Effect of Previous Night Alcohol on Thermoregulatory and Physiological Strain During Prolonged Physical Work in the Heat

Many occupational workers engage in strenuous physical work in hot environments for prolonged periods, placing them at risk of heat-related illness due to increasing physiological strain identified by increasing core temperature (Tcore) and heart rate (HR). Lifestyle behaviors, such as smoking, caffeine and alcohol consumption, and sleep deprivation, may further exacerbate heat strain and increase susceptibility to heat-related illness. Notably, alcohol consumption the night before work, and the subsequent hangover, may amplify physiological strain by impairing heat dissipation. However, no previous studies have evaluated the impact of alcohol hangover on heat strain during physical work in the heat. PURPOSE: To investigate whether previous night alcohol consumption (ALC) would increase heat strain during prolonged physical work in the heat during the next day. METHODS: 12 participants (7 female) completed four visits in a randomized, counterbalanced, crossover design. Trials consisted of four hrs (simulating half a workday) of treadmill walking in a heated chamber (dry bulb temperature: 38 °C, relative humidity: 40%), with 10 min rest each hour, after a night of alcohol consumption (blood alcohol content ≥0.11) or 48 hr of no alcohol. HR, Tcore, and 4-site skin temperature (Tskin) were recorded every 10 min. Blood pressure (BP) was measured during the second and final rest period. Urine was collected before, after, and one hour post-trial. RESULTS: Average Tcore was 0.2 °C higher in ALC (p = 0.02), although peak Tcore was not different (p = 0.18). Tskin was higher in ALC (p = 0.003), with peak Tskin being 0.3 ± 0.4 °C higher on average (p = 0.02). HR was higher during ALC, with no difference in peak HR (p = 0.23). Mean arterial BP was on average 2 mmHg higher (p = 0.01) in ALC. Sweat rate (SR) was lower in ALC (p = 0.05). Urine specific gravity (USG) was higher in ALC (p = 0.001), and urine flow rate (UFR) was lower (p = 0.005). CONCLUSION: Previous night alcohol consumption increases both physiological (BP, HR) and thermoregulatory strain (Tcore, Tskin, SR, USG, and UFR) during prolonged physical work in the heat. These findings suggest that previous night alcohol impairs heat dissipation, such as evaporative cooling, and exacerbates heat strain, potentially elevating risk for heat-related illness in occupational settings.