Cancer diagnoses, referrals, and survival in people with a learning disability in the UK: a population-based, matched cohort study

Abstract

Background
People with a learning disability (LD, also known as intellectual disability) face poorer health outcomes, yet the burden of cancer in this population is poorly understood. This study investigated cancer-related outcomes in people with a LD compared to the general population.

Methods
A matched cohort study was conducted using linked primary care, hospital, mortality, and cancer registry data from Clinical Practice Research Datalink (CPRD) Aurum. In total, 180,911 individuals with a LD were matched with 3,405,467 controls. Outcomes included urgent suspected cancer (USC) referrals, cancer diagnoses, treatment within six months, and overall survival (OS) post-diagnosis.

Findings
Individuals with a LD had fewer USC referrals within 28 days of possible cancer symptoms (adjusted risk ratio [aRR] 0.52, 95% confidence interval [CI] 0.49–0.55). LD was associated with several cancers, including sarcoma (adjusted hazard ratio [aHR] 1.98, 1.65–2.39), central nervous system (aHR 3.42, 2.99–3.90), testicular (aHR 2.06, 1.61–2.62), and uterine cancers (aHR 1.69, 1.40–2.05) as well as cancer before age 50 years (aHR 1.74, 1.63–1.86). Absolute incidence was lower in individuals with a LD compared to without (3396 [1.9%] vs 67,506 [2.0%]) due to increased all-cause mortality (aHR 3.19, 3.12–3.27). LD was associated with fewer diagnoses via USC referrals (aRR 0.81, 0.76–0.86), fewer treatments within six months (aRR 0.83, 0.80–0.85) and shorter OS (median 4.4 years, 95% CI 3.9–5.1 vs 9.1 years, 8.8–9.5; aHR 1.73, 1.65–1.83). Melanoma, breast, and prostate cancers were less common but had up to a fourfold increased risk of death after diagnosis in individuals with a LD.

Interpretation
Individuals with a LD have higher cancer risk, more diagnoses outside USC pathways, fewer treatments, and poorer prognosis. Fewer diagnoses of some cancers, alongside worse outcomes, may indicate under-investigation. As premature all-cause mortality improves, cancer burden in this population may rise disproportionately.