Researchers said patients who take them for more than a year, were 30% more likely to develop dementia. The research also analyzed over 27 million prescriptions, making this study the first of its kind.
A 2015 study, for example, showed a 54% increased risk of dementia among individuals prescribed high levels of anticholinergics over a 10-year period, compared with a control group.
Other antidepressants (mainly selective serotonin reuptake inhibitors) with an ACB score of 1 were linked to dementia, but only close to the time of prescription, which the researchers say is unlikely to represent a direct (causal) link.
Dr Carol Routledge, director of research at Alzheimer's Research UK, said: "While the results don't paint a straightforward picture, they do reveal a link between dementia risk and the use of certain drugs that may be prescribed to treat depression, urological conditions or the symptoms of Parkinson's disease. Previously, antihistamines have been implicated (in dementia risk), but we've not found any association between those specifically and dementia, as well as the gastrointestinal drugs", Savva said.
"Current guidelines for doctors say that anticholinergic drugs should be avoided for frail older people due to their impact on memory and thinking, but doctors should consider these new findings for all over-65s as long-term use could raise the risk of dementia", said Dr. Doug Brown, Chief Policy and Research Officer at the Alzheimer's Society, said in a statement.
But this doesn't mean that these medications are directly causing dementia, and experts say patients should not stop taking any medicine without talking to their doctor. The early symptoms of dementia include depression and urinary incontinence, so it is possible the drugs were sometimes being prescribed for people who already had the early stages.
Prof Chris Fox, Professor of Clinical Psychiatry at UEA's Norwich Medical School and Consultant Psychiatrist, said: "While the associations are moderate, given the high incidence of dementia, they reflect a potentially important risk to patients. Doctors, nurses and pharmacists need to work with older people and their carers to ensure that they only take medication if the benefits clearly outweigh the harms". "Not taking prescribed drugs could have serious consequences". The data was compared to the data of 283,933 people that didn't have dementia.
However the dose-response link was only seen for certain classes of anticholinergic drugs, including the antidepressants amitriptyline, dosulepin and paroxetine, and urologicals including oxybutyrin and tolterodine.
"Many of the treatment options for these conditions involve medication with anticholinergic effects". Of the controls, 30 percent were prescribed at least one anticholinergic drug; of the cases, 35 percent were.
"But the headline claim that some drugs, especially antidepressants, can cause dementia up to 20 years later should be looked at closely". "Don't stop taking your medication".
"Doctors and patients should therefore be vigilant about using anticholinergic medications". This type of study imagines that patients actually take their drugs as they were prescribed for them.