Smoking cessation reduced risk for stroke among middle-aged women after 2 to 4 years
ACP J Club. 1993 July-Aug;119:27. doi:10.7326/ACPJC-1993-119-1-027
Kawachi I, Colditz GA, Stampfer MJ, et al. Smoking cessation and decreased risk of stroke in women. JAMA. 1993 Jan 13;269:232-6.
To study the association of time since stopping smoking with the risk for stroke in middle-aged women.
Cohort followed for 12 years (Nurses' Health Study, 1976 to 1988).
117 006 registered nurses (100% women, 98% white) who were 30 to 55 years of age in 1976 and free of coronary heart disease, stroke, and cancer at baseline. Follow-up for fatal and nonfatal stroke was 95%.
Assessment of risk factors
Age; current and previous cigarette smoking; height; weight; history of oral contraceptive use; postmenopausal use of hormones; and history of diabetes, hypertension, hypercholesterolemia, and other major illnesses were assessed by questionnaire at baseline and every 2 years thereafter. Alcohol intake was assessed by questionnaire in 1980.
Main outcome measures
Fatal and nonfatal incident strokes ascertained by review of hospital records, autopsy reports, death certificates, the National Death Index, or a blinded review of medical charts. Strokes were categorized as subarachnoid hemorrhage, intracerebral hemorrhage, or ischemic.
448 incident strokes occurred during follow-up: 275 ischemic strokes, 108 subarachnoid hemorrhages, 53 cerebral hemorrhages, and 12 unspecified strokes. For all types of stroke combined, the overall age-adjusted relative risk (RR) among current smokers when compared with those who never smoked was 2.58 (95% CI 2.08 to 3.19). The RRs for subtypes of stroke were 4.96 (CI 3.13 to 7.87) for subarachnoid hemorrhage, 2.25 (CI 1.72 to 2.95) for ischemic stroke, and 1.46 (CI 0.77 to 2.78) for cerebral hemorrhage. The risk for stroke increased with the number of cigarettes smoked daily. The RR for total stroke among former smokers was 1.34 (CI 1.04 to 1.73). This excess risk among former smokers largely disappeared during the interval between 2 and 4 years after cessation (RR vs current smokers 0.46, CI 0.25 to 0.85). The same pattern of decline was observed after adjusting for other risk factors for stroke, age at starting to smoke, and number of cigarettes smoked daily.
Cigarette smoking was a risk factor for ischemic and hemorrhagic stroke among middle-aged women. Smoking cessation reduced the risk for stroke, with most of the benefit occurring 2 to 4 years after stopping.
Source of funding: National Institutes of Health.
For article reprint: Dr. I. Kawachi, Channing Laboratory, 180 Longwood Avenue, Boston, MA 02115-5899, USA. FAX 617-432-3755.
Smoking is a strong risk factor for coronary heart disease and stroke, but the cardiac risks associated with smoking drop substantially after quitting, even for heavy smokers. This report shows that the risks for hemorrhagic and nonhemorrhagic stroke also fall markedly after quitting smoking. The explanation for the temporal effects of smoking on stroke are speculative (changes in blood pressure, arterial tone, fibrinogen activity, or platelet function) and may differ for hemorrhagic and nonhemorrhagic strokes.
This careful study adds to our understanding of stroke in women. Smoking may be a leading, treatable cause of stroke in women aged < 65 years. The conclusion that the effects of smoking on stroke largely disappear within a few years of quitting may not apply to all populations. The participants were relatively young and free of heart disease and stroke at baseline, and the risks among long-term, heavy smokers who quit were not specifically examined. The risk for subarachnoid hemorrhage appears elevated even years after quitting, suggesting a component of persistent damage to large cerebral vessels (1). Smoking also contributes to carotid atherosclerosis and congestive heart failure, conditions that may have lasting effects on the incidence of stroke. Additional follow-up of this cohort may show whether these findings apply in older women, where the toll of stroke is much higher. In the meantime, clinicians should emphasize the key finding of this study to their smoking patients: It is never too late to quit (2).
David Atkins, MD
University of WashingtonSeattle, Washington, USA