Heavy Smoking Linked to Brain Bleed Risk

Heavy smoking is a major risk factor for subarachnoid hemorrhage (SAH) in both sexes, but the risk is especially high among women, according to a new study.

Researchers at the University of Helsinki (Finland) conducted a prospective study of 65,521 people participating in the FINRISK study, a large population survey of potential risk factors in chronic, non-communicable diseases; the study cohort of was followed up for 1.38 million person-years. The researchers calculated hazard ratios and additive and multiplicative interactions between all study variables, with all analyses adjusted for known SAH risk factors and smoking habits. In all, the researchers identified 492 SAHs (266 in women and 226 in men).

The results of the analysis showed that women who smoked more than 20 cigarettes per day had a hazard ratio of 8.35 for SAH, compared with a lower hazard ratio of 2.76 in men who smoked the same amount of cigarettes per day. The hazard ratios differed by sex in all cigarettes-per-day and pack-year categories, with the association being stronger in women in all categories. In addition, former smokers had a markedly decreased risk for SAH in both sexes when compared with current smokers.

When the researchers adjusted for interactions between cigarettes smoked per day and sex, and pack years and sex, female sex was no longer an independent risk factor for SAH. An adjusted model that included only never smokers also failed to show female sex to be an independent risk factor for hemorrhage, leading the researchers to conclude smoking had a dose-dependent and cumulative association with SAH risk, and the risk is highest in female heavy smokers. The study was published in the August 2016 issue of Stroke.

“Female sex has been considered to be an independent risk factor for subarachnoid bleeds, but the new findings suggest that smoking, especially heavy smoking, explains this increase in risk,” said lead author Joni Valdemar Lindbohm, MD. “This effect modification seems to explain why previous studies report female sex as an independent risk factor for SAH. The results emphasize the importance of worldwide smoking cessation agendas and active treatment of nicotine dependence.”

SAH occurs between the arachnoid membrane and the pia mater surrounding the brain. It may occur spontaneously, usually from a ruptured cerebral aneurysm, or as a result of head injury. Considered a form of stroke, up to half of all cases are fatal, and those who survive often have neurological or cognitive impairment. Symptoms include a severe, rapid onset headache, vomiting, confusion or a lowered level of consciousness, and sometimes seizures. Diagnosis is confirmed with a CT scan of the head, or occasionally by lumbar puncture, and treatment is by neurosurgery or radiologically guided interventions.

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