• Cigarette smoking causes brain shrinkage, and the more and longer a person smokes, the greater the damage is, according to a new study.
  • Loss in brain volume raises the risk of cognitive decline, dementia, and Alzheimer’s disease.
  • Smoking cessation can help stop brain shrinkage, but it cannot be reversed.
  • The study authors recommend that anyone at any age who smokes should prioritize quitting.

Cigarette smoking causes the brain to shrink, according to a new study from researchers at Washington University School of Medicine in St. Louis, MO (WashUMed).

Brain shrinkage is also associated with an increased risk of cognitive impairment, dementia, and Alzheimer’s disease (AD).

The study’s results show that quitting smoking at any time stopped further gray matter loss. However, the brain does not recover its original mass once shrinkage occurs.

It has long been known that smoking is harmful to the lungs and heart, though not as much research has been dedicated to its effect on the brain.

The research team, led by senior author Dr. Laura J. Bierut, director of WashUMed’s Health & Behavior Research Center, aimed to fill a gap in the current understanding of the harmful effects of smoking.

The study’s findings were recently published in Biological Psychiatry: Global Open Science.

Previous research has indicated that smokers are more likely to develop dementia. It’s estimated that 14% of Alzheimer’s cases may be attributed to smoking.

Investigating the connection between brain shrinkage and cigarette smoking requires untangling behavioral and genetic factors.

Brain shrinkage and a desire to smoke can both be influenced by one’s genes — the authors say that about half of one’s preference for smoking is due to genetics.

The researchers considered factors like genetic predisposition to smoking, smoking, and brain volume. They concluded that genetics may lead to smoking but that smoking significantly drives brain shrinkage.

The study analyzes data released in 2019 from the UK Biobank. It included 32,094 participants of European descent, along with their brain-imaging data. Participants self-reported their smoking.

Researchers calculated the number of smoking years for individuals who reported smoking one pack or 20 cigarettes daily. Their brain scans were compared to people who never smoked or smoked fewer than 100 cigarettes.

Those who smoked more experienced a greater level of brain shrinkage.

Dr. Dung Trinh of the Healthy Brain Clinic in Long Beach, CA, told Medical News Today: “Brain shrinkage, or atrophy, involves the loss of neurons and the connections between them.” Dr. Trinh was not involved in the study.

“This loss can impair the brain’s ability to function correctly,” Dr. Trinh said.

Dr. Trinh noted that in conditions such as Alzheimer’s disease and dementia in general, certain critical areas shrink, resulting in a loss of function.

“For example, the hippocampus, crucial for memory formation, often shows significant atrophy in Alzheimer’s disease,” he noted.

Such atrophy can inhibit communication between different brain regions, resulting in cognitive decline.

Dr. Bierut pointed out that decreased brain volume is associated with aging. “In other words, people who smoke have an ‘older’ brain,” she said.

Dr. Bierut explained that when you smoke, you ingest many toxic chemicals. She added that people who smoke have chronically lower oxygen levels in their blood.

“The brain loves oxygen, and these chronic levels of lower oxygen are slowly starving the brain,” Dr. Bierut said.

Dr. Trinh listed various ways in which smoking can harm the brain. He said vascular damage can reduce blood flow to the brain, resulting in cell death and atrophy.

Dr. Trinh cited the oxidative stress and inflammatory effects associated with smoking, saying, “These processes can damage brain cells and the supporting structures.”

Some chemicals in cigarettes are neurotoxic and capable of directly damaging brain cells.

“Smoking affects the levels of various neurotransmitters in the brain, which may contribute to neural damage and atrophy over time,” Dr. Trinh added.

“Quitting smoking is one of the most important things that you can do for your health,” Dr. Bierut said.

“The more you smoke and the longer you smoke, the more you age your brain. The other thing I always say to people who are older and who smoke — it is never too late to quit. There are health benefits of quitting even later in life.”

“Overall, the world’s population is getting older, and we have a wave of older people who will be developing dementia. This is a major public health problem, and we need to focus on reducing the modifiable risk factors for dementia so that we can have a healthy older population.”

— Dr. Laura J. Bierut, senior study author and director of WashUMed’s Health & Behavior Research Center

At the same time, Dr. Trinh noted that it’s not just adults who should stop smoking.

“Teenage and young adult brains are still developing, and exposure to the harmful effects of smoking during these critical periods could lead to more significant long-term damage, Dr. Trinh said.

“It is known that the earlier an individual starts smoking, the greater the potential harm over their lifetime.”

Dr. Robert Miller, a doctor of internal medicine with Vista Staffing, which offers physician search services in the United States, suggested a multi-modal approach to smoking cessation that involves counseling therapy. Dr. Miller was not involved in the study.

He said the aim of this approach is behavioral modification and supportive pharmacotherapy.

Dr. Miller cited seven medications approved by the Food and Drug Administration (FDA) that can help with smoking cessation, including:

“Working with others who have also beaten the habit and gaining success through a shared common goal can help individuals in their own journey,” Dr. Miller said.

It may also be helpful to replace the urge to smoke with healthy activities, such as reading or exercising.

Some people, noted Dr. Miller, find that their desire to smoke may be a response to certain triggers. Identifying and avoiding personal triggers can help break the smoking habit.

For those considering e-cigarettes as a means of quitting, vaping is not considered a safe or effective way to stop smoking.

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