Given considerable variation in diagnostic and therapeutic practice, there is a need for national guidance on the use of neuroimaging, fluid biomarkers, cognitive testing, follow-up and diagnostic terminology in mild cognitive impairment (MCI). MCI is a heterogenous clinical syndrome reflecting a change in cognitive function and deficits on neuropsychological testing but relatively intact activities of daily living. MCI is a risk state for further cognitive and functional decline with 5–15% of people developing dementia per year. However, ~50% remain stable at 5 years and in a minority, symptoms resolve over time. There is considerable debate about whether MCI is a useful clinical diagnosis, or whether the use of the term prevents proper inquiry (by history, examination and investigations) into underlying causes of cognitive symptoms, which can include prodromal neurodegenerative disease, other physical or psychiatric illness, or combinations thereof. Cognitive testing, neuroimaging and fluid biomarkers can improve the sensitivity and specificity of aetiological diagnosis, with growing evidence that these may also help guide prognosis. Diagnostic criteria allow for a diagnosis of Alzheimer’s disease to be made where MCI is accompanied by appropriate biomarker changes, but in practice, such biomarkers are not available in routine clinical practice in the UK. This would change if disease-modifying therapies became available and required a definitive diagnosis but would present major challenges to the National Health Service and similar health systems. Significantly increased investment would be required in training, infrastructure and provision of fluid biomarkers and neuroimaging. Statistical techniques combining markers may provide greater sensitivity and specificity than any single disease marker but their practical usefulness will depend on large-scale studies to ensure ecological validity and that multiple measures, e.g. both cognitive tests and biomarkers, are widely available for clinical use. To perform such large studies, we must increase research participation amongst those with MCI.

With population ageing worldwide, dementia poses one of the greatest global challenges for health and social care in the 21st century. In 2019, around 55 million people were affected by dementia, with the majority living in low- and middle-income countries. Dementia leads to increased costs for governments, communities, families and individuals. Dementia is overwhelming for the family and caregivers of the person with dementia, who are the cornerstone of care and support systems throughout the world. To assist countries in addressing the global burden of dementia, the World Health Organisation (WHO) developed the Global Action Plan on the Public Health Response to Dementia 2017–2025. It proposes actions to be taken by governments, civil society, and other global and regional partners across seven action areas, one of which is dementia risk reduction. This paper is based on WHO Guidelines on risk reduction of cognitive decline and dementia and presents recommendations on evidence-based, multisectoral interventions for reducing dementia risks, considerations for their implementation and policy actions. These global evidence-informed recommendations were developed by WHO, following a rigorous guideline development methodology and involved a panel of academicians and clinicians with multidisciplinary expertise and representing geographical diversity. The recommendations are considered under three broad headings: lifestyle and behaviour interventions, interventions for physical health conditions and specific interventions. By supporting health and social care professionals, particularly by improving their capacity to provide gender and culturally appropriate interventions to the general population, the risk of developing dementia can be potentially reduced, or its progression delayed.

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Background The potential economic value of interventions to prevent late-onset dementia is unknown. We modelled this for potentially modifiable risk factors for dementia.Methods For this modelling study, we searched PubMed and Web of Science from inception to March 12, 2020, and included interventions that: successfully targeted any of nine prespecified potentially modifiable risk factors (hypertension, diabetes, hearing loss, obesity, physical inactivity, social isolation, depression, cigarette smoking, and less childhood education); had robust evidence that the intervention improved risk or risk behaviour; and are feasible to enact in an adult population. We established when in the life course each intervention would be delivered. We calculated dementia incidence reduction from annual incidence of dementia in people with each risk factor, and population attributable fraction for each risk, corrected for risk factor clustering, and how effectively the intervention controls the risk factor. We calculated the discounted value of lifetime health gain and effect on cost (including NHS, social care and carer costs) per person eligible for treatment. We estimated annual total expenditure on the fully operational intervention programme in England. Findings We found effective interventions for hypertension, smoking cessation, diabetes prevention, and hearing loss.Treatments for stopping smoking and provision of hearing aids reduced cost. Treatment of hypertension was costeffective by reference to standard UK thresholds. The three interventions when fully implemented would save £1•863 billion annually in England, reduce dementia prevalence by 8•5%, and produce quality-adjusted life-year gains. The intervention for diabetes was unlikely to be cost-effective in terms of effect on dementia alone.Interpretation There is a strong case for implementing the three effective interventions on grounds of costeffectiveness and quality-of-life gains, as well as for improvements in general health. The interventions have the potential to remain cost-saving or cost-effective even with variations in dementia incidence and costs and effectiveness of interventions.

Brain health is essential for physical and mental health, social well-being, productivity, and creativity. Current neurological research focuses mainly on treating a diseased brain and preventing further deterioration rather than on developing and maintaining brain health. The pandemic has forced a shift toward virtual working environments that accelerated opportunities for transdisciplinary collaboration for fostering brain health among neurologists, psychiatrists, psychologists, neuro and socio-behavioral scientists, scholars in arts and humanities, policymakers, and citizens. This could shed light on the interconnectedness of physical, mental, environmental, and socioeconomic determinants of brain disease and health. We advocate making brain health the top priority worldwide, developing common measures and definitions to enhance research and policy, and finding the cause of the decline of incidence of stroke and dementia in some countries and then applying comprehensive customized cost-effective prevention solutions in actionable implementation units. Life cycle brain health offers the best single individual, communal, and global investment.