Brain shrinks, stroke risk rises in smokers

Blog Post created by Thomas3.20.2010 on Aug 14, 2012

We know that smoking tobacco increases a person’s risk of cancer, heart attacks and strokes. But what do we know about how much harm smoking does to the brain?

Way back in 1848, The Boston Medical and Surgical Journal described tobacco as a “Passage of an Iron Rod Through The Head.” This statement is not an exaggeration when we consider the devastating effects of smoking on the brain.

Consider what’s inside a cigarette. Tobacco is only one of many ingredients. To create a cigarette’s taste, artificial flavorings are added. Other chemicals are added to make cigarettes burn longer. Of the 4,000 chemicals found in a cigarette, about 50 are carcinogenic. The rest are plain poisonous.

A 2000 report by toxicologist Jefferson Fowles and scientist Michael Bates of New Zealand lists the chemical constituents in cigarettes. They include:

  • arsenic (found in rat poison)
  • cyanide (a deadly poison)
  • ammonia (in cleaning supplies)
  • sulfuric acid (in car batteries)
  • DDT (insecticide).

The three most common chemicals are carbon monoxide (car exhaust), tar (makes roads and blackens the lungs), and nicotine (used in bug spray). It is hard to imagine anyone wanting to contaminate their brains with these chemicals and poisons.

The brain is a wonderful creation—it loves, imagines, plans, makes beautiful poetry and invents iPhones. To function, it needs a large supply of blood flow to feed its 100 billion neurons. Carbon monoxide, a toxic gas in cigarette smoke, interferes with oxygen flow in the blood’s arteries.

Carbon monoxide levels are significantly higher in the blood of smokers; a 2004 study published in Radiotherapy and Oncology found that carbon monoxide decreased the oxygen-carrying ability of red blood cells in smokers compared to nonsmokers.


Besides cutting off blood supply, tobacco has a compound that causes inflammation by attacking healthy nerve cells, a process that causes further damage, according to 2009 research published in the Journal of Neurochemistry.

Tobacco damages the basic structure of the brain and alters its chemistry. Therefore, humans’ greatest asset take a hit.

In smokers, we see a decline in memory, verbal and mathematical capabilities. We also see diminished attention and reasoning, plus problems with mood control.

This cognitive decline is a double-edged sword, as it disables the smoker’s ability to calculate and reason that the odds are against them—smoking causes cancer, for example. Others around them are, of course, fully aware of the risks.



Smoking shrinks the brain through the gradual destruction of neurons and their connections. What that means for a young person who smokes is a lower intelligence quotient (IQ).

This effect of smoking on IQ was confirmed by a large study of men between the ages of 18-21, published in the 2010 February issue of Addiction.

In the later years of adulthood, smoking continues to shrink the brain and contributes to dementia. Several studies indicate that chronic smoking leads to an increased risk for different types of dementia, especially Alzheimer’s.

In fact, smoking accelerates brain aging. A study from the Netherlands, published in the journal Neurology in 1999, showed that the risk of Alzheimer’s dementia was significantly higher in smokers, especially in men, than in non-smokers.

On a hopeful note, the study also showed that previous smokers who quit had a slight reduction it the risk of Alzheimer’s dementia.

Because of modern technology, we can now look at pictures of smokers’ brains. What MRIs of a smoker’s brain show us is atrophy—the brain shrinks in volume and density. In fact, studies show that smokers have a smaller volume of gray matter and density in the pre-frontal cortex.

The more packs of cigarettes a person smokes, the worse the loss of brain matter, according to a study done at the Veterans Affairs in Los Angeles and published in the 2004 January issue of Biological Psychiatry.

Gray matter is crucial. It’s home to the neurons that help you make straight As in school and come up with smart ideas in your career.



Another risk of smoking: It more than doubles the risk of having a brain hemorrhage, according to a study published in Stroke in 2003.

Smoking also doubles the risk of having a stroke, which is like a heart attack of the brain. It happens when normal blood flow to the brain is interrupted either because of a clot or because a blood vessel breaks.

Strokes can cause death, and they can cause debilitating problems. The risk of stroke increases with the number of cigarettes smoked, according to the Framingham Heart Study, published in the Journal of the American Medical Association in 1988.

On a hopeful note, stroke risk decreased significantly after two years of quitting and by five years, the risk had dropped to the level of non-smokers.


There are some things in life worth the pleasure. Others are not. If you smoke, ask yourself: Is this worth it?


Tobacco use is responsible for about 443,000 deaths—about one in five—each year in the United States, according to the Centers for Disease Control and Prevention report. Nearly 20 percent of American adults smoke.