An investigation of healthcare and health inequalities experienced by people with intellectual disabilities, and improving their inclusion in health research

Henderson, Angela (2026) An investigation of healthcare and health inequalities experienced by people with intellectual disabilities, and improving their inclusion in health research. PhD thesis, University of Glasgow.

Abstract

Background
People with intellectual disabilities experience health care and health inequalities across the life course. Compared to the general population, they are more likely to experience multimorbidity, poor mental and physical health, premature mortality and poorer quality care. Despite increasing recognition of these inequalities, much of the existing research has been methodologically limited, often using small unrepresentative samples that are not generalisable. Also, the voices of people with intellectual disabilities are typically excluded from research and research processes that seek to understand and address these inequalities.

The objectives of this thesis are to:
1. Investigate the health care experienced by people with intellectual disabilities, and health care inequalities compared to the general population.
2. Investigate the health outcomes experienced by people with intellectual disabilities, and health inequalities compared with the general population.
3. Develop and implement a novel methodological approach to inclusive health research for people with intellectual disabilities.

Methods
This is a mixed methods thesis which includes 11 studies (9 quantitative and 2 qualitative). Seven of the quantitative studies use Scottish administrative datasets linked using the unique Community Health Index number to construct large, population-level cohorts of children, young people and adults with and without intellectual disabilities. Data sources include Scotland’s 2011 Census, the annual Scottish Pupil Census, Prescribing Information System, health and social care expenditure, and death registrations. These data enabled analysis of health and care expenditure, medication use, multimorbidity and mortality.

In the qualitative studies an adapted Citizens’ Jury was developed and implemented to ascertain its effectiveness in engaging people with intellectual disabilities in deliberations on inclusive research and academic peer review. These juries incorporated capacity building workshops, accessible materials and communications support to enable meaningful participation and coproduction in research.

Results
Health and social care expenditure for adults with intellectual disabilities in Scotland fell in real terms by 3.41% over three years (2012/13, 2013/14 and 2014/15), with disproportionate reductions in health funding and wide regional variation. Psychotropic prescribing, a marker of health care, was consistently high, 50.7% of adults were prescribed psychotropic medications in 2002-04 (T1) and 48.2% in 2014 (T2); antipsychotics: 24.5% (292/1190) in T1 and 16.7% (653/3906) in T2; antidepressants: 11.2% (133/1190) in T1 and 19.1% (746/3906) in T2. 21.2% (62/292) prescribed antipsychotics in T1 had psychosis or bipolar disorder, 33.2% (97/292) had no mental ill health or problem behaviours, 20.6% (60/292) had problem behaviours but no psychosis or bipolar disorder. A longitudinal, linked cohort, which included 545 adults for whom data was available at both T1 and T2, was established. In this group psychotropic prescribing increased over time and 77.3% of those prescribed antipsychotics in T1 remained on them 10 years later. Those with problem behaviours at T1 were over six times more likely to be prescribed antipsychotics (OR 6.45, 4.41-9.45) than those with no problem behaviours. Children and young people with intellectual disabilities were also more likely than their peers to be prescribed antipsychotics (OR 16.85, 15.29-18.56) and antidepressants (OR 2.28, 2.03-2.56). However, the magnitude of the difference between those with and without intellectual disabilities fell over time. Adults with intellectual disabilities were at greater risk of higher anticholinergic burden than their peers at all ages. Anticholinergic polypharmacy was more common, 61.3% vs, 54.7%, (OR 1.61, 1.41-1.83) as was psychotropic polypharmacy, 33.7% vs, 14.3%, (OR 2.79, 2.41-3.23).

A national e-cohort study linking >92% of the Scottish population to other administrative datasets, was established to create a resource for future academic research, including cancer and mortality studies. Of the whole population 0.5% (n=22,538) had intellectual disabilities, 12,837 males and 9,701 females. Analysis of data from Scotland’s largest health board reported that almost all adults (98.7%) with intellectual disabilities had multimorbidity, with an average of 11 cooccurring conditions. The pattern of multimorbidity observed was different to that of the general population. Multimorbidity was present across the life course. Adults with intellectual disabilities also had a higher mortality risk (Standardised Mortality Ratio (SMR) 2.24, 1.99-2.50), particularly those with Down syndrome (SMR 5.28, 3.98-6.57). Those with intellectual disabilities were twice as likely to experience avoidable deaths (29.8% vs, 14%). Children had an even higher mortality risk (SMR 11.6, 9.6-14.0) and were 3.6 (2.2-5.8) times more likely to experience avoidable deaths. During the COVID-19 pandemic, adults with intellectual disabilities had higher rates of infection (SIR 2.61, 1.81-3.40) and severe disease and/or death (SMR 3.26, 2.19-4.32), especially under the age of 65.

Inclusive research methods using adapted citizens’ juries enabled people with intellectual disabilities to deliberate on inclusive research practices and peer review. In the Research Voices citizens’ jury members produced a consensus report of 10 recommendations to improve the inclusion of people with intellectual disabilities in research. The peer review citizens’ jury proposed adaptations to the peer review process to enable inclusion of people with intellectual disabilities in reviewing research, including proposing the establishment of group-based reviews and improvements to the accessibility of academic publishing.

Impact
The research has already influenced national policy and data systems in Scotland, including the decision by Scottish Government to prioritise people with intellectual disabilities for COVID-19 vaccination and the inclusion of intellectual disabilities as a specific data field in Scotland’s National Hub for reviewing child deaths. It has advanced methodological innovation through the creation of a national e-cohort, enabling robust population-based research that continues to inform health and care policy.

Conclusions
This thesis provides strong evidence of the persistent health care and health inequalities experienced by people with intellectual disabilities and highlights the value of inclusive methodologies in amplifying their voices within complex research processes. The thesis also highlights the need for ongoing investment in high quality research to address the evidence gaps, inform policy and ensure responsive, equitable health and care for people with intellectual disabilities.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Subjects: R Medicine > RA Public aspects of medicine > RA0421 Public health. Hygiene. Preventive Medicine; R Medicine > RC Internal medicine > RC0321 Neuroscience. Biological psychiatry. Neuropsychiatry
• Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Health & Wellbeing > Mental Health and Wellbeing
• Supervisor's Name: Cooper, Professor Sally-Ann
• Date of Award: 2026
• Depositing User: Theses Team
• Unique ID: glathesis:2026-85839
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 25 Mar 2026 16:20
• Last Modified: 27 Mar 2026 10:48
• Thesis DOI: 10.5525/gla.thesis.85839
• URI: https://theses.gla.ac.uk/id/eprint/85839

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