Association of sleep characteristics and respiratory symptoms at a smelting factory

Sleep disturbance including insomnia and poor sleep quality has been shown to be a major health determinant in occupational settings. Specific occupational exposures to hazards in most workplaces can lead to various health problems, especially sleep problems.

The study aimed to investigate sleep characteristics, and their relationships with work-related exposures, demographics, and other related variables in workers of a smelting factory.

This cross-sectional study was carried out on workers in a 40-year smelting factory located in the East of Tehran Province. A total of 200 male participants were included in the study. Among them, 51 workers were from the production process staff and the rest were office workers. Their shifts were from 6 AM to 5 PM. All participants were asked about demographic characteristics and exposure to respiratory pollutants. All participants answered validated Persian versions of the Insomnia Severity Index (ISI) and the Pittsburgh Sleep Quality Index (PSQI).

The means (SD) of age and BMI were 39.1 (8.9) years and 26.8 (4.5) kg/m2, respectively. Among all participants, 51 (25.5%) experienced exposure to a respiratory pollutant. Among all workers, 96 (48%) experienced poor sleep quality and 87 (43.5%) and 10 (5%) had subthreshold and clinical insomnia, respectively. The mean (SD) night sleep duration was 6.4 (0.96) hours. Data analysis illustrated a significant positive relationship between exposure to respiratory pollutants and insomnia (p-value = 0.03). Howewer, this association between sleep quality and exposure to repiratory pollutants was not significant (p-value = 0.25). Further analysis with binominal regression showed participants with exposure to respiratory pollutants were more susceptible to clinical insomnia (p-value = 0.02, exp(B) = 0.213), and after regressing out the effect of smoking, participants with exposure to respiratory pollutants remained susceptible to clinical insomnia. A lower night sleep duration was observed among participants with exposure to inhalational material (p-value = 0.05).

Occupational exposures to hazardous material, including inhalational exposures, could cause sleep disturbance, which warrants more attention paid by sleep specialists.