Recent studies suggest that there is a higher rate of dementia among people who use certain commonly used medicines for long periods of time. Benzodiazepines (used for sleeping disorders and anxiety) and medications with ‘anticholinergic’ activity have been particularly implicated.
Data routinely collected in general practice provides an opportunity to examine these effects in the UK population. We are using data from the Clinical Practice Research Datalink to estimate the effect of regularly taking these medications on dementia diagnosis rates, taking into account known individual risk factors.
A major methodological challenge is to account for the possibility of confounding by indication. We are carefully exploring the possibility that the disease or symptom for which a medicine is prescribed is the cause of excess dementia risk or is a prodromal symptom of dementia, rather than the medicine itself conferring the excess risk.
Work package 1 - Primary Care Studies
We are using routine primary care data collected through the Clinical Practice Research Datalink (CPRD), to examine whether long-term prescriptions for Anticholinergics, Benzodiazepines and Z-drug are associated with greater dementia incidence in the older UK population.
Work package 2 - Cohort Studies
We are using data from various cohort studies, including the MRC Cognitive Function and Ageing Study (MRC CFAS) and The Irish Longitudinal Study on Ageing (TILDA), to examine whether Anticholinergic, Benzodiazepine and Z-drug use are associated with cognitive decline. Using MRC CFAS we are also able to look at whether neuropathological changes occur for those with long-term exposure to Anticholinergics, Benzodiazepines or Z-drugs.
Work package 3 - Systematic Reviews
Finally, we will evaluate and synthesise the available international evidence from various sources as well as the results from our observational studies to answer the questions as to whether Anticholinergic, Benzodiazepine and Z-drug use are associated with cognitive decline and increased dementia incidence.
Public Patient Involvement
We are working closely with the Alzheimer's Society who have funded Research Network Volunteers to act as study monitors and service user representatives on our study steering committee. The monitors contribute to our protocol development by sharing their experiences of psychoactive medication use and their view of the balance between the benefits of medication use and potential cognitive decline. Monitors meet the study team to regularly discuss study progress. They will be particularly concerned with the dissemination phase of our study, making sure that lay summaries of results are accessible and avoid possible misinterpretation.