Developing a heat health warning system for Thailand : an investigation into the associations between climatic variables and heat-related illnesses with stakeholder consensus exercises

Abstract

Introduction: The earth’s climate is changing in ways that could have serious consequences for public health. For example, heat-related illnesses (HRIs) are increasing yearly. Many countries have developed heat health warning systems (HHWSs) to protect people from the adverse effects of heat and reduce the incidence of HRIs. In Thailand, a HHWS has not yet been established. As a result, the aims of this work were to explore the nature of HRIs in Thailand, examine any associations between heat index and heat-related hospitalisations within the general Thai population, and to develop a structure for a HHWS model in Thailand based on the results of statistical analyses and experts’ opinion. Methods: This study was divided into three phases using a mixed methods approach. In phase 1, a daily tally of HRI hospitalisations from the International Classification of Diseases 10 Revision (ICD10) database with diagnosis T67 (effects of heat and light) were obtained between January 2010 and December 2014 from the Bureau of Policy and Strategy, Department of Disease Control, Ministry of Public Health, Thailand. Daily temperature and humidity figures from the same period were obtained from the Meteorological Department, Ministry of Digital Economy and Society. The heat index was calculated according to the Steadman equation. Time series and Poisson regression analysis were used to explore the relationship between HRIs and the heat index controlling for day of the week and holiday indicator, with lag times of 0–7 days. Relative Risk (RR) and 95% confidence intervals were calculated based on a Poisson model from each region of Thailand. Next, a consensus exercise was conducted to establish the key components of a HHWS in Thailand. This included an e-Delphi exercise with 16 experts in climate research (phase 2) and a focus group with key stakeholders and policy makers (phase 3). Results: The relative risks at the 75th percentile of the heat index at a lag 0 (on the same day as exposed to heat compare to non-exposed to heat) of Southern, Northern, Central and Northeast regions were 5.56 (95% CI = 1.62 – 19.04), 21.76 (95% CI = iii 11.33 – 41.81), 79.59 (95% CI = 33.76 – 187.64), and 39.75 (95% CI = 21.66 – 72.94), respectively. The threshold levels for a HHWS in each region were divided into three levels: pre-alert, higher alert and highest alert. Based on expert opinion, the pre-alert level is the level of the heat index below the 75th percentile (< 92 ºF (33.3°C), < 90 ºF(32.2°C), < 94 ºF (34.4°C)< 90 ºF(32.2°C) in the north-eastern, northern, central and southern regions, respectively). The higher level is the level of the heat index from the 75th percentile to the 90th percentile (92 ºF - 95 ºF (33.3 °C - 35°C), 90 ºF-94 ºF (32.2 °C-34.4°C), 94 ºF - 98ºF (34.4°C – 36.7°C), 90 ºF-92 ºF (32.2°C – 33.3°C) in the north-eastern, northern, central and southern regions, respectively). Lastly, the highest level is the level of the heat index from the 90th percentile (>95 ºF (35°C), >94 ºF (34.4°C), >98 ºF (36.7°C), >92 ºF (33.3°C) in the north-eastern, northern, central and southern regions, respectively). All thresholds were applied depending on the relationship between HRIs and the heat index in each region of Thailand. These threshold levels were in the first of four components of a HHWS for Thailand, on which consensus was sought with policy makers and stakeholders. Additional components identified in the consensus exercise related to methods of communication of health warnings and individual and community level interventions to mitigate the effects of heat on health. Conclusion: This study found the heat index had positive associations with HRI hospitalisations. Moreover, the suitable warning threshold levels for a HHWS in Thailand varied according to region. Importantly, the results of this study support the view that Thailand should have a bespoke HHWS which is different from those operated elsewhere. The threshold of warning levels and interventions to protect from heat hazards must be explored in each country to ensure success and effectiveness.