Sleep disorders among Yusho patients highly intoxicated with dioxin-related compounds: A 140-case series.

Purpose: Patients with Yusho, a condition caused by exposure to dioxins and dioxin-like compounds, have diverse mental and physical complaints. However, the relationship between dioxins and sleep disorders has not yet been examined. This cross-sectional study was designed to investigate problems associated with sleep among patients with Yusho.

Methods: A total of 140 participants (52.9% men, average age: 67.1 ± 12.2 years) were examined using questionnaires and medical interviews by an expert on sleep medicine. Demographic and clinical characteristics, including blood concentrations of 2,3,4,7,8-pentachlorodibenzofuran (PeCDF), which is the major cause of Yusho, were obtained from the results of recent surveys conducted by the Yusho Study Group.

Results: Moderate to severe symptoms of insomnia were present in 51.8% of the patients. The median Pittsburgh Sleep Quality Index global score (PSQI GS) was 8 (interquartile range: 5-11). The prevalence of restless legs syndrome/Willis-Ekbom disease (RLS/WED) was 30.7%; 24.3% of patients had severe RLS/WED (distressing symptoms with a frequency ≥ 1day per week). A higher blood concentration of 2,3,4,7,8-PeCDF (≥72.27 pg/g lipid) and severe RLS/WED were associated with higher odds of a PSQI GS ≥8, after adjusting for covariates (odds ratio [95% confidence interval]: 4.84 [1.10-21.25] and 4.15 [1.53-11.28], respectively).

Conclusions: Symptoms of insomnia were frequent, and the prevalence of RLS/WED was high in patients with Yusho. In addition to the presence of RLS/WED, a higher blood concentration of 2,3,4,7,8-PeCDF was associated with lower subjective sleep quality.