Smoking and risk of multiple sclerosis: evidence of modification by NAT1 variants

Risk factors for multiple sclerosis in the context of Epstein-Barr virus infection

Compelling evidence indicates that Epstein Barr virus (EBV) infection is a prerequisite for multiple sclerosis (MS). The disease may arise from a complex interplay between latent EBV infection, genetic predisposition, and various environmental and lifestyle factors that negatively affect immune control of the infection. Evidence of gene-environment interactions and epigenetic modifications triggered by environmental factors in genetically susceptible individuals supports this view. This review gives a short introduction to EBV and host immunity and discusses evidence indicating EBV as a prerequisite for MS. The role of genetic and environmental risk factors, and their interactions, in MS pathogenesis is reviewed and put in the context of EBV infection. Finally, possible preventive measures are discussed based on the findings presented.

Sex, aging and immunity in multiple sclerosis and experimental autoimmune encephalomyelitis: An intriguing interaction

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) with a profound neurodegenerative component early in the disease pathogenesis. Age is a factor with a well-described effect on the primary disease phenotype, namely, the relapsing-remitting vs. the primary progressive disease. Moreover, aging is a prominent factor contributing to the transition from relapsing-remitting MS (RRMS) to secondary progressive disease. However, sex also seems to, at least in part, dictate disease phenotype and evolution, as evidenced in humans and in animal models of the disease. Sex-specific gene expression profiles have recently elucidated an association with differential immunological signatures in the context of experimental disease. This review aims to summarize current knowledge stemming from experimental autoimmune encephalomyelitis (EAE) models regarding the effects of sex, either independently or as a factor combined with aging, on disease phenotype, with relevance to the immune system and the CNS.

Trends in the environmental risks associated with earlier onset in multiple sclerosis

BACKGROUND

Several environmental and lifestyle factors relating to sunlight/vitamin D, body mass index (BMI), and smoking are associated with the risk of developing multiple sclerosis (MS). However, their relation to disease progression, particularly age at symptomatic onset, remains inconsistent, which may be the result of significant changes in human-environment interactions over the last century. This study investigates historical trends in the association between common MS environmental risk factors and age at disease onset.

METHODS

Using a narrative approach, we evaluated the current literature for published studies assessing the association between vitamin-D, BMI, and tobacco smoking exposures with the risk of early/pediatric-onset MS and direct correlations with age at MS onset using MEDLINE, EMBASE, and Web of Science. Measures were plotted by the average calendar year of disease onset for each cohort to examine trends over time. In total, 25, 9, and 11 articles were identified for vitamin D, BMI, and smoking-related exposures, respectively.

RESULTS

Higher sun exposure habits and residential solar radiation were associated with older age at onset. On the contrary, two studies observed a negative correlation between age at onset and serum 25-hydroxyvitamin D (25(OH)D) levels. Higher adolescent BMI was generally associated with younger age at onset, although genetic susceptibility for childhood obesity was not significantly associated. Tobacco smoking was associated with later disease onset, despite being a risk factor for MS. Association with age at onset was inflated for more recent studies relating to smoking, while often weaker for serum vitamin D and BMI.

CONCLUSION

Current findings indicate a likely association between age at onset and environmental risk factors, such as sun exposure, adolescent BMI, and tobacco smoking, in certain populations. However, findings are often inconsistent and assessment of the relationships and potential changes over time require further investigation.

Nicotinic acetylcholine receptors α7 and α9 modifies tobacco smoke risk for multiple sclerosis

INTRODUCTION

Tobacco smoke exposure is an established risk factor for multiple sclerosis (MS), yet how it confers risk is not known. Evidence from observational studies suggests nicotine may be a protective component. Animal studies further support this hypothesis, demonstrating nicotine's protective effect in MS is mediated by the presence and absence of α7 and α9 nicotinic acetylcholine receptors (nAChRs), respectively.

OBJECTIVE

To determine if variation in the genes encoding α7 and α9 nAChRs (cholinergic receptor nicotinic alpha 7 (CHRNA7) and alpha 9 (CHRNA9)) will modify MS risk conferred by tobacco smoking.

METHODS

A multi-stage gene-environment (G×E) framework was utilized, including a case-control analysis (286 cases, 176 controls) with haplotype- and gene-based analyses, followed by an extension case-only (1053 cases) analysis for overlapping variants.

RESULTS

The results suggest that CHRNA7 and CHRNA9 modifies MS risk conferred by tobacco smoke, where risk among smokers was increased in carriers of the minor CHRNA9 haplotype and in non-carriers the minor CHRNA7 haplotype. The findings are consistent with the pharmacology of these receptors and animal studies of MS.

CONCLUSION

This study implicates novel processes in MS initiation and demonstrate the need for further G×E studies to advancing our understanding of the missing heritability of MS.

Gene-Environment Interactions in Multiple Sclerosis: A UK Biobank Study

Objective

We sought to determine whether genetic risk modifies the effect of environmental risk factors for multiple sclerosis (MS). To test this hypothesis, we tested for statistical interaction between polygenic risk scores (PRS) capturing genetic susceptibility to MS and environmental risk factors for MS in UK Biobank.

