Reducing the risk of dementia
Published:May 18, 2019DOI:https://doi.org/10.1016/S0140-67
Dementia is one of the fastest growing public health problems. According to data from the 2016 Global Burden of Disease Study, the number of people living with dementia worldwide more than doubled from 20·2 million in 1990, to 43·8 million in 2016. This number is expected to double again by 2030, with the steepest rises in low-income and middle-income countries where the effects of rapid population ageing are driving the increase in dementia. The 2015 World Alzheimer Report estimated that the annual global cost of dementia was more than US$800 billion, more than 85% of which relates to family and social costs rather than medical care. In response to this inescapable public health challenge, this week WHO published new guidelines on risk reduction of cognitive decline and dementia. These guidelines form the first response to one of seven priority areas established in May, 2017, at the 70th World Health Assembly and endorsed a global action plan on the public health response to dementia. Other priority areas include dementia as a public health policy, research and innovation, and diagnosis, treatment, care, and support.
Similar to the Lancet Commission on dementia prevention and care, the new WHO guidelines summarise the knowledge base for health-care providers, governments, policy makers, and other stakeholders on factors known to reduce the risk of cognitive decline and dementia. The guidelines make strong recommendations on the potential of physical activity interventions and tobacco cessation for risk reduction. For management of hypertension and diabetes, the guidelines suggest that the evidence for risk modification of cognitive decline is low but recommend management according to current WHO guidelines related to prevention and control of non-communicable diseases. There are also conditional recommendations on diet and weight management as risk reduction strategies. The committee found insufficient evidence to recommended management of depression or hearing loss specifically as risk reduction strategies. The guidelines did choose to endorse cognitive stimulation therapy and cognitive training, even though the evidence is of low-quality at present. The omission of education in childhood as a risk reduction strategy is disappointing, given the strong evidence that cognitive reserve built by education can act as a buffer for cognitive decline.
The release of these guidelines by WHO is clearly a welcome and important step. The clinical situation for dementia is one in which no disease-modifying treatment is available. After the trials of aducanumab, which many thought was the best hope for a disease-modifying drug for Alzheimer's, were recently halted for futility, foreseeable areas of development seem very unlikely to create an advance that could alter the trajectory of the looming public health emergency in the next decade. The role of risk reduction and of WHO in leading this public health approach is therefore paramount. However, by taking a relatively conservative approach towards dementia, which has only quite recently become a research priority, with the consequence of less accumulated evidence, the ensuing guidelines are potentially rather unambitious. WHO has also not provided much guidance on execution, lacking recommendations for measurement and targets, or an assessment of economics. Waiting for a high-quality evidence base for simple prevention interventions, which are of demonstrable value for other reasons, will not stem the tide of this public health problem, and there is a need to consider how member states can create useful policy in uncertainty when there is a pressing need.
Although these guidelines, summarising risk factors, inform clinicians and policy makers, there remains a pressing need for recommendations on stronger public health policies. There is clear agreement coalescing around some of the risk factors for dementia, many of which overlap with those for other non-communicable diseases, such as cardiovascular disease and diabetes. Global action is needed to prioritise people over vested interests in the international public health threats of tobacco, alcohol, diet, and sedentary lifestyle. WHO needs to step up towards a global leadership role, be bolder, and demonstrate true leadership to effect the desperately needed change in the trajectory of dementia and other non-communicable diseases, in order to truly serve the needs of the millions of people living in the shadow of dementia.
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