Prevalence of dementias in a cohort of people with intellectual disability and general population – a registry-based study

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Introduction: There are few large registry-based studies comparing disease prevalence among people with intellectual disabilities (ID) compared to general populations, despite older people with ID having more comorbidities and health care utilization. This study aimed to explore differences in prevalence of dementia and age at first diagnosis between people with ID and the general population in Skåne, the southernmost region of Sweden.

Methods: A cohort of people with intellectual disability (n=6 699) and general population (n=888 317) was collected from Skåne Health Care Register for 2014-2021. Dementia diagnoses were based on ICD-10, and relative risks and 95% confidence intervals of having a diagnosis were estimated using Poisson regression. Age differences were explored using linear regression models. All analyses were performed in IBM SPSS Statistics 29.0.

Results: Adults (25-44 years) with ID were found more likely to have any diagnosis of dementia (F01-03, G30-31) compared to the general population (RR 44.1, 95% CI 29.8-65.4), and more specifically be diagnosed with Alzheimer’s Disease (G30) (RR 132.4, 95% CI 64.3-272.7), unspecified dementia (F03) (RR 132.4, 95% CI 64.3-272.7) as well as other degenerative diseases of the nervous system (G31) (RR 30.4, 95% CI 13.5-68.3). Increased risk for any dementia was found in all age groups except for those 65+. Regardless of diagnosis, people with ID were younger at first diagnosis recorded during the study
period.

Conclusions: The increased risks for dementia diagnoses in people with ID deserve further attention both clinically and in research to clarify diagnostic challenges and clinical assessments as well as to ensure that diagnoses and care are person-centred.