Methods

People with MS were identified within UK Biobank using ICD-10–coded MS or self-report. Associations between environmental risk factors and MS risk were quantified with a case-control design using multivariable logistic regression. PRS were derived using the clumping-and-thresholding approach with external weights from the largest genome-wide association study of MS. Separate scores were created including major histocompatibility complex (MHC) (PRS_MHC) and excluding (PRS_non-MHC) the MHC locus. The best-performing PRS were identified in 30% of the cohort and validated in the remaining 70%. Interaction between environmental and genetic risk factors was quantified using the attributable proportion due to interaction (AP) and multiplicative interaction.

Results

Data were available for 2,250 people with MS and 486,000 controls. Childhood obesity, earlier age at menarche, and smoking were associated with MS. The optimal PRS were strongly associated with MS in the validation cohort (PRS_MHC: Nagelkerke's pseudo-R² 0.033, p = 3.92 × 10⁻¹¹¹; PRS_non-MHC: Nagelkerke's pseudo-R² 0.013, p = 3.73 × 10⁻⁴³). There was strong evidence of interaction between polygenic risk for MS and childhood obesity (PRS_MHC: AP = 0.17, 95% CI 0.06–0.25, p = 0.004; PRS_non-MHC: AP = 0.17, 95% CI 0.06–0.27, p = 0.006).

Conclusions

This study provides novel evidence for an interaction between childhood obesity and a high burden of autosomal genetic risk. These findings may have significant implications for our understanding of MS biology and inform targeted prevention strategies.

Mining Complex Genetic Patterns Conferring Multiple Sclerosis Risk

(1) Background: Complex genetic relationships, including gene-gene (G × G; epistasis), gene(n), and gene-environment (G × E) interactions, explain a substantial portion of the heritability in multiple sclerosis (MS). Machine learning and data mining methods are promising approaches for uncovering higher order genetic relationships, but their use in MS have been limited. (2) Methods: Association rule mining (ARM), a combinatorial rule-based machine learning algorithm, was applied to genetic data for non-Latinx MS cases (n = 207) and controls (n = 179). The objective was to identify patterns (rules) amongst the known MS risk variants, including HLA-DRB1*15:01 presence, HLA-A*02:01 absence, and 194 of the 200 common autosomal variants. Probabilistic measures (confidence and support) were used to mine rules. (3) Results: 114 rules met minimum requirements of 80% confidence and 5% support. The top ranking rule by confidence consisted of HLA-DRB1*15:01, SLC30A7-rs56678847 and AC093277.1-rs6880809; carriers of these variants had a significantly greater risk for MS (odds ratio = 20.2, 95% CI: 8.5, 37.5; p = 4 × 10⁻⁹). Several variants were shared across rules, the most common was INTS8-rs78727559, which was in 32.5% of rules. (4) Conclusions: In summary, we demonstrate evidence that specific combinations of MS risk variants disproportionately confer elevated risk by applying a robust analytical framework to a modestly sized study population.

Little evidence for an effect of smoking on multiple sclerosis risk: A Mendelian Randomization study

The causes of multiple sclerosis (MS) remain unknown. Smoking has been associated with MS in observational studies and is often thought of as an environmental risk factor. We used two-sample Mendelian randomization (MR) to examine whether this association is causal using genetic variants identified in genome-wide association studies (GWASs) as associated with smoking. We assessed both smoking initiation and lifetime smoking behaviour (which captures smoking duration, heaviness, and cessation). There was very limited evidence for a meaningful effect of smoking on MS susceptibility as measured using summary statistics from the International Multiple Sclerosis Genetics Consortium (IMSGC) meta-analysis, including 14,802 cases and 26,703 controls. There was no clear evidence for an effect of smoking on the risk of developing MS (smoking initiation: odds ratio [OR] 1.03, 95% confidence interval [CI] 0.92-1.61; lifetime smoking: OR 1.10, 95% CI 0.87-1.40). These findings suggest that smoking does not have a detrimental consequence on MS susceptibility. Further work is needed to determine the causal effect of smoking on MS progression.

Role of Smoking in the Pathogenesis of Multiple Sclerosis: A Review Article

Multiple sclerosis (MS) is a complex and unpredictable neurological condition. It is the most commonly seen autoimmune disorder. The incidence of disease and its prevalence are growing worldwide. Early identification of the disease and accurate diagnosis is important to prevent further complications and disability. The etiology remains unclear, and it is believed that complex gene-environment interactions play an essential role. Genetic predisposition only describes a portion of the disease risk, whereas lifestyle and environmental factors are significant contributors. Smoking was identified as an important risk factor for MS. The main objectives of this review were to examine the underlying mechanisms of immune dysregulation in the development of MS, explore the association between smoking and MS, and identify other genetic and environmental factors that alter the risk of developing the disease. We searched PubMed for articles relevant to the study topic published between 2000 and 2020 using the search terms "multiple sclerosis," "cigarette smoking," "risk factors," and, "epigenetics." Studies reveal a marked association between smoking and the risk of MS. Unlike genetic risk factors, many lifestyles and environmental factors can be adjusted, with potential for prevention, particularly for people at the highest risk, such as families of individuals with MS.

