Previous research found that smoking increases the risk of dementia by damaging the way the brain works, but now a study from the University of Cambridge has shown that people exposed to high levels of second-hand smoke are 44% more likely to suffer cognitive impairment - affecting things like memory and ability to perform calculations.
Researchers, writing in the British Medical Journal, split 4,800 non-smoking adults in England based on their levels of cotinine - a marker of nicotine exposure.
After undergoing neuropsychological tests, they found that those with the highest concentration were 44% more likely to suffer cognitive impairment compared with those in the lowest group.
The end results were similar for people who had never smoked and those who had been smokers once but had later quit.
The researchers suggested that exposure to second-hand smoke could lead to dementia because smoke increases the risk of heart disease and stroke - both known to increase the risk of cognitive impairment and dementia.
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