Environmental determinants of juvenile idiopathic arthritis: current evidence and future directions

The hypothesis that environmental factors may contribute to the development of juvenile idiopathic arthritis (JIA) arises from the variability observed in the incidence of its various subtypes across different geographic regions and ethnic groups. However, despite decades of research, the evidence of most associations remains weak and subject to confounding factors. In recent years, a number of environmental factors have been investigated for a possible role in the development of JIA, as risk factors or protective agents. As a result, the most plausible pathogenic pathway involves early-life gut microbiota disruption, particularly in relation to early antibiotic exposure. Prenatal factors such as maternal diet and weight gain, and smoking and pollutant exposures during pregnancy require further clarification and should be interpreted with caution given the limitations of existing data. Other associations with perinatal events, such as breastfeeding and caesarean section delivery, living or socioeconomic conditions, and infections, remain suggestive but not definitive. Furthermore, the complexity of JIA as a heterogeneous group of diseases underscores the difficulty of identifying universal environmental drivers. In order to better define the role of environmental factors in JIA development, there is a need for a shift from retrospective, population-based studies to an integrated and longitudinal research approach. This step requires international, harmonized datasets and collaborative consortia, possibly employing existing international networks. Until robust evidence emerges, the current knowledge should be interpreted cautiously, avoiding oversimplified or causal claims.