Using strong anticholinergic medication every day for three years or more is associated with a nearly 50% increased risk of dementia in those aged 55 years and over, a study published in JAMA Internal Medicine has found (24 June 2019).
Researchers at the University of Nottingham carried out a large nested case–control study of 58,769 patients with a diagnosis of dementia and 225,574 matched controls, all aged 55 years and over, in order to assess the associations between anticholinergic drugs treatments and risk of dementia.
Anticholinergic drug exposure was assessed using prescription information from 1 to 11 years before diagnosis of dementia (or the equivalent dates in control patients). Further analysis looked at prescriptions for anticholinergic drugs up to 20 years before diagnosis of dementia.
The researchers found that the risk of developing dementia increased from 6% in the lowest overall anticholinergic exposure category (1–90 total standardised daily doses) to 49% in the group exposed to daily anticholinergics for three years or more, compared with no anticholinergic drug prescriptions in the 1–11 years before the index date.
Significant increases in dementia risk were seen in the anticholinergic antidepressants, anti-Parkinson medicines, bladder antimuscarinics, antipsychotics and antiepileptic drugs.
No significant increase in risk was found for the other types of anticholinergic drug studied such as antihistamines and gastrointestinal medicines.
The researchers also found that the association was stronger in cases diagnosed before the age of 80 years and in those diagnosed with vascular dementia, rather than Alzheimer’s disease.
They recommended that the adverse effects of these medicines should be considered alongside the benefits and alternative treatments considered where possible, such as other types of antidepressant or non-pharmacological treatments for depression, alternative antiparkinsonian drugs and bladder training or medication for overactive bladders.
“This study provides further evidence that doctors should be careful when prescribing certain drugs that have anticholinergic properties,” said Tom Dening, head of the centre for dementia at the University of Nottingham and one of the researchers in this study.
“However, it’s important that patients taking medications of this kind don’t just stop them abruptly, as this may be much more harmful.”
The study was observational and was, therefore, unable to evaluate causality; however, the authors said that if the association was causal, the findings indicated that around 10% of dementia diagnoses were attributable to anticholinergic drug exposure, equating to around 20,000 of the 209,600 new cases of dementia per year in the UK.