How we calculated our ‘one in two’ dementia statistic – and what we’ll do about it

It’s news no one wants to hear, but our new analysis, released today, has estimated if nothing changes, one in two people will be directly affected by dementia. They will either care for someone with the condition, develop it themselves, or both.

This statistic goes a long way to demonstrate the scale of the challenge we have on our hands. It’s a sobering outlook and highlights the urgent need for action.  

Understandably this news will be frightening to many – after all, we also know that dementia is one of the UK public’s most feared health conditions. And we know that it’s the UK’s biggest killer – nearly 66,000 people lost their lives to dementia last year in England and Wales alone.  

But we want you to reassure you that, at Alzheimer’s Research UK, we are not afraid of the work we need to do to put a stop to dementia. We are the charity leading the search for a cure. And we won’t stop until everyone is free from the heartbreak of dementia. 

How was the analysis done?

We wanted to better understand the potential future impact of dementia, so we commissioned the Office of Health Economics – a research consultancy – to use publicly available data to predict future trends.  

To do this, their analysts first developed separate estimations of the ‘lifetime risk’ – the risk of something happening during one’s lifetime – for both developing dementia, and for becoming an informal carer (someone, usually a spouse or child, who provides unpaid care to a loved one). To do this, they used a similar statistical approach that Cancer Research UK used to calculate their well-known 1 in 2 cancer statistic, something you may be familiar with.  

The analysis drew on data from two key sources: a large UK study known as the Cognitive Function and Ageing Study II, and also the Office of National Statistics (ONS) database. As a result, it was able to take into account how different factors varied throughout people’s lives as they age, including estimates of both dementia incidence (i.e., the number of new cases of dementia that would be expected to occur each year) and mortality (the number of people that would be expected to die from dementia each year). It also considered how these factors varied between men and women.  

The figures generated were then used to estimate a combined figure for the overall lifetime risk of either developing dementia, becoming a carer, or both. This final estimate also considers genetic factors – for example, a carer’s risk of later developing dementia themselves is higher if they are genetically related to the person they are caring for (although we should note that most cases of dementia are not directly caused by genes we inherit from our parents). 

By applying these lifetime risks to a hypothetical population of 100 people, the researchers were able to separate out the estimated number of individuals who will develop dementia and add the carers who do not develop dementia, both with or without a genetic link. This left us with a final figure – 55%, which is effectively one in two of us.  

What does this mean for the future?

Of course, this figure is based on a number of estimates – projections for future mortality and dementia incidence – which no matter how carefully they are calculated, rely on several assumptions.  

For one, the analysts weren’t able to incorporate the effect of any modifiable risk factors (i.e. aspects of our lives that we can control, such as our diet, alcohol consumption, and smoking habits).  

They have also assumed that the proportion of people with dementia will remain the same across different age groups over time. This means that any increase in the overall numbers of people living with dementia are only driven by the population getting older, rather than other factors such as modifiable risk factors or earlier detection of the condition.  

They’ve also assumed that the ONS’s predicted demographic changes to the UK population are reliable (although we think they’re the best we’ve got to go on). 

Avoiding this worst-case scenario

The ‘1 in 2’ figure paints a picture of what could happen if no progress is made in our efforts to tackle dementia: the very worst-case scenario. At Alzheimer’s Research UK, our hope is for a different kind of future, one where dementia can no longer destroy lives.  

That’s why today we’ve also launched our new 10-year plan, which outlines the changes we want to see for people affected by dementia, as we accelerate progress towards a cure.    

We will focus on making real, rapid progress on three fronts: treatment, diagnosis and prevention. And in the next decade, we want to see a world where:   

• people can access life-changing treatments for the diseases that cause dementia.  
• people get an earlier and more accurate diagnosis of the diseases that cause their dementia, so they can access treatments and research studies.   
• fewer people to develop the diseases that cause dementia.   

And while we know these are huge changes, we’ve never been more hopeful that we can make this future a reality. In recent months, two drugs for early Alzheimer’s, lecanemab and donanemab, have proved what we’ve always known – that through research we will begin to overcome the diseases that cause dementia.  

But we won’t stop there. With your support, we will keep going until everyone is free from the heartbreak of dementia – and that means finding a cure.  

We owe it to the people living with dementia now, and to future generations, to strive for better treatments and preventions, and a future where dementia is a thing of the past. 

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