London, Aug 7 (IANS) Middle-aged smokers are 70 percent more likely to develop dementia than those who don't smoke, a new study has warned, prompting experts to advise regular physical and mental exercises.

The study published in Britain's Journal of Neurology, Neurosurgery and Psychiatry says people who smoke, have high blood pressure or diabetes massively increase their risk of developing dementia.

Under-55s who smoke increase their risk five-fold, and smokers aged between 46 and 70 have a 70 percent higher risk of developing chronic memory loss, according to the study.

Diabetes will more than triple the risk of dementia, says the study.

A separate study published this week in the American journal Neurology shows that people may be able to ward off the onset of dementia by stimulating their brain regularly through everyday activities such as reading, writing and playing card games.

Dr Susanne Sorensen, head of research at Britain's Alzheimer's Society, said: 'Interestingly this research has found that memory loss in people who are in the very early stages of the condition may be delayed by ordinary activities that engage the brain, whether they were well-educated in early life or not.

'This research suggests that exercising your brain as well as your body may play a role in the fight against dementia.'

The results in the British journal show that middle-aged people should immediately quit smoking and make lifestyle changes that will help control dementia rather than waiting until they are pensioners.

'A healthy heart means a healthy brain,' said Neil Hunt, Chief Executive of Alzheimer's Society, adding that people should keep active, eat a balanced diet, not smoke and have their blood pressure and cholesterol checked regularly.

In Britain alone, 700,000 people now live with dementia, and the figure is expected to rise to more than a million people by 2025 and 1.7 million by 2051.

The study in the British journal said: 'Smoking, hypertension and diabetes were associated with a higher risk of the outcome.'

'Our results suggest that, for prevention of dementia, control of cardiovascular risk factors starting in midlife is likely to be more important in the prevention of dementia than control starting later on,' it said.

The researchers, based in the universities of Minnesota, North Carolina and Johns Hopkins and the University of Mississippi Medical Center, studied more than 11,000 people aged 46-70.

Rebecca Wood, chief executive of the Alzheimer's Research Trust, said: 'Although this latest research recommends mid-life as a critical time to change our lifestyles, it's never too early, or late, to take steps towards improving heart-health.

'We should all consider stopping smoking, taking regular exercise and adopting a healthy, Mediterranean-style diet.'

On brain exercise study, she said: 'This adds to the 'use it or lose it' hypothesis that we can reap the benefits of stimulating our minds regularly, perhaps by doing crosswords, playing chess or adding up the shopping before getting to the till.'