Abstract
Cases of exertional heat stroke have been reported every year during basic training for Royal Thai Army (RTA) conscripts. Prevention is an important strategy to reduce the incidence of heat-related illnesses. We conducted a study to identify potential indicators for the prevention and monitoring of heat-related illnesses among military conscripts undergoing basic training in Thailand. All newly inducted RTA conscripts in 5 basic training units in 5 regions in Thailand were invited to participate in a prospective cohort study from May 1 to July 9, 2013. The incidence rate of heat-related illnesses and the incidence rate ratio (IRR) based on a Poisson regression model were used to identify the independent factors associated with heat-related illnesses, daily tympanic (body) temperatures higher than 37.5°C, >3% decreases in body weight in one day, and the production of dark brown urine. Eight hundred and nine men aged 21.4 (±1.13) years were enrolled in this study. The prevalence of a body mass index (BMI) ≥30 kg/m2 was 5.5%. During the study period, 53 subjects (6.6%) representing 3.41/100 person-months (95% confidence interval (CI), 2.55–4.23) developed heat-related illnesses (excluding heat rash), and no subjects experienced heat stroke. The incidence rates of a daily tympanic temperature >37.5°C at least once, body weight loss of >3% per day, and the production of dark brown urine at least once were 8.27/100 person-months (95% CI, 7.69–8.93), 47.91/100 person-months (95% CI, 44.22–51.58), and 682.11/100 person-months (95% CI, 635.49–728.52), respectively. The sole identified independent factor related to the incidence of heat-related illnesses was a BMI ≥30 kg/m2 (adjusted IRR = 2.66, 95% CI, 1.01–7.03). In conclusion, a high BMI was associated with heat-related illnesses among conscripts undergoing basic training in Thailand. Daily monitoring of heat-related illnesses, body temperature, body weight and urine color in each new conscript during basic military training was feasible.
Highlights
Heat-related illnesses, including heat stroke, are major public health problems that have particular relevance to military operations
Prior to 2012, the Royal Thai Army (RTA) implemented a heat-related illness prevention program during basic training, using the environmental temperature and humidity to guide the duration of training and rest periods and the amount of water consumption recommended during each hour of training
In terms of occupation prior to entering the RTA, the majority (58.2%) of the participants reported a work history consisting of indoor activities, whereas 41.8% of the participants had worked in professions based on outdoor activities
Summary
Heat-related illnesses, including heat stroke, are major public health problems that have particular relevance to military operations. Heat-related illnesses comprise a group of symptoms that occur in response to heat accumulation in the body caused by exercise or work in a hot and humid environment for a long period of time until the body is unable to regulate its temperature. Military conscripts and athletes in training who have not undergone heat acclimatization are at risk for heat-related illness [6]. Risk factors for heat-related illness include both personal and environmental variables [2,7,8]. Personal factors include physical condition, ethnicity, genetics and behavior; because personal factors differ among individuals, people who are in the same environment can experience the effects of heat-related illnesses differently [15,16]. Studies in athletes have found that risk factors for heat-related illness comprise external factors, including the temperature, humidity, level of activity and clothing worn, in addition to internal factors, including age at first alcohol use, dehydration, obesity, current illness, history of heat-related illness, medication, inadequate heat acclimatization and insufficient rest and sleep at night [15,17,18,19,20,21]
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