Aims and Method We aimed to determine the prevalence of risk factors for obstructive sleep apnoea (OSA) in patients with mild cognitive impairment (MCI) or dementia. Using patient records across a 5 year period, we identified 16 855 patients with dementia or MCI. We gave scores for keywords relating to each modified STOP BANG parameter in patient progress notes. Based on individual scores, we stratified the population into groups with low, intermediate and high risk of OSA. Results Our population had a high prevalence of risk factors and consequently high risk scores for OSA (18.21% high risk). Parameters directly related to sleep had a low prevalence. Clinical implications The risk of developing or having OSA is high among patients with MCI and dementia. Low sleep parameter frequency probably suggests poor documentation of sleep rather than true prevalence. Our findings support the implementation of the STOP BANG or a similar screening tool as a standardised method to identify OSA risk in memory clinics.