Occupational Risks of Auto-Immune Diseases among Female Workers Based on a Korean National Female Worker Cohort

Abstract

Introduction Autoimmune diseases predominate in women and are a high social health risk due to their chronic nature. Several autoimmune diseases are increasing in frequency in industrialized countries, and although the etiology remains unknown, it is known that they are associated with multiple factors such as gender, genetics, drug use, lifestyle, infection, and environmental factors. They are also related to occupational exposure, and although previous studies have been conducted, they provided insufficient epidemiological evidence. They are also receiving less attention from the perspective of work-related disorders. Therefore, the purpose of this study is to elucidate the basic epidemiology of autoimmune diseases of female workers by industry and to establish their relationships with industry. Methods This study utilized the 185,144-member Korean National Female Worker Cohort, which was a simple random sampling of 5% of 3.71 million women aged 15–64 years, based on the working-age population registered in the National Health Insurance System. Additionally, the 6th Korean Standard Classification of Diseases for autoimmune diseases and the Korean Standard Industrial Classification including subcategories of manufacturing were used. Two cohort methods were utilized. The baseline cohort reflects the industry at the starting point of follow-up, and the dynamic cohort includes workers who participated in that industry at least once. In this study, the standardized incidence ratio for workers in each industry was compared by selecting total workers and education industry workers as reference groups for each disease. Results The order of the total period prevalence of the analyzed autoimmune diseases consisted of Hashimoto autoimmune disease, psoriasis, rheumatoid arthritis, Grave's disease, and iridocyclitis. Polyarteritis nodosa, primary adrenocortical insufficiency, celiac disease, and Reiter disease, which each had less than 10 cases during the entire period, were also observed. Additionally, in the case of annual prevalence, overall prevalence showed an upward or sideways trend. According to the cohort analyses of workers using baseline and dynamic methods to observe relationships between industry type and the incidence of autoimmune disease, autoimmune diseases with significantly and characteristically increased risk existed within specific industries. In the human health industry, dermatitis herpetiformis had a SIR of 1.85 (95% CI 1.52–2.23) relative to total workers in the baseline cohort, and in the electricity, gas and water supply, and wastewater processing industry, Hashimoto autoimmune disease was 1.63 (95% CI 1.01–2.48). Within the manufacturing industry, rheumatoid arthritis was observed with a dynamic cohort SIR of 1.49 (95% CI 1.05–2.07) for total workers in the chemical manufacturing industry, while Guillain-Barré syndrome was 10.42 (95% CI 1.27–37.56) and Crohn's disease was as high as 3.66 (95% CI 1.19–8.53) in the wood, pulp manufacturing industry. In the electronics manufacturing industry, iridocyclitis was 1.31 (95% CI 1.02–1.66) higher than the total workers in the dynamic cohort, and in the medical, precision, and optical device manufacturing industry, the SIR of ulcerative colitis was 4.85 (95% CI 1.58–11.32). Discussion In this study, the prevalence of autoimmune diseases among Korean female workers was reconfirmed to not be falling, and occupational exposure by industry can influence the incidence of autoimmune diseases. Substances used or exposure in certain industries may be risk factors for autoimmune diseases. In the wood pulp manufacturing industry, bacterial or fungal infection can occur in contaminated bark, which can trigger Guillain-Barré syndrome, and in the chemical manufacturing industry, exposure to various solvents can cause rheumatoid arthritis. To summarize the mechanisms of occupational exposure that can explain disease occurrence, the harmful agents may activate polyclonal B cells or induce autoantibodies through direct toxic effects on cells. Additionally, cross-reactions can occur through molecular mimicry by substances with structural similarities, and autoimmune reactions can occur by changing structures by acting on self-proteins to create new epitopes. Additionally, occupational exposure is diverse and variable. It may include continuous exposure during the working hours of a specific job, and some women may be exposed throughout a lifetime, resulting in synergistic and interactive effects. Therefore, it is expected that the cohorts established for each industry from which risks are derived for this study can be either continuously used as a long-term monitoring system, or as basic data to improve the working environment and protect workers. However, work environments differ for each workplace, and health impact assessment is limited to individual agents due to the lack of information on what substances are used by each industry. Nevertheless, this study is significant in that it is the first to conduct a nationwide analysis of the industrial relationship of autoimmune disease, which is important and of increasing interest in recent years. Conclusion We found that the risk of certain autoimmune diseases was increased in certain industrial groups of female Korean workers. As already known, occupational exposure is an important risk factor for certain autoimmune diseases. Additionally, based on the findings of this study, it is necessary to create policies that can compensate and protect workers who are at risk of autoimmune diseases, which is a major social and economic problem in modern society. Furthermore, various additional tools and studies such as exposure assessment methods, experimental studies, and epidemiological studies are needed to protect workers by more precisely revealing the relationships between individual hazardous substances, processes, and autoimmune diseases.