According to GRADE and EBM methodology, here is what ideal scientific evidence would look like to definitively prove or disprove this specific claim, ordered from strongest to weakest evidence.
Randomized Controlled Trial
A double-blind, placebo-controlled RCT enrolling 10,000 UK adults aged 40–70 without prior sildenafil use, randomly assigning them to daily sildenafil (50mg) or placebo for 5 years, with all-cause mortality as the primary endpoint, and stratification by age, sex, smoking, cancer history, and diabetes status. A prospective cohort study tracking 50,000 UK adults aged 40–70 over 10 years, identifying those newly prescribed sildenafil versus matched non-users, adjusting for confounders (age, sex, smoking, cancer, diabetes), and measuring all-cause mortality via national death registries. Nested Case-Control Study
A nested case-control study within a UK biobank of 100,000 individuals aged 40–70, identifying 2,000 individuals who died from any cause during follow-up and matching each to 4 living controls by age, sex, smoking, cancer, and diabetes status, then comparing prior sildenafil prescription rates. A cross-sectional analysis of UK health survey data comparing prevalence of sildenafil use among living individuals aged 40–70 versus those who died within the past year, adjusting for age, sex, smoking, cancer, and diabetes. Systematic Review and Meta-Analysis
A systematic review and meta-analysis of all observational studies reporting hazard ratios for all-cause mortality in sildenafil users versus non-users aged 40–70, with strict adjustment for age, sex, smoking, cancer, and diabetes, and assessment of heterogeneity and publication bias.