Association between Blood Lead Level and Sleep Quality in Lead- Zinc Factories in Zanjan: A Cross-Sectional Study

Abstract

Background and Objective: Adult lead poisoning commonly occurs due to workplace exposures. Neuro- psychological symptoms such as insomnia are reported as the early symptoms of chronic lead intoxication. This study aimed to evaluate association between blood lead level (BLL) of workers from lead-zinc factories and their sleep quality.
Materials and Methods: A cross-sectional study was performed and 425 workers were enrolled with eligi- bility criteria of the study. BLL of workers were measured using atomic absorption spectrophotometry. Clinical assessment of workers was performed regarding their sleep problems through a self-administered questionnaire consisting of demographic characteristics, Insomnia Severity Index (ISI), Epworth Sleepiness Scale (ESS), and Pittsburg Sleep Quality Index (PSQI).  Multiple linear regression and ANOVA tests were used for analysis of data.
Results: Among 425 workers studied, mean (±SD) BLL was 34.7(± 16.7) µg/dl. BLL was significantly asso- ciated with total scores of ISI, ESS, and PSQI questionnaires adjusted for age, sex, job experience, shift work, and body mass index (Adjusted R2 was 0.19, 0.08, and 0.18, respectively; P<0.001). Difficulty with falling asleep, difficulty of staying asleep and waking up too early were more prevalent among workers with increased BLL (P<0.001).
Conclusions: Workers exposed to lead and with increased BLL may have more sleep problems including in- somnia, excessive daytime sleepiness, and poor sleep quality. This warrants further attention toward different types of sleep problems in workers with lead exposure especially those with increased BLL.