Although dementia is common, with an expected prevalence of 13 in 1000 in people aged 65-69 and 122 in 1000 in those over 80, only about half of those affected are diagnosed.1 Without a diagnosis, patients and carers cannot access the services they need, so earlier diagnosis is a key component of the National Dementia Strategy in the United Kingdom.2 3 However, early diagnosis is not easy and no definitive test exists. In the linked cross sectional study (doi:10.1136/bmj.b2030), Brown and colleagues assess the effectiveness of the “test your memory” cognitive test in detecting Alzheimer’s disease. The test was designed to minimise operator time and to be suitable for non-specialists to use.4

Cognitive function in established dementia is clearly different from the cognitive changes of normal ageing, but the onset of dementia is gradual. Diagnosis requires consideration of the person’s education, culture, and circumstances; dementia presents when a person’s cognitive abilities are no longer adequate for them to cope with their environment. A high flying executive may experience problems early in the neuropathological process, whereas a resident of a care home may …