Progression to dementia in patients with isolated memory loss

Background The diagnosis of dementia requires both memory loss and at least one other type of cognitive impairment. The natural history of patients with severe memory loss but no other type of cognitive impairment is poorly understood. We studied progression to dementia in patients with isolated memory loss. Methods From a registry of 811 patients with cognitive complaints, 21 patients with severe isolated memory loss of unknown cause were identified and followed up for a mean of 48 months. A comparison group of 198 patients on the same register was identified with newly recognised cognitive complaints but without dementia or isolated memory loss (mean follow-up 31 months). We did a range of neuropsychological tests at intake. Findings During follow-up, 48% (n=10) of patients with isolated memory loss developed dementia compared with 18% (n=36) of the comparison group. Life-table analysis showed the mean times to a diagnosis of dementia was 3.77 years (95% CI 2.99-4.56) and 5.96 years (5.60-6.31), respectively (p=0.01). The neuropsychological tests did not predict which patients would progress to dementia. Interpretation Patients with severe isolated memory loss have an increased risk of developing dementia and should be closely followed-up.