Research from Washington University shows that smoking shrinks the brain and speeds up brain aging, a process that is irreversible even after quitting. The study, analysing data from the UK Biobank, highlights the crucial role of quitting smoking in preventing further brain damage and reducing dementia risk.
Daily cigarette smoking reduces the size of your brain, a new study of more than 32,000 people suggests. It’s well-known that smoking can cause long-term effects on health and increases the risk of cancer, and cardiovascular diseases. Now, a new study reveals that it can also cause premature brain ageing.
Scientists have previously found that people who smoke tend to have smaller brains compared to non-smokers, in terms of volume, but it was unclear whether smoking causes the brain to shrink or if people with smaller brains are more likely to start smoking. Now, researchers provide strong evidence that smoking causally shrinks the brain in a new report.
The scientists analysed brain imaging data from the U.K. Biobank, a massive repository of genetic and health data from U.K.-based participants. In addition to brain scans, the team analysed participants’ self-reported smoking habits, as collected in surveys. Participants took these surveys twice, once between 2006 to 2010 and again between 2012 and 2013. In the second time window, participants’ brains were also imaged using a method called magnetic resonance imaging (MRI).
The scientists found that, compared to people who’d never smoked daily, participants who smoked on a daily basis at some point prior to having their brains imaged had brain volumes that were 0.4 cubic inches (7.1 cubic centimetres smaller, on average. Next, the researchers found that, among the past daily smokers, participants who smoked more heavily showed even larger differences in grey matter volume.
This difference in brain volume included a 0.3 cubic inch (5.5 cc) decrease in the grey matter of the brain, which contains the bulky bodies of brain cells, or neurons. Smoking daily at some point in the past was also linked to a 0.1 cubic inch (1.6 cc) decrease in the white matter of the brain, which includes the long insulated wires that connect neurons to each other.
This difference in brain volume included a 0.3 cubic inch (5.5 cc) decrease in the gray matter of the brain, which contains the bulky bodies of brain cells, or neurons. Smoking daily at some point in the past was also linked to a 0.1 cubic inch (1.6 cc) decrease in the white matter of the brain, which includes the long insulated wires that connect neurons to each other.
Findings help explain how smoking is linked to Alzheimer’s, dementia
Smoking shrinks the brain, according to a study by researchers at Washington University School of Medicine in St. Louis. The good news is that quitting smoking prevents further loss of brain tissue — but still, stopping smoking doesn’t restore the brain to its original size. Since people’s brains naturally lose volume with age, smoking effectively causes the brain to age prematurely, the researchers said. In contrast, how heavily people smoked did not significantly impact their white matter volume.
The Neglected Effects of Smoking on the Brain
“Up until recently, scientists have overlooked the effects of smoking on the brain, in part because we were focused on all the terrible effects of smoking on the lungs and the heart,” said senior author Laura J. Bierut, MD, the Alumni Endowed Professor of Psychiatry. “But as we’ve started looking at the brain more closely, it’s become apparent that smoking is also really bad for your brain.”
Link Between Smoking, Brain Size, and Genetics
Scientists have long known that smoking and smaller brain volume are linked, but they’ve never been sure which is the instigator. And there is a third factor to consider: genetics. Both brain size and smoking behavior are heritable. About half of a person’s risk of smoking can be attributed to his or her genes.
To disentangle the relationship between genes, brains, and behavior, Bierut and first author Yoonhoo Chang, a graduate student, analyzed data drawn from the UK Biobank, a publicly available biomedical database that contains genetic, health and behavioral information on half a million people, mostly of European descent. A subset of over 40,000 UK Biobank participants underwent brain imaging, which can be used to determine brain volume. In total, the team analyzed de-identified data on brain volume, smoking history, and genetic risk for smoking for 32,094 people.
Key Facts :
- Smoking causes brain shrinkage, effectively aging the brain prematurely, and this damage is irreversible even after quitting.
- The study analyzed data from the UK Biobank, involving over 32,000 participants, to establish the link between smoking, genetics, and brain volume.
- The research reinforces the critical importance of quitting smoking to prevent further brain damage and reduce the risk of dementia.
As the study found that the shrinkage was irreversible. Analyzing data on people who had quit smoking years before showed that their brains remained permanently smaller than those of people who had never smoked. The researchers emphasised quitting smoking is an important factor in stopping the ageing of the brain and decreasing the risk of dementia.
Previous studies have also shown that quitting smoking can significantly decrease health risks. For instance, a 2019 study published in the Journal of the American Medical Association (JAMA), showed that when heavy cigarette smokers with at least a 20 pack-year smoking history quit smoking, their risk of cardiovascular disease decreased by 39% within five years.
