Forgive me if this has been posted before:

A study published June 1995 in the British Journal of Rheumatology, by Brun,
J.G., Nilssen, S., and Kvale, G.  "Breast feeding, other reproductive
factors, and rheumatoid arthritis: A prospective study."

Abstract: The evidence regarding reproductive events as risk factors for
rheumatoid arthritis (RA) is not conclusive.  In the present study a
population-based cohort consisting of 63,090 women were followed from 1961
to 1989.  Detailed data on reproductive factors were collected through
personal interviews in the period 1956-59.  The endpoint used was mention of
RA on the death certificate.  Mortality rate ratios were estimated by
Poisson regression, controlling for various demographic variables.  During
1,484,400 person-yr of observation, a total of 355 cases with RA mentioned
on the death certificate were identified.  Total time of lactation was
associated with a decreased mortality of RA, with an approximate
dose-response relationship.  The results did not support a role of parity,
age at first and last birth, or age at menarche and menopause in the
development of RA.  This protective effect of lactation on the development
of RA has not previously been described, and since a definite biological
explanation is lacking, the association should be confirmed in other
populations.

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Katherine A. Dettwyler, Ph.D.                         email: [log in to unmask]
Anthropology Department                               phone: (409) 845-5256
Texas A&M University                                    fax: (409) 845-4070
College Station, TX  77843-4352