Can we really reduce the number of people living with dementia by 40%?

Understanding dementia risk is a complex task. There are lots of different factors that can contribute to a person’s risk and these can sometimes interact with each other in ways that are difficult to study and understand. But we know that if we can understand what increases the risk of developing dementia, governments and individuals can be better informed about how to reduce that risk.

In 2017 the Lancet Standing Commission on dementia prevention, intervention, and care identified potential “modifiable” risk factors for dementia – meaning factors that may be in our power to change. The researchers also suggested that eliminating these risk factors could significantly reduce the number of people living with dementia.

But scientists are constantly learning, and dementia research is always pushing forward. So, The Lancet Commission authors have now published an updated list of modifiable risk factors which considers new research that has happened since the original report.

What did we already know about reducing dementia risk?

First, it is important to understand how these risk factors are identified and what they really mean. Often these individual risk factors are identified through observational studies. Researchers can take a group of people and try to understand if those with certain behaviors or conditions are more or less likely to develop dementia. This type of research is incredibly useful for finding these links, but it does not explain WHY two things may be connected (i.e. whether there is cause and effect).

The Lancet Commission takes all these individual studies to build the most comprehensive picture of dementia risk. However, this picture is still incomplete and there are many things about dementia risk that we do not understand.

In 2017, the report identified nine modifiable risk factors. Our age and our genetics determine most of our risk for dementia. While there is nothing we can do to change these aspects of our risk, modifiable risk factors are things we as individuals, or policymakers, may be able to do something about. Those nine factors were:

• Early life education
• Hearing loss
• Smoking
• Depression
• Lack of physical activity
• Social isolation
• High blood pressure
• Diabetes
• Obesity

What is new in 2020?

As well as adding further evidence to the nine factors identified in 2017, the researchers have also added three more risk factors for dementia to their list. These are:

• Higher alcohol consumption (more than 21 units a week)
• Traumatic brain injury
• Exposure to air pollution

These three risk factors have now been added to the list of modifiable risk factors as more evidence has come to light since 2017. This means that scientists have determined there has been enough research to demonstrate a link between these factors and increased dementia risk.

Scientists have also calculated how these factors may impact the number of people living with dementia. They estimate that if all the 12 modifiable factors were eliminated then the number of dementia cases would fall by 40%.

Can we really reduce the number of people living with dementia by 40%?

Even though this research provides policymakers and individuals with ideas on how to minimise risk there are other important things to consider when thinking about dementia risk.

While it is estimated that 40% of dementia cases could be due to these risk factors combined, that still leaves 60% of cases that are not linked to these. It may be that these are down to things that we cannot change, like aging or our genes. There may also be other modifiable risk factors that are yet to be included in this list. For instance, the scientists in this study note that there is some evidence that sleep can impact dementia risk. However, currently there have not been enough large-scale studies in this area for sleep to be included on the list.

And while there are steps that people and policymakers can take to reduce the impact of the modifiable risk factors identified in this report, it will never be possible to entirely eliminate these. That means that alongside action to mitigate against these risk factors, research into new life-changing treatments for dementia is also essential.

The report highlights some things to consider when interpreting these results. Most of the data is collected from high income countries and the calculations around case reduction are also based on those same countries. Much more research is needed to understand how dementia risk differs across the world.

It can also be difficult to separate some of these risk factors from one another. For instance, we know that hearing loss and depression can lead to social isolation. There is also a debate around whether depression later in life is in fact an early symptom of dementia, rather than something that increases the risk of developing dementia.

What does this mean for me?

These studies are all done at a population level, across large numbers of people, not for individuals. The most important thing to remember is that there is never any blame attached to a dementia diagnosis. Even if someone avoids all these risk factors there is no guarantee that they will avoid developing dementia. There are lots of things that are outside our individual control.

More research needs to be done to fully understand dementia risk, and to unpick why some of these factors may impact the number of people living with dementia. At Alzheimer’s Research UK we are committed to funding scientists doing exactly that. We have funded 45 studies looking at risk reduction in dementia, totalling £7 million of investment. However, now more than ever we need your help to continue to support this vital research.

In the meantime, the best advice is that what’s good for your heart is good for your head: that means eating a balanced diet with plenty of fruit and vegetables, staying mentally and physically active, and keeping blood pressure, weight and cholesterol in check. For more information on how to reduce your risk of dementia, head to our dementia information pages.