Longer-Term Outdoor Temperatures and Health Effects: A Review

Our goal was to assess current literature and knowledge on associations between characteristics (mean, variability, extremes) of ambient temperatures and human health. We were motivated by concerns that climate change, which operates on a time frame of decades or longer, may influence not only shorter-term associations between weather and health (daily/weekly) but also have enduring implications for population health. We reviewed papers published between 2010 and 2017 on the health effects of longer-term (3 weeks to years) exposures to ambient temperature. We sought to answer: 'What health outcomes have been associated with longer-term exposures?' We included studies on a diverse range of health outcomes, with the exception of vector borne diseases such as malaria. Longer-term exposures were considered to be exposures to annual and seasonal temperatures and temperature variability.

We found 26 papers meeting inclusion criteria, which addressed mortality, morbidity, respiratory disease, obesity, suicide, infectious diseases and allergies among various age groups. In general, most studies found associations between longer-term temperature metrics and health outcomes. Effects varied by population subgroup. For example, associations with suicide differed by sex and underlying chronic illness modified effects of heat on mortality among the elderly.

We found that regional and local temperatures, and changing conditions in weather due to climate change, were associated with a diversity of health outcomes through multiple mechanisms. Future research should focus on evidence for particular mechanistic pathways in order to inform adaptation responses to climate change.