[The association between shift work and lower extremity osteoarthritis among retired workers]

Objective: To investigate the association between shift work and the risk of lower extremity osteoarthritis. Methods: The study population came from the Dongfeng-Tongji cohort established in 2008. In September 2008, the Dongfeng Motor Company in Hubei Province was to recruit all retired workers who voluntarily participated in the survey as the research objects. During the follow-up conducted from April to October 2013, a total of 14 438 retired workers, i.e. all of the participants who underwent physical examination were investigated about demographic characteristics, lifestyles, occupation history, and lower extremity joint-related medical history, and additionally completed lower extremity joint examinations. After excluding individuals with missing data regarding lower extremity osteoarthritis, with the history of lower extremity joint trauma, or with history of rheumatoid arthritis (N=532), data from 13 906 participants was analyzed in the study. Multivariate logistic regression models were used to estimate the association between shift work and lower extremity osteoarthritis. After stratified by the duration of shift work, multivariate logistic regression models were used to analyze the relationship between the duration after leaving from shift work and lower extremity osteoarthritis. Results: Finally, a total of 13 906 retired employees included 7 560 (54.4%) females with a mean age of 64.74 (standard deviation 8.23) years old. 5 537 (39.8%) workers had ever engaged in shift work, including 2 004 (14.4%) workers with 1-9 years of shift work and 3 533 (25.4%) workers with ≥ 10 years of shift work. The prevalence of lower extremity osteoarthritis was 7.0%, while the prevalence of knee osteoarthritis and hip osteoarthritis were 6.7% and 0.7%, respectively. Compared with daytime workers, shift workers showed a 22% increase in the risk of lower extremity osteoarthritis (OR=1.22, 95%CI:1.06-1.40). Each 5-year increase in the duration of shift work was associated with a 4% increase in the risk of lower extremity osteoarthritis (OR=1.04, 95%CI:1.01-1.08). With the extension of the duration after leaving from shift work, the risk of lower extremity osteoarthritis decreased. Similar relationships were found between shift work and the risk of knee osteoarthritis, as well as hip osteoarthritis. Conclusion: Shift work was associated with the increased risk of lower extremity osteoarthritis.