Having diabetes makes you more prone to dementia than being genetically at-risk, research suggests.
Oxford and Exeter University experts believe suffering a heart attack or stroke may pose the same threat.
Adults with all three obesity-fuelled conditions were three times more likely to get dementia, compared to ‘healthy’ people without any.
Charities today said the evidence was now clear that ‘what’s good for your heart is also good for your head’.
The findings, from an analysis of over 200,000 Britons, reiterate the importance of exercising and eating healthily, especially .
Dozens of studies have linked poor heart health with dementia, which affects nearly 1million people in the UK and 6.5million in the US.
A study rated the diet of more than 1,000 older people for anti-inflammatory foods and tracked them over an average of three years. Those with the most anti-inflammatory diet consumed around 20 pieces of fruit, 19 servings of vegetables, four servings of legumes and 11 cups of coffee or tea in the average week. Compared to this group, those with the least anti-inflammatory diet were three times more likely to get dementia
The new study, published in The Lancet Healthy Longevity, is one of the biggest to probe the link.
Lead author Dr Xin You Tai said: ‘Dementia is a major global issue, with predictions that 135million worldwide will have the devastating condition by 2050.
‘We found having such heart-related conditions is linked to dementia risk to a greater extent than genetic risk.
‘So whatever genetic risk you were born with, you can potentially make a big impact on reducing risk of dementia by looking after heart and metabolic health throughout life.’
Experts studied over-sixties in the UK Biobank, a database which contains the health records of half a million Britons, including brain imaging and genetic data.
They divided 200,000 participants into low medium and high-risk categories, based on their genetic likelihood of getting dementia by carrying genes such as APOE.
The team also logged which patients suffered cardiometabolic conditions, which are also known risk factors for dementia.
Of the participants studied, nearly 20,000 had been diagnosed with one of the three cardiometabolic conditions — diabetes, stroke or heart attack.
Around 2,000 people suffered from two, while 122 had all three.
The team found that the more of these three condition that a person had, the higher their risk of dementia.
Brain scans, available for 12,000 participants, showed widespread brain damage for those with more than one heart-related health condition.
Adults with a high genetic risk of dementia only had deteriorations in isolated areas of their brains.
Brain cells need a constant supply of blood and oxygen to work properly. Heart attacks and strokes interrupt this blood supply and can lead to loss of brain function.
Experts believe diabetes can lead to dementia as it triggers high blood sugar which is known to damage the hippocampus — the memory centre of the brain.
Exeter’s Professor David Llewellyn, senior study author said: ‘Many studies look at the risk of a single condition in relation to dementia, but health is more complex than that.
‘We know that many patients actually have a range of conditions.
‘Our study tells us that for people who have a diagnosis of diabetes, stroke or a heart attack it is particularly important to look after their health and ensure they are on the right treatment, to prevent further problems as well as to reduce their dementia risk.’
Dr Kenneth Langa, study co-author and medicine expert at the University of Michigan, said: ‘Our research indicates that protecting the heart throughout life likely also has significant benefits for the brain.
‘To look after your heart, you can engage in regular exercise, eat a healthy diet and do everything possible to ensure blood pressure, blood sugar and cholesterol levels fall within guidelines.’