Paracetamol use and risk of epithelial ovarian cancer: A nationwide nested case-control study.

OBJECTIVE: To investigate whether paracetamol use is associated with a reduced risk of epithelial ovarian cancer (EOC). DESIGN: A nationwide nested case-control study. SETTING: Danish female population. POPULATION: A total of 9589 EOC cases diagnosed from 2000 to 2019 were age-matched with 383 549 randomly selected female controls using risk set sampling. METHODS: Paracetamol use, reproductive history, history of medication and history of surgery were retrieved from Danish national registers. Paracetamol use was defined as at least two prescriptions for up to 1 year before the index date, and was further classified according to recency, duration, cumulative dose and intensity of dose. MAIN OUTCOME MEASURES: Conditional logistic regression was used to estimate odds ratios and 95% confidence intervals for the association between paracetamol and EOC risk, overall and by histological subtypes. RESULTS: 'Ever' use of paracetamol was associated with a reduced EOC risk after adjusting for potential confounding factors (OR 0.92, 95% CI 0.87-0.97). The association was only significant among recent users (OR 0.89, 95% CI 0.84-0.95). The risk declined further with the increasing level of cumulative dose and intensity; women from the group with a high cumulative dose and a high intensity had a 13% (OR 0.87, 95% CI 0.80-0.94) and 14% (OR 0.86, 95% CI 0.79-0.93) reduced risk, respectively. In the histological subtype analysis, reduced risk with 'ever' use was most pronounced for serous and clear cell tumours. CONCLUSIONS: Paracetamol use was associated with a decreased risk of EOC in a dose-response manner. Future studies are needed to validate the findings and investigate the mechanisms behind the association.