Recovery from a stroke ranges from full recovery to disability or death. Although previous research has shown a link between smoking and poor stroke recovery, it has been unclear whether or not smoking actually contributes to the problem.
A new study published today in the medical journal of the American Academy of Neurology found that a genetic predisposition to smoking makes a person more likely to recover more slowly from an ischemic stroke. Ischemic strokes occur when the brain doesn’t get enough blood. This is the most common type of stroke.
“Recovery from stroke can vary greatly from person to person, from full recovery to severe disability or death,” explains study author Xinfeng Liu, PhD, of Nanjing University in China. “While previous studies have found links between smoking and worse recovery after stroke, it has been unclear whether smoking is a cause. By examining gene variants that increase a person’s risk of smoking, we found that smoking causes poorer stroke outcomes.”
Researchers examined the results of a meta-analysis of 12 studies on genetics and post-stroke recovery in the United States, Europe and Australia to assess the genetic link between smoking and post-stroke recovery. There were a total of 6,021 ischemic stroke patients with European genetic background. 3 months after stroke recovery was measured.
Recovery was categorized as either ‘good’ or ‘poor’. “Good” meant a person had made a full recovery or had a mild disability but did not require help from others. “Poor” meant a person had a moderate disability, needed assistance, had a severe disability, or had died. Overall, 3,741 patients had successful stroke recovery, while 2,280 had less than optimal outcomes.
To determine if there was a causal link between 373 genetic variations known as single nucleotide polymorphisms (SNPs) and poor recovery after stroke, the team used an experimental strategy known as Mendelian randomization. SNPs are widespread and can serve as biological markers to identify disease-associated genes.
Adjusting for age, gender and the severity of the stroke, the researchers found that people who were genetically more likely to smoke had a 48% higher chance of recovering from a stroke than others. When the researchers made further adjustments for genetically predicted alcohol consumption, the results remained unchanged.
“Our results provide genetic support for the theory that smoking leads to poor recovery after ischemic stroke,” Liu adds. “These findings have important implications for stroke recovery. Not only should doctors encourage everyone not to smoke, but people who have had a stroke should be encouraged to quit smoking.”
Both the small size of the study and the fact that all subjects were of European descent call for larger studies involving other populations.
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