Reviewed by Dori F. Zaleznik, MD; Associate Clinical Professor of Medicine, Harvard Medical School, Boston and Dorothy Caputo, MA, BSN, RN, Nurse Planner

Smokers have nearly triple the likelihood of having a subarachnoid hemorrhage, but the risk for many individuals falls significantly 5 years after kicking the habit, a case-control study demonstrated.

The adjusted odds ratio for subarachnoid hemorrhage among individuals who currently smoked was 2.84 (95% CI 1.63 to 4.97) compared with those who had never smoked, according to Byung-Woo Yoon, MD, and colleagues from Seoul National University Hospital in Korea.

But 5 years after quitting, there had been a significant 59% reduction in risk (aOR 0.41, 95% CI 0.17 to 0.97) among those who smoked less than a pack a day, the researchers reported in the Journal of Neurology, Neurosurgery, and Psychiatry.

The risk remained elevated, however, for individuals who had been heavy smokers (aOR 0.84, 95% CI 0.40 to 1.78), they found.

The many benefits of smoking cessation on cardiovascular health are well recognized, with excess risks for coronary heart disease and ischemic stroke all but disappearing 5 to 10 years after smoking cessation.

Less is known, however, about the effects of smoking — and quitting — on risks for subarachnoid hemorrhage, which carries a death rate of approximately 50%.

To examine these concerns, Yoon and colleagues conducted a national multicenter study that included 426 cases diagnosed either with brain imaging or detection of xanthochromia in cerebrospinal fluid, and an equal number of matched controls.

Smoking history and other factors including dietary habits, alcohol use, occupation, and personal and family medical histories were obtained using structured questionnaires.

Mean age was 51 and 60% were women. Among cases, 34.7% were current smokers and 6.8% were past smokers, while among controls the numbers were 24.2% and 8.5%.

Cases and controls were generally well matched at baseline, except that cases more commonly had a family history of stroke (21.6% versus 14.6%) or a personal history of hypertension (32.4% versus 13.8%, P<0.01 for both).

The risk of subarachnoid hemorrhage rose with increasing pack-years of smoking (P<0.01):

• 1 to 9 pack-years: aOR 2.09 (95% CI 1.07 to 4.11)
• 10 to 19: aOR 2.05 (95% CI 1.03 to 4.09)
• 20 to 29: aOR 3.25 (95% CI 1.52 to 6.94)
• 30 or more: aOR 5.69 (95% CI 2.51 to 12.9)

And while the risk rose in a dose-dependent fashion, it also decreased over time, with an odds ratio of 0.80 (95% CI 0.64 to 0.99) per year of abstention.

The overall risk remained at 2.7 times higher for smokers who quit less than 5 years before.

When not associated with trauma, subarachnoid hemorrhage most often results from a ruptured aneurysm in the brain.

The potentially reversible effects of smoking that could contribute to this event include structural effects on vessel walls as well as increased coagulability and elevations in blood pressure.

And while some changes to blood vessel walls caused by smoking may be irreversible, the findings of this study suggest that smoking could be considered “a modifiable risk factor for subarachnoid hemorrhage.”

“Vigorous efforts of government officials and health workers to promote smoking cessation should be performed to reduce the risk of [subarachnoid hemorrhage], a disastrous disease for patients and family members,” Yoon and colleagues concluded.

Limitations of the study included likely recall bias associated with self-report of smoking, possible unmatched confounding factors, and the use of a hospital-based population.

“To confirm our results, population-based case control studies or prospective large cohort studies are needed,” the authors concluded.

The study was funded by the Korean Health Technology Project, Ministry of Health and Welfare, Republic of Korea.