Childhood deprivation linked to rheumatoid arthritis in adults

By Andrew Czyzewski, MedWire Reporter

Adults with rheumatoid arthritis (RA) are more likely to have grown up in a low socioeconomic environment during childhood than those without RA, a large US case-control study shows.

Nevertheless, the researchers say the findings do not support the idea that lower childhood socioeconomic status (SES) alone increases RA risk, but rather suggest a cumulative effect of lower SES throughout the person's lifespan.

Noting a lack of research on early life risk factors for adult-onset autoimmune diseases, Christine Parks (National Institute of Environmental Health Sciences [NIEHS], Durham, North Carolina) drew on data from the NIEHS Sister Study cohort.

The sample analyzed included 50,884 women, aged 35-74 years, enrolled during 2004 to 2009. The women completed questionnaires at the start of the study where they were asked to report any diagnosis of RA after the age of 16; use of disease-modifying antirheumatic drugs or steroids for RA; and bilateral joint swelling for 6 weeks or more.

Additional questions included those on food insecurity ("When you were growing up, were there times your family didn't have enough to eat?"), highest household education level of parent when respondent was aged 13 years, single-parent household (age 13), self-assessed household income while growing up (well off, middle income, low income or poor), and maternal and paternal age at participants' birth.

A cumulative summary score was collated which included four factors initially related to RA: lower education (high school or less), low income or poor, young maternal age, and food insecurity.

Parks and colleagues found that the 424 patients who had a history of RA were more likely to report lower childhood household education (<12 years vs college degree; odds ratio [OR]=1.7), food insecurity (OR=1.5), and young maternal age (<20 vs 20-34 years; OR=1.7), than their peers without RA.

There was also a trend for an increasing number of SES adverse factors carrying an increasing risk for adult RA (2 vs 0 factors, OR=1.6; 4 vs 0 factors, OR=3.0).

The researchers then modelled SES trajectory using the childhood score stratified by adult education. This showed that lower childhood SES was associated with RA primarily in women who remained on a low SES trajectory.

This supports the hypothesis that "sustained experience of lower SES may be a risk factor for RA," say Parks et al.

They add: "Lower SES represents a wide range of factors and experiences that may contribute to disease risk. Identifying the role of underlying developmental, environmental and psychosocial factors is an important next step."

The research is published in the Annals of the Rheumatic Diseases.

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