A shocking study published today in the British Medical Journal, highlighted a 44 per cent increase in the risk of cognitive impairment when people are exposed to high levels of second-hand smoke. While earlier research found an increased risk of dementia in smokers, this is the first time a link has been made between second-hand smoke and development of dementia in elderly non-smokers. Researchers at Cambridge University measured levels of cotinine (a by-product of nicotine) in the saliva of nearly 5,000 non-smoking adults over the age of 50, to map out the amount of exposure they had to second-hand smoke. After a series of neuro-psychological tests, they were able to assess aspects of brain function like verbal memory and fluency, and mathematical calculations. The results were then added to together to make a global score for cognitive function, and those who scored in the lowest 10 per cent were identified as suffering from cognitive impairment. From those findings, the scientists concluded that second-hand smoke exposure may be linked to an increased chance of developing cognitive impairments like dementia. The researchers believe that passive smoking increases the risk of heart disease and stroke which are known to increase the likelihood of neurological problems.