Family history, obesity, urological factors and diabetic medications and their associations with risk of prostate cancer diagnosis in a large prospective study

BACKGROUND: Prostate cancer (PC) aetiology is unclear. PC risk was examined in relation to several factors in a large population-based prospective study. METHODS: Male participants were from Sax Institute’s 45 and Up Study (Australia) recruited between 2006 and 2009. Questionnaire and linked administrative health data from the Centre for Health Record Linkage and Services Australia were used to identify incident PC, healthcare utilisations, Prostate Specific Antigen (PSA) testing reimbursements and dispensing of metformin and benign prostatic hyperplasia (BPH) prescriptions. Multivariable Cox and Joint Cox regression analyses were used to examine associations by cancer spread, adjusting for various confounders. RESULTS: Of 107,706 eligible men, 4257 developed incident PC up to end 2013. Risk of PC diagnosis increased with: PC family history (versus no family history of cancer; HR(adjusted) = 1.36; 95% CI:1.21–1.52); father and brother(s) diagnosed with PC (versus cancer-free family history; HR(adjusted) = 2.20; 95% CI:1.61–2.99); severe lower-urinary-tract symptoms (versus mild; HR(adjusted) = 1.77; 95% CI:1.53–2.04) and vasectomy (versus none; HR(adjusted) = 1.08; 95% CI:1.00–1.16). PC risk decreased with dispensed prescriptions (versus none) for BPH (HR(adjusted) = 0.76; 95% CI:0.69–0.85) and metformin (HR(adjusted) = 0.57; 95% CI:0.48–0.68). Advanced PC risk increased with vasectomy (HR(adjusted) = 1.28; 95% CI:1.06–1.55) and being obese (versus normal weight; HR(adjusted) = 1.31; 95% CI:1.01–1.69). CONCLUSION: Vasectomy and obesity are associated with an increased risk of advanced PC. The reduced risk of localised and advanced PC associated with BPH, and diabetes prescriptions warrants investigation.