Relative survival after exposure to polychlorinated biphenyls and dioxins: A follow-up of Japanese patients affected in the Yusho incident

Objectives: Little information is available on conditional survival among Yusho patients, who were accidentally exposed to PCBs and other dioxin-related compounds. In this study, we estimated relative survival among Yusho patients to quantify time trends in excess mortality compared to the general population. Methods: A total of 1664 Yusho patients (860 males, and 804 females) were analyzed as Yusho cohort subjects. Relative survival ratio (RSR) was calculated as a measure of patient survival. Results: Overall, 1-, 5-, 10-, and 15-year RSRs were 1.00 (95% confidence interval (CI): 0.99, 1.00), 1.00 (95% CI: 0.99, 1.01), 0.99 (95% CI: 0.98, 1.00), and 0.99 (95% CI: 0.98, 1.01), respectively. We did not observe meaningful increases or decreases in RSRs in either sex, which remained the same in all age groups for 1-, 5-, 10-, and 15-year RSRs. Conclusions: This study provides quantitative evidence that Yusho patients have no significant difference in relative survival compared with the general Japanese population. Our results suggest that PCBs and dioxin exposure confers no excess mortality. This information may be important for both the clinical management of and patient coping with Yusho disease.