Smoking lowers IQ and increases risk of dementia, experts warn.

SMOKING can lower your IQ and increases the risk of dementia later in life, experts warned yesterday.

Long-term smokers suffer significant damage to their memory and their ability to think quickly and solve problems.

Researchers warn that this may lead to difficulties in simple everyday tasks such as counting change – and may hasten the onset of dementia and Alzheimer’s disease.

Experts from Aberdeen and Edinburgh universities say the study offers the first conclusive evidence that cigarettes are bad for your intelligence as well as your physical health.

They believe that toxic chemicals in smoke get into the bloodstream and harm the blood vessels that provide the brain with vital oxygen supplies.

‘Our findings are significant because they show for the first time the long-term effect of smoking on cognitive ability,’ said Dr John Starr, of Edinburgh University. ‘The impact of smoking on the IQ of the people involved may appear small, but it will impair their quality of life.

‘They will experience niggly problems with any task that requires some sort of mental agility – whether that’s organising their daily life, remembering what to buy at the shops, doing crossword puzzles or playing bridge.’

In the study, detailed in New Scientist magazine today, researchers looked at 465 individuals, all of whom were born in 1936 and had taken part in the same IQ survey at the age of 11.

The team asked these people, around half of whom were former or current smokers, to take a series of five tests designed to measure their mental functioning and IQ between 2000 and

2002 when they were aged 64 on average.

After taking into account other factors which may influence their intelligence, such as education and alcohol consumption, the results showed that smokers tended to fare worse than non-smokers.

Professor Lawrence Whalley, of Aberdeen University, said that the smokers – who had been smoking for around 40 years on average – had experienced IQ reductions of around 2 per cent as a result of their habit.

Further analysis showed that when the effect of smoking on lung function was taken into account, the negative effect on IQ was around 4 per cent.

Scientists have previously shown that damaged lung function is associated with impaired mental ability, possibly because the brain is being fed less oxygen.

Professor Whalley said former smokers – most of whom had smoked for around ten years early in adulthood – also had slightly lower scores than nonsmokers.

He said the findings contradict the belief of some smokers that a nicotine rush can actually help boost their brain power.

He added: ‘Smokers are likely to be functioning at 2 per cent lower than if they had not smoked.

‘This becomes critical if you think of the decline you see in dementia – if you are starting from a lower point then it may come on earlier.’