Early health does not influence adult-onset RA

Neither preterm birth nor being breastfed is significantly associated with the incidence of rheumatoid arthritis (RA). These findings are consistent with those of previous investigations for a null association between RA and gestational age, but the previously reported protective effect of being breastfed was not confirmed.

Simard and associates examined the relationship between preterm birth and breastfed status and RA in 2 large cohorts: the Nurses' Health Study (NHS) and the Nurses' Health Study II. Both studies have linked adult-onset lupus with high birth weight and preterm birth. Data were collected via questionnaire.

A total of 913 women had adult-onset RA. Preterm birth was associated with low birth weight but had no bearing on RA; this was true regardless of rheumatoid factor (RF) status. Similarly, being breastfed was not a determinant of adult-onset RA. The only relationship between these variables occurred in the NHS study, where a history of breastfeeding for longer than 9 months appeared to confer protection against RF-negative RA.

The authors noted that the study population was restricted to adult women who did not have a diagnosis of RA at enrollment, limiting generalizability to adult-onset RA after age 25 years in women.