Supplementary Material for: Waterpipe tobacco smoking and multiple sclerosis: a systematic review and meta-analysis

Background: Multiple sclerosis (MS), as an autoimmune disease of the central nervous system (CNS), has a significant burden among people worldwide. Tobacco smoking is one of the most prevalent habits of patients with different diseases including those with MS and among the methods of use, waterpipe tobacco smoking is gaining popularity. Herein, we aimed to systematically evaluate the association between waterpipe smoking and MS.
Methods: Relevant studies were identified to be included in this systematic review and meta-analysis through a systematic search in PubMed, Scopus, Web of Science, and Embase. Studies were screened by title/abstract and then by their full text. Extraction of data was performed for relevant studies. Odds ratios (OR) and their 95% confidence intervals (CIs) of the association between waterpipe smoking and MS were used to pool the results observed in each study.
Results: After the screening, a total of five studies were included in our systematic review, comprised of 3087 individuals, among which there were 1135 cases with MS. Random-effect meta-analysis revealed that ever-smoking waterpipe had a significant association with MS (OR 1.73, 95% CI 1.38-2.17, p-value <0.0001). Similarly, past waterpipe smoking was significantly higher in those with MS, compared with controls (OR 2.17, 95% CI 1.61-2.92, p-value < 0.0001). Based on the reported results, smoking both tobacco and waterpipe had an additive association with MS. Finally, no association was found between the Expanded Disability Status Scale (EDSS) and waterpipe smoking.
Conclusion: Waterpipe as one of the common ways of tobacco smoking becoming popular has an association with MS and even the use of waterpipe for a certain period in the lifetime has a significant correlation with MS. Further large-scale studies are needed to confirm these findings. These results could help clinicians in risk-stratifying the patients and to provide better care for the MS population.

背景：多发性硬化症（Multiple sclerosis, MS）是一种中枢神经系统（central nervous system, CNS）自身免疫性疾病，在全球人群中造成了沉重的疾病负担。吸烟是包括多发性硬化症患者在内的多种疾病患者最普遍的不良习惯之一，而在各类烟草使用方式中，水烟（waterpipe tobacco smoking）的流行度正日益提升。本研究旨在系统评估水烟吸烟与多发性硬化症之间的关联。
方法：本研究通过在PubMed、Scopus、Web of Science及Embase数据库中开展系统性检索，筛选符合纳入标准的相关研究以进行本系统评价与荟萃分析。研究筛选流程为先通过标题/摘要进行初筛，再对全文进行复筛。随后提取纳入研究的相关数据，采用比值比（odds ratios, OR）及其95%置信区间（confidence intervals, CIs）合并各单项研究中关于水烟吸烟与多发性硬化症关联的结果。
结果：经筛选后，本系统评价共纳入5项研究，涉及3087名受试者，其中多发性硬化症患者1135例。随机效应荟萃分析结果显示，既往曾吸食水烟与多发性硬化症存在显著关联（OR=1.73，95%CI：1.38~2.17，P<0.0001）。类似地，与对照组相比，多发性硬化症患者的既往水烟吸烟率显著更高（OR=2.17，95%CI：1.61~2.92，P<0.0001）。基于报告结果显示，同时吸食烟草与水烟与多发性硬化症存在叠加关联。最后，未发现扩展残疾状态量表（Expanded Disability Status Scale, EDSS）得分与水烟吸烟存在关联。
结论：水烟作为一种日益流行的常见烟草使用方式，与多发性硬化症存在关联；即使仅在人生某一阶段吸食过水烟，也与多发性硬化症存在显著相关性。未来仍需开展大规模研究以验证上述发现。本研究结果可帮助临床医生对患者进行风险分层，并为多发性硬化症人群提供更优质的诊疗照护。