Workplace noise exposure and sleep among small-scale industrial metal workers in Dar es Salaam, Tanzania: a cross-sectional study

This study aimed to investigate the relationship between workplace noise exposure and sleep outcomes among high noise exposed small-scale industrial metal workers and a low noise exposed control group in Dar es Salaam, Tanzania. A cross-sectional design was employed, where 66 metal workers from small-scale metal industries in informal sectors (high noise exposed) and 22 cleaners from university teaching hospital in Dar es Salaam, Tanzania (low noise exposed) were included. Noise levels were assed using personal noise dosimeters (Brüel and Kjær type 4448), while sleep parameters were measured using ActiWatch devices. Data were analyzed using SPSS version 27. The average 8-h noise exposure level (LAeq,8 h) among the high noise exposed workers was 97.9 ± 5.5 dBA, compared to 76.6 ± 3.3 dBA among the low noise exposed workers. Sleep efficiency averaged 80.4 ± 7.7% and 74.7 ± 11.7%, and average sleep duration was 454.4 ± 93.3 min and 360.7 ± 90.0 min in high noise exposed workers and low noise exposed workers, respectively. There was a statistically significant difference among the two groups in terms of sleep duration (p = 0.001) and sleep efficiency (p = 0.023), when adjusting for age and education. No statistically significant differences were found in sleep onset latency and wake after sleep onset when comparing the two groups. Workers exposed to high daytime noise levels demonstrated longer sleep duration and better sleep efficiency compared to workers exposed to low noise levels. Further longitudinal studies with larger sample sizes and extended monitoring periods are needed to confirm the findings. The study is unique, as few studies have been able to assess sleep in similar settings. These industries have a high occupational noise exposure level, exceeding recommended threshold of 85 dBA. Such elevated exposure may contribute to adverse health outcomes, including disrupted sleep. Given the critical role of sleep for workers’ health, this study examined the role of occupational noise exposure on sleep parameters, using ActiWatch devices for objective measurements of sleep. Interestingly, workers exposed to high noise levels demonstrated longer sleep duration and better sleep efficiency compared to those exposed to lower noise levels.