Multiple Sclerosis and Smoking

Multiple sclerosis (MS) is a common, severe neurological disease that affects millions of people worldwide. Nevertheless, the actual cause of MS remains unknown. Smoking has been studied with respect to MS development and progression. The objectives of this review were to examine the relationship between smoking and MS and to understand the possible molecular mechanisms underlying the association. PubMed was searched for articles related to the study topic published between 2012 and 2020 using the search terms "multiple sclerosis," "smoking," "risk factors," "cigarettes," and "molecular mechanisms." Studies show a significant relationship between smoking and the risk of MS. Furthermore, smoking has been linked to the progression of MS at the patient and population levels. However, the underlying mechanism remains to be explored in further studies; researchers still disagree on how the relationship between smoking and MS arises in different populations. Evidence from randomized controlled trials, systematic reviews, and epidemiological studies shows that smokers have a higher risk of developing MS and experiencing related adverse symptoms and complications.

A matched case-control study of risk factors associated with multiple sclerosis in Kuwait

Background

Genetic and environmental factors seem to have etiologic roles in multiple sclerosis (MS). Kuwait is regarded as medium to high risk country for MS. However, there is a paucity of published data on the risk factors for MS in Kuwait. Therefore, this matched case-control study examined the association between various factors including family history, stressful life events, exposure to tobacco smoke, vaccination history, comorbidities and MS risk in Kuwait.

Methods

Confirmed 110 MS cases and age (± 5 years), gender and nationality matched controls (1:1) were enrolled. A pre-tested structured questionnaire was used to collect the data through face-to-face interviews both from cases and controls. Conditional logistic regression was used to analyze the data.

Results

Among both cases and controls, majority were Kuwaiti (82.7%), and female (76.4%). Multivariable model showed that cases compared to controls were significantly more likely to have had a family history of MS (adjusted matched odds ratio (mOR_adj) = 5.1; 95% CI: 2.1–12.4; p < 0.001) or less likely to have been vaccinated against influenza A and B viruses before MS onset (mOR_adj = 0.4; 95% CI: 0.2–0.8; p = 0.010). None of the other variables considered were significantly related to MS status in this study.

Conclusions

Family history of MS had significantly direct, whereas, vaccination against influenza A and B viruses had inverse associations with MS status. Future studies may contemplate to verify the observed results.

Identification of key genes associated with multiple sclerosis based on gene expression data from peripheral blood mononuclear cells

The aim of this study was to identify the potential key candidate genes of multiple sclerosis (MS) and uncover mechanisms in MS. We combined data from the microarray expression profile of three MS stages and performed bioinformatics analysis. Differentially expressed genes (DEGs) were identified among the distinct stages of MS and healthy controls, and a total of 349 shared DEGs were identified. Gene ontology (GO) and pathway enrichment analyses showed that the DEGs were significantly enriched in the biological processes (BPs) of purine-related metabolic processes and signaling, especially the common DEGs, which were enriched in some immunological processes. Most of the DEGs were enriched in signaling pathways associated with the immune system, some immune diseases and infectious disease pathways. Through a protein-protein interaction (PPI) network analysis and a gene expression regulatory network constructed with MS-related miRNAs, we confirmed FOS, TP53, VEGFA, JUN, HIF1A, RB1, PTGS2, CXCL8, OAS2, NFKBIA and OAS1 as candidate genes of MS. Furthermore , we explored the potential SNPs associated with MS by database mining. In conclusion, this study provides the identified genes, SNPs, biological processes, and cellular pathways associated with MS. The uncovered candidate genes may be potential biomarkers involved in the diagnosis and therapy of MS.

Environmental Influencers, MicroRNA, and Multiple Sclerosis

Multiple sclerosis (MS) is a complex neurological disorder characterized by an aberrant immune system that affects patients' quality of life. Several environmental factors have previously been proposed to associate with MS pathophysiology, including vitamin D deficiency, Epstein-Barr virus (EBV) infection, and cigarette smoking. These factors may influence cellular molecularity, interfering with cellular proliferation, differentiation, and apoptosis. This review argues that small noncoding RNA named microRNA (miRNA) influences these factors' mode of action. Dysregulation in the miRNAs network may deeply impact cellular hemostasis, thereby possibly resulting in MS pathogenicity. This article represents a literature review and an author's theory of how environmental factors may induce dysregulations in the miRNAs network, which could ultimately affect MS pathogenicity.

Multiple Sclerosis Risk Factors and Pathogenesis

PURPOSE OF REVIEW

This article summarizes recent advances in the identification of genetic and environmental factors that affect the risk of developing multiple sclerosis (MS) and the pathogenic processes involved in acute relapses and relapse-independent disability progression.

