The first major case-control study, published by Janet Lane-Claypon in 1926, provided the first epidemiologic evidence that low fertility increases breast cancer risk. This study in the United Kingdom was replicated in 1931 by JM Wainwright using a US sample. Neither study used modern statistical inference to interpret their data. We have evaluated and reanalyzed data from both studies to assess the validity of the original conclusions about the etiology of breast cancer.
We abstracted data from the published contingency tables for age at menarche, age at menopause, parity, age at marriage (as a proxy for age at first birth), and duration of lactation for each childbirth (as a proxy for lifetime duration of lactation). Study-specific odds ratios and associated 95% confidence intervals were calculated.
Findings from the quantitative reanalysis were consistent with contemporary epidemiologic evidence for age at menopause, parity, age at first birth, and duration of lactation.
Lane-Claypon's scientific efforts, as manifested in the 1926 UK study, are an excellent example of how one investigator's work can help develop a field of scientific inquiry.
From the Departments of aPublic Health and Primary Care and bOncology, University of Cambridge, Cambridge, United Kingdom.
Submitted 25 July 2009; accepted 23 January 2010; posted 24 May 2010.
Editor's note: A commentary on this article appears on page 573.
Correspondence: David J. Press, USC Keck School of Medicine, 3375 South Hoover St, UVI-E210, Los Angeles, California 90089–7798. E-mail: firstname.lastname@example.org.