A multinational study of the effects of smoking cigarettes on the people of China has led to the alarming conclusion that smokers face serious risk of stroke, with the risk increasing the longer and heavier a person smokes.

The link between smoking and stroke in western populations has been well documented but this study, started in 1991 as a collaboration between Tulane University in New Orleans and the Chinese Academy of Medical Sciences in Beijing, leads to the same conclusion in the Asian population as well.

The study’s findings are based on continued participation over many years’ time of 83,533 Chinese men and 86,336 Chinese women, all age 40 and older, from 17 provinces in mainland China. Participants were followed for an average of 8.3 years each as part of the China National Hypertension Survey.

At the beginning of the study, 59.1% of the men and 13% of the women identified themselves as smokers. During the course of the study, 6,780 participants suffered stroke, with 3,979 strokes causing death.

When age and blood pressure measures were taken into consideration for each stroke fatality, the incidence of smoking was determined to be a very strong predictor of the likelihood of stroke.

Male smokers suffered strokes about seven times more often than the general population, accounting for 14.2% of all strokes in men, with a fatality rate of 7.1%. Women experienced 3.1% of the strokes, with 2.4% resulting in death.

When comparing strokes in smokers to the non-smoking population, those who lit up one to 19 times a day raised their stroke risk to 21%. Heavier smoking raised the risk to 36%.

Length of time smoking, measured in “pack-years,” was also taken into consideration. One pack-year is the equivalent of smoking a standard pack of cigarettes, containing 20 individual cigarettes, every day for a year and multiplying by the number of years smoking. In other words, smoking one pack of cigarettes every day for 10 years is 10 pack-years. Smoking only a half a pack of cigarettes every day but doing so for 20 years is also the equivalent of 10 pack-years.

Smokers in the 1 to 11 pack-year range increased risk of stroke by 18%. Those measured at 12 to 26 pack-years saw an increased risk by 25% and those smoking longer, or heavier as the case may be, increased stroke risk by 34%.

The kind of stroke suffered changed with smoking, too. Ischemic stroke, which is caused by blood clot in the brain, accounted for 51% of smokers’ strokes. Smoking increased the risk of hemorrhagic stroke by 20%. Hemorrhagic stroke is caused when a blood vessel in the brain ruptures.

Strokes are influenced by many factors but only two of them – smoking and high blood pressure – can be controlled easily by the individual. The research team hopes the findings of the study will add some significance to China’s current anti-smoking campaigns, which are not publicized in government-owned media outlets such as television and newspapers.

If more Chinese made the effort to reduce smoking, researchers expect a 5% drop in the number of deaths caused by stroke.

Full details of the study can be found in the current issue of Stroke: Journal of the American Heart Association.