Ambient Outdoor Heat and Heat-related Illness in Florida

Environmental heat stress results in adverse health outcomes and lasting physiological damage. These outcomes are highly preventable via behavioral modification and community-level adaption. For prevention, a full understanding of the relationship between heat and heat-related outcomes is necessary. The study goals were to highlight the burden of heat-related illness (HRI) within Florida, model the relationship between outdoor heat and HRI morbidity/mortality, and to identify community-level factors which may increase a population’s vulnerability to increasing heat. The heat-HRI relationship was examined from three perspectives: daily outdoor heat, heat waves, and assessment of the additional impact of heat waves after accounting for daily outdoor heat. The study was conducted among all Florida residents for May-October, 2005–2012. The exposures of interest were maximum daily heat index and temperature from Florida weather stations. The outcome was work-related and non-work-related HRI emergency department visits, hospitalizations, and deaths. A generalized linear model (GLM) with an overdispersed Poisson distribution was used. GLMs were run for each sub-region within Florida and statewide estimates were obtained via random effects meta-regression. The results of the burden analysis indicated that the rates of HRI varied by geography, data source, and work-related status. The sub-groups with the highest relative rates were for males and rural residents. HRI rates increased with increasing heat index/temperature. The strongest effect was associated with the current day’s heat index/temperature. As heat index/temperature increased, at higher heat index/temperature values, there appeared to be some heat adaptation. For a Florida specific heat wave definition, duration should be two days or more above an intensity threshold which is defined by a constant value for heat index or an area varying relative value. Focus on heat waves is not appropriate for Florida. Community-level factors which may identify vulnerable Florida populations include populations with a high proportion of: impervious surfaces, renters, or individuals reporting Black race alone. This is the first study to explore the heat-HRI relationship stratified by work-related status and is the first to fully evaluate the heat-HRI relationship in Florida. This study highlights the importance of studying and mitigating the effects of heat in a humid sub-tropical climate.Doctor of Philosoph