Effect of Smoking Cessation on the Risk of Subarachnoid Hemorrhage: A Nested Case-Control Study in Korean Men

Smoking is a well-established risk factor for subarachnoid hemorrhage (SAH), and current smokers have an increased risk of SAH. However, there are insufficient data on whether smoking cessation in current smokers reduces the risk of SAH. A nested case-control study was conducted based on the National Health Insurance Service-National Health Screening Cohort, which comprises nationwide health claims data and a national health screening program in Korea (2002-2019). We constructed a cohort of current male smokers without a history of stroke at the baseline health screening (2002-2003). From this cohort, cases were defined as individuals who experienced a nontraumatic SAH during the follow-up period up to 2019. Five controls were matched to each case using incidence density sampling. Smoking status (continuation or cessation) before the occurrence of SAH was evaluated using the repeated national health screening program. We conducted a multivariable conditional logistic regression analysis, adjusting for alcohol consumption, physical activity, body mass index, systolic blood pressure, and fasting blood glucose levels, to evaluate the association between SAH risk and smoking cessation. At baseline, there were 112 142 current male smokers. After excluding individuals with prior stroke or insufficient data, the cohort consisted of 105 223 eligible participants (mean age, 50.3±8.5 years). Among them, we identified 318 cases of SAH and 1590 matched controls. Those who quit smoking had a significantly lower risk of SAH compared with current smokers (adjusted odds ratio, 0.55 [95% CI, 0.41-0.73]). The risk of SAH decreased with a longer period of smoking cessation. The risk reduction with smoking cessation was consistent even among prior heavy smokers. Smoking cessation in current male smokers reduced the risk of SAH, and the risk reduction was greater as the cessation period increased. These findings warrant intensive efforts to encourage smokers, even heavy smokers, to quit.