Alzheimer's disease (AD) is the leading cause of dementia, and because the primary risk factor for AD is old age, the prevalence of the disease is increasing dramatically with ageing populations worldwide. Even in high-income countries, the cost of medical care and associated societal burdens of dementia threaten to become overwhelming as more people live into old age. In view of the lack of progress in developing a cure for AD and the rapidly increasing costs of dementia, policy makers and governments have a powerful incentive to provide more resources to develop AD therapeutics. The Lancet Neurology Commission was formed with the overarching aim to provide information and expert recommendations to policy makers and political leaders about...