Ovarian cancer rates may be affected by several factors. Hormonal factors include a woman's age when menstruation began, the number of menstrual cycles she has had, and reaching menopause at a late age, In addition, nulliparity (never having children) or a low parity (e.g. having only borne children 1-2 times) has also been associated with increased risk of this type of cancer, while use of oral contraceptives has been associated with a decreased risk. Other factors include heredity, with ovarian cancer tending to run in families, and diet, although this relationship remains uncertain.
Researchers led by Freddie Bray of the International Agency for Research on Cancer in Lyon, France studied trends of ovarian cancer incidence and mortality in 28 European countries from 1953 until 2000 in order to try and understand the variation in trends among countries. They examined ovarian cancer data from 119 cancer registries in Europe according to year of diagnosis and age group, and mortality data from the World Health Organization (WHO) mortality database, again according to year of death and age group.
Results show an overall levelling of ovarian cancer rates across Europe, with declining incidence, and especially mortality rates, in most northern countries, particularly in younger age groups. In southern and eastern European countries, however, cancer incidence and mortality rates are increasing. The trends observed may be partially due to improvements in diagnostic techniques. Changing patterns of ovariectomy (removal of ovaries) and hysterectomy across different countries over time may have influenced the rates reported in the study. But the most important factor for declining cancer rates in some countries is most likely the spread of oral contraceptive use in younger women, which has taken place earlier and to a larger extent in northern Europe, the authors note. In addition, lower parity in some European countries has probably played a role in the increase in ovarian cancer, while changing lifestyle habits may have also influenced the incidence and outcome of the disease.
The authors conclude: "There are, therefore, several reasons to believe that the diverse patterns of ovarian cancer incidence and mortality trends registered in Europe over the last four decades are largely real, and can be explained by a combination of changing risk factors for incidence and, additionally for mortality, improving treatment."
Article: "Ovarian Cancer in Europe: Cross-Sectional Trends in Incidence and Mortality in 28 Countries, 1953-2000," Freddie Bray, Anja Helena Loos, Sandro Tognazzo, Carlo La Vecchia, International Journal of Cancer; Published Online: October 25, 2004 (DOI: 10.1002/ijc.20649).
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