RECENT FINDINGS

The number of single-nucleotide polymorphisms associated with increased risk of MS has increased to more than 200 variants. The evidence for the association of Epstein-Barr virus infection, vitamin D deficiency, obesity, and smoking with increased risk of MS has further accumulated, and, in cases of obesity and vitamin D deficiency, the evidence for causal association has strengthened. Interactions between genetic and environmental factors have been studied more extensively. Dietary factors and changes in the gut microbiota are emerging as possible modulators of the disease risk. Several processes important to MS pathogenesis have been newly investigated or investigated more comprehensively, including the role of B cells, innate immune cells, meningeal inflammation, cortical and gray matter demyelination, and early axonal and neuronal loss.

SUMMARY

MS is a complex disease in which the interaction between genetic and environmental factors causes a cascade of events, including activation of the adaptive and innate immune system, blood-brain barrier breakdown, central nervous system demyelination, and axonal and neuronal damage with variable degrees of repair. These events manifest as potentially reversible focal neurologic symptoms or progressive nonremitting physical and cognitive disability, or both. Advances in the understanding of the risk factors and pathogenic mechanisms of MS have resulted in improved therapeutic strategies. The results of ongoing or future studies are needed to successfully and fully translate these advances into clinical practice.

NAT1 genetic variation increases asthma risk in children with secondhand smoke exposure

OBJECTIVE

We previously reported that children exposed to secondhand smoke (SHS) that carried variants in the NAT1 gene had over two-fold higher hair cotinine levels. Our objective was to determine if NAT1 polymorphisms confer increased risk for developing asthma in children exposed to SHS.

METHODS

White participants in the Cincinnati Childhood Allergy and Air Pollution Study (n = 359) were genotyped for 10 NAT1 variants. Smoke exposure was defined by hair cotinine and parental report. Asthma was objectively assessed by spirometry and methacholine challenge. Findings were replicated in the Genomic Control Cohort (n = 638).

RESULTS

Significant associations between 5 NAT1 variants and asthma were observed in the CCAAPS exposed group compared to none in the unexposed group. There was a significant interaction between NAT1 rs13253389 and rs4921581 with smoke exposure (p = 0.02, p = 0.01) and hair cotinine level (p = 0.048, p = 0.042). Children wildtype for rs4921581 had increasing asthma risk with increasing hair cotinine level, whereas those carrying the NAT1 minor allele had an increased risk of asthma regardless of cotinine level. In the GCC, 13 NAT1 variants were associated with asthma in the smoke-exposed group, compared to 0 in the unexposed group, demonstrating gene-level replication.

CONCLUSIONS

Variation in the NAT1 gene modifies asthma risk in children exposed to secondhand-smoke. To our knowledge, this is the first report of a gene-environment interaction between NAT1 variants, smoke exposure, cotinine levels, and pediatric asthma. NAT1 genotype may have clinical utility as a biomarker of increased asthma risk in children exposed to smoke.

Environmental and genetic risk factors for MS: an integrated review

Recent findings have provided a molecular basis for the combined contributions of multifaceted risk factors for the onset of multiple sclerosis (MS). MS appears to start as a chronic dysregulation of immune homeostasis resulting from complex interactions between genetic predispositions, infectious exposures, and factors that lead to pro-inflammatory states, including smoking, obesity, and low sun exposure. This is supported by the discovery of gene-environment (GxE) interactions and epigenetic alterations triggered by environmental exposures in individuals with particular genetic make-ups. It is notable that several of these pro-inflammatory factors have not emerged as strong prognostic indicators. Biological processes at play during the relapsing phase of the disease may result from initial inflammatory-mediated injury, while risk factors for the later phase of MS, which is weighted toward neurodegeneration, are not yet well defined. This integrated review of current evidence guides recommendations for clinical practice and highlights research gaps.

Lifestyle and Environmental Factors in Multiple Sclerosis

Lifestyle and environmental factors potently influence the risk of multiple sclerosis (MS), because genetic predisposition only explains a fraction of the risk increase. There is strong evidence for associations of Epstein-Barr virus (EBV) infection, smoking, sun exposure/vitamin D, and adolescent obesity to risk of MS. There is also circumstantial evidence on organic solvents and shift work, all associate with greater risk, although certain factors like nicotine, alcohol, and a high coffee consumption associate with a reduced risk. Certain factors, smoking, EBV infection, and obesity interact with human leukocyte antigen (HLA) risk genes, arguing for a pathogenic pathway involving adaptive immunity. There is a potential for prevention, in particular for people at greater risk such as relatives of individuals with MS. All of the described factors for MS may influence adaptive and/or innate immunity, as has been argued for MS risk gene variants.

Correlation Between Smoking and Passive Smoking with Multiple Sclerosis and the Underlying Molecular Mechanisms

Multiple sclerosis (MS) is a chronic immune-mediated disease of the spinal cord and brain. Many studies have shown that smoking and passive smoking are key environmental risk factors for MS.

Here, we provide an overview of the human leukocyte antigen (HLA) gene studies on smoking and MS risk, and we discuss recent studies on between epigenetics and smoking-induced MS. In addition, in this review we also summarize current research advances in biological pathways and smoking-induced MS.

This review provides an overview of studies on the association between smoking, passive smoking, and MS susceptibility, and the underlying molecular mechanism.

