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A team of UK researchers has been investigating the association between prescription medications and dementia using a dataset funded by Dementias Platform UK (DPUK).

A box of medication spills out over a flat surface

The scientists found that over 200 common medications were associated with an increased risk of dementia, while four travel vaccines were linked to a lower risk of dementia. The researchers state that the drugs are unlikely to be causing this increased risk, rather that what the medications are treating could be an early sign of dementia.

Researchers scoured the Secure Anonymised Information Linkage Dementia e-cohort (SAIL-DeC) to find links between commonly prescribed medications and dementia. Funded by DPUK, SAIL-DeC contains routinely collected healthcare data from the Welsh population.

The research team – led by Dr Tim Wilkinson, Clinical Lecturer from the Centre for Clinical Brain Sciences at the University of Edinburgh – describes its findings in a new paper, published in the Journal of Epidemiology & Community Health.

Dr Tim Wilkinson said: ‘Although we found that many drugs were associated with an increased dementia risk, we think it is unlikely that the drugs themselves are causing this increased risk. Patients should certainly not stop their medications based on these findings.’

Of the 744 prescription medications that the team investigated, 217 were associated with an increased risk of dementia – meaning people taking those drugs were more likely to develop dementia. These medications included treatments for epilepsy, bipolar affective disorder, infections, pain, nausea, anxiety, diarrhoea, and constipation.

Interestingly, the researchers found that these medications could easily be grouped around certain conditions based on the strength of their association with dementia, even if they worked in different ways. This suggests that the symptoms they treat are common in the years before dementia diagnosis, which could shed light on the early stages of dementia.

Dr Wilkinson’s team also found four medications that were associated with a lower risk of dementia, meaning people who took them were less likely to develop dementia. These medications – all of which are travel vaccines – are given to holidaymakers to prevent hepatitis A, typhoid, and diphtheria.

The underlying theme in these medications suggests that other factors are involved in the lower risk of dementia, rather than the association being a direct cause of the vaccines. For example, education level or socioeconomic status could influence whether someone gets a travel vaccine.

Another theory is reverse causation: that subclinical dementia is the cause of the association. For example, people experiencing signs of dementia could be less likely to travel abroad, so wouldn’t need a travel vaccine. For most medications studied, when only those prescribed more than five years prior to a dementia diagnosis were analysed, their association with dementia fell significantly. This implies that reverse causality was behind the initial high associations between these drugs and dementia.

The authors acknowledge that there are many ways to interpret their data, so encourage more in-depth investigation of hypotheses generated by their findings. They recommend exploring whether varying doses of the medications or the number of times they were prescribed affects their association with dementia. To facilitate this research by other scientists, Dr Wilkinson and his team have made their results publicly available.