Heat Acclimatization among New Conscripts in Army Training Units in Bangkok, Thailand: A Prospective Cohort Study

Abstract

Heat-related illness (HRI) remains a major occupational health concern among new conscripts undergoing military training in tropical environments. This study aimed to evaluate heat acclimatization and its influencing factors among new military conscripts in Bangkok, Thailand. A prospective cohort study was conducted among 383 conscripts recruited from 11 randomly selected training units during November–December 2022. Eligible participants aged 21–29 years were classified by body mass index (BMI) and participation in the Health Promotion and Prevention Medicine (HPPM) exercise program, which incorporated aerobic and resistance training with progressive overload, structure rest, and supervision to enhance cardiovascular and thermoregulatory adaptation. Heat acclimatization was assessed using repeated measures of skin temperature, heart rate, and sweat response. Associations were analyzed using chi-square tests and multiple logistic regression. Overall, 18.5% of conscripts achieved full heat acclimatization by week 4. Participation in the HPPM program was associated with a higher rate of acclimatization in later training weeks (20.8% vs 17.1%). Higher BMI was negatively associated with acclimatization (AOR = 0.271, 95% CI: 0.102–0.719, p = 0.009), whereas higher knowledge levels (AOR = 4.054, p = 0.019) and strong peer support (AOR = 2.654, p = 0.006) significantly increased the likelihood of acclimatization. Environmental factors, including temperature and humidity, were also significant. In conclusion, heat acclimatization remains limited among new conscripts. The HPPM program shows beneficial effects, and targeted interventions for high-risk groups should be integrated into military training policies to reduce HRI risk and improve occupational health outcomes.