According to researchers at King’s College London, smoking “rots” the brain by damaging memory, learning and reasoning.
A study of 8,800 people over 50 showed high blood pressure and being overweight also seemed to affect the brain, but to a lesser extent.
Scientists involved said people needed to be aware that lifestyles could damage the mind as well as the body.
Their study was published in the journal Age and Ageing.
Researchers at King’s College London were investigating links between the likelihood of a heart attack or stroke and the state of the brain.
Data about the health and lifestyle of a group of over-50s was collected and brain tests, such as making participants learn new words or name as many animals as they could in a minute, were also performed.
They were all tested again after four and then eight years.
Researchers at the King’s College London found that smoking rots the brain by damaging memory, learning and reasoning
The results showed that the overall risk of a heart attack or stroke was “significantly associated with cognitive decline” with those at the highest risk showing the greatest decline.
It also said there was a “consistent association” between smoking and lower scores in the tests.
One of the researchers, Dr. Alex Dregan, said: “Cognitive decline becomes more common with ageing and for an increasing number of people interferes with daily functioning and well-being.
“We have identified a number of risk factors which could be associated with accelerated cognitive decline, all of which, could be modifiable.”
He added: “We need to make people aware of the need to do some lifestyle changes because of the risk of cognitive decline.”
The researchers do not know how such a decline could affect people going about their daily life. They are also unsure whether the early drop in brain function could lead to conditions such as dementia.
According to new studies, a daily multivitamin tablet may boost the memory and slow mental decline.
Taking supplements has a beneficial effect on memory and may work by increasing efficiency of brain cells.
One study showed that after just four weeks there were measurable changes in electrical activity in the brain when carrying out memory tests, not seen in a comparison group taking a placebo pill.
The body needs 13 vitamins to function properly and maintain health.
Vitamins A, C, D, E and K and the eight B vitamins each have specific job in the body.
Vitamin C keeps cells healthy, D regulates calcium and E maintains cell structure, while the B vitamins, including folic acid, have a wide range of functions.
One study at Monash University in Australia looked at whether multivitamins can improve cognitive abilities, and involved 3,200 men and women.
The results showed that those who used a multivitamin had improved ability to recall events or information.
The second study at Australia’s Swinburne University looked at women aged over 64 who had complained about poor memory.
Results showed that those taking a multivitamin supplement had improved rates of electrical activity in the brain while carrying out a memory test.
Researchers say it may work by increasing nerve cells’ efficiency and improving memory.
Professor David Kennedy, of the Brain, Performance and Nutrition Research Centre at Northumbria University, said: “The evidence is still limited but the studies hint at some possible beneficial effects.
“Optimal brain function depends on an adequate level of all of the vitamins. Multivitamins are likely to be more effective because people have different deficiencies.”
British researchers are to begin a study to find out if stress can trigger dementia.
The investigation, funded by the Alzheimer’s Society, will monitor 140 people with mild cognitive impairment or “pre-dementia” and look at how stress affects their condition.
The researchers will take blood and saliva samples at six-monthly intervals over the 18 months of the study to measure biological markers of stress.
They hope their work will reveal ways to prevent dementia.
The results could offer clues to new treatments or better ways of managing the condition, they say.
British researchers are to begin a study to find out if stress can trigger dementia
People who have mild cognitive impairment are at an increased risk of going on to develop dementia – although some will remain stable and others may improve.
And past work suggests mid-life stress may increase a person’s risk of Alzheimer’s disease.
A Swedish study that followed nearly 1,500 women for a period of 35 years found the risk of dementia was about 65% higher in women who reported repeated periods of stress in middle age than in those who did not.
Scottish scientists, who have done studies in animals, believe the link may be down to hormones the body releases in response to stress which interfere with brain function.
Prof. Clive Holmes, from the University of Southampton, who will lead the study, said: “All of us go through stressful events. We are looking to understand how these may become a risk factor for the development of Alzheimer’s.
“Something such as bereavement or a traumatic experience – possibly even moving home – are also potential factors.
“This is the first stage in developing ways in which to intervene with psychological or drug-based treatments to fight the disease.
“We are looking at two aspects of stress relief – physical and psychological – and the body’s response to that experience.”
Dr. Simon Ridley, of Alzheimer’s Research UK, said: “We welcome any research that could shed new light on Alzheimer’s disease and other causes of dementia.
“Understanding the risk factors for Alzheimer’s could provide one piece of the puzzle we need to take us closer to a treatment that could stop the disease in its tracks.”
A Korean study has found that obesity in later life puts people at higher risk of brain decline.
The study included 250 people aged between 60 and 70 found those with a high body mass index (BMI) and big waists scored more poorly in cognitive tests.
The Alzheimer’s Society said the research, published in the journal Age and Ageing, added to evidence that excess body fat can affect brain function.
Lifestyle changes can help make a difference, it said.
The study looked at the relationship between fat levels and cognitive performance in adults aged 60 or over.
The study included 250 people aged between 60 and 70 found those with a high body mass index (BMI) and big waists scored more poorly in cognitive tests
The participants underwent BMI – a calculation based on a ratio of weight to height – and waist circumference measurements, a scan of fat stored in the abdomen and a mental test.
Both a high BMI and high levels of abdominal fat were linked with poor cognitive performance in adults aged between 60 and 70.
In individuals aged 70 and older, high BMI, waist circumference and abdominal body fat were not associated with low cognitive performance.
The lead author of the study, Dae Hyun Yoon, said: “Our findings have important public health implications. The prevention of obesity, particularly central obesity, might be important for the prevention of cognitive decline or dementia.”