WEDNESDAY, Jan. 7, 2009 (Health.com) — Everyone knows that smoking is bad for your health. But a new study suggests that smoking might be particularly dangerous for people with a family history of stroke.
In fact, smokers with close family members who have had an aneurysmal subarachnoid hemorrhage—a type of bleeding in the brain that accounts for 10% of all strokes—are more than six times as likely to have a stroke themselves.
The combination of smoking and a family history is a more potent risk factor than either alone, says researcher Daniel Woo, MD, who published the results this week in the journal Neurology.
In the study, Dr. Woo and colleagues matched 339 people who had an aneurysmal subarachnoid hemorrhage to more than 1,000 of their healthy peers. Compared to nonsmokers without a close relative with stroke, the risk of a subarachnoid hemorrhage was 2.5 times higher in nonsmokers with a family history, 3.1 times higher in smokers without a family history, and 6.4 times greater in people who were both smokers and had a family history.
“What we found was greater than additive risk,” says Dr. Woo, an associate professor of neurology at the University of Cincinnati. The finding is particularly serious, Dr. Woo says, because subarachnoid hemorrhages tend to strike at younger ages.
Most strokes occur when a clot blocks a blood vessel in the brain, and this type of stroke occurs at an average age of 75. However, people with an aneurysmal subarachnoid hemorrhage, which is caused by a rupture of blood vessel between the surface of the brain and the skull, tend to experience them at younger ages. The average patient is in his 50s,and it’s not unheard of to have such strokes in one's 30s or 40s, Dr. Woo says.
“People liken it to a hand grenade going off in your brain,” he says. “Your skull is a closed space, and when you now are shooting blood into that closed space, it raises pressure inside the head, so people pass out, they fall unconscious, they have loss of blood flow to the brain; there’s a high mortality rate.”
One-third to 40% of patients die of the hemorrhage and many survivors are left with severe disability.
Smoking has always been known to be a risk factor for this type of bleeding; 70% to 75% of patients who have them have some history of smoking, and 50% to 60% are current smokers. (Only about 20% of people in the general population are smokers.)
But the family history connection has been less clear, says Dr. Woo. While roughly 10% to 20% of people who have an aneurysm have a family history, researchers have had trouble nailing down a gene that’s clearly responsible.
The new study suggests that smoking may be the smoking gun, so to speak. “There may be a gene that makes someone sensitive to smoking and that’s why aneurysms tend to rupture in some families,” says Dr. Woo.
The finding once again emphasizes that people should quit smoking, or never start, says Dr. Woo. But it also hints that some people might have enough risk to justify brain scans for an unruptured aneurysm, which can sometimes be treated with surgery.
Anywhere from 0.5% to 6% of the population is walking around with these types of unruptured aneurysms, which are sometimes picked up as incidental findings during brain scans (they are usually asymptomatic), says Italo Linfante, MD, director of endovascular neurosurgery and interventional neuroradiology at Baptist Cardiac and Vascular Institute, in Miami.
“We are still scratching our heads as to what causes these aneurysms,” he says. Drinking alcohol, female gender, and certain conditions, such as polycystic kidney disease, are associated with aneurysms.
“Some of those will rupture, so we are trying to figure out how can we predict which of these aneurysms will tend to rupture—we can either watch it or fix it,” he says.
Aneurysms can be corrected with open surgery, or with a technique in which a catheter is snaked through a leg artery and up in the brain. However, the risks of surgery outweigh the benefits if there’s a low likelihood that the aneurysm will burst.
“This study is trying to address, what are the factors that will make an unruptured aneurysm turn into a ruptured aneurysm?” says Dr. Linfante, who wasn’t involved in the new research. “It’s an interesting study.”