A new Swedish study that examined family history as a risk factor for rheumatoid arthritis (RA) concludes that a lot more work needs to be done.
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“To fully explain RA heritability, a huge number of genetic risk factors are needed, and so far we have not identified that many,” co-first author and doctoral student Xia Jiang of the Institute of Environmental Medicine at the Karolinska Institutet in Stockholm writes in an e-mail to The Rheumatologist.
Family history is considered one of the strongest risk factors for developing RA, so Jiang and colleagues attempted to explain the risk via established non-genetic risk factors. Published online recently in Arthritis & Rheumatology, the report adjusted for combinations of non-genetic risk factors such as smoking, amount of alcohol intake, parity, silica exposure, body-mass index, fatty-fish consumption, and socio-economic status; as well as genetic risk factors, including shared epitope and 76 single nucleotide polymorphisms.1
But those factors “did not explain any significant part of the familial risk in either seropositive or seronegative RA. Genetic risk factors explained a limited proportion of the familial risk for seropositive RA,” the report concludes.
“For those environmental factors that might be shared by family members, for example, smoking, it’s always good to change behavior to avoid possible risk,” Jiang writes. “For those genetic factors, they are very useful in predicting disease risk in the future.”
Jiang says she is confident of her findings, but expects more work will yield further breakthroughs.
“We think that family history is a combination of (or caused by) a lot of factors and large numbers of non-genetic and genetic risk factors for RA have already been identified due to the success of well-conducted epidemiological investigations and (genome-wide association study),” writes Jiang. “If we could summarize all the currently identified genetic and non-genetic factors, and control their effects, how much would RA family history (heritability) be explained? (posted 1/2/15)
Richard Quinn is a freelance writer in New Jersey.
1. Jiang X, Frisell T, Askling J, et al. 2014. To which extent may the familial risk of rheumatoid arthritis be explained by established RA risk factors? Arthritis Rheumatol. Nov 24. DOI: 10.1002/art.38927. [Epub ahead of print].