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Certain events of reproductive life, especially completed pregnancies, have been found to influence a woman's risk of breast cancer. Prior studies of the relationship between breast cancer and a history of incomplete pregnancies have provided inconsistent results. Most of these studies included women beyond the early part of their reproductive years at the time induced abortion became legal in the United States.We conducted a case-control study of breast cancer in young women born recently enough so that some or most of their reproductive years were after the legalization of induced abortion to determine if certain aspects of a woman's experience with abortion might be associated with risk of breast cancer.Female residents of three counties in western Washington State, who were diagnosed with breast cancer (n = 845) from January 1983 through April 1990, and who were born after 1944, were interviewed in detail about their reproductive histories, including the occurrence of induced abortion. Case patients were obtained through our population-based tumor registry (part of the Surveillance, Epidemiology, and End Results Program of the National Cancer Institute). Similar information was obtained from 961 control women identified through random digit dialing within these same counties. Logistic regression analysis was used to estimate odds ratios and confidence intervals (CIs).Among women who had been pregnant at least once, the risk of breast cancer in those who had experienced an induced abortion was 50% higher than among other women (95% CI = 1.2-1.9). While this increased risk did not vary by the number of induced abortions or by the history of a completed pregnancy, it did vary according to the age at which the abortion occurred and the duration of that pregnancy. Highest risks were observed when the abortion was done at ages younger than 18 years--particularly if it took place after 8 weeks' gestation--or at 30 years of age or older. No increased risk of breast cancer was associated with a spontaneous abortion (RR = 0.9; 95% CI = 0.7-1.2).Our data support the hypothesis that an induced abortion can adversely influence a woman's subsequent risk of breast cancer. However, the results across all epidemiologic studies of this premise are inconsistent--both overall and within specific subgroups. The risk of breast cancer should be reexamined in future studies of women who have had legal abortion available to them throughout the majority of their reproductive years, with particular attention to the potential influence of induced abortion early in life.Epidemiologists compared data on 845 white women who were diagnosed with breast cancer between January 1983 and April 1990, were born after 1944, and lived in King, Pierce, or Snohomish counties in Washington State with data on 961 white women with no breast cancer from the same counties. They wanted to determine whether induced abortion increases the risk of breast cancer. Restricting cases to women born after 1944 allowed the researchers to focus only on legal induced abortions. When the researchers limited the analysis only to women who had been pregnant at least once, the risk of developing breast cancer in women who had had at least 1 induced abortion was 50% greater than those who had not had an induced abortion. This risk differed depending on the age at which the women underwent the induced abortion and the duration of that pregnancy. A gestational age (at the time of the first aborted pregnancy) of 9-12 weeks carried the highest risk of breast cancer (RR = 1.9 vs. 1.4 for =or 8 weeks and =or 13 weeks). Further, the breast cancer risk was greatest among women who underwent the induced abortion when they were less than 18 years old (relative risk [RR] = 2.5). It was especially high for women who were less than 18 years old and who had the abortion between 9 and 24 weeks of gestation (RR = 9). It was also high for those who were at least 30 years old at the time of the abortion (RR = 2.1). Spontaneous abortion was not associated with an increased risk (RR = 0.9). Neither the number of induced abortions nor the history of a completed pregnancy were associated with an increased risk of breast cancer. These findings suggest that an induced abortion during the last month of the first trimester increases the risk of breast cancer and that women who were at a very young age at the time of the first induced abortion face an increased risk of breast cancer.

This study examined the changes over time in the residential status of telephone numbers and the characteristics of households with telephone numbers that changed from nonresidential to residential. The authors determined the status in 1987 of all phone numbers (n = 9,107) that had been found to be nonresidential in six case-control studies conducted between 1979 and 1986 in Washington State. A telephone interview to obtain information on household characteristics was completed for 1,333 of the 1,901 phone numbers that had become residential by 1987. The interviews revealed that households with phone numbers that had previously been nonresidential differed from the general population with respect to household income, the age of household members, and the education of the head of the household. Data for the same area showed that the proportion of all phone numbers that were residential changed differentially according to the prefix (which roughly defines geographic area) during a 12-month period between 1987 and 1988, with some prefixes showing increases in residential phone numbers of more than 20%, while other prefixes decreased or stayed the same over the same period. We conclude that methods of random digit dialing that use two-stage designs or exclude previously dialed numbers may result in biased sampling unless changes over time are considered.

Two hundred nine female enrollees of the Group Health Cooperative of Puget Sound who developed advanced-stage breast cancer during the period 1982-1988 were interviewed about their practice of breast self-examination (BSE), use of other breast cancer screening modalities, and medical and reproductive histories. Each subject's description of how she performed the examination was scored according to her mention of up to 10 recommended BSE techniques. A random sample of 433 women without advanced-stage breast cancer from the same population was interviewed for comparison. Relative to women not practicing BSE, the risk of advanced-stage breast cancer among BSE users was 1.15 (95% confidence interval, 0.73-1.81). Frequency of BSE did not differ between women with advanced-stage breast cancer and control subjects, whether in all subjects or in subgroups defined by age, use of mammography, or frequency of clinical breast examinations. While self-described proficiency in BSE was generally low in both case and control subjects, the small percentage of women reporting more thorough self-examinations, regardless of frequency, had about a 35% decrease in the occurrence of advanced-stage breast cancer compared to women who did not perform BSE. These results suggest that, while carefully performed BSE may avoid the development of some advanced-stage breast cancers, BSE as practiced by most Seattle-area women is of little or no benefit.

Random digit dialing is a method commonly used to select random population samples in epidemiologic research. Although random digit dialing is generally presumed to provide representative samples, coverage and nonresponse errors may affect the degree to which the sample is representative. The present investigation was undertaken to determine whether the geographic distributions of samples selected using variations of the basic random digit dialing technique accurately reflect the underlying population distribution, and if not, whether such samples tend to be either more or less dispersed than the populations from which they were selected. Data regarding control groups from three case-control studies conducted from 1983–1986 were utilized. The residence addresses of 998 controls were located and assigned an X-Y coordinate and census tract designation within a three-county geographic area in northwest Washington State. Initially, the spatial distributions of controls were examined graphically in relation to the age-sex structure of the underlying population. No differences in geographic pattern were apparent A more formal statistical evaluation was conducted based on centrographic techniques utilizing two measures to describe the spatial distribution of a set of points. Results indicate that the samples chosen were neither more nor less dispersed than the underlying populations. However, the geographic centers of samples selected using primary numbers tended to be shifted from the centers of their respective populations. Several possible explanations for such shifts are considered, and extensions of the analytical approach are suggested in relation to the further evaluation of population sampling and the investigation of space-time aggregations of disease.