Political drive to screen for pre-dementia: not evidence based and ignores the harms of diagnosis

Clinical context—Dementia is age related and with an ageing global population is predicted to become an overwhelming and costly problemDiagnostic change—Introduction of broader diagnostic criteria for mild cognitive impairment and pre-dementia based on new cognitive screening tests coupled with cerebrospinal fluid biomarkers and neuroimagingRationale for change—Past neglect of services and research in dementia has fuelled international calls for action and earlier treatmentLeap of faith—People with mild symptoms will eventually develop dementia and interventions are more likely to be effective at an early stageImpact on prevalence—The current prevalence of dementia is thought to be 10-30% in people over the age of 80, but the adoption of new diagnostic criteria will result in up to 65% of this age group having Alzheimer’s disease diagnosed and up to 23% of non-demented older people being diagnosed with dementiaEvidence of overdiagnosis—Screening for cognitive impairment and measurement of biomarkers and neuroimaging are increasing the diagnosis of mild cognitive impairment, which in many people will improve spontaneouslyHarms from overdiagnosis—Unnecessary investigation and treatments with side effects; adverse psychological and social outcomes; and distraction of resources and support from those with manifest dementia in whom need is greatestLimitations—Current case identification and screening policy relies mostly on anecdotal and observational data from potentially biased sources, including those with vested commercial interests, rather than evidence from clinical trials. There is a lack of research focused on older people, in whom dementia is most prevalentConclusions—Current policy is rolling out untested and uncontrolled experiments in the frailest people in society without a rigorous evaluation of its benefits and harms to individuals, families, service settings, and professionals