wileyonlinelibrary.com/journal/ane Acta Neurol Scand. 2018;138:62–69.
© 2018 John Wiley & Sons A/S.
Published by John Wiley & Sons Ltd
1 | INTRODUCTION
Multiple sclerosis (MS) is an inflammatory demyelinating disease
of the central nervous system affecting 2.3 million people world-
An umbrella review of systematic reviews and meta- analysis
revealed that strongest evidence of environmental factors associ-
ated with increased MS risk are IgG seropositivity to Epstein- Barr
virus (EBV), infectious mononucleosis, and smoking.
Smoking is a
modifiable lifestyle behavior associated with a modest increase in
MS risk (Risk Ratio: 1.52, 95% CI 1.39- 1.66).
In a population- based
incident case- control study waterpipe smoking, tobacco smoking,
and passive smoking have been associated with increased MS
Both duration and intensity of smoking independently in-
creased MS risk.
Recently, it was suggested that non- smokers had
Accepted: 16 February 2018
Smoking and worsening disability in multiple sclerosis:
A meta- analysis
| A. Manouchehrinia
| O. Beiki
| S. E. Mousavi
| M. Moradi -Lakeh
| M. A. Sahraian
MS Research Center, Neuroscience
Institute, Tehran University of Medical
Sciences, Tehran, Iran
Department of Clinical
Neuroscience, Karolinska Institutet,
Kermanshah University of Medical
Sciences, Kermanshah, Iran
Social Health Determinants Research
Center, Shahrekord University of Medical
Sciences, Shahrekord, Iran
Department of Community Medicine, Iran
University of Medical Sciences, Tehran, Iran
M. A. Sahraian, MS Research Center,
Tehran University of Medical Sciences,
Dr. Sahraian has received educational,
research grants, lecture honorarium, travel
supports to attend scientific meetings from
Biogen- Idec, Merck- Serono, Bayer- Schering,
Novartis, Cinnagen, Osveh, Zistdaru,
Zahravi, and Genzyme
Objectives: Multiple sclerosis (MS) is a chronic demyelinating disorder affecting
young adults. Environmental factors and lifestyle behaviors are pivotal in MS patho-
physiology. Smoking has been considered as an important risk factor in MS. Various
recent studies have been conducted to measure the role of smoking on worsening
disability in patients with MS, thus we intended to systematically assess effect of
smoking on evolution of disability in this study.
Materials & methods: We queried MEDLINE, EMBASE and Cochrane Library with
following keywords “Multiple Sclerosis, Smoking, Tobacco Use, Disability” on
December 1st 2016. Original articles were included when smoking history was men-
tioned, disability was measured via expanded disability status scale (EDSS) or multi-
ple sclerosis severity score (MSSS). Studies with insufficient outcome data,
non- human, or in other languages than English were excluded.
Results: Through literature review after duplicate removals, 268 articles were re-
trieved. A total of 56 articles were screened and 15 articles were assessed for eligibil-
ity, finally, eleven articles were included in this systematic review and meta- analysis.
Ever smoking was significantly associated with increased EDSS (standardized mean
difference (SMD) = 0.15, 95% CI = 0.01- 0.28), but had no significant association with
risk of reaching EDSS 4 (HR = 1.24, 95% CI = 0.89- 1.72) or EDSS 6 (HR = 1.17, 95%
CI = 0.88- 1.57). Smoking had no effect on MSSS (SMD = 0.14, 95% CI = −0.04- 0.32)
or T2 lesion volume (SMD = 0.07, 95% CI = −0.08- 0.22).
Conclusions: This meta- analysis showed smoking increased EDSS, insignificant find-
ings were possibly due to the small number of studies, significant differences in
methodologies, and variations in reporting of disability outcomes.
disability, meta-analysis, multiple sclerosis, smoking, systematic review