title: An appendectomy increases the risk of rheumatoid arthritis: a five-year follow-up study.
abstract: Many studies have reported a possible association of an appendectomy with rheumatoid arthritis (RA). However, findings of the relationship between an appendectomy and RA remain inconsistent. Furthermore, all such studies were conducted in Western societies, and relevant studies on the relationship between an appendectomy and RA in Asian countries are still lacking. In this study, we investigated the relationship between an appendectomy and the subsequent risk of RA using a population-based dataset. We retrieved data for this retrospective cohort study from the Taiwan "Longitudinal Health Insurance Database 2005". We included 4,294 subjects who underwent an appendectomy in the study cohort and 12,882 matched subjects in the comparison cohort. We individually tracked each subject for a 5-year period from their index date to identify those who developed RA. A stratified Cox proportional hazard regression was performed to calculate the hazard ratio (HR) and its corresponding 95% confidence interval (CI) for the subsequent development of RA during the 5-year follow-up period between subjects who underwent an appendectomy and comparison subjects. Of the sampled subjects, 93 (0.54%) received a diagnosis of RA during the 5-year follow-up period: 33 from the study cohort (0.77% of subjects who underwent an appendectomy) and 60 from the comparison cohort (0.47% of comparison subjects) (p<0.001). After censoring individuals who died during the follow-up period and adjusting for subjects' monthly income and geographic region, the HR of RA during the 5-year follow-up period was 1.61 (95% CI = 1.05~2.48) for subjects who underwent an appendectomy compared to comparison subjects. We found that among females, the adjusted HR of RA was 1.76 (95% CI = 1.04~2.96) for subjects who underwent an appendectomy compared to comparison subjects. However, there was no increased hazard of RA for males who underwent an appendectomy compared to comparison subjects. We concluded that female subjects who undergo an appendectomy have a higher risk of RA than comparison female subjects.
authors.affiliation: Graduate Institute of Life Science, National Defense Medical Center, Taipei, Taiwan.
authors.forename: Ya-Mei
authors.initials: YM
authors.lastname: Tzeng
authors.affiliation: School of Public Health, National Defense Medical Center, Taipei, Taiwan.
authors.forename: Li-Ting
authors.initials: LT
authors.lastname: Kao
authors.affiliation: School of Public Health, National Defense Medical Center, Taipei, Taiwan.
authors.forename: Senyeong
authors.initials: S
authors.lastname: Kao
authors.affiliation: Sleep Research Center, Taipei Medical University Hospital, Taipei, Taiwan.
authors.forename: Herng-Ching
authors.initials: HC
authors.lastname: Lin
authors.affiliation: Division of Gastroenterology, Department of Internal Medicine, Cathay General Hospital, Taipei, Taiwan.
authors.forename: Ming-Chieh
authors.initials: MC
authors.lastname: Tsai
authors.affiliation: Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan.
authors.forename: Cha-Ze
authors.initials: CZ
authors.lastname: Lee
mesh_terms: D000328:Adult; D000368:Aged; D001062:Appendectomy / Q000009:adverse effects*; D001172:Arthritis, Rheumatoid / Q000453:epidemiology / Q000209:etiology*; D016022:Case-Control Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D012189:Retrospective Studies; D012307:Risk Factors; D017678:Sex Distribution