An interventional study of Air Conditioner and Electricity subsidy in Hot Weather; Adverse Effect, Heat Effect and Heat Stress, sponsored by Harvard School of Public Health (HSPH). Recruiting at 1 site in United States. Open to participants aged 55 Years to 95 Years. Per ClinicalTrials.gov, last updated 2026-01-22.
Sponsored by Harvard School of Public Health (HSPH) · Not applicable, Interventional, and Prevention
The goal of this stepped wedge trial is to assess the practical effects of air conditioners on hot weather impacts among older adults. The main questions it aims to answer are:
How does the presence of an air conditioning unit affect heat stress, heat strain, mental health, and healthcare utilization among older adults who did not previously have access to air conditioning?
How, and in what conditioners, do older adults use air conditioning once it is installed in their home?
Researchers will compare participants in arms with (A) and without (B) air conditioning units in the first summer season; this will allow them to assess the effect of air conditioners. In the second summer season, both arms will have air conditioning units, but those in the year two distribution arm (B) will receive an electricity subsidy, while those in the year one AC distribution arm (A) will not, allowing researchers to assess the effect of an electricity subsidy.
Participants will be randomized to receive an air conditioner and financial support for electricity costs in either the first summer season or the second summer season of the study.
This community-based, randomized stepped wedge trial investigates whether the provision of educational resources and air conditioning (AC) improves thermal comfort and health outcomes among older adults with chronic disease and material hardships. The study will enroll 100 participants residing in at risk neighborhoods. Eligibility criteria include adults aged 55-95 who speak English or Spanish, lack access to home cooling systems, and have at least one qualifying chronic health condition or a history of recent hospitalization (see Eligibility section) .
Participants will be randomly assigned (1:1) to receive window AC units and an electricity cost subsidy either in Year 1 or Year 2. All participants in both arms will receive a baseline intervention including heat health educational materials and cooling kits. Data collection will occur over two warm seasons (April-September) and involve pre- and post-intervention assessments using structured surveys, real-time environmental monitoring, and AC usage tracking.
Surveys administered at enrollment and in late summer each year will capture a broad range of covariates including sociodemographic data, housing conditions, health service utilization, self-reported symptoms, and adaptive behaviors. Heat stress, heat strain, mental health, and healthcare utilization outcomes will be assessed via surveys that include previously validated survey instruments. Specific emphasis will be placed on measures of energy insecurity, such as utility shutoff notices, receipt of energy assistance, and trade-offs between essential expenses. Environmental sensors will log indoor temperature, humidity, and pollutant data throughout the study period.
The primary outcome is self-reported health status as measured by a modified ESQ-IV, supplemented by secondary metrics including ASHRAE thermal comfort scores, POMS, emergency department presentations, and hospitalizations. Statistical analysis will employ two-sample t-tests to detect treatment effects, with a minimum detectable effect size of 5.66 assuming a standard deviation of 10 and balanced sample sizes.
This study aims to empirically quantify the health benefits of cooling interventions in high-risk older adults and inform scalable public health strategies that address the intersecting challenges of urban heat, chronic disease management, and housing-related inequities.
21 studies on the registry are indexed under Heat Stroke; 10 are open to participants now.
This study's planned enrollment of 100 is above the median of 34 across 13 interventional studies indexed under Heat Stroke.
Browse Heat Stroke studies →Harvard School of Public Health (HSPH) is the lead sponsor of 154 studies on the registry; 10 are open to participants now.
Compared within Heat Stroke, this study's primary condition as ClinicalTrials.gg classifies it; the registry's first condition term is Heat Stress Disorders. The counts are of registry records indexed under each term, refreshed daily. How we classify →
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
- Lack a location in their home suitable for installation of the AC unit provided during the research study.
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Chronic obstructive pulmonary disease: long-term lung disease that makes it hard to breathe out, including emphysema and chronic bronchitis.
COPD
Chronic obstructive pulmonary disease: long-term lung disease that makes it hard to breathe out, including emphysema and chronic bronchitis.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Year 1: Participants receive a window AC unit and a financial subsidy for electricity. Year 2: Participants continue to have their AC unit, but do not receive a financial subsidy for electricity.
Other: Air Conditioner · Other: Electricity subsidy
Year 1: No intervention. Year 2: Participants receive an AC unit along with a financial subsidy for electricity.
Air conditioners will be window-mounted units powered by 110v AC.
Electricity subsidies will consist of a single block subsidy of USD 100, intended to provide support for the electricity costs associated with operating an air conditioning unit.
Environmental Symptoms Questionnaire (ESQ-IV)
The primary outcome will be a two-sample t-test for differences in means in the treatment and control groups in responses to the Environmental Symptoms Questionnaire (ESQ-IV). We will assess self-reported health impacts across all sites using a modified (truncated) version of the Environmental Symptoms Questionnaire (ESQ-IV), referred to as the Heat Stress Symptoms Questionnaire. Originally developed for assessing the health impacts of environmental exposures (Sampson et al, 1993), the ESQ-IV has been validated for assessing health impacts associated with heat illness in soldiers (Johnson \& Merullo, 1993). More recently, smaller subsets of the ESQ-IV's questions have served as a health endpoint for assessing the impacts of heat stress and acclimatization in the general population and older adults (McGarr et al, 2023; Manning et al, 2023). In an urban population, a question using similar language in a simplified format was used to assess prior experiences of heat-related illness (Card
Time frame: Difference in self-reported symptoms on HSSQ administered in the late summer season, 2-12 weeks after enrollment.
Air Conditioner Utilization
Air conditioner utilization will be prospectively assessed throughout the study. In year 1, air conditioner utilization will be analyzed in relation to indoor air temperature to identify threshold temperatures that trigger AC utilization. In Year 2, utilization rates and thresholds will be compared between the the two arms to assess the impact of electricity subsidies on AC utilization.
Time frame: From enrollment to study completion, approximately 2 years.
Plan to share: Yes — Non-identifiable study dataset, specifically data on treatment arm assignment and survey results including primary endpoint
Supporting information: Study protocol, Statistical analysis plan, Informed consent form
Time frame: Data will be made available at the time of publication of study results.
Access criteria: Data will be available upon reasonable request.
No publications or documents are linked to this record.
Started May 2025 (actual). Primary completion is estimated for Oct 2026, 16 months after the start.
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