Prevalence of asthma in multiple sclerosis: A United States population-based study

BACKGROUND

Multiple sclerosis (MS) and asthma are complex multifactorial diseases which adversely impact daily functioning. However, the prevalence of asthma in those with MS is not clear. The objective of this study is to characterize the prevalence of asthma in those with MS, with considerations for age, gender, and race.

METHODS

We conducted a U.S. population-based, cross-sectional study of electronic health record information for 56.6 million Americans available in the IBM® Explorys EPM: Explore database. We evaluated the prevalence of asthma in MS (N = 141,880) and non-MS (N = 56,416,790) cohorts, stratifying by age, gender, and race (All, White Americans, and African Americans).

RESULTS

The prevalence of asthma was significantly greater among those with MS than the general population across age, gender, and racial subpopulations. Adjusting for age and gender, asthma was three times more common in MS. In the MS cohort, the prevalence of asthma had a U-shaped distribution with respect to age, with the greatest asthma prevalence among the young and the elderly (> 20% prevalence among those <30 or ≥80 years; prevalence range: 15 to 30%); this significantly differed from the fairly uniform distribution observed in the non-MS cohort (prevalence range: 4 to 9%). These patterns were relatively consistent when stratifying by gender and race.

CONCLUSION

Asthma is significantly more common in those with MS than in the general population - particularly in the young and elderly - irrespective of gender and race. The results add to the growing MS comorbidity literature, and emphasizes the need for comorbidity management as a part of comprehensive MS patient care.

Multiple sclerosis risk factors contribute to onset heterogeneity

BACKGROUND

The phenotypic presentation of multiple sclerosis (MS) may predict long-term outcomes and little is known about factors contributing to heterogeneity at MS onset. Given temporality, it is likely MS risk factors also influence presentation of the disease near onset.

METHODS

Using a retrospective cross-sectional study of MS cases, we investigated: age of onset (AOO), number of impaired functional domains (NIFDs), time to second relapse (TT2R), and early relapse activity (ERA). Machine learning variable selection was applied to epidemiologic data for each outcome, followed by multivariable regression models. The models were further adjusted for HLA-DRB1*15:01 carrier status and a MS genetic risk score (GRS). The TT2R and ERA analyses were restricted to relapsing remitting MS cases.

RESULTS

HLA-DRB1*15:01, GRS, and smoking were associated with earlier AOO. Cases who were male, obese, had lower education, or had primary progressive MS were older at onset. For NIFDs, those with relapsing remitting MS and of lower SES had increased NIFDs. Among relapsing remitting cases, those who were older at onset, obese, and had polyfocal presentation had shorter TT2R, while ERA was greater among those younger at onset and who were obese.

CONCLUSION

Individual characteristics including age, genetic profiles, obesity, and smoking status contribute to heterogeneity in disease presentation and modulate early disease course evolution.

Smoking and its interaction with genetics in MS etiology

The etiology of multiple sclerosis (MS) involves multifaceted interactions between genetic loci and environmental factors. Smoking is an important risk factor for MS that overall increases the risk of the disease with approximately 50%. However, the precise effects of smoking on MS development vary considerably in different contexts and in different populations. This review focuses on the influence of smoking on MS risk and its interaction with genetics in MS etiology. The possible biological mechanisms are presented in this paper. Further research is needed to establish the mechanisms of causality and to explore preventive strategies.

Cardiovascular conditions in persons with multiple sclerosis, neuromyelitis optica and transverse myelitis

BACKGROUND

Cardiovascular conditions are associated with poorer outcomes in multiple sclerosis (MS). Whether the burden of cardiovascular conditions differs between those with demyelinating disease and unaffected controls is not clear. The objective of this study is to investigate the burden and age of onset of cardiovascular conditions in a US population with MS, neuromyelitis optica spectrum disorder (NMOSD), or transverse myelitis (TM) to unaffected controls adjusting for likely confounders.

METHODS

Using a case-control study design, we compared the burden of self-reported diabetes mellitus type 2, heart disease, hyperlipidemia, and hypertension in cases with MS (N = 1,548), NMOSD (N = 306), and TM (N = 145) to controls (N = 677), adjusting for demographics, smoking history, obesity, family history of individual cardiovascular conditions, and presence of other cardiovascular conditions. The age of onset for individual cardiovascular conditions were also compared between cases and controls.

RESULTS

MS cases were 48% more likely to have ever had hypertension than controls (p = 0.01). The prevalence of other cardiovascular conditions did not differ across cases and controls. There were also no differences in the age of cardiovascular disease onset between cases and controls.

CONCLUSION

Cardiovascular conditions are as common in those with demyelinating diseases compared to unaffected individuals, with hypertension being more common among those with MS.

Effect of smoking on multiple sclerosis: a meta-analysis

Background

Despite our awareness of the significant effect of smoking on multiple sclerosis (MS), there was a serious lack of information about the effect of different types of smoking habit on MS as well as the dose-response relationship between smoking and MS, but this gap was addressed by this meta-analysis.

