Every day people are stricken by stroke. There are two kinds of this brain injury: The first occurs when a blood clot blocks blood flow to the brain, denying oxygen to the brain cells. The other kind of stroke occurs when a person has a hemorrhage in the brain or the surrounding structures. Hemorrhagic strokes are devastating. Forty percent of people who experience one will die. Most surviving patients are left with significant disability.
Daniel Woo, a researcher at the University of Cincinnati, says most of these hemorrhagic strokes are caused by aneurysms. Woo explains an aneurysm is caused by a weakness in the wall of an artery. Under pressure, those aneurysms can expand like balloons, stretching the arterial wall.
"And if that enlarges badly enough, it can also burst and cause a hemorrhage," Woo says.
Now Woo has done research that looks at the relationship between hemorrhagic strokes and smoking. He says researchers have known smoking is a risk factor for aneurysm formation.
"We also know that having a family member who had a history of aneurysm rupture was also a risk factor for aneurysm formation," Woo says.
Woo looked at several hundred people who had had ruptured aneurysms and compared them to people who did not have aneurysms. He found that people who smoked had double the risk for aneurysm. His analysis also found that those with a family history of aneurysm also had twice the risk of forming one. But people who had the family history and who smoked were six times more likely to have a hemorrhagic stroke. He says that means hundreds of thousands, if not millions of people are at much greater risk of having a hemorrhagic stroke due to a combination of genes and behavior.
"Twenty percent of the population [in the U.S.] smokes, and 1 percent of the population has an aneurysm in their head that they just don't know about," Woo says. "So the rates can be fairly high of people having this, but so we're still talking about maybe 1 percent of the population, maybe one in 100 people."
Woo says it doesn't sound large, but he maintains it's still a significant percentage of the population.
Woo says that studies have indicated that aneurysms form gradually over time. He proposes that something about smoking causes them to form more readily.
Woo says one message from this research is clear: Quitting smoking almost immediately reduces the risk of rupturing an aneurysm.
His research is published in Neurology, the journal of the American Academy of Neurology.