Evaluating the effectiveness of heat warning systems: systematic review of epidemiological evidence

Objectives: To review the existing research on the effectiveness of heat warning systems (HWSs) in saving lives and reducing harm. Methods: A systematic search of major databases was conducted, using "heat, heatwave, high temperature, hot temperature, OR hot climate" AND "warning system". Results: Fifteen articles were retrieved. Six studies asserted that fewer people died of excessive heat after HWS implementation. HWS was associated with reduction in ambulance use. One study estimated the benefits of HWS to be 468millionforsaving117livescomparedto210,000 costs of running the system. Eight studies showed that mere availability of HWS did not lead to behavioral changes. Perceived threat of heat dangers to self/others was the main factor related to heeding warnings and taking proper actions. However, costs and barriers associated with taking protective actions, such as costs of running air conditioners, were of significant concern particularly to the poor. Conclusions: Research in this area is limited. Prospective designs applying health behavior theories should establish whether HWS can produce the health benefits they are purported to achieve by identifying the target vulnerable groups