Smoking and its interaction with genetics in MS etiology

Personality traits in patients with multiple sclerosis: their association with nicotine dependence and polypharmacy

Background

The modifiable risk factor exerting the most substantial influence on the development and disease course of multiple sclerosis (MS) is cigarette smoking. Furthermore, smoking is associated with a higher risk of suffering from one or more comorbidities and potentially contributes to polypharmacy. We aimed to use personality tests to explore health-promoting and harmful patient characteristics.

Objective

To investigate two important factors influencing the course of MS - the degree of smoking dependence and the status of polypharmacy - in association with personality traits.

Design

This is a bicentric, cross-sectional study.

Methods

We collected sociodemographic, clinical and medical data from patients with MS (n = 375) at two German neurological clinics. The participants were asked to complete the NEO Five-Factor Inventory (NEO-FFI) and the Temperament and Character Inventory-Revised (TCI-R). Relationships between variables were examined using correlation analyses, and differences between groups were examined using linear models. Current smokers with MS were also asked to complete the Fagerström questionnaire to categorize them into patients with mild, moderate and severe smoