Is planned adaptation to heat reducing heat-related mortality and illness? A systematic review

Background: Extreme heat is an important public health risk. Climate change will likely increase the temperatures humans are exposed to through exacerbated heat wave intensity and frequency, possibly increasing health risks from heat. To prevent adverse effects on human health, heat prevention plans and climate change adaptation strategies are being implemented. But are these measures effectively reducing heat-related mortality and morbidity? This study assesses the evidence base in 2014. Methods: We conducted a systematic review of peer-reviewed published literature. We applied a combined search strategy of automated search and journal content search using the electronic databases PubMed, Web of Knowledge, Biological Abstracts, CAB Abstracts and ProQuest Dissertation & Theses A&I. Quality appraisal was conducted using CASP checklists, and we identified recurrent themes in studies with content analysis methodology. We conducted sub-group analyses for two types of studies: survey and interview research on behavioral change and perception, and observational studies with regression. Results: 30 articles were included in the review. The majority of studies (n = 17) assessed mortality or morbidity reductions with regression analysis. Overall, the assessments report a reduction of adverse effects during extreme heat in places where preventive measures have been implemented. Population perception and behavior change were assessed in five studies, none of which had carried out a pre-test. Two themes emerged from the review: methodological challenges are a major hindrance to rigorous evaluation, and what counts as proof of an effective reduction in adverse health outcomes is disputed. Conclusions: Attributing health outcomes to heat adaptation remains a challenge. Recent study designs are less rigorous due to difficulties assigning the counterfactual. While sensitivity to heat is decreasing, the examined studies provide inconclusive evidence on individual planned adaptation measures.