Methods

Major electronic databases, including PubMed, Web of Science and Scopus were searched until July 2015. Epidemiological studies addressing the association between smoking and MS were enrolled. The heterogeneity across studies was investigated by Q-test and I2 statistic. The probability of publication bias was explored using Begg's and Egger's tests. The results were expressed as odds ratio (OR) with 95% confidence intervals (CI) using a random effects model.

Results

We identified a total of 10 687 references and included 34 studies involving 623 852 participants. Compared with nonsmokers, the OR estimate of MS was 1.46 (1.33, 1.59) among ever smokers, 1.57 (1.34, 1.80) among current smokers, 1.36 (1.27, 1.46) among ex-smokers and 1.12 (0.87, 1.36) among passive smokers. In addition, analyzing the effect of cigarette pack-year on MS indicated that the OR estimate of MS was 1.34 (1.06, 1.61) for 1-5 cigarette pack-years, 1.56 (1.15, 1.97) for 6-10 cigarette pack-years, 1.74 (1.16, 2.33) for 11-15 cigarette pack-years and 1.46 (0.49, 2.43) for more than 15 cigarette pack-years.

Conclusions

Smoking habits are significantly associated with MS, although the association is not very strong. However, there is a dose-response relationship between the smoking habits and MS.

Symptom Management and Lifestyle Modifications in Multiple Sclerosis

PURPOSE OF REVIEW

This article reviews the rationale and approach to symptom management and lifestyle modifications in multiple sclerosis (MS).

RECENT FINDINGS

MS symptoms are important to treat because they affect quality of life and daily activity. Appreciation of cluster symptoms (where one symptom contributes to another), changes over time, and multimodality therapeutic approaches are guiding optimized symptom management. Equally important are lifestyle modifications that enhance central nervous system reserve and function. These modifications are the foundation for a health maintenance, wellness, and vascular risk factor control program.

SUMMARY

Symptom management and lifestyle modifications are important therapeutic targets to improve the lives of patients with MS.

Smoking affects the interferon beta treatment response in multiple sclerosis

Objective

To investigate whether smoking in patients with relapsing-remitting multiple sclerosis (RRMS) treated with interferon beta (IFN-β) is associated with the relapse rate and whether there is an interaction between smoking and human leukocyte antigen (HLA)–DRB1*15:01, HLA-A*02:01, and the N-acetyltransferase-1 (NAT1) variant rs7388368A.

Methods

DNA from 834 IFN-β–treated patients with RRMS from the Danish Multiple Sclerosis Biobank was extracted for genotyping. Information about relapses from 2 years before the start of treatment to either the end of treatment or the last follow-up visit was obtained from the Danish Multiple Sclerosis Treatment Register. Smoking information came from a comprehensive questionnaire.

Results

We found that the relapse rate in patients with RRMS during IFN-β treatment was higher in smokers compared to nonsmokers, with an incidence rate ratio (IRR) of 1.20 (95% confidence interval [CI] 1.021–1.416, p = 0.027) and with an IRR increase of 27% per pack of cigarettes per day (IRR 1.27, 95% CI 1.056–1.537, p = 0.012). We found no association or interaction with HLA and the NAT1 variant.

Conclusion

In this observational cohort study, we found that smoking is associated with increased relapse activity in patients with RRMS treated with IFN-β, but we found no association or interaction with HLA or the NAT1 variant.

Epigenetic research in multiple sclerosis: progress, challenges, and opportunities

Multiple sclerosis (MS) is a chronic inflammatory and demyelinating disease of the central nervous system. MS likely results from a complex interplay between predisposing causal gene variants (the strongest influence coming from HLA class II locus) and environmental risk factors such as smoking, infectious mononucleosis, and lack of sun exposure/vitamin D. However, little is known about the mechanisms underlying MS development and progression. Moreover, the clinical heterogeneity and variable response to treatment represent additional challenges to a comprehensive understanding and efficient treatment of disease. Epigenetic processes, such as DNA methylation and histone posttranslational modifications, integrate influences from the genes and the environment to regulate gene expression accordingly. Studying epigenetic modifications, which are stable and reversible, may provide an alternative approach to better understand and manage disease. We here aim to review findings from epigenetic studies in MS and further discuss the challenges and clinical opportunities arising from epigenetic research, many of which apply to other diseases with similar complex etiology. A growing body of evidence supports a role of epigenetic processes in the mechanisms underlying immune pathogenesis and nervous system dysfunction in MS. However, disparities between studies shed light on the need to consider possible confounders and methodological limitations for a better interpretation of the data. Nevertheless, translational use of epigenetics might offer new opportunities in epigenetic-based diagnostics and therapeutic tools for a personalized care of MS patients.

Environmental factors influencing multiple sclerosis in Latin America

It is generally accepted that autoimmune diseases like multiple sclerosis (MS) arise from complex interactions between genetic susceptibility and environmental factors. Genetic variants confer predisposition to develop MS, but cannot be therapeutically modified. On the other hand, several studies have shown that different lifestyle and environmental factors influence disease development, as well as activity levels and progression. Unlike genetic risk factors, these can be modified, with potential for prevention, particularly in high-risk populations. Most studies identifying particular lifestyle and environmental factors have been carried out in Caucasian patients with MS. Little or no data is available on the behavior of these factors in Latin American populations. Ethnic and geographic differences between Latin America and other world regions suggest potential regional variations in MS, at least with respect to some of these factors. Furthermore, particular environmental characteristics observed more frequently in Latin America could explain regional differences in MS prevalence. Site-specific studies exploring influences of local environmental factors are warranted.

