Design classification. Population-based matched cohort: 29,554 men with intellectual disability (ID) matched to 518,739 comparators by index date, sex, and age (±2y); exposure = ID status at baseline, followed forward for symptoms→PSA→referral→biopsy→diagnosis→PC-specific death using Poisson/Cox regression with adjusted IRR/RR/HR — this is Module C (forward incidence trajectory), not a case-control design, because exposure is fixed at baseline and outcomes accrue prospectively over up to 18 years of follow-up (Kennedy et al., Eur Urol Oncol 2026).
Hub / textbook-path summary
No-ID modal path: symptom → PSA test → referral → biopsy → diagnosis → death, with attrition at each step but comparatively even losses. ID modal path follows the same nodes but with a sharper, compounding drop-off after PSA testing — each subsequent step loses proportionally more men than in the no-ID band, and the pathway acquires two extra "hub" nodes not seen at meaningful frequency in the no-ID band: diagnosis-at-death and de novo metastatic presentation (Table 2, Kennedy et al. 2026).
Outlier / divergence summary
Node
Why notable
Biopsy→Diagnosis step
Largest proportional gap between arms in the whole pathway (RR 0.51-0.54) — the single point where the ID trajectory most sharply diverges from the no-ID one.
Diagnosis recorded at death
Almost 6-fold more frequent in ID men (RR 5.96) — an extreme, low-frequency but clinically critical outlier node.
Severe-ID subgroup
Mortality HR (5.10) more than double the overall ID HR (2.11), showing the aggregate estimate masks a much steeper trajectory for the most severely affected subgroup (Table 3).
References
Kennedy OJ, Chauhan U, Gorman L, Lorigan P, Merriel SWD, Van Staa T, Wright A, Ashcroft DM. Prostate Cancer Care for Men with an Intellectual Disability: A Population-based Cohort Study of Symptoms, Diagnosis, Treatment, and Survival. Eur Urol Oncol. 2026. https://doi.org/10.1016/j.euo.2026.01.004