Background/Purpose: There is extensive research into the association between breastfeeding (BF) and the occurrence of autoimmune diseases, although results have been conflicting. Studies have suggested that BF may influence the presentation of juvenile idiopathic arthritis (JIA), with a higher prevalence of BF among children with polyarticular presentation. The aim of this analysis was to study the influence of BF on the presentation of JIA in a large prospective inception cohort of children with childhood-onset arthritis.

Methods: The Childhood Arthritis Prospective Study (CAPS) recruits children ≤ 16 years old with new onset (≥2 weeks) inflammatory arthritis from five tertiary hospitals in the United Kingdom. At presentation to pediatric rheumatology, a physician performs an examination and completes a Physician Global Assessment (PGA). Families also complete a Childhood Health Assessment Questionnaire (CHAQ) including a Parent General Evaluation (PGE) and pain visual analogue scale (VAS). Detailed demographic data is collected including age at onset, gender, ethnicity, and household factors including parental education and income. Families were also asked if the child was BF and for how long. Baseline characteristics were compared between those children who were and were not BF using descriptive statistics. The association between BF and a high CHAQ score (>0.75) at presentation were determined using multivariate logistic regression, adjusted for age at onset, symptom duration, ILAR subtype, hospital, ethnicity and socioeconomic status (SES). Using postcodes, SES was determined by calculating the Index of Multiple Deprivation score and categorised into three groups: low, medium and high.   

Results: 927 children (65% female) were included in the analysis: median age at onset 6.4 years. Overall, 54% were breastfed, although the majority for <6 months. BF children reported a lower median age at onset (5.7 vs 7.5 years; p<0.001), a lower CHAQ score, lower PGE and lower pain at baseline (see Table).There was a trend towards a higher proportion of BF children with rheumatoid factor negative polyarthritis but lesser enthesitis related and psoriatic arthritis. There was a statistically significant inverse association between BF and high CHAQ (OR 0.62, 95% CI 0.41, 0.95) which was no longer significant after adjustment (OR 0.66, 95% CI 0.41, 1.07).

Conclusion:  There is an association between breastfeeding and an earlier and less severe presentation of JIA, although this could be explained in part by socioeconomic factors. Further work to elucidate the association between breastfeeding and later presentation of autoimmune diseases is required.