"For the general population our findings do not apply,'' says researcher Monique H.M. Vlak, MD, a neurologist at the University Medical Center in Utrecht, Netherlands.
It applies, she tells WebMD, to those who have an untreated brain aneurysm. This is a weakness in the wall of a blood vessel in the brain. It often causes the wall to balloon out. If it ruptures, it can lead to a stroke known as a subarachnoid hemorrhage. It involves bleeding between a membrane that covers the brain and the brain.
While 2% of the population has this brain aneurysm, few rupture, according to Vlak.
Vlak and colleagues surveyed 250 patients who had a stroke after a brain aneurysm ruptured. They asked them about exposure to 30 potential triggers in the period shortly before the stroke.
They also asked how often and how intensely they were typically exposed to the potential triggers.
The eight triggers that increased the risk for the stroke included:
- Vigorous physical exercise
- Nose blowing
- Sexual intercourse
- Straining to defecate
- Drinking cola
- Being startled
- Being angry
Next, Vlak calculated what is known as population-attributable risk. This is the percent of these strokes that can be attributed to a single trigger. Coffee and vigorous exercise were linked to the highest risk.
All these triggers, Vlak tells WebMD, are superimposed on known risk factors for stroke, such as advancing age or having uncontrolled high blood pressure.
The risk related to the specific triggers is also short-lived, she says. "The risk due to these trigger factors only lasts one hour."
She believes the common mechanism for the triggers is the temporary increase in blood pressure produced by all of them.
Vlak says people who know they have an untreated aneurysm should avoid at least some of the triggers when possible.
"I think drinking no coffee or cola and avoiding straining for defecation are easy to do and can prevent some of the subarachnoid hemorrhages," she tells WebMD. "However, we do not advise patients to refrain from physical exercise, since this is also an important factor in lowering the risks of other cardiovascular diseases."
The study has some built-in limitations, such as people's ability to recall exactly what they did in the period before the stroke, says Ralph L. Sacco, MD, professor and chair of neurology at the Miller School of Medicine, University of Miami. Sacco, who is also president of the American Heart Association, reviewed the findings for WebMD but was not involved in the research.
Even so, he says, "this is a novel study design that suggests that certain triggers may be important in the rupture of brain aneurysms causing bleeding strokes."
These strokes, he says, "can occur in younger people and are more frequent in women, smokers, and hypertensives."
He calls the triggers plausible. He says the supposed mechanism, the elevation in blood pressure, makes sense.
"People with known brain aneurysms may need to avoid such triggers," he says.
Putting that advice in more perspective, he says: "Quitting smoking or never starting, and controlling blood pressure are still more important factors to control than giving up coffee."