Impact of tobacco smoking on disease-specific outcomes in common neurological disorders: A scoping review

Although the association of smoking with the risk of incident neurological disorders is well established, less is known about the impact of smoking and smoking cessation on outcomes of these conditions. The objective of this scoping review was to synthesize what is known about the impact of smoking and smoking cessation on diseasespecific outcomes for seven common neurological disorders. We included 67 studies on the association of smoking and smoking cessation on disease-specific outcomes. For multiple sclerosis, smoking was associated with greater clinical and radiological disease progression, relapses, risk for disease-related death, cognitive decline, and mood symptoms, in addition to reduced treatment effectiveness. For stroke and transient ischemic attack, smoking was associated with greater rates of stroke recurrence, post-stroke cardiovascular outcomes, post-stroke mortality, post-stroke cognitive impairment, and functional impairment. In patients with cognitive impairment and dementia, smoking was associated with faster cognitive decline, and smoking was also associated with greater cognitive decline in Parkinson's disease, but not motor symptom worsening. Patients with amyotrophic lateral sclerosis who smoked faced increased mortality. Last, in patients with cluster headache, smoking was associated with more frequent and longer cluster attack periods. Conversely, for multiple sclerosis and stroke, smoking cessation was associated with improved disease-specific outcomes. In summary, whereas smoking is detrimentally associated with disease-specific outcomes in common neurological conditions, there is growing evidence that smoking cessation may improve outcomes. Effective smoking cessation interventions should be leveraged in the management of common neurological disorders to improve patient outcomes.