A new study finds that smoking not only hurts your lungs, but may also affect your brain. Previous studies have shown that people who start smoking early in life have significantly lower memory and cognitive flexibility in later life compared to non-smokers, and some researchers estimate that about 14 percent of Alzheimer’s disease (dementia) cases are related to smoking. But the extent to which smoking is associated with changes in brain structure is unclear. This new study, however, found that long-term smoking may lead to a thinning of the cerebral cortex, which can reduce a person’s cognitive ability. The study was published in February in the journal Molecular Psychiatry, a division of Nature Publishing Group (NPG), by Zhang Zhaoge of the Department of Neurology at the First People’s Hospital of Nanning. [Literature Read: Mol Psychiatry 2015 Feb 10] The study was a collaboration between researchers from McGill University in Canada and the University of Edinburgh in the United Kingdom. In the study, 504 elderly people from the city of Edinburgh, UK, with an average age of 73 years and without Alzheimer’s disease were recruited. Of the 504 seniors, 245 had never smoked; 223 had previously smoked and had stopped; and 36 were still smoking. The researchers measured the thickness of each elderly person’s cerebral cortex by magnetic resonance imaging (MRI). The results showed a dose-effect relationship between smoking and cortical thickness – the thickness of the cerebral cortex became thinner as the amount of smoking increased. In the study, the thickness of the cerebral cortex decreased sequentially in non-smokers, quitters and smokers. The cerebral cortex, the outermost layer of the brain, is associated with a person’s memory, language skills, and perceptual abilities. In non-smoking adults, the thickness of the cerebral cortex slowly decreases with age, while smoking accelerates this process, which in turn accelerates the decrease in a person’s cognitive ability. Once the cerebral cortex is damaged, it can take up to 25 years to return to its normal state.