Relationship between earlier and later mammography screening--California Medicare, 1992 through 1994.

Regular screening mammography is recommended to reduce breast cancer mortality. Although predictors of mammography have been studied, factors that influence adherence to guidelines are less understood. We examined the relationship between an index mammogram and subsequent mammograms among California Medicare beneficiaries. Medicare billing data for 1992, 1993, and 1994 were used to estimate the association between screening mammography in 1992 and subsequent screening in 1993 or 1994. We found that women with a 1992 mammogram were more than twice as likely to have a mammogram in 1993 or 1994 than women without a 1992 mammogram (relative risk = 2.58; 95% confidence interval, 2.57-2.59). This relationship was somewhat stronger for black women compared with white women and increased with age. Although further study of regular screening patterns is needed, these findings provide some evidence that encouraging a single mammogram may lead to continued adherence.