Sleep Quality in Populations Exposed to Toxic Substances at Work and Environmentally in Brazil

Introduction: Work organization and chemical exposures may affect mental and physical health. Chemical exposure can also significantly impact sleep quality through various mechanisms and molecular pathways. In addition, inadequate sleep has been linked to impairments in bodily functions. Therefore, this study aimed to analyze sleep quality in three populations exposed to chemicals, based on health parameters.

Methods: A cross-sectional study was conducted with 189 residents in the city of Volta Redonda (Rio de Janeiro, Brazil), and 66 endemic workers. Assessments on health, work, Pittsburgh Sleep Quality Index (PSQI), self-reported questionnaire, clinical and toxicological tests were performed. Sleep quality was evaluated by an actigraphy (ActTrust) for ten consecutive days. Cd, Pb, Ni, Mn, BZN, and TLN concentrations in blood and urine were determined by GFAAS and GC/MS, and genotyping was performed using PCR.

Results: Study 1: Regarding the chronotype of the participants, 47% were afternoon,11% were morning, and 42% were indifferent. Higher urinary Mn levels were associated with the morning chronotype (p < 0.01). The evening chronotype was associated with poor sleep quality, higher Pb blood levels, and BZN and TLN levels in urine (p < 0.01) in non-occupationally exposed individuals (p < 0.01); as well as the highest BZN (p < 0.01) and TLN (p < 0.01) levels detected in residents from the influence zone 2. Moreover, most participants (57%) reported poor sleep quality. Residents with higher scores for daytime dysfunction (p = 0.01) and sleep disturbance (p < 0.01) were associated with higher Cd levels in urine; for sleep disturbance with both Mn (p < 0.01) and Ni (p = 0.03); and for sleep duration, with TLN (p < 0.05). Study2: The average score of sleep quality was 7.8 points in the PSQI score, and 60% of the population was classified as having unhealthy sleep (PSQI > 5). Additionally, the total sleep time was 5 to 6 hours, the sleep efficiency was 80%, and WASO was ~60 minutes. Sleep stability and variability were 0.48 and 0.80 respectively, and a positive correlation between the hormone free T4 and total sleep time (p < 0.05) was observed, also, the Intraday variability had a negative correlation with the hormone levels. Moreover, a positive correlation (0.66; p < 0.05) was found between the scales of common mental disorders and PSQI, with greater confidence intervals between the most extreme levels of poor sleep quality and common mental disorder.

Conclusion: Exposure to contaminants influenced sleep patterns and the different chronotypes in the population exposed to toxic substances. These contaminants potentially act as activators of the neural circadian system, affecting sleep quality. Support: Carlos Chagas Filho Foundation for Research Support of the State of Rio de Janeiro (FAPERJ) under Grant [number E-26/203.263/2016]; Foundation Coordination for the Improvement of Higher Education Personnel (Capes) and Oswaldo Cruz Foundation (Fiocruz). FM Fischer receives a grant from CNPq (306963/2021–3).