Ovarian cancer is one of the most aggressive reproductive cancers among women. The purpose of this review is to summarize epidemiological factors that contribute to the ovarian cancer risk. This review discusses relevant primary research articles, reviews, cohort studies, population-based studies, pooled data and meta-analysis on ovarian cancer epidemiology and summarizes the positive and negative risk factors for ovarian cancer development. Several search engines including PubMed have been utilized. Epidemiologic factors were discussed under five subheadings including hereditary factors, cancer stem cells, hormonal influences, environmental factors, and lifestyle choices. Hereditary factors such as mutations in BRCA and KRAS genes, hormone levels such as androgens and gonadotrophins, and cytokines have been shown to increase ovarian cancer risk. Ovarian cancer stem cells that reside within the tumor play a role in cancer recurrence and progression. While progesterone shows protective effects, exposure to excessive levels of estrogen may increase the risk for ovarian cancer.Though the association is somewhat weak, exposure to environmental toxicants could be associated with ovarian carcinogenesis. Cigarette smoking is reported to be associated with subtype specific ovarian cancer. Although the association between general obesity or body mass index and the ovarian cancer risk is inconclusive, central obesity could be a risk factor for ovarian cancer. Consumption of a diet rich in glutathione and other antioxidants, maintaining a healthy weight, and regular exercise may provide protective measures against ovarian cancer. Some of the risk factors for ovarian cancer are sub-type specific and further studies are required to completely understand its complex etiology. Although some reviews are available on this topic, this review is comprehensive and provides novelty as it includes the role of cancer stem cells in ovarian cancer development in addition to other risk factors.

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