relationship between oral temperature and sleepiness among night workers in a hot industry

night work can have a significant impact on health, well-being, performance and occupational safety of workers. night workers often complain about the sleep disorder characterized by excessive sleepiness.  the aim of the study was to determine the level of sleepiness among night workers and investigate its relationship with oral temperature in a hot industry. this cross-sectional study involved 80 night workers. stanford sleepiness scale (sss) has been used to measure the level of sleepiness. oral temperature and sss were recorded at different hours of night shift (23 pm to 4 am) for two consecutive nights. the analysis of results showed that there was a positive linear trend in the sleepiness scale (pvalue<0.001) and an increasing trend in the oral temperature between 23pm and 1am. then a decreasing trend has been observed after 1am for both of them (pvalue <0.001).  comparison of the results for two nights indicated that the mean sleepiness index in the second night is higher than the first (pvalue <0.001), but the mean oral temperature in the second night was equal to that in the first night. findings suggest a weak negative association between sleepiness and oral temperature. (r=-0.24, pvalue =0.03). a substantial proportion of subjects were working while sleepy, especially at late night and early morning hours. the combination of heat stress and sleepiness can lead to impaired performance. the growing amount of sleepiness index indicates the high risk of sleep disorders and the other possible problems related health among night shift workers.