Extreme Heat Tied to Higher Dementia Risk in Adults Aged 50+

TOPLINEOlder adults exposed to a heat index (HI) of at least 103 °F (39.4 °C) for even a few days a year had a higher incidence of dementia over up to 20 years of follow-up, a study showed. The association was strongest among residents of socioeconomically disadvantaged neighborhoods and areas with low prevalence of central air conditioning (AC), suggesting that structural barriers to heat mitigation may be linked to dementia risk.METHODOLOGYResearchers analyzed data from the Health and Retirement Study, a nationally representative cohort of US adults aged 50 years or older, followed every 2 years from 2000 to 2020.A total of 28,512 community-dwelling, dementia-free participants (weighted mean age at baseline, 59.8 years; 52.5% women; 76.6% non-Hispanic White individuals) were included. The unweighted average follow-up period was 10.5 years.Outdoor heat exposure was assessed using census-tract-level daily HI estimates, categorized into 'extreme caution' (90 °F to 102 °F [32.2 °C to 39.3 °C]) and 'danger+' (≥ 103 °F [39.4 °C]) levels, with cumulative exposure calculated over a 5-year window preceding each follow-up wave.Incident dementia was assessed using the validated Langa-Weir algorithm.Death was assessed as a competing event. The analysis was adjusted for sociodemographic factors, health conditions, behavioral factors, US Census region, calendar year, and census-tract-level social vulnerability and AC prevalence.TAKEAWAYCompared with individuals with low exposure (≤ 0.2 days per year) to 'danger+' heat, a higher risk for dementia was observed in those with moderate exposure (0.4-1.8 days per year; subdistribution hazard ratio [SHR], 1.14; 95% CI, 1.01-1.27) and high exposure (≥ 7.2 days per year; SHR, 1.23; 95% CI, 1.08-1.40). The association for moderate-high exposure (2-7 days per year) was not significant.No statistically significant associations were observed between exposure to 'extreme caution' heat and incidence of dementia, suggesting a potential threshold effect at more extreme temperatures. Neither heat category was associated with mortality.Among residents of high social vulnerability neighborhoods, high 'danger+' heat exposure was associated with a higher dementia risk than among residents of low-vulnerability areas (predicted SHRs, 1.40 vs 1.11; pairwise contrast P = .004). Differences were not significant at lower exposure levels.In areas with low central AC prevalence, high exposure to 'danger+' heat was associated with a higher dementia risk than in areas with high AC prevalence (predicted SHRs, 1.36 vs 1.13; pairwise contrast P = .026). Differences were not significant at lower exposure levels.IN PRACTICE"This suggests that dementia prevention strategies should consider local heat burden and prioritize reducing cumulative thermal stress," the investigators wrote."Priority should be given to identifying populations facing socioeconomic and infrastructural constraints that may benefit most from targeted heat-mitigation resources and support," they added.SOURCEThe study was led by Eun Young Choi, PhD, School of Social Work, Arizona State University, Phoenix, Arizona. It was published online on October 22 in Alzheimer's & Dementia.LIMITATIONSOutdoor temperature was estimated at the census-tract level and may not have reflected personal exposure or indoor thermal environments. Tract-level AC prevalence data were available only for 2016 and applied to all years, and data on dementia subtypes were unavailable. Dementia status was derived from a survey-based algorithm, potentially leading to misclassification of some individuals. Additional limitations included residual confounding, potential reverse causation, lack of examination of genetic susceptibility to cognitive decline, and lack of evaluation of long-term exposures.DISCLOSURESThe study was funded by the National Institutes of Health National Institute on Aging and the Alzheimer's Association. The authors reported no relevant conflicts of interest.This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.