Using national cancer registration data for female breast cancer
incidence in eight European countries—England & Wales,
Scotland, Northern Ireland, the Irish Republic, Sweden, the Czech
Republic, Finland, and Denmark—for which there
comprehensive data on abortion incidence, trends are examined
and future trends predicted. Seven reproductive risk factors are
considered as possible explanatory variables. Induced abortion is
found to be the best predictor, and fertility is also a useful predictor.
Forecasts are made using a linear regression model with these
explanatory variables. Previous forecasts using the same model
and incidence data for years through 1997 for England & Wales are
compared with numbers of cancers observed in years from
1998–2004 in an Appendix. The forecast predicted 100.5% of the
cancers observed in 2003, and 97.5% of those observed in 2004.
The Challenge ofAbortion for Epidemiologists
in Female Breast Cancer Research
It is difficult for epidemiologists to discover women’s abortion
history. In any study the numbers of women who have had abortions
may be underreported.
National data on abortions in most countries tends to be
deficient, with abortions underreported. Official abortion statistics
in the United States and France are known to understate the
numbers of legal induced abortions. The countries considered in this
study are believed to have nearly complete official abortion counts.
The long lag time for the development of breast cancer
magnifies the problem. The average age of diagnosis is over 60,
while most abortions and live births occur at ages under 30. The
modern increase in breast cancer incidence is obvious at ages over
45, and Figure 1 for England & Wales shows the increase is small
below age 45.
Abortion did not become legal in most Western countries until
the 1970s, and earlier abortions among older women are not
recorded. Consequently, the older women, whose breast cancer
incidence is known, have abortions not detectable by a longitudinal