Mixed methods assessment of personal heat exposure, sleep, physical activity, and heat adaptation strategies among urban residents in the Boston area, MA

Abstract

The growing frequency, intensity, and duration of extreme heat events necessitates interventions to reduce heat exposures. Local opportunities for heat adaptation may be optimally identified through collection of both quantitative exposure metrics and qualitative data on perceptions of heat. In this study, we used mixed methods to characterize heat exposure among urban residents in the area of Boston, Massachusetts, US, in summer 2020. Repeated interviews of N = 24 study participants ascertained heat vulnerability and adaptation strategies. Participants also used low-cost sensors to collect temperature, location, sleep, and physical activity data. We saw significant differences across temperature metrics: median personal temperature exposures were 3.9 °C higher than median ambient weather station temperatures. Existing air conditioning (AC) units did not adequately control indoor temperatures to desired thermostat levels: even with AC use, indoor maximum temperatures increased by 0.24 °C per °C of maximum outdoor temperature. Sleep duration was not associated with indoor or outdoor temperature. On warmer days, we observed a range of changes in time-at-home, expected given our small study size. Interview results further indicated opportunities for heat adaptation interventions including AC upgrades, hydration education campaigns, and amelioration of energy costs during high heat periods. Our mixed methods design informs heat adaptation interventions tailored to the challenges faced by residents in the study area. The strength of our community-academic partnership was a large part of the success of the mixed methods approach.

A systematic review of ambient heat and sleep in a warming climate

“…64,79 Among the five remaining studies: (i) two observed a positive effect of temperature on sleep, with one study performed in China reporting a positive association between temperature and self-reported sleep duration, 68 another, performed in Brazil, showing that apnea-hypopnea index was inversely correlated with ambient temperature; 77 (ii) two other studies were not explicit in their conclusion about this specific temperature-sleep association, with one not observing a significant association between temperature and sleep duration (but delayed sleep timing), 62 and another observing a significant association between temperature and the number of awakenings but focusing on sleep adaptation in expatriates (not the impact of heat); 61 and (iii) one study showing a nonsignificant association (neither positive nor negative) between indoor temperature and sleep duration. 75 In regards to sleep apnea specifically, the abovementioned result 77 contradicts two other studies included in the present review showing a significant and positive association between temperature and apnea-hypopnea indexes; 76,78 while a fourth study did not observe significant relationships between temperature (indoor) and apnea-hypopnea indexes. 69 Results are less contrasted with other sleep outcomes and assessment methods.…”

“…One study measured and reported results for both indoor (via local sensor) and outdoor (via weather station) temperature outcomes (see Table 2). 66 Sleep measures showed a greater diversity of assessment methods with ten articles using self-reported questionnaires or diaries, 33, 34, 64–71 eight studies using commercial activity monitors, 24, 62, 63, 71–75 five studies using polysomnography 61, 69, 76–78 , four studies using research-grade accelerometers 64, 79–81 and three studies using specific sleep sensors 60, 82, 83 . Beyond assessment methods, 15 articles used daily (24-hour) aggregated measures of temperature, the remaining 12 articles focused on average nighttime temperature (see Table 3, column “sample period”).…”

“…For example, the four studies using research-grade accelerometers 64,[79][80][81] all found that higher temperature was associated with poorer sleep (i.e., notably reduced sleep duration and sleep efficiency, as well as increased WASO). In the same vein, four of the six studies using commercial-grade activity monitors found negative associations between ambient temperature and sleep duration, 24,63,71 efficiency 71,73 (but see 74,75 for a non-significant association), WASO and REM sleep, 71 nighttime body-movements 72 and slow wave sleep. 74 Eight studies using questionnaires reported that higher temperature was associated with poorer subjective sleep.…”

“…2). 66 Sleep measures showed a greater diversity of assessment methods with ten articles using self-reported questionnaires or diaries, 33,34,[64][65][66][67][68][69][70][71] eight studies using commercial activity monitors, 24,62,63,[71][72][73][74][75] five studies using polysomnography 61,69,[76][77][78] , four studies using researchgrade accelerometers 64,[79][80][81] and three studies using specific sleep sensors 60,82,83 Figure 3 illustrates the range of observed ambient temperatures and latitudes for each of the studies in this review. Aggregating these ranges suggests a greater observational density for hotter compared to colder temperatures (bottom heat bar, Figure 3A) and for northern latitudes compared to both the equatorial region and the southern hemisphere (right heat bar, Figure 3B).…”

A Mixed-Methods Approach for Evaluating the Influence of Residential Practices for Thermal Comfort on Electricity Consumption in Auroville, India

“…Milando et al adopted a mixedmethod approach to monitoring (temperature, location, sleep, and physical activity data with low-cost sensors) and interviewed urban residents in the Boston area, Massachusetts, US. They examined personal heat exposure, sleep, physical activity, and heat adaptation strategies to evaluate heat adaptation interventions tailored to their challenges [15]. In the context of a university campus, Eslamirad et al used mixed methods to explore improving the quality of cities by considering the relationship between microclimatic conditions, thermal sensation, and human preferences [16].…”