Comorbidity Patterns and Temporal Associations of Multiple Long-Term Conditions in Adults with Intellectual Disability: an observational study in the United Kingdom

Objectives: To examine the distribution, temporal associations, and age/sex-specific patterns of multiple long-term conditions (MLTCs) in adults with intellectual disability (ID). Study Design: Observational study using longitudinal healthcare data. Methods: Analysis of 18144 adults with ID (10168 males and 7976 females) identified in the Clinical Practice Research Datalink, linked to Hospital Episode Statistics Admitted Patient Care and Outpatient data (2000-2021). We used temporal analysis to establish directional associations among 40 long-term conditions, stratified by sex and age groups (under 45, 45-64, 65 and over). Results: The high prevalence of enduring mental illness across all age groups is an important finding unique to this population. In males, mental illness occurred along with upper gastrointestinal conditions (specifically reflux disorders), while in females, mental illness presented alongside reflux disorders, chronic pain, and endocrine conditions such as thyroid problems. Among young males with intellectual disability, the combination of cerebral palsy with dysphagia, epilepsy, chronic constipation, and chronic pneumonia represents a distinctive pattern. In those aged 45-64, we observed early onset of lifestyle conditions like diabetes and hypertension, though notably these conditions co-occurred with mental illness and anaemia at rates exceeding those in the general population. The health conditions in those aged 65 and over largely mirrored those seen in the general aging population. Conclusions: Our findings highlight the complex patterns of MLTCs in this population, revealing sex-specific associations across age groups, and identified temporal associations, thus providing insights into disease progression, which can inform targeted prevention strategies and interventions to prevent premature mortality.