A new study, published in the BMJ, has highlighted a potentially concerning aspect of a certain class of drugs that may warrant further investigation. Specifically, they’ve been linked to an increased risk of getting dementia, but as ever, a number of caveats are present.
This new comprehensive research endeavor looked at anticholinergic drugs. It’s a diverse group, with each individual drug used to treat a huge list of conditions, from hay fever and lung conditions to incontinence and depression, and millions around the world take them daily.
Their name refers to their ability to block acetylcholine, a neurotransmitter, which helps deal with said conditions. Stronger anticholinergic drugs can sometimes have powerful side-effects, though, including memory loss and confusion, and in the past, they’ve been linked to dementia, although not conclusively.
This new study, then, took another look, wanting to know if there was an association between the duration and level of exposure to various anticholinergic drugs and dementia risk.
In order to find out, they perused through patient records of people in the UK, including 40,770 aged 65-99 diagnosed with dementia between 2006 and 2015, and 283,933 controls without it. Of the controls, 30 percent were prescribed at least one anticholinergic drug; of the cases, 35 percent were.
Looking for a statistical correlation, the team found that there was, overall, a “robust association between some classes of anticholinergic drugs and future dementia incidence.” This means that some, but not all, anticholinergic drugs were implicated.
Specifically, anticholinergic antidepressant, urological, and antiparkinson drugs, prescribed 4-20 years before the diagnosis, seemed to increase the dementia risk. The more of these drugs taken over this period, the more likely the person was to get dementia in later life. These had to be drugs with very definitive anticholinergic effects, though, ranking a 3 on the anticholinergic cognitive burden scale.
Overall, there was an 11 percent increase in the incidence of dementia with people treated in the long-term with these drugs.
As pointed out by the Guardian, this risk change is fairly small: The absolute, actual risk of getting dementia for an individual taking these drugs in the long term was 13 percent, compared to everyone’s base risk of 10 percent during this time period.
Conversely, gastrointestinal anticholinergic drugs, as well as antihistamines used for hay fever and those used to treat muscle spasms, were “not distinctively linked to dementia.”
What this study absolutely didn’t show was that any of these drugs cause dementia. It’s not entirely clear what does cause it, but it’s likely to be multiple factors. This paper demonstrates that the use of these drugs boosts risk somewhat.
In any case, this is an associative link uncovered in what independent experts agree is an excellent study, one that warrants further investigation.
Independent expert Rob Howard, professor of Old Age Psychiatry at University College London, said that this “large and very well-conducted epidemiological study” doesn’t mean people prescribed these drugs should stop taking them. “People should talk to their doctors before stopping or changing and if the medications implicated,” he stressed.
It also must be stressed that all antidepressant drugs, for example, aren't anticholinergic.
Dr Carol Routledge, director of research at Alzheimer’s Research UK, agreed that this work “adds to existing evidence of a link between certain anticholinergic drugs and an increased risk of dementia.” She did, however, also point out that “anticholinergics can have many beneficial effects which doctors need to weigh against any potential side effects.”