BACKGROUND: Amid current changes in health care access across the United States, the importance of health insurance status and insurance type relative to demographic, actual, and perceived health variables as determinants of screening for breast, colorectal, and cervical cancer is uncertain. This analysis evaluates the hypothesis that health insurance independently predicts cancer screening in the Women's Health Initia tive Observational Study cohort.

METHODS: Questionnaire data from 55,278 women en rolled in the Women's Health Initiative Observational Study between September 1994 and February 1997 were analyzed by multiple logistic regression to identify predictors of self-reported mammography within 2 years, Pap smear within 3 years, and stool guaiac or flexible sigmoidoscopy within 5 years.

RESULTS: Positive determinants of reporting cancer screening were age, ethnic origin, household income, educational level, family history of cancer, having a usual care provider, time since last provider visit, and insurance status and type. Smoking, diabetes, and, among older women, prior cardiovascular events were negative determinants of cancer screening. Among women younger than 65, lacking health insurance or having fee-for-service insurance was strongly associated with failure to report cancer screening, independently of having or using a usual care provider and of demographics, self-perceived health, and health characteristics. Among women 65 and older, those with Medicare alone were less likely, whereas those with Medicare + prepaid insurance were more likely, to report cancer screening.

CONCLUSIONS: In the Women's Health Initiative Obser vational Study, a large, diverse group of older women, health insurance type and status were among the most important determinants of cancer screening indepen dent of demographics, chronic health conditions, and self-perceived health characteristics.