Seasonal influence on cognitive and psycho-physiological responses to a single 11-h day of work in outdoor mine industry workers

Abstract

ABSTRACT This study investigated the seasonal effects that working outdoors had on various parameters in mining industry workers over the course of a work-shift. Workers (n = 27) were assessed in summer (33.3 ± 4.2°C, 38 ± 18% RH; n = 13, age = 46 ± 14 y, BMI = 29.1 ± 5.7 kg/m2) and winter (23.6 ± 5.1°C, 39 ± 20% RH; n = 14, age = 44 ± 12 y, BMI = 31.2 ± 4.1 kg/m2). Core temperature and heart-rate were measured continuously (analyzed at five time points), while perceptual measures, cognitive and manual dexterity performance were assessed at various times over an 11-h shift at the start of a 14-day swing. Hydration was assessed (urine specific gravity) pre- and post-shift. Working memory was impaired in summer compared to winter (−10%; p = 0.039), however did not change throughout the shift. Processing efficiency was significantly reduced at 12 pm (−12%; p = 0.005) and 5 pm (−21%; p < 0.001) compared to 9 am, irrespective of season (p > 0.05). Manual dexterity (dominant-hand) improved over the shift (+13%, p = 0.002), but was not different between seasons. Perceived fatigue had no main effect of season or shift. Core temperature, heart-rate, thermal sensation and rating of perceived exertion increased throughout the shift, with only core temperature and thermal sensation showing a seasonal effect (summer: +0.33°C, +18%, respectively; p < 0.002). Notably, 23% of workers in summer and 64% in winter started work significantly dehydrated, with 54% and 64% in summer and winter, respectively, finishing work with significant to serious dehydration. Impairment in working memory in summer combined with high levels of dehydration over the work-shift reinforces the need for workplace education on the importance of hydration and risk of occupation heat stress. Abbreviations: Core temperature: Tc; Fly-in fly-out: FIFO; Ratings of perceived exertion: RPE; Relative humidity: RH; Urinary specific gravity: USG; Wet bulb globe temperature: WBGT.