A similar occurrence of this bias was reported from US Physicians, in whom aspirin-taking was associated with a reduction in prostate cancer (HR 0.59; 95% CI 0.43–0.81) ‘before the PSA era’, while ‘during the PSA era’ the association with aspirin was lost (HR 1.01; 95% CI 0.60–1.69) [24]. This evidence concerns the gene KLK3 and prostate cancer.