NATIONAL HARBOR, MD. – Follow-up of a cohort of patients in the United Kingdom has demonstrated associations between smoking and a higher risk of development of multiple sclerosis (MS), progression of MS-related disability, higher risk of premature death, and shortened life expectancy.
The findings highlight the need for clinical trials of the effects of quitting smoking and provide data that will be useful in the development of effective intervention strategies.
Dr. Cris S. Constantinescu
Dr. Cris S. Constantinescu of the University of Nottingham (England) discussed findings from the Nottingham University Hospitals MS Clinics database at the annual meeting of the Consortium of Multiple Sclerosis Centers.
“Although smokers had higher levels of comorbid conditions, it appeared that the influence of smoking is independent of the presence of comorbid conditions. Those who gave up smoking could do as well as nonsmokers,” said Dr. Constantinescu.
While ample epidemiologic evidence indicates that smoking is a driver of the development and progression of MS, there are few hard data. To gain insight, the researchers analyzed data on over 1,200 MS patients throughout England who were followed up beginning in the mid-1990s. About 60% of the patients had relapsing-remitting MS. The duration of MS and smoking were both about 20 years. About 60% of men and 50% of women were current smokers.
Regular smokers were 64% more likely to develop MS than were nonsmokers. Having ever smoked carried a 44% increased risk of MS (both P less than .001). MS patients who grew up in a household where one parent smoked were 50% more likely to become regular smokers. The risk climbed to 85% if both parents were smokers.
No association was evident between smoking and the development of primary progressive MS, but current smokers were almost 2.5 times more likely to develop secondary progressive MS. Smoking correlated with more severe MS disability, compared with nonsmokers. Ex-smokers had risks similar to those of nonsmokers of developing secondary MS and in the level of disease severity.
Every year a person refrained from smoking decreased the risk of severe disability by 5%. Current and ex-smokers displayed increased psychological and physical detriments of MS.
In a subgroup of 923 patients, of whom 80 died, current smokers were almost 3 times and 1.5 times more likely to die, compared with never smokers and ex-smokers, respectively, and were twice as likely to die as were people without MS in the UK general population.
The findings have prompted studies into major aspects of smoking, such as the age when smoking begins, the success of various smoking cessation programs, and development of interventions. Some of the data discussed at the meeting were published in 2013 (Brain;136:2298-2304) and some are part of a manuscript in preparation.