According to the results of an ecological study published in the BMJ Open, a significant association between oral contraceptive (Ocs) and prostate cancer (Pca) has been shown, and it is hypothesised, that the OC effect may be mediated through environmental oestrogen levels.

Researchers evaluated the association between Pca incidence and mortality and population-based use of oral contraceptives (OCs). Data from the International Agency for Research on Cancer were used to retrieve age-standardised rates of prostate cancer in 2007, and data from the United Nations World Contraceptive Use 2007 report were used to retrieve data on contraceptive use. These analyses were performed by individual nations and by continents worldwide.

According to the researchers, OC use was associated with a higher PCa incidence and mortalitly, whilst all other forms of contraceptives (i.e. intra-uterine devices, condoms or vaginal barriers) were not correlated with prostate cancer incidence or mortality.

They conclude that OC effect may be mediated through environmental oestrogen levels. However, they also emphasise that this is an ecological study and thus has, as with all correlational studies, significant limitations with respect to causal inference. “As such, it must be considered hypothesis generating”.

The BBC had also reported this study.