No studies to date have investigated cumulative anticholinergic exposure and its effects in adults with intellectual disabilities.

To determine the cumulative exposure to anticholinergics and the factors associated with high exposure.

A modified Anticholinergic Cognitive Burden (ACB) scale score was calculated for a representative cohort of 736 people over 40 years old with intellectual disabilities, and associations with demographic and clinical factors assessed.

Age over 65 years was associated with higher exposure (ACB 1–4 odds ratio (OR) = 3.28, 95% CI 1.49–7.28, ACB 5+ OR = 3.08, 95% CI 1.20–7.63), as was a mental health condition (ACB 1–4 OR = 9.79, 95% CI 5.63–17.02, ACB 5+ OR = 23.74, 95% CI 12.29–45.83). Daytime drowsiness was associated with higher ACB (P<0.001) and chronic constipation reported more frequently (26.6% ACB 5+ v. 7.5% ACB 0, P<0.001).

Older people with intellectual disabilities and with mental health conditions were exposed to high anticholinergic burden. This was associated with daytime dozing and constipation.