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

Workplace noise exposure was far higher in the metal workers than in the control group.

• Average 8-h noise exposure (LAeq,8h) was 97.9 ± 5.5 dBA in high-noise-exposed metal workers versus 76.6 ± 3.3 dBA in low-noise-exposed workers.
• Noise was measured with personal noise dosimeters (Brüel and Kjær type 4448).
• The sample was 66 small-scale informal-sector metal workers and 22 cleaners from a university teaching hospital in Dar es Salaam.

High-noise-exposed workers had significantly longer sleep duration than low-noise-exposed workers.

• Mean sleep duration was 454.4 ± 93.3 min in the high-noise group versus 360.7 ± 90.0 min in the low-noise group.
• The difference was statistically significant (p = 0.001) after adjusting for age and education.
• Sleep was measured with ActiWatch devices.

High-noise-exposed workers had significantly better sleep efficiency than low-noise-exposed workers.

• Mean sleep efficiency was 80.4 ± 7.7% in the high-noise group versus 74.7 ± 11.7% in the low-noise group.
• The difference was statistically significant (p = 0.023) after adjusting for age and education.

Sleep onset latency and wake after sleep onset did not differ significantly between the groups.

• No statistically significant differences were found for either measure when comparing high- and low-noise-exposed workers.
• Analyses were adjusted for age and education and run in SPSS version 27.

The direction of the association was opposite to the expected adverse effect of noise: higher daytime noise was associated with better sleep.

• The authors concluded that workers exposed to high daytime noise had longer sleep duration and better sleep efficiency than workers exposed to low noise.
• The design was cross-sectional with a small sample (66 vs 22), so the authors recommend longitudinal studies with larger samples and longer monitoring periods to confirm the findings.