Nearly three-quarters of dementia cases could be prevented, study suggests.
Researchers looked at a long list of 210 factors that could be linked to an increased risk of dementia.
They found among them 62 probable preventable causes of this disease.
These causes are estimated to be responsible for 47 to 73 percent of dementia cases.
This knowledge could save hundreds of thousands of people from a devastating diagnosis, with dementia currently affecting more than 900,000 people in the UK.
An unhealthy lifestyle, such as a sedentary lifestyle, has been shown to contribute to more cases of preventable dementia.
Too much time watching TV and sleeping less than seven hours or more than nine hours were among the lifestyle issues linked to a higher risk of dementia that people might be able to change.
Indeed, an unhealthy lifestyle has been found to contribute to a greater number of preventable cases of dementia – almost 17 percent – than a person’s medical history.
Exciting new findings from the study show that feeling tense or “very nervous” and rarely feeling able to confide in others could increase your risk of dementia.
But the most important among the 62 factors include things like frailty, measured by weak hand grip, and medical conditions like diabetes, disability or having previously had a stroke.
These medical risks can also be reduced by adopting a healthier lifestyle, such as regular physical activity and a healthy diet.
The study involved more than 344,000 Britons, who were interviewed in detail about their lives as part of the UK Biobank Health Study and followed for an average of 15 years.
The 62 probable causes of preventable dementia were identified because they were seen more often in the 4,654 study volunteers who developed the disease.
Professor David Smith, co-author of the study from the University of Oxford, said: “Many people still think that the risk of developing dementia is an inevitable part of aging.
“But these results show that dementia is much more preventable than previously thought.”
“This is extremely important because, in the absence of highly effective treatments for dementia, our priority must be to prevent its onset.”
The study, published in the journal Nature Human Behavior, found that a lifestyle including poor sleep, not having joined a sports club or gym and water consumption insufficient, could be the cause of 16.6% of cases of dementia.
Medical history, including disability, stroke, diabetes and depression, could account for 14 percent of cases.
Socioeconomic status, such as being unemployed or having lower income, which can make healthy choices more difficult, is estimated to be responsible for 13.5 percent of dementia cases.
The study also concludes that the risk of dementia can be reduced through physical measures, such as a stronger grip, and can be affected by social and psychological factors like loneliness and isolation.
People’s local environment, such as green spaces, was found to be less important, and early life, such as being breastfed as a child, was not linked to dementia.
The study found that people with a poor lifestyle could have a 62% higher risk of developing dementia than those with a good lifestyle.
It is estimated that improving all six categories – lifestyle, medical history, physical measurements, socio-economic status, social and psychological factors and local environment – from poor to good or intermediate would prevent 47 percent cases of dementia.
Improving them all to a good level prevented 73 percent of cases.
The results were seen in people regardless of age or gender, and remained similar even when accounting for genetic risk of dementia.
Patrick Holford, chief executive of the charity Food for the Brain, which offers a free online dementia risk questionnaire, said: “We already know that having a healthy lifestyle can significantly reduce your risk of dementia , and because this disease is not reversible, people really need to take the right steps in middle age to maintain cognitive function.
“Dementia is a completely preventable disease.”
