- Design
- systematic review and meta-analysis of 8 observational studies using validated anticholinergic burden scores
- Population
- patients with Parkinson's disease, higher versus lower anticholinergic burden
- Primary outcome
- dementia, cognitive decline, fracture and emergency department attendance
- Effect
- fracture OR 1.53 (95% CI 1.28 to 1.84); emergency attendance OR 1.25 (1.15 to 1.36); dementia OR 1.71 (0.93 to 3.17), not significant
Eight studies comparing higher with lower anticholinergic burden in Parkinson's disease, using validated scoring systems, were pooled. The condition is a natural place to look: anticholinergic agents are used for tremor, for bladder symptoms, for sialorrhoea and for depression, so the cumulative load builds from several directions at once.
The significant associations were physical. Higher burden carried a higher risk of fracture (OR 1.53, 95% CI 1.28 to 1.84) and of emergency department attendance (OR 1.25, 1.15 to 1.36). The cognitive associations - dementia OR 1.71 (0.93 to 3.17) and cognitive decline, standardised mean difference -0.71 (-1.51 to 0.08) - both crossed the line of no effect and were not significant overall. A subgroup of European cohorts did show a significant dementia association (OR 2.91, 1.02 to 8.28), on the kind of wide interval that should not carry much weight.
This matters because the usual argument for reducing anticholinergic load in Parkinson's disease is made on cognition, and here the cognitive evidence is the weaker half. The stronger case is fractures and acute attendances - outcomes that are immediate, measurable and, in a population already falling because of postural instability, entirely plausible mechanistically through sedation, blurred vision and orthostatic hypotension. So make the argument you can support: run an anticholinergic burden score at each review, target the drugs contributing most - oxybutynin, tricyclics, first-generation antihistamines, trihexyphenidyl - and justify the deprescribing on falls and fractures rather than on a promise about memory.
- Calculate an anticholinergic burden score at every Parkinson's disease review
- Target oxybutynin, tricyclics, first-generation antihistamines and trihexyphenidyl first
- Justify deprescribing on fracture and fall risk, which is where the evidence is significant
- Substitute rather than simply stop - bladder symptoms and tremor still need managing
- Check lying and standing blood pressure after each reduction, and document the change
Why it matters
The case for cutting anticholinergic load in Parkinson's disease is usually made on memory, and the evidence actually supports it on fractures.
Don't overread it
Eight observational studies; confounding by disease severity is not excluded, and the cognitive associations were not statistically significant.
The statistics, in plain English
The fracture odds ratio of 1.53 with a tight interval of 1.28 to 1.84 is the most reliable number here - consistent across studies and precise. The dementia estimate of 1.71 with an interval from 0.93 to 3.17 crosses 1.0, which means no association was demonstrated, and the European subgroup result at 1.02 to 8.28 is barely distinguishable from chance. These are observational studies: patients on more anticholinergics have more symptoms and more advanced disease, which independently cause falls.
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