High birthweight linked to arthritis

BEING HEAVY at birth could double the risk of developing rheumatoid arthritis in later life, according to a new study. Research in the US has found that women who weighed over 4.54 kilos (10lbs) at birth were twice as likely to have the joint condition in adulthood, when compared with their lighter-birthweight peers.

Rheumatoid arthritis is a chronic, autoimmune, inflammatory disease that affects around 1 per cent of the population in Ireland and typically develops in adulthood. Symptoms include joint pain and deformity, and it affects around four times as many women as men.

The new study, released this week ahead of publication in the journal Annals of the Rheumatic Diseases, looked at health and lifestyle data from over 87,000 participants on the US Nurses’ Health Study between 1976 and 2002. Of these women, more than 600 were diagnosed with rheumatoid arthritis for the first time during the study period.

The researchers took into account factors that can affect birthweight, such as diabetes in the mother during pregnancy and socio-economic status. They also accounted for factors that can raise or reduce an individual’s risk of rheumatoid arthritis, including smoking, body mass index, individuals breastfeeding their own children and the use of oral contraceptives.

Even with these controls in place, they still found that women with birthweights of over 4.54 kilos (10lbs) had twice the relative risk of developing the condition compared with women who had a birthweight of between 3.2 and 3.85 kilos (5.6 to 7lbs).

“Our data suggest a birthweight threshold above which risk of increases,” wrote the study authors, who are based at Cornell Medical School and Harvard University.

Their findings reflect results from a smaller study in Sweden and tie in with the theory that the environment in the womb, which affects birthweight, can influence the risk of the child developing certain diseases in adulthood.

Diabetes, coronary heart disease, and high blood pressure have been linked to low birthweight, while high birthweight has been linked to an increased risk of breast cancer and a type of leukaemia, the authors noted.

The biological connection between birthweight and rheumatoid arthritis is unknown, but the researchers speculated that the hormonal disruption seen in rheumatoid arthritis could be triggered during development in the womb. If this is the case, they suggested it could open new routes to lowering the risk of developing the condition by modifying the mother’s diet during pregnancy.