From the article:
The research found people who smoked and had a family history of stroke were more than six times more likely to suffer a stroke than those who did not smoke and did not have a family history of stroke or brain aneurysm. The study also found that people with a family history of stroke could cut their risk by more than half by quitting smoking. The results were the same regardless of high blood pressure, diabetes, alcohol use, body mass index and education level.