[The influence of catecholamines on Th17-cells in multiple sclerosis]

AIM

Тo investigate the possible association between clinical characteristics of multiple sclerosis (MS), quantitative and qualitative characteristics of Th17, dopamine and norepinephrine concentrations in the serum in patients with multiple sclerosis (MS).

MATERIAL AND METHODS

A comprehensive neurological and immunological examination of 43 patients with relapsing-remitting-MS (RR-MS) was performed. All patients were subjected to a standard neurological examination with assessment of the EDSS score. Dopamine and norepinephrine concentrations in serum were measured by enzyme-linked immunosorbent assay (ELISA). Percentage of Th17-cells was determined by flow cytometry. The functional activity of Th17- and Th1-cells was assessed by the production of interleukin-17 (IL-17) and interferon-gamma (IFN-γ), respectively, by peripheral blood mononuclear cells (PBMC) stimulated with microbeads coated with anti-CD3 and anti-CD28-antibodies.

RESULTS

The percent Th17-cells and cytokine production was significantly higher in MS patients with the exacerbation of disease than in the control group or remission, while the dopamine level was lower. Norepinephrine levels in MS patients in the acute stage and remission were comparable, but nevertheless, reliably lower than in the control group.

CONCLUSION

The results suggest the inhibitory effect of catecholamines on Th17 cells.

Interactions between genetic, lifestyle and environmental risk factors for multiple sclerosis

Genetic predisposition to multiple sclerosis (MS) only explains a fraction of the disease risk; lifestyle and environmental factors are key contributors to the risk of MS. Importantly, these nongenetic factors can influence pathogenetic pathways, and some of them can be modified. Besides established MS-associated risk factors - high latitude, female sex, smoking, low vitamin D levels caused by insufficient sun exposure and/or dietary intake, and Epstein-Barr virus (EBV) infection - strong evidence now supports obesity during adolescence as a factor increasing MS risk. Organic solvents and shift work have also been reported to confer increased risk of the disease, whereas factors such as use of nicotine or alcohol, cytomegalovirus infection and a high coffee consumption are associated with a reduced risk. Certain factors - smoking, EBV infection and obesity - interact with HLA risk genes, pointing at a pathogenetic pathway involving adaptive immunity. All of the described risk factors for MS can influence adaptive and/or innate immunity, which is thought to be the main pathway modulated by MS risk alleles. Unlike genetic risk factors, many environmental and lifestyle factors can be modified, with potential for prevention, particularly for people at the greatest risk, such as relatives of individuals with MS. Here, we review recent data on environmental and lifestyle factors, with a focus on gene-environment interactions.

The risk of smoking on multiple sclerosis: a meta-analysis based on 20,626 cases from case-control and cohort studies

Background. Multiple sclerosis (MS) has become a disease that represents a tremendous burden on patients, families, and societies. The exact etiology of MS is still unclear, but it is believed that a combination of genetic and environmental factors contribute to this disease. Although some meta-analyses on the association between smoking and MS have been previously published, a number of new studies with larger population data have published since then. Consequently, these additional critical articles need to be taken into consideration.

Method. We reviewed articles by searching in PubMed and EMBASE. Both conservative and non-conservative models were used to investigate the association between smoking and the susceptibility to MS. We also explored the effect of smoking on the susceptibility to MS in strata of different genders and smoking habits. The association between passive smoking and MS was also explored.

Results.The results of this study suggest that smoking is a risk factor for MS (conservative model: odds ratio (OR) 1.55, 95% CI [1.48–1.62], p < 0.001; non-conservative model: 1.57, 95% CI [1.50–1.64], p < 0.001). Smoking appears to increase the risk of MS more in men than in women and in current smokers more than in past smokers. People who exposed to passive smoking have higher risk of MS than those unexposed.

Conclusion.This study demonstrated that exposure to smoking is an important risk factor for MS. People will benefit from smoking cessation, and policymakers should pay attention to the association between smoking and MS.

What role does tobacco smoking play in multiple sclerosis disability and mortality? A review of the evidence

There is increasing evidence of tobacco smoking as an associative factor in multiple sclerosis (MS). Numerous studies have been conducted investigating the effects of smoking before the onset of MS as well as its impact on disease course. This special report reviews the available evidence and summarizes the contribution of smoking to increased mortality in patients with MS. It also explores some putative mechanisms for the involvement of tobacco constituents in the pathology of MS and the effects of smoking on disease-modifying treatments.

