BMJ 1994; 308 doi: https://doi.org/10.1136/bmj.308.6923.282 (Published 22 January 1994) Cite this as: BMJ 1994;308:282

Twenty years ago the received belief was that lactation had no effect on the risk of breast cancer, but more recent research has shown that it does protect - in premenopausal women (New England Journal of Medicine 1994;330:81-7). Breast cancers in premenopausal women, however, account for less than one quarter of the total, and the relative risk is reduced only to 0.72 (confidence interval 0.51 to 0.99) for 24 months of lactation, so the effect is not dramatic. Nevertheless, it is another good reason to encourage women to feed their babies for as long as possible.

The lactation data are important because breast feeding is one of the few modifiable risk factors for young women concerned to protect themselves. Women under 50 have been eager participants in mammographic screening in the United States - the only country to encourage it - but a review in JAMA (1994;271:152-3) concludes that such screening does not reduce deaths. It is older women who benefit from regular mammography.

In the past 30 years the prevalence of Huntington's disease in County Donegal in Ireland has fallen from 4.4 to 1.6 per 100 000 (Ulster Medical Journal 1993;63:141-4). The explanation …

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