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WHO dementia guidelines highlight a lack of evidence for lifestyle interventions

BMJ 2019; 365 doi: https://doi.org/10.1136/bmj.l2218 (Published 14 May 2019) Cite this as: BMJ 2019;365:l2218
  1. Elisabeth Mahase
  1. The BMJ

People can reduce their risk of dementia by adapting their lifestyle—such as getting regular exercise, not smoking, and maintaining healthy blood pressure, cholesterol, and blood sugar levels—according to World Health Organisation guidelines.1

Researchers have criticised the guidance, however, saying there is a lack of evidence for the effectiveness of many of the recommendations on how to prevent cognitive decline and an absence of cost or benefit calculations.

The guidance, which brings together decades of research, outlines a number of recommendations and indicates the quality of evidence behind them.

It is targeted at healthcare providers and aims to give them evidence based recommendations on lifestyle behaviours and interventions and advice on the management of specific physical and mental health conditions, to delay or prevent cognitive decline and dementia.

Recommendations advise that all adults should follow a healthy and balanced diet and that those with normal cognition should take up physical activity.

They advise against the use of vitamins B and E, polyunsaturated fatty acids, and multi-complex supplementation to reduce the risk of cognitive decline, and say that although there is “insufficient evidence” to recommend the use of hearing aids to reduce the risk of cognitive decline, these should still be offered to people with hearing loss.

Many of the recommendations included in the report were rated as having low or moderate quality evidence, highlighting the need for further investigation.

According to WHO, approximately 50 million people worldwide now have dementia, with around 10 million new cases every year. It is estimated that by 2030 there will be 82 million people living with the condition.

The new guidelines follow the launch of the WHO Global Dementia Observatory in December 2017 to compile information about what countries are doing around dementia, such as national plans, dementia friendly initiatives, awareness campaigns, and facilities for care. The observatory has so far collected data from 21 countries, including Bangladesh, Chile, France, Japan, Jordan, and Togo.

Bart De Strooper, director of the UK Dementia Research Institute at University College London, said: “The WHO report summarises a series of recommendations for a healthy lifestyle, which may also have beneficial effects on the incidence of dementia. Overall, however, little hard evidence is available to show that modifying environmental factors modify the risk for dementia strongly.

“Absence of evidence is not evidence of absence, and hypertension, obesity, diabetes, social isolation, and depression are all strongly correlated with poor health and decreased life expectancy, although the effects on the prevention of dementia needs further clarification.”

Gill Livingston, professor of psychiatry of older people at UCL, said: “It is difficult to distinguish between lack of evidence that intervention decreases the risk (say with obesity) and lack of evidence that decreasing the risk reduces cognitive impairment and dementia (say, for example, social interventions around isolation—studies on this have not been done and theoretically are very hard to do). Also, there is no formal calculation of the cost and benefits.”

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