Breast cancer in Europe: the importance of factors operating at an early age.

Breast cancer incidence varies considerably among European countries, with highest rates found in western and northern and lowest rates in eastern and southern European countries. The objective of this ecological correlation study was to investigate to what extent variation in breast cancer incidence within Europe can be attributed to differences in the prevalence of the following risk factors: age at menarche, age at first birth, parity, body height and body weight. The results of the study showed that particularly age at first birth and body height correlated positively and significantly with breast cancer incidence. If in eastern and southern European countries changes take place with respect to reproductive behaviour and nutritional status in the same way as has happened in western and northern European countries, breast cancer incidence in the countries included in this study may increase by 11%. This means that, by the time the 0- to 10-year-old female population in the European countries being studied reaches the age of 64, the number of women with breast cancer may be 1,198,369, which is almost 135,000 higher than would be the case if breast cancer risk remained stable.