Researchers suggest smoking may increase women's vulnerability to subarachnoid hemorrhage.
Subarachnoid hemorrhage is a form of stroke characterized by bleeding in the subarachnoid region of the brain - the area between the brain the tissues that cover it.
While subarachnoid hemorrhage is rare, accounting for around 3 percent of all strokes, it can have serious consequences, causing paralysis, coma, and death.
A sudden, severe headache is the primary symptom of subarachnoid hemorrhage, and this most commonly occurs at the back of the head. Other symptoms include reduced consciousness and alertness, changes in mood and personality, and eye discomfort in response to bright light.
The condition is more common among women than men, though the reasons for this have been unclear.
Now, study leader Dr. Joni Valdemar Lindbohm, of the University of Helsinki in Finland, and colleagues say their findings indicate that smoking may increase women's vulnerability to subarachnoid hemorrhage.
To reach their findings, the team analyzed the data of 65,521 adults of an average age of 45 who had taken part in Finnish national surveys, beginning in 1972. More than half of the participants were women.
As part of the surveys, subjects completed a number of health questionnaires and physical assessments. Specifically, Dr. Lindbohm and colleagues looked at subjects' smoking status and the incidence of subarachnoid hemorrhage.
Participants were followed-up for an average of 21 years from study baseline. Follow-up continued until December 31, 2011, or until subjects had their first stroke or died.
Female smokers have eight times greater subarachnoid hemorrhage risk
Compared with non-smokers, the researchers found that smokers were more likely to experience a subarachnoid hemorrhage. The more cigarettes subjects smoked daily, the higher their risk, and women fared worse than men.
Among light smokers - defined as smoking 1-10 cigarettes daily - men were 1.93 times more likely to have a subarachnoid hemorrhage than non-smokers, while women were at 2.95 times greater risk.
Among those who smoked 11-20 cigarettes a day, men were 2.13 times more likely to have a subarachnoid hemorrhage than non-smokers, while the risk was 3.89 times greater for women.
Women who smoked 21-30 cigarettes a day were 8.35 times more likely to experience a subarachnoid hemorrhage than non-smokers, while men who smoked 21-30 cigarettes daily were at 2.76 times greater risk.
These results, say the authors, may help explain why subarachnoid hemorrhage is more common among women than men.
"Female sex has been described as an independent risk factor for subarachnoid hemorrhage, but we found strong evidence that the elevated risk in women is explained by vulnerability to smoking.
Our results suggest that age, sex, and lifestyle risk factors play a critical role in predicting which patients are at risk for subarachnoid hemorrhage and emphasize the importance of effective smoking cessation strategies."
Dr. Joni Valdemar Lindbohm
Quitting smoking can reduce risk of subarachnoid hemorrhage
But it is not all bad news; the researchers found that quitting smoking can significantly reduce the risk of subarachnoid hemorrhage.
The results of the analysis revealed that men and women who had not smoked for at least 6 months had a risk of subarachnoid hemorrhage that was comparable to non-smokers.
"There is no safe level of smoking," stresses Dr. Lindbohm. "Naturally the best option is never to start. Quitting smoking, however, can reduce the risk for subarachnoid hemorrhage in both sexes."
The authors admit there are some limitations to their study. For example, they point out that subjects' alcohol intake, use of blood pressure medication, or incidence of high cholesterol could have influenced the results.
Still, they believe their findings highlight the importance of smoking cessation in order to lower the chances of a potentially life-threatening condition.