Harvard researchers have pinpointed over a dozen risk factors for dementia and other brain disorders - and all of them are preventable.

Researchers at Mass General Brigham analyzed 37 studies on dementia, stroke and late-life depression and found at least two of the disorders could be caused by 17 modifiable risk factors.

More obvious risks included conditions and lifestyle issues like diabetes, high cholesterol, alcohol use, obesity, sleep and hearing loss, among others.  

And common factors high blood pressure, diet and physical activity could increase the risk of all three disorders. 

But 'overlooked' ones like fulfillment in life, hearing quality, and pain sensitivity were also linked to brain disorders.

Researchers behind the study described the findings as 'hopeful' and believe they could help lower rates of dementia, stroke, and depression, all of which are on the rise in the US.   

However, they emphasized the findings are based on associations rather than direct causes.

The team called for more research on modifiable brain health factors and stopping diseases like dementia before they occur.

Dr Jasper Senff, lead study author and post-doctoral fellow at the Singh Lab at the Brain Care Labs, said: 'Dementia, stroke, and late-life depression are connected and intertwined, so if you develop one of them, there's a substantial chance you may develop another one in the future.

'And because they share these overlapping risk factors, preventive efforts could lead to a reduction in the incidence of more than one of these diseases, which provides an opportunity to simultaneously reduce the burden of age-related brain diseases.'

The review was published earlier this month in the Journal of Neurology, Neurosurgery & Psychiatry.

The researchers analyzed 37 articles. Of those, 36 were on stroke, 16 were on dementia, and two were on late-life depression. 

They then combined the data to identify modiable risk factors, or those that can be altered with behavioral changes, shared by at least two of the three diseases. 

The 17 risk factors associated with at least two of the diseases were: blood pressure, kidney disease, fasting plasma glucose, total cholesterol, alcohol use, diet, hearing loss, pain, physical activity, purpose in life, sleep, smoking, social engagement, and stress.

Of these, the team found high blood pressure and severe kidney disease had the greatest impact on incidence and burden of stroke, dementia, and late-life depression.

High blood pressure damages blood vessels in the brain, limiting blood flow to areas like the brain. This causes brain cells to die, resulting in dementia, particularly vascular dementia.

It is also a leading cause of stroke due to this blood vessel damage, as blood vessels become more prone to blockages. Elevated blood pressure also weakens the inner lining of the arteries, causing plaque to build up and clots to form.

Additionally, high blood pressure can cause inflammation in the brain, which is thought to increase the risk of depression.

Kidney disease, on the other hand, prevents the body from filtering out harmful toxins, which can damage brain cells and arteries, leading to dementia, stroke and late-life depression.

Physical activity and leisure time cognitive activity, such as completing puzzles, were associated with the lowest risk of brain disorders. 

However, the researchers suggested these associations may be 'symptomatic rather than causal,' as people with brain disorders like dementia may be less capable of exercising or doing puzzles. 

High blood pressure, diet and physical activity were the three risk factors shared by all three diseases. 

The team also looked at more 'overlooked' factors like fulfillment in life, hearing quality, and pain sensitivity. 

Emerging evidence suggests having a purpose in life can protect against changes in the brain that lead to dementia, such as brain cell death and a buildup of toxic proteins. 

A high quality of life also reduces the risk of depression.

Hearing loss has also been shown to cause cognitive strain and prevent social interactions, which add stress to the brain and can increase dementia and stroke risk. That lack of interaction may also influence depression.

Chronic pain has also been shown to lead to depression, as it can be limiting, and it can attack areas of the brain responsible for cognitive function.

Dr Sanjula Singh, senior study author and principal investigator at Brain Care Labs at Massachusetts General Hospital, said: 'Our study identified 17 modifiable risk factors shared between stroke, dementia, and/or late-life depression, emphasizing that there are many different steps individuals can take to lower their risks for these age-related brain diseases.'

There were several limitations to the study, such as relying only on existing reviews, meaning other risk factors may have been missed.