We know that smoking is bad for our lungs and heart, but now we know that it harms the brain as well. As part of ourStaying Sharpseries, Dr Sherif Karama of McGill University, Canada, reveals the evidence.
My advice
- Don’t smoke. Smoking accelerates ageing of the brain.
- If you smoke, quit. Partial reversal of the damage to the brain caused by smoking can occur after quitting but it’s a long process, so don’t delay quitting.
- Brain ageing doesn’t suddenly start happening at a given age. Rather, it appears to be the consequence of factors, both genetic and environmental, that have been playing a role throughout our lives.
Lifestyle choices affect brain ageing
People with good cognitive abilities (i.e. thinking skills) in old age tend to be those who have had good cognitive abilities throughout their lives. Nonetheless, in old age, most, if not all, of us exhibit a certain degree of decline in some thinking skills, like learning new information and being able to quickly shift from one mental task to another.
However, some of us show a steeper rate of decline than others. The factors that affect this rate of decline are still being researched but some are already clear and one of them is smoking.
Smoking speeds up brain ageing
While the effect of smoking on cognitive abilities is relatively small and requires large studies to be able to be detected, it is nonetheless present. Recently, we also looked at the effect on the structure of the brain by examining data from theLothian Birth Cohort 1936(LBC1936) at age 73.
We found that smokers had a thinnercerebral cortexthan non-smokers – in other words, smoking was destroying the grey matter in smokers. This is important because the cerebral cortex is a part of the brain that is crucial for thinking skills including memory and learning, so thicker is better.
The cortex does tend to thin with age naturally but we found that, all else being equal, the more people had smoked, the more they tended to have a thin cortex. These results suggest that smoking accelerates the normal thinning of the cortex that occurs with age.
Why quitting matters
Importantly, people in the LBC1936 who stopped smoking early enough in their life seemed to partially recover with time. However, this recovery can be a long process.
In this group of people, we worked out the average number of cigarettes that they had smoked in their lifetime. This was around 196,000 cigarettes, that is, 20 a day for 26.9 years.
For those who had smoked the average number, it took roughly 25 years for complete recovery of the affected areas of the cortex. Those who had smoked less than the average recovered faster, while those who had smoked the most still had a long way to go to recover at age 73.
Overall, this shows that cognitive and brain ageing is a dynamic lifelong process. It is not something that simply happens in old age and does not appear to be determined simply by one thing that you do or avoid as you reach old age.
Rather, it appears to be the consequence of multiple factors that include genetic and environmental factors and the lifestyle choices we make, that have been playing a role throughout our lives.
About the author
Dr Sherif Karamais a Fellow of the Royal College of Physicians and Surgeons of Canada (Psychiatrist) and Assistant Professor in the Department of Psychiatry at McGill University, Canada. His research is on understanding the impacts that genes and environment, and interactions between the two, have on brain development and cognitive ability.
Key references
Karama, S., Ducharme, S., Corley, J., Chouinard-Decorte, F., Starr, J.M., Wardlaw, J.M., Bastin, M.E. and Deary, I.J., 2015.Cigarette smoking and thinning of the brain’s cortex. Molecular psychiatry, 20(6), pp.778-785.
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I am Dr. Sherif Karama, a Fellow of the Royal College of Physicians and Surgeons of Canada (Psychiatrist) and Assistant Professor in the Department of Psychiatry at McGill University, Canada. My expertise lies in understanding the impacts that genes and the environment, as well as their interactions, have on brain development and cognitive ability. I have conducted extensive research, and my work has been published in reputable journals, including the study titled "Cigarette smoking and thinning of the brain’s cortex," published in Molecular Psychiatry in 2015.
Now, let's delve into the concepts discussed in the article:
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Smoking and Brain Aging:
- The article emphasizes that smoking is not only harmful to the lungs and heart but also accelerates the aging of the brain.
- Smoking has been linked to a thinner cerebral cortex in smokers compared to non-smokers. The cerebral cortex is crucial for thinking skills, including memory and learning.
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Brain Aging and Lifestyle Choices:
- The aging of the brain is not a sudden occurrence at a specific age; instead, it is influenced by factors such as genetics, environment, and lifestyle choices.
- People with good cognitive abilities in old age typically maintained such abilities throughout their lives.
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Factors Affecting Cognitive Decline:
- While some cognitive decline is normal in old age, the rate of decline varies among individuals.
- Smoking is identified as one of the factors that contribute to a steeper rate of cognitive decline.
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Effect of Smoking on Brain Structure:
- The study examined data from the Lothian Birth Cohort 1936 at age 73, revealing that smokers had a thinner cerebral cortex compared to non-smokers.
- Thicker cortex is associated with better thinking skills, and smoking accelerates the natural thinning of the cortex that occurs with age.
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Recovery after Quitting Smoking:
- Importantly, individuals who quit smoking early enough in their lives showed partial recovery over time.
- The study found that the average number of cigarettes smoked in a lifetime was around 196,000, and it took approximately 25 years for complete recovery of affected areas of the cortex for those who had smoked the average number.
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Dynamic Lifelong Process of Brain Aging:
- Cognitive and brain aging is depicted as a dynamic lifelong process influenced by multiple factors, including genetics, environment, and lifestyle choices.
This information underscores the importance of making healthy lifestyle choices, such as avoiding smoking, to promote brain health and mitigate the effects of aging on cognitive abilities. It also highlights the potential for recovery through smoking cessation, albeit over an extended period.
