Extreme heat poses significant hazards for older individuals, increasing their vulnerability to heatstroke and mortality. Recent research suggests that elevated temperatures may also influence DNA functioning, potentially accelerating the aging process itself.
A groundbreaking study published in Science Advances explored this concept by analyzing data from over 3,600 older adults across the United States. The researchers discovered that individuals residing in neighborhoods frequently experiencing extreme heat—defined as temperatures of 90 degrees Fahrenheit or above—exhibited more rapid biological aging at a molecular level compared to those living in areas with fewer instances of extreme heat.
The implications are profound, linking heat waves exacerbated by climate change to chemical modifications in DNA that could hasten biological aging. The researchers estimate that individuals in regions where temperatures soar to 90 degrees or higher for 140 days or more annually may age approximately 14 months quicker than peers in locales with fewer than 10 days of extreme heat each year.
The study utilized three aging biomarkers known as epigenetic clocks, derived from blood samples of individuals aged 56 and older involved in a national population study. Researchers correlated these biomarker age estimates with six years of daily climate data across different geographical locations. These epigenetic clocks serve as measures of biological changes that can predict future risks of disease or mortality linked to advanced age. According to Eun Young Choi, a postdoctoral associate at USC Leonard Davis School of Gerontology and co-author of the study, while DNA remains constant since birth, external influences like stress and pollution can instigate molecular changes, activating or deactivating genes and modifying their functionality. Choi likened DNA to a blueprint and epigenetic modifications to a switchboard controlling which aspects of that blueprint become active.
This research represents the first population-scale analysis linking heat exposure to epigenetic aging in humans, building upon earlier studies that indicated similar changes in species such as fish, mice, and guinea pigs. Health expert Nancy Krieger from Harvard T.H. Chan School of Public Health noted that this research provides valuable insights into geographical health discrepancies.
However, the study does not establish causation; it indicates a correlation between heat exposure and accelerated aging. The researchers highlighted that additional factors may contribute, as the analysis lacked lifestyle variables like air conditioning access or time spent indoors.
Some scientists remain skeptical about the efficacy of epigenetic clocks as definitive aging measures, as noted by Rachel Morello-Frosch from UC Berkeley. The ongoing research in this area raises questions about biomarkers and their predictive capabilities regarding future health outcomes.
Furthermore, not all epigenetic changes are negative. The study does not clarify if these changes might reflect adaptive responses to heat, such as increased indoor activity. Environmental epidemiologist Greg Wellenius emphasized that demonstrating cellular-level changes is an essential step toward understanding heat’s impact on health.
Significant questions remain: What roles do air conditioning and other interventions play in epigenetic aging? Can short-term exposure to extreme heat have lasting effects? Can relocating from hot areas reverse aging? Jennifer Ailshire from USC Leonard Davis highlighted the necessity for longitudinal data to comprehensively understand these dynamics.
This study lays the groundwork for future investigations into interventions, such as increased access to air conditioning and shady environments, potentially mitigating heat-related aging effects. Mariana Arcaya from MIT pointed out the prevailing focus on emergency medical interventions for heat survival, underlining that this research highlights potential long-term health effects from heat, even in those who do not face immediate medical crises. —NYT
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