Background: A subset of patients are diagnosed with lethal prostate cancer early in life, before PSA screening is typically initiated. To identify opportunities for improved detection we evaluated patient clinical and sociodemographic factors associated with advanced versus localized prostate cancer diagnosis across the age spectrum. Methods: We conducted a retrospective cohort study using the National Cancer Database, identifying patients diagnosed with prostate cancer in 2004-2016. We compared characteristics of patients diagnosed at advanced (cN1 or M1) versus localized (cT1-4N0M0) stage. Using multivariable logistic regression, we evaluated the associations among patient clinical and sociodemographic factors and advanced diagnosis, stratifying patients by age as <55 (before screening is usually initiated), 55-65, 65-75, and >75 years. Results: We identified668,486 patients who met inclusion criteria (mean age at diagnosis=64.6 years), including 33,455 (5.0%) with advanced disease at diagnosis. Uninsured (odds ratio, OR=3.78, 95% confidence interval, CI 3.56-4.02) and Medicaid-insured (OR 2.84, 95% CI 2.70-3.00) versus commercially insured patients were more likely to be diagnosed with advanced disease, however this effect was more pronounced for younger patients. Among patients <55 years, uninsured (OR 4.63, 95% CI 4.08-5.25) and Medicaid (OR 3.59, 95% CI 3.22-3.99) versus commercial insurance were associated with greater odds of advanced cancer at diagnosis. Similarly, residence in the lowest versus highest income quintile (OR 1.21, 95% CI 1.04-1.40) was associated with increased odds of advanced prostate cancer in patients <55 years. Black versus White race was associated with increased odds of advanced prostate cancer at diagnosis later in life (OR 1.15, 95% CI 1.11-1.19), however race was not significantly associated with stage of prostate cancer in those <55 years (p=0.29). Conclusions: Sociodemographic disparities in advanced stages of prostate cancer diagnosis were more pronounced in younger patients, particularly with respect to insurance status. These findings may support greater attention to differential use of early prostate cancer screening by health insurance.