Epstein-Barr virus and multiple sclerosis. From evidence to therapeutic strategies

Multiple sclerosis is caused by a complex interaction between genetic predisposition and environmental factors. Epstein-Barr virus (EBV) is an environmental risk factor that is strongly related to multiple sclerosis (MS), since EBV seropositivity is linked to a significant risk of developing MS. EBV may be involved in the pathogenesis of the disease and it is possibly a prerequisite for the development of MS. EBV infection persists in B-cells during the lifetime of the host and can modulate their function. In addition, MS patients might have a deficient capacity to eliminate latent EBV infection in the central nervous system and this would promote the accumulation of infected B cells. Several mechanisms of pathogenesis, including a direct and indirect function of infected B cells, have been postulated in inflammation and neurodegeneration. A relationship between EBV and human endogenous retroviruses in the pathogenesis of MS has also been reported. If EBV is important in the pathogenesis of MS, different therapeutic strategies seem possible for MS treatment.

Smoking is a major preventable risk factor for multiple sclerosis

BACKGROUND

Both smoking and exposure to passive smoking have repeatedly been associated with increased multiple sclerosis (MS) risk, but have never before been studied together. We assessed the public health impact of these factors.

METHODS

In a Swedish population-based case-control study (2455 cases, 5336 controls), we calculated odds ratios of developing MS associated with different categories of tobacco smoke exposure, together with 95% confidence intervals, by using logistic regression. The excess proportion of cases attributable to smoking and passive smoking was calculated as a percentage.

RESULTS

Both smoking and exposure to passive smoking contribute to MS risk in a dose-dependent manner. At the population level, 20.4% of all cases were attributable to smoke exposure. Among subjects carrying the genetic risk factor HLA-DRB1*15 but lacking HLA-A*02, 41% of the MS cases were attributable to smoking.

CONCLUSIONS

From a public health perspective, the impact of smoking and passive smoking on MS risk is considerable. Preventive measures in order to reduce tobacco smoke exposure are, therefore, essential. In particular, individuals with a history of MS in the family should be informed regarding the impact of smoking on the risk of MS, and the importance of preventing their children from being exposed to passive smoke.

Role of socioeconomic position in multiple sclerosis etiology

Multiple sclerosis (MS) is a debilitating autoimmune disease with a prominent inflammatory component. There have been strides identifying genetic and environmental MS risk factors, though much of the disease risk remains unknown. Recent large observational studies suggest adverse socioeconomic position increases the risk for MS, however the mediating biological processes are not understood. We hypothesize a prominent role for stress response, both the autonomic nervous system and the hypothalamic–pituitary–adrenal axis, which become maladaptive under frequent or chronic stimulation resulting in a proinflammatory phenotype. Thus, adverse SEP and chronic stress may predispose individuals for MS.

Modifiable environmental factors in multiple sclerosis

Potential environmental modifiable factors involved in multiple sclerosis (MS) include low adherence to treatment, smoking, obesity, low levels of liposoluble vitamins A and D, high consumption of salt, and a sedentary lifestyle. Chronic tobacco use, obesity, sedentarism and insufficient levels of these vitamins all contribute to maintenance of a proinflammatory state. It is unlikely that there will be noticeable improvement in the inflammatory condition of MS if stopping smoking, reducing weight, exercising, increasing vitamin levels are done in an isolated and erratic manner. Modification of each and every one of these environmental risk factors is likely to be an important approach in the management of MS. The present review presents the arguments for an association between these hazardous modifiable factors and the chronic inflammatory state observed in MS.

Environmental factors in multiple sclerosis

Although multiple sclerosis (MS) is recognized as a disorder involving the immune system, the interplay of environmental factors and individual genetic susceptibility seems to influence MS onset and clinical expression, as well as therapeutic responsiveness. Multiple human epidemiological and animal model studies have evaluated the effect of different environmental factors, such as viral infections, vitamin intake, sun exposure, or still dietary and life habits on MS prevalence. Previous Epstein-Barr virus infection, especially if this infection occurs in late childhood, and lack of vitamin D (VitD) currently appear to be the most robust environmental factors for the risk of MS, at least from an epidemiological standpoint. Ultraviolet radiation (UVR) activates VitD production but there are also some elements supporting the fact that insufficient UVR exposure during childhood may represent a VitD-independent risk factor of MS development, as well as negative effect on the clinical and radiological course of MS. Recently, there has been a growing interest in the gut-brain axis, a bidirectional neuro-hormonal communication system between the intestinal microbiota and the central nervous system (CNS). Indeed, components of the intestinal microbiota may be pro-inflammatory, promote the migration of immune cells into the CNS, and thus be a key parameter for the development of autoimmune disorders such as MS. Interestingly most environmental factors seem to play a role during childhood. Thus, if childhood is the most fragile period to develop MS later in life, preventive measures should be applied early in life. For example, adopting a diet enriched in VitD, playing outdoor and avoiding passive smoking would be extremely simple measures of primary prevention for public health strategies. However, these hypotheses need to be confirmed by prospective evaluations, which are obviously difficult to conduct. In addition, it remains to be determined whether and how VitD supplementation in adult life would be useful in alleviating the course of MS, once this disease has already started. A better knowledge of the influence of various environmental stimuli on MS risk and course would certainly allow the development of add-on therapies or measures in parallel to the immunotherapies currently used in MS.