Study Shows Rheumatoid Arthritis Risk May Be Tied To Birth Weight
Results from a Swedish study, reported in the May 17, 2003 issue of the British Medical Journal, indicate that there is a correlation between birth weight and the risk of developing rheumatoid arthritis later in life.
Genetics and environmental factors have long been suspect as possible causes of rheumatoid arthritis, yet rheumatoid arthritis remains a disease of "unknown aetiology".
About The Study
In the Swedish study, Dr. Lennart Jacobsson and colleagues selected study participants from a local register of all patients seen in either the outpatient clinic at the department of rheumatology (Malmo University Hospital, southern Sweden), or seen by any of the three private practice rheumatologists in the same city. The researchers selected 77 people to be study participants from the register of all people who were born between 1940 and 1960 and were still living in Malmo. Of the 77 people:
- the median age of onset of rheumatoid arthritis was 46 years.
- 76% were positive for rheumatoid factor.
- 85% had erosive disease.
For each of the cases, the researchers selected the consecutive four births of the same sex at the same delivery unit in Malmo as controls (308 people without arthritis). From the birth records, researchers analyzed:
- the mother's age
- father's occupation
- breast-feeding started during hospital stay after delivery
- the baby's weight at birth
- length at birth
- gestational length
- weight of placenta
- maternal diseases during pregnancy
- history of miscarriage
- length of hospital stay after delivery
Birth Weight
High birth weight (defined as babies weighing more than 4000 grams (~9 pounds) were three times more likely to develop rheumatoid arthritis later in life than those babies of average weight (viewed as birth weight between 4000 and 3000 grams, or about 6.6 pounds). Birth weight less than 3000 grams did not increase the risk of rheumatoid arthritis.
Breast-fed babies were less likely to develop rheumatoid arthritis as adults as were the babies of fathers employed in non-manual labor positions.
These factors are accounted for by considering:
- the development of the immune system in utero.
- perinatal or postnatal modulation of the immune system.
- other unmeasured confounding factors.
Related Resources
Sources: Perinatal characteristics and risk of rheumatoid arthritis, BMJ 2003;326:1068-1069, May 17, 2003; Rheumatoid Arthritis Tied To Birth Weight, HealthScout, May 16, 2003; Smaller Babies, Smaller Rheumatoid Arthritis Risk, Reuters, May 16, 2003
