Danish study on the effect of screening for breast cancer.
bcmortA data frame with 24 observations on the following 4 variables.
agea factor with levels 50-54, 55-59,
60-64, 65-69, 70-74, and 75-79
cohorta factor with levels Study gr.,
Nat.ctr., Hist.ctr., and Hist.nat.ctr..
bc.deathsa numeric vector, number of breast cancer deaths.
p.yra numeric vector, person-years under study.
Four cohorts were collected. The “study group” consists of the population of women in the appropriate age range in Copenhagen and Frederiksberg after the introduction of routine mammography screening. The “national control group” consisted of the population in the parts of Denmark in which routine mammography screening was not available. These two groups were both collected in the years 1991--2001. The “historical control group” and the “historical national control group” are similar cohorts from 10 years earlier (1981--1991), before the introduction of screening in Copenhagen and Frederiksberg. The study group comprises the entire population, not just those accepting the invitation to be screened.