Work

Early-life animal and farming exposures and the risk of rheumatoid arthritis: findings from the E3N French cohort study

Year: 2025

Type: article

Abstract: OBJECTIVE: The objective of this study is to assess the association between childhood exposure to pets and farm animals and the risk of developing rheumatoid arthritis (RA) in adulthood, using data from a large prospective cohort. METHODS: We analysed 78 473 women from the Etude Epidémiologique auprès des femmes de la Mutuelle générale de l'Education Nationale cohort, among whom 698 incident cases of RA were identified and validated. Childhood exposure to domestic pets (cats, dogs) and farm animals, as well as the age at first exposure, was self-reported by participants using predefined categorical options (eg, never, <1 year, 1-2 years, etc). HRs were estimated using Cox models, with confounders selected via directed acyclic graphs. RESULTS: Early exposure to pets (cats/dogs) between the ages of 1 year and 2 years compared with no exposure was associated with a lower risk of RA (adjusted HR (aHR) 0.57, 95% CI 0.34 to 0.95), regardless of smoking status. However, no association was observed with pet exposure at earlier (<1 year) or later ages. Conversely, exposure to farm animals (cows, sheep, pigs) during childhood was borderline associated with an increased risk of RA (aHR 1.26, 95% CI 1.00 to 1.59), irrespective of age at exposure. CONCLUSION: How and when children are exposed to animals could affect the risk of developing RA. Our results suggest a potential inverse association restricted to pet exposure at ages 1-2 years, but not at other ages, whereas exposure to farm animals was positively associated. These findings should be interpreted cautiously and warrant further investigation. TRIAL REGISTRATION NUMBER: NCT03285230.

Source: RMD Open

DOI: 10.1136/rmdopen-2025-005954