A Longitudinal Study on the Impact of Indoor Temperature on Heat-Related Symptoms in Older Adults Living in Non–Air-Conditioned Households

Abstract

Background: Both chronic and acute heat result in a substantial health burden globally, causing particular concern for at-risk populations, such as older adults. Outdoor temperatures are often assessed as the exposure and are used for heat warning systems despite individuals spending most of their time indoors. Many studies use ecological designs, with death or hospitalizations rates. Individual-level outcomes that are directly related to heat-symptoms should also be considered to refine prevention efforts. Objectives: In this longitudinal study, we assessed the association between indoor temperature and proximal symptoms in individuals of age living in non–air-conditioned households in Montérégie, Quebec, during the 2017–2018 summer months. Methods: We gathered continuously measured indoor temperature and humidity from HOBO sensors and repeated health-related questionnaires about health-related symptoms administered across three periods of increasing outdoor temperatures, where the reference measurement (T1) occurred during a cool period with a target temperature of 18–22°C and two measurements (T2 and T3) occurred during warmer periods with target temperatures of 28–30°C and 30–33°C, respectively. We used generalized estimating equations with Poisson regression models and estimated risk ratios (RRs) between temperature, humidity, and each heat-related symptom. Results: Participants ( ) had an average age of . Higher indoor temperatures were associated with increased risk of dry mouth (T3 ; 95% CI: 1.8, 3.5), fatigue ( ; 95% CI: 1.8, 3.0), thirst ( ; 95% CI: 2.5, 4.5), less frequent urination ( ; 95% CI: 1.8, 7.3), and trouble sleeping ( ; 95% CI: 1.6, 3.2) compared with T1. We identified a nonlinear relationship with indoor temperatures across most symptoms of interest. Discussion: This study identified that increasing indoor temperatures were associated with various health symptoms. By considering the prevalence of these early stage outcomes and indoor temperature exposures, adaptation strategies may be improved to minimize the burden of heat among vulnerable communities. https://doi.org/10.1289/EHP10291

Effects of Daylong Exposure to Indoor Overheating on Thermal and Cardiovascular Strain in Older Adults: A Randomized Crossover Trial

“…This temperature was chosen based on indoor temperatures measured in the homes of older adults during hot summer days in Detroit. 20 It is also comparable to conditions measured in non-air-conditioned homes in Montérégie, Quebec, Canada (warm summer continental climate, Köppen Subtype Dfb, from Ottawa) 21 and in low-rent share housing (doss-houses) occupied by older adults in Seoul, South Korea (hot summer continental climate, Köppen subtype Dfw, from Ottawa). 34 36°C, 45% relative humidity (heat index: 41°C) to simulate peak indoor temperatures during extreme heat waves when ambient cooling (e.g., air conditioning) is unavailable or otherwise not used.…”

“…Consistent with these findings, Teyton et al. 21 reported progressive increases in the incidence of heat-related symptoms (e.g., thirst, reduced urine output, headache, nausea) with elevations in indoor ambient temperature in older persons living in Montérégie, Quebec, Canada (warm summer continental climate, Köppen Subtype Dfb, from Ottawa). These reports, when considered alongside the current data, support a 26°C indoor temperature limit for reducing physiological strain and discomfort and protecting health and well-being for individuals living in continental climates, 15 like those characterizing large areas of North America and Europe.…”

“…Supporting this postulate, we recently observed that although type 2 diabetes is associated with reduced heat loss during moderate exercise in the heat, 96 physiological responses did not differ between older adults with or without well-controlled type 2 diabetes during a resting 3-h exposure to 44°C and 35% relative humidity 97 conditions exceeding those measured indoors during heat waves. 20 , 21 , 34 Likewise, we recently showed no differences in body temperature 98 or cellular strain 99 between older adults with and without well-controlled type 2 diabetes and/or hypertension during 9-h of exposure to 40°C, 9% relative humidity. Furthermore, although maintaining high levels of aerobic fitness has been shown to prevent the age-related decline in thermoregulatory function during exercise heat-stress, these effects are considerably reduced at lower levels of heat stress like those that might be experienced by vulnerable groups indoors during hot weather.…”

“…10 , 11 To this end, recent work has evaluated associations between indoor temperature and heat-related symptoms (e.g., thirst, nausea) in community-living older adults. 21 However, subjective self-assessments underestimate heat strain in this population because of age-related declines in body temperature and thirst perception. 11 , 22 , 23 To support the development of evidence-based policy and guidance on safe indoor temperatures in continental climates, like those characterizing large swaths of North America and Europe, we conducted a laboratory-based randomized trial to quantify the effect of daylong indoor overheating on surrogate physiological outcomes linked with heat-related mortality and morbidity in older adults, including indices of thermal and cardiovascular strain, cardiac autonomic function, and dehydration.…”

Hot Instantaneous Temperature and Affect: Meaningful Activities as a Buffer for Older Adults With Low Socioeconomic Status

“…Due to declining physical health and thermoregulatory function, older adults are more susceptible to heat-related symptoms versus younger adults (e.g., heat syncope, heat cramps; Teyton et al, 2022 ). Research found that increased ambient temperature in Hong Kong from 2000 to 2016 was associated with higher risk of acute psychiatric disorder episodes in adults aged 65 years and older ( Qiu et al, 2022 ).…”