RT Journal A1 Snowdon DA, Gonzalez N, O'Leary BM, Ostwald SK T1 MAking mammography a habit JF JAMA JO JAMA YR 1989 FD July 14 VO 262 IS 2 SP 207 OP 207 DO 10.1001/jama.1989.03430020049016 UL http://dx.doi.org/10.1001/jama.1989.03430020049016 AB To the Editor.—  Approximately 50% of the 114 000 Roman Catholic sisters (nuns) in the United States are 65 years of age or older (New York Times. May 30, 1986:1), and virtually 100% of sisters of all ages are nulliparous. Since old age and lack of reproduction are major risk factors for breast cancer,1 Catholic sisters have an especially high risk of developing breast cancer. The probability of dying of breast cancer in US Catholic sisters has been shown to be as high as 1% among those aged 60 through 69 years, 2% among those aged 70 through 79 years, and 3% among those 80 years of age and older (which is approximately 50%, 110%, and 180% higher, respectively, than probabilities for the general US female population).2 Based on these considerations, we investigated the frequency of routine (screening) mammography in a population of elderly Catholic sisters.Study.—  In 1986,