Example 9.1. The relationship between use of conjugated estrogens and the
risk of endometrial cancer was examined among 188 white women aged
40–80 years with newly diagnosed endometrial cancer and 428 controls of
similar age hospitalized for non-malignant conditions requiring surgery at
the Boston Hospital for Women Parkway Division, Massachusetts, between
January 1970 and June 1975. The data on drug use and reproductive variables
were extracted from hospital charts and from the medical records of
each woman’s private physician. Thirty-nine per cent of the cases and 20%
of the controls had used conjugated estrogens in the past (Buring et al.,
1986).