Rising Temperatures, Rapid Aging: How Ambient Heat Affects DNA in Seniors

Extreme heat events are becoming more frequent due to global warming and pose severe health risks to senior citizens. Research indicates that heat-related effects will impact more than 100 million Americans before the year 2050 and will increase hospital admissions alongside cardiovascular diseases and death rates. Medical research recognizes the health effects of the phenomenon, but the biological mechanisms underlying these effects remain unclear. 

The effects of heat stress is linked to subclinical age-related deterioration. Results from animal research suggest that epigenetic changes mainly through DNA methylation influence the process. Scientific studies showed heat exposure leads to persistent heart tissue and immune system alterations in various animal populations including mice. However, research on human populations remains limited. 

Research from Germany and Taiwan describes connections between temperature rises and faster epigenetic aging but does not address broader applicability. Research using a representative sample of American older adults investigates short- and long-term heat effects while examining population demographic characteristics. 

Research participants averaged 68.6 years in age while comprising 54% female participants. A total of 78% belong to the non-Hispanic white group while the sample includes 10% non-Hispanic Black participants alongside 3.4% representing other races combined with 8.6% identifying as Hispanic. Older U.S. adults have an average education of 13.3 years while their household wealth measures at $169,670. The participants exhibited three health behaviors such as 35.7% obesity, 11% smoking and 43.7% alcohol consumption. Physical activity rates for participants fall at 61.8% sufficient. Participants live in urban 49.9% and suburban 24% and ex-urban 26.1% locations of which the social vulnerability score average stands at 0.48. 

Heat exposure rates in the United States showed regional patterns between 2010 and 2016 with peak exposure occurring in the southern parts of the country. The research data showed no instances of extreme danger-level heat days. On the BC day, 42.6% experienced caution+ heat, 18.6% extreme caution+, and 2% danger+. The study participants experienced 126.8 caution+ heat days on average throughout a year and also encountered 53.8 extreme caution+ days together with 6.1 danger+ days. The population segment of older adults, women, individuals who consumed alcohol infrequently, those of lower socioeconomic status and non-Hispanic Black participants experienced greater heat exposure than other groups. 

This research evaluated HRS 2016 Venous Blood Study (VBS) DNAm subsample data (N = 3,875) to assess the impact of heat exposure on epigenetic aging in older U.S. adults. Data from gridMet provided heat index (HI) estimates at the census tract scale which researchers used to connect with participants through address geocoding procedures. Analysis included only participants with complete data results in 3,686 cases. The heat exposure assessment included three risk levels labeled as caution, extreme caution and danger that examined different time periods from daily to 7-day and 1-year and 6-year duration. The analysis examined epigenetic aging through PhenoAge, GrimAge and DunedinPACE DNAm clocks after controlling for demographic variables and health behaviors and area-level characteristics. Researchers analyzed short-term and long-term heat exposure effects through relocation adjustments while performing individual and environmental factors control. 

The research examines epigenetic aging effects caused by short-term and mid-term and long-term heat exposure among nationally representative U.S. adults aged over 65. A detailed analysis which combined daily climate data with participant blood collection dates allowed researchers to establish that prolonged heat exposure (terminating 1 year to 6 years) rapidly advances epigenetic aging using measurement methods. A direct correlation emerged between short- and mid-term heat exposure leading to PCPhenoAge acceleration suggesting that immediate physiological stress affects participants. 

The study results verify existing research that demonstrates how heat exposure extends to modify DNA methylation and immune system performance which produces aging impacts throughout the body. The analysis of different epigenetic clocks indicates PCPhenoAge shows better sensitivity to heat exposure by measuring a wider range of biological aging changes, but the GrimAge and DunedinPACE clocks provide information about accumulated physiological problems. 

This study builds on previous findings through its utilization of detailed climate data in census tracts together with analysis of residential shift patterns. This study has certain limitations such as missing repeated epigenetic data and uncontrolled confounding factors and the lack of consideration for individual air-conditioning utilization.  

References: Choi EY, Ailshire JA. Ambient outdoor heat and accelerated epigenetic aging among older adults in the US. Sci Adv. 2025;11:eadr0616. doi:10.1126/sciadv.adr0616