A healthy lifestyle that includes regular exercise, a balanced diet, not smoking and watching alcohol intake could reduce the risk of dementia – even in those with a genetic predisposition to such conditions, researchers say.

Recent figures suggest there are 850,000 people living with dementia in the UK, and it is the leading cause of death for women in England. Many studies have indicated that lifestyle changes can reduce the risk of developing such conditions. A recent report suggested a third of cases could be prevented by tackling factors such as exercise, blood pressure, hearing and diet. In May, the World Health Organisation released guidelines on how to lead a brain-healthy lifestyle.

However, it remained unclear whether such measures could have the same effect on those whose genes predispose them to dementia. Now experts say it seems they do.

“We think there is a similar reduction in your risk of dementia associated with lifestyle, regardless of your genetic risk,” said Prof David Llewellyn of Exeter University, who led the research.

Llewellyn said the study also underscored that a high genetic risk or family history of dementia did not make it inevitable the condition would occur.

Writing in the Journal of the American Medical Association, Llewellyn and colleagues report how they came to their conclusions by studying data, collected as part of a wider research endeavour called the UK Biobank, from almost 200,000 individuals of European ancestry aged 60 or older and who did not have dementia or cognitive problems at the outset.

The team split participants into five equal groups based on their combination of almost 250,000 genetic variants linked to Alzheimer’s disease in those of European ancestry. From this it produced three categories of low, intermediate and high genetic risk for dementia – the former and latter each comprising 20% of participants.

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The researchers also looked at participants’ lifestyles, and the four key factors previously associated with a reduced dementia risk: meeting recommended guidelines for exercise, not smoking, eating from multiple food groups with little processed meat and lots of fruit and fish, and drinking one or fewer standard alcoholic drinks a day for women and two or fewer for men. Participants were given a score to reflect the overall “healthiness” of their lifestyle.

The team tracked participants for about eight years, during which time 1,769 people – fewer than 1% of participants – developed some form of dementia.

The results show that dementia prevalence was greater in the group with the highest genetic risk compared with the lowest: 1.2% and 0.6% respectively. A lower proportion of those with a healthy lifestyle developed dementia than those living unhealthily: 0.8% and 1.2%.

Crucially, these trends appeared independently of each other. When the team took into account factors including age, sex and socioeconomic status, it found that a healthy lifestyle was linked to about a 30% lower risk of dementia compared with an unhealthy lifestyle, regardless of a high or low genetic predisposition.

While the impact might seem small, the team said participants were at the younger end of older age, and that it would continue to follow the group to explore the link between lifestyle factors and dementia risk as people aged and more cases of dementia appeared.

The study has limitations, including that lifestyle data was collected at one point in time and was self-reported, and it does not prove a healthier lifestyle is driving a lower risk of dementia. The study looked only at those of European ancestry, while some cases of dementia could have been missed.

Prof Gill Livingston, an expert on dementia prevention at University College London who was not involved in the research, noted that the study looked at a small number of lifestyle factors and that participants had, in general, a healthier lifestyle than the general population.

Nonetheless, she welcomed the study. “This is a very important paper, with a clear message that healthy lifestyle reduces dementia risk no matter what your genes are,” she said.