The association between multimorbidity and subsequent dementia: a descriptive cohort study in a representative UK database

Study type
Protocol
Date of Approval
Study reference ID
23_003176
Lay Summary

Multimorbidity refers to the presence of two or more long-term conditions within one person, and our primary aim is to investigate whether multimorbidity is associated with a subsequent dementia diagnosis. Polypharmacy refers to five or more medications being taken simultaneously by one person, and is common in people with multiple health conditions. Polypharmacy is problematic when drugs interact with each other, when medication regimes get too complicated to manage, or when drugs have harmful effects on the body. In such cases, clinicians may conduct medication reviews or deprescribing interventions to streamline a medication regime or reduce the number of drugs a person is taking. Therefore, the secondary aim of this study is to investigate how well deprescribing, medication reviews or polypharmacy are coded in CPRD data and whether presence of these alters the outcome of dementia – either positively or negatively. This study will also investigate whether people from different groups have different experiences i.e., whether there are inequalities present in a patient journey from multimorbidity to dementia. We will consider geographical region, ethnicity, sex and deprivation as possible sources of inequality.

The current study will define multimorbidity as 2 or more of a possible 37 conditions and conduct analyses in a large database which accurately represents the makeup of the UK population (CPRD GOLD). This research will benefit patients in England and Wales by informing reorganisation of services to best treat patients with multimorbidity and adding to the knowledge base of patients with dementia.

Technical Summary

The primary aim is to investigate whether multimorbidity at a younger age is associated with an earlier subsequent dementia diagnosis. The secondary aim is to investigate how well deprescribing, medication reviews or polypharmacy are coded in CPRD data and, if there are sufficient records, whether presence of these alters the outcome of dementia. This study will also investigate the inequalities in trajectory from multimorbidity to dementia in those with at least 20 years of follow-up, considering geographical region, ethnicity, sex and deprivation. We will use CPRD GOLD primary care data and Index of Multiple Deprivation at practice and patient level, conduct cox proportional hazards models to determine risk of dementia, Fine-Gray models to account for competing risk of death, sensitivity analyses to consider patients with <20 years of follow-up, and describe the patients with multimorbidity who have the greatest risk of dementia.

One recent longitudinal study has shown that multimorbidity at a younger age is more strongly associated with dementia than older ages, however this study considered only 13 multimorbidity conditions and used a population likely to be biased towards healthier participants. The current study will expand the definition of multimorbidity to include 37 conditions and conduct analyses in a large representative sample of the UK general population.

Health systems are increasingly treating patients with multimorbidity yet are structured primarily to treat single diseases. This research will benefit patients in England and Wales by informing existing research into how diseases interact with each other to influence patient outcomes, informing reorganisation of services to best treat patients with multimorbidity, and adding to the knowledge base of patients with dementia.

Health Outcomes to be Measured

Primary: first ever diagnosis of dementia

Exploratory: presence of medication review, polypharmacy or deprescribing record in the primary care data

Collaborators

Adam Todd - Chief Investigator - Newcastle University
Hilary Shepherd - Corresponding Applicant - Newcastle University
Andrew Kingston - Collaborator - Newcastle University
Charlotte Richardson - Collaborator - Newcastle University
David Sinclair - Collaborator - Newcastle University
Fiona Matthews - Collaborator - Newcastle University

Former Collaborators

Adam Todd - Collaborator - Newcastle University

Linkages

Patient Level Index of Multiple Deprivation;Practice Level Index of Multiple Deprivation