Study says millions of dementia cases could be prevented or delayed

Millions of dementia cases could be avoided or postponed by tackling a range of risks, including smoking and air pollution, according to a major new study. However, external experts have cautioned that these steps have limits.

The debilitating condition gradually deprives people of memory, cognitive skills, language and independence, and currently affects more than 55 million people worldwide.

Dementia results from a range of diseases, with Alzheimer's being the most common.

A vast review of the available evidence, published in The Lancet on Wednesday, said there is a "potential for prevention is high" in efforts to combat dementia.

The research updates an earlier 2020 report, which likewise underlined the value of prevention.

That international group of researchers had estimated that 40 percent of dementia cases were associated with 12 risk factors.

Those factors were lower educational attainment, hearing difficulties, high blood pressure, smoking, obesity, depression, physical inactivity, diabetes, excessive alcohol consumption, traumatic brain injury, air pollution and social isolation.

The latest update includes two further risks: sight loss and high cholesterol.

"Nearly half of dementias could theoretically be prevented by eliminating these 14 risk factors," the study said.

EU rejects new dementia drug

Despite decades of research and billions of dollars in investment, no cure or genuinely effective dementia medicine has been developed.

Since the beginning of last year, however, two Alzheimer's treatments have received approval in the United States: Biogen's lecanemab and Eli Lilly's donanemab.

The medicines target the accumulation of two proteins - tau and amyloid beta - which is thought to be one of the principal ways the disease advances.

Yet their benefits are still limited, they can cause serious side effects and they are frequently very costly.

Unlike the US, the European Union's medicines regulator declined to approve lecanemab last week, while it continues to assess donanemab.

Some scientists hope that the fact the new medicines have any effect at all will open the door to more effective treatments later on.

Others would rather concentrate on preventing dementia before it develops.

Masud Husain, a neurologist at the UK's University of Oxford, said that focusing on risk factors "would be far more cost effective than developing high-tech treatments which so far have been disappointing in their impacts on people with established dementia".

'How much more could we do?'

Specialists in the field welcomed the Lancet study, for whom the importance of prevention is scarcely in dispute.

Nevertheless, some said claims that almost half of all dementia cases could be prevented need to be viewed in context.

As the study's authors recognised, it has not been demonstrated that the risk factors directly cause dementia.

For instance, might dementia lead to depression, rather than depression leading to dementia?

Untangling the separate risk factors is also challenging, although the researchers attempted to do so.

Certain factors may be inherently connected, including depression and isolation, or smoking and high blood pressure.

Most importantly, many of these risk factors are longstanding social problems that have proved almost impossible to eliminate entirely.

The study sets out recommendations that range from individual actions, such as wearing a helmet when cycling, to government measures, such as improving access to education.

"It is not clear whether we could ever completely eliminate any of these risk factors," Charles Marshall, a neurologist at Queen Mary University of London, told AFP.

"We already have public health programmes to reduce smoking and hypertension (high blood pressure), so how much more could we do?"

Tara Spires-Jones, a neuroscientist at the University of Edinburgh, said it was vital that "we do not blame people living with dementia for their brain disease".

This is because "it is clear that a large portion of dementias could not be prevented due to genes and things beyond people's control, like opportunities for education as children," she added.

© Agence France-Presse