. The key difference is duration and intensity—sustained exposure to extreme temperatures is what accelerates cellular ageing, while brief, intentional heat stress can be therapeutic.For individuals living in warm climates or heat-prone regions, Dr Choi advises proactive measures: stay hydrated, seek shade, use air-conditioned spaces when possible, and minimise prolonged outdoor exposure. Older adults and people with underlying health conditions should be particularly cautious. The study underscores the importance of recognising heat not just as discomfort, but as a factor influencing long-term biological health.
