Screening for cognitive impairment in the elderly using the mini-mental state examination.

The use by non-medical staff of a brief screening instrument (the mini-mental state examination) to detect cognitive impairment among the elderly in primary care is described. Patients aged 75 years and over registered with nine general practices in north and north west London were invited by their general practitioners to take part in the study and 1170 patients participated, a response rate of 90%. The prevalence of possible or probable cognitive impairment (score below 25 on the mini-mental state examination) was 12.8%. Six per cent of patients scored below 19, at which score a high probability of dementia exists, although less than a third of this group had a diagnosis of dementia in their medical records. There was no significant difference between men and women or by social class in the proportion of patients with low scores, but the proportion with dementia rose from 2.5% in those aged 75-79 years to 29.0% among those aged 90 years and over. Under the new general practitioner contract there is a requirement to provide annual services to the elderly, including a 'mental assessment'. In a practice with a list size of 2000 around 130 patients are likely to be aged 75 years and over. Of these around 17 would require further assessment for possible dementia on the basis of results obtained using the mini-mental state examination.