Residential indoor temperatures and health: A scoping review of observational studies.

Adults spend most of their time indoors, especially in higher income countries. Indoor temperature exposures can vary substantially across households, even within a single geographic area. It is therefore critical to understand links between indoor temperature exposures and health or well-being outcomes, and to understand safe maximum indoor residential temperature thresholds that support health, well-being, and comfort. We systematically identified peer-reviewed, observational studies that quantified associations between residential indoor temperatures and mortality/morbidity outcomes. We extracted information on study location; population, health or well-being outcomes; indoor temperature exposure assessment methods; and, when available, empirically quantified safe maximum indoor temperature thresholds. In total, 29 papers were included in the review. The studies were conducted in the following continents: North America (N = 10), Europe (N = 5), Asia (N = 9), Australia (N = 4), and Africa (N = 1). The most common outcomes were cardiovascular morbidity (N = 10) and respiratory morbidity (N = 8) and thermal comfort (N = 9). Exposure assessment methods included data sensors, thermometers, data-driven models, and energy-based simulations. Despite variation in exposure assessment methods and outcomes assessed, results predominately suggested that warmer indoor temperatures were associated with adverse health or well-being outcomes, although in a handful of studies, associations were either null or in the unexpected, protective direction. Empirically identified safe thresholds for indoor temperature ranged from 18 °C to 35 °C and varied according to outcome. Results from this review may be used to inform the design of future studies of associations between indoor temperatures and morbidity or mortality outcomes.