Number of cigs smoked daily ups ischaemic stoke risk in dose–response way
Male smokers under the age of 50 years are at risk of developing ischaemic stroke, and this risk increases with the number of cigarettes smoked daily, according to data from the Stroke Prevention in Young Men Study.
“The clinical implications of our finding are, that while complete cessation of smoking is the goal, even reducing the number of cigarettes smoked may have beneficial health effects,” the investigators said.
A total of 615 ischaemic stroke patients and 530 matched nonstroke controls aged 15–49 years were included in the study. Stroke patients were more likely to have lower educational levels and comorbidities such as hypertension, diabetes mellitus, myocardial infarction, angina and obesity (body mass index >30 kg/m2; p<0.05 for all).
Overall, there were 428 current smokers (those who had smoked >100 cigarettes in their lifetime and had smoked in the 30 days preceding their stroke [for patients] or interview [for controls]) and 192 former smokers (those who had smoked >100 cigarettes in their lifetime but had not smoked in the 30 days before their stroke/interview). The remaining 525 were never smokers.
In adjusted logistic regression models, current smokers were >80 percent as likely as never smokers to develop stroke (adjusted odds ratio [aOR], 1.88; 95 percent CI, 1.44–2.44). When analysis was stratified according to the number of cigarettes smoked, a strong dose–response association emerged. [Stroke 2018;49:1276-1278]
Specifically, the aORs for developing ischaemic stroke were 1.46 (1.04–2.06) with <11 sticks per day, 1.74 (1.21–2.49) with 11–20 sticks, 4.29 (2.09–8.80) with 21–39 sticks and 5.66 with ≥40 sticks.
Former smokers, on the other hand, had slightly lower odds of stroke (aOR, 1.42; 1.01–1.99) compared with never smokers.
“Our finding is consistent with results from prior studies of women and young adults in general,” the investigators said. “There is evidence for a dose–response relationship between cigarette smoking and risk of stroke in middle-aged and older adults as well; however, the association is less strong.” [Circulation 2016;133:e38-e360; Stroke 2008;39:2439-2443; BMJ 1995;311:1530-1533]
“These studies demonstrate that smoking amount is an important risk factor for ischaemic stroke but do not characterize the dose–response relationship in young male smokers,” they continued.
Despite including a more ethnically diverse population and adjusting for education, the current study has several limitations. First, there was no data on the use of other tobacco products. Second, variables such as alcohol consumption and physical activity could not be controlled for. Finally, the case–control design of the study allowed for the possibility of differential recall bias.