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Four in 10 dementia cases could be prevented or delayed by targeting risk factors, report says

BMJ 2020; 370 doi: https://doi.org/10.1136/bmj.m3050 (Published 03 August 2020) Cite this as: BMJ 2020;370:m3050
  1. Elisabeth Mahase
  1. The BMJ

Around 40% of dementia cases worldwide could have potentially been delayed or prevented if 12 risk factors had been targeted, the Lancet commission on dementia has said.1

The 28 dementia experts on the commission have added three modifiable risk factors to the nine they advised on in 2017: excessive alcohol consumption, traumatic brain injury, and air pollution.

The nine factors they previously highlighted were less education, hypertension, hearing impairment, smoking, obesity, depression, physical inactivity, diabetes, and low social contact.

“Together the 12 modifiable risk factors account for around 40% of worldwide dementias, which consequently could theoretically be prevented or delayed. The potential for prevention is high and might be higher in low-income and middle-income countries where more dementias occur,” the report said.

Around 50 million of the world’s people have dementia, and this number is projected to increase to 152 million by 2050, rising particularly in low and middle income countries, where around two thirds of people with dementia live.

The report said that the three new risk factors are associated with 6% of all dementia cases—with an estimated 3% of cases attributable to head injuries in mid-life, 1% to excessive alcohol consumption in mid-life, and 2% to exposure to air pollution in later life.

The other nine risk factors are associated with 34% of all dementia cases, with less education in early life, hearing loss in mid-life, and smoking in later life associated with the greatest proportion of dementia cases: 7%, 8%, and 5%, respectively.

“Our report shows that it is within the power of policy makers and individuals to prevent and delay a significant proportion of dementia, with opportunities to make an impact at each stage of a person’s life,” said the report’s lead author, Gill Livingston, from University College London. “Interventions are likely to have the biggest impact on those who are disproportionately affected by dementia risk factors, like those in low and middle income countries and vulnerable populations, including black, Asian, and minority ethnic communities.”

The authors have called for nine ambitious recommendations for policy makers and individuals. These include maintaining a systolic blood pressure of 130 mm Hg or less in midlife from around age 40 years, encouraging the use of hearing aids for hearing loss and reducing hearing loss by protecting ears from high noise levels, and reducing exposure to air pollution and secondhand tobacco smoke.

Preventing head injury (particularly by targeting high risk occupations and transport), preventing alcohol misuse, and limiting drinking to less than 21 units a week, as well as stopping smoking uptake and helping individuals stop smoking, have also been suggested.

All children should receive primary and secondary education, and people should be encouraged to lead an active life into mid, and possibly later life, to reduce obesity and diabetes.

Rosa Sancho, head of research at Alzheimer’s Research UK, said, “With no treatments yet able to slow or stop the onset of dementia, taking action to reduce these risks is an important part of our strategy for tackling the condition. Prevention strategies must be underpinned by robust evidence, and while our understanding of dementia risk is growing, there is still much we need to know about the different risk factors for dementia. This report underlines the importance of acting at a personal and policy level to reduce dementia risk.”

These actions are especially important in low and middle income countries, where the prevalence of dementia is rising more rapidly than in high income countries, the report said.

Coauthor Adesola Ogunniyi, from the University of Ibadan, Nigeria, said, “In low and middle income countries the higher prevalence of dementia risk factors means an even greater proportion of dementia is potentially preventable than in higher income countries. In this context, national policies addressing dementia risk factors, like primary and secondary education for all and stopping smoking policies, might have the potential for large reductions in dementia and should be prioritised. We also need more dementia research coming from low and middle income countries, so we can better understand the risks particular to these settings.”

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