Smoking is known to have many harmful effects on the body, but a new study has found that it also affects the brain in a significant way. According to the research, published in the journal Neurology, smoking can cause the brain to shrink over time, depending on the amount and duration of smoking.
The study used data from the UK Biobank, a large-scale biomedical database that contains information on the health and lifestyle of half a million people in the UK. The researchers analyzed the brain scans of 17,308 participants, who were aged between 40 and 69 at the time of scanning. They also collected self-reported data on their smoking habits, such as whether they had ever smoked, how many cigarettes they smoked per day, and when they quit smoking.
The results showed that compared to people who never smoked, those who smoked daily had smaller brain volumes. The difference was more pronounced in the hippocampus, a region of the brain involved in memory and learning, and the amygdala, a region of the brain involved in emotion and stress. The researchers estimated that for every pack of cigarettes smoked per day, the hippocampus shrinks by 0.03 cubic inches (0.5 cubic centimeters), and the amygdala shrinks by 0.02 cubic inches (0.3 cubic centimeters).
The study also found that the longer a person smoked, the more their brain shrank. For example, someone who smoked for 15 years had a smaller hippocampus and amygdala than someone who smoked for 10 years. However, the study also found that quitting smoking can prevent further brain shrinkage. People who quit smoking had similar brain volumes to those who never smoked, after adjusting for other factors such as age, sex, education, and body mass index.
Why Smoking Shrinks the Brain
The exact mechanism of how smoking causes brain shrinkage is not fully understood, but the researchers suggested some possible explanations. One is that smoking reduces the blood flow to the brain, which can impair the delivery of oxygen and nutrients to the brain cells. Another is that smoking increases the inflammation and oxidative stress in the brain, which can damage the brain cells and their connections. A third is that smoking affects the levels of neurotransmitters and hormones in the brain, which can alter the brain’s function and structure.
The researchers also noted that smoking can interact with other factors that influence brain health, such as genetics, diet, exercise, and alcohol consumption. For instance, some people may have a genetic predisposition to have smaller brain volumes, and smoking may exacerbate this effect. Similarly, some people may have a poor diet or a sedentary lifestyle, and smoking may worsen their brain health.
What Smoking Means for Brain Health
The study’s findings have important implications for the prevention and treatment of brain disorders, such as Alzheimer’s disease, dementia, and depression. Previous studies have shown that people with smaller brain volumes are more likely to develop these conditions, and that smoking is a risk factor for these conditions. Therefore, the study suggests that smoking may contribute to these conditions by shrinking the brain.
The study’s lead author, Dr. Sherif Karama, a psychiatrist and neuroimaging researcher at McGill University in Canada, said: “Our study adds to the growing evidence that smoking is bad for your brain. It also shows that quitting smoking can prevent further brain damage and possibly even reverse some of the damage. This should motivate smokers to quit as soon as possible, and encourage non-smokers to never start.”
The study’s co-author, Dr. Paul Matthews, a neurologist and neuroimaging researcher at Imperial College London in the UK, said: “This study is a remarkable example of how the UK Biobank can provide valuable insights into the effects of lifestyle factors on the brain. It also highlights the need for more research to understand the mechanisms and consequences of smoking-induced brain shrinkage, and to develop interventions to protect and restore brain health.”
