Smoking Plus Family History Compound Risk for Aneurysmal SAH

Susan Jeffrey

January 09, 2009

January 9, 2009 — Current smoking appears to interact with a family history of aneurysmal subarachnoid hemorrhage (aSAH), increasing the risk to 6-fold that of an individual without a family history who never smoked, a new study shows.

The findings have implications for counseling family members and for screening for intracranial aneurysm (IA), the authors say.

"Clinically, family members of persons with aSAH should be advised of the markedly increased risk for aSAH with the combination of family history and smoking exposure," Daniel Woo, MD, from the University of Cincinnati College of Medicine, in Ohio, and colleagues conclude. "Information from the current study may help to increase the potential for quitting prior to life-threatening aSAH, which is fatal in 35% to 40% of patients."

Their findings are published in the January 6 issue of Neurology.

Compounding the Risk

Smoking and a family history of aSAH are both independent risk factors for aSAH, the authors write. "Using a population-based case-control study of hemorrhagic stroke, we hypothesized that having both a first-degree relative with a brain aneurysm or SAH and current smoking interact to increase the risk of aSAH," Dr. Woo and colleagues write.

A total of 339 cases were recruited prospectively from 17 hospitals in the 5-county region around the University of Cincinnati, and 1016 controls were identified through random digit dialing. Controls and cases were matched by age, race, and sex.

The risk for aSAH was compared between current nonsmokers with a family history of aSAH (+FH), current smokers with (+FH) and without (-FH) a family history, and a referent group of those without either current smoking or a family history.

The researchers found an increase in the risk for aSAH with both a family history and current smoking alone, but the risk was compounded when both factors were present.

Risk for Aneurysmal SAH by Smoking Status and Family History

Risk Factors Odds Ratio 95% CI
No smoking, -FH Referent
No smoking, +FH 2.5 0.9 – 6.9
Current smoker -FH 3.1 2.2 – 4.4
Current smoker, +FH 6.4 3.1 – 13.2

Former smoking was not associated with such a high risk of aSAH, even when family history was present.

Risk for Aneurysmal SAH in Former Smokers With and Without Family History

Risk Factors Odds Ratio 95% CI
No smoking, -FH Referent
Former smoker, +FH 1.8 0.5 – 6.4
Former smoker, -FH 0.8 0.5 – 1.3

"We report evidence of an interaction between current smoking and the familial aggregation of IA/SAH," the authors conclude. "We were unable to find a similar association with former smoking and family history of IA/SAH, which suggests that the risk conferred by the interaction may be lowered by quitting smoking."

Their findings also have implications for investigation of the clinical epidemiology of aSAH, they add.

"An understanding of the interaction between smoking exposure and family history of aSAH is necessary to enable future genetic research that will allow us to best understand the biology of aneurysm formation and rupture,"' the authors conclude.

The study was funded by a grant from the National Institute of Neurological Disorders and Stroke. The authors report no disclosures.

Neurology. 2009;72:69-72. Abstract