RESEARCH - Women's reproductive factors and the risk of RA

[Guest guest]

04/11/2004

Women's reproductive factors and the risk of rheumatoid arthritis

Study suggests prolonged preventive effect of breastfeeding and links

irregular menstrual cycles to increased risk of disease

Rheumatoid arthritis (RA), an inflammatory disease of the immune

system, is between two and four times more likely to strike women than men.

Among women, RA is more likely to develop when reproductive hormonal levels

are changing, such as in the first few months following a pregnancy and

around the time of menopause. Although previous researchers have studied

this topic, the relationship between hormones and the risk of developing RA

remains unclear.

Seeking more conclusive evidence, a team of researchers led by

Karlson, M.D. at Brigham and Women's Hospital in Boston drew on a

large sample - 121,700 women - to explore the contribution of hormonal

factors occurring prior to the onset of RA and the impact of postmenopausal

hormone replacement therapy on the risk of disease. Their findings,

published in the November 2004 issue of Arthritis & Rheumatism, strongly

support the lasting benefits of breastfeeding in protecting against the

disease. What's more, the researchers identified a new risk factor for RA:

irregular menstrual cycles.

The study's subjects were all women enrolled in the Nurses' Health

Study, a sweeping investigation of disease, health, and lifestyle, ongoing

since 1976. Through extensive questionnaires, the research team documented

each woman's reproductive history with attention to potential RA risk

factors, including age at menarche, age at first birth, history of

breastfeeding, use of oral contraceptives, and regularity of menstrual

cycles and in older women studied the use of estrogen after menopause. Among

these women, the researchers confirmed 674 RA patients, diagnosed anywhere

between 1976 and 2002. Most of the women were middle-aged at disease onset;

the mean age was 56 years.

Upon analyzing the data, adjusting for variables such age and

cigarette smoking, the researchers noted several interesting trends. One of

the strongest was a decreasing risk of RA with increasing duration for

breastfeeding. Looking at total lifetime breastfeeding, regardless of number

of children, women who had breast-fed for between 13 and 23 months had a 20

percent reduction in the risk of RA compared with women who did not

breastfeed. Women who had breast-fed for at least 24 months - two full years

out of their childbearing years - increased their risk reduction to 50

percent. " Our data suggest breast-feeding confers long lasting protection

against developing RA, " Dr. Karlson states, " because the mean time since the

last pregnancy among women with RA was 25 years. " In addition, women who

experienced irregular menstrual cycles between the ages of 20 and 35 were

shown to have an increased risk of subsequent RA. Women who had begun

menstruating at an early age, 10 or younger, were more likely to develop

seropositive RA. The study's results did not show any association between a

history of oral contraceptive use and disease risk, or any significant

differences in disease risk related to a woman's number of pregnancies.

Focusing on the sample of RA patients, compared to women who did not

develop RA, the researchers confirmed that the risk of RA increases with age

and demonstrated a peak risk at the typical time of menopause, age 50 to 54.

Because the onset of RA often coincides with menopause, some studies have

linked the disease to falling estrogen levels, indicating the potential

benefits of estrogen therapy. In this study, however, estrogen therapy among

postmenopausal women did not protect against RA. " These findings suggest

avenues for further research into the hormonal mechanisms involved in RA,

because the complex relationships between RA and reproductive hormones

clearly warrant further study, " Dr. Karlson concludes.

Not an MD

I'll tell you where to go!

Mayo Clinic in Rochester

http://www.mayoclinic.org/rochester

s Hopkins Medicine

http://www.hopkinsmedicine.org