Overall, 14,453 cases (35%) and 86,403 controls (30%) were prescribed at least one anticholinergic drug with an ACB score of 3 (definite anticholinergic activity) during the exposure period. People prescribed greater dosage quantities over time of probable (ACB category 2) and definite (ACB category 3) anticholinergics had a higher risk of dementia, the researchers reported.
For example, anticholinergic use consistent with the highest dose category (more than 1,460 defined daily doses) was associated with an adjusted odds ratio for dementia of 1.57 (95% confidence interval, 1.18-2.09) for probable and 1.31 (95% CI, 1.22-1.41) for definite anticholinergics.
However, no increased risk was found for anticholinergics used to treat gastrointestinal, cardiovascular, or respiratory conditions. The research team also found no evidence for a cumulative harm of drugs considered “possibly” anticholinergic.
“A typical patient aged 65-70 might normally expect a period incidence of dementia of around 10% over the next 15 years, so this odds ratio would be consistent with an absolute risk increase of 2% (1% to 3%) over that period, corresponding to a number needed to harm of 50 (33 to 100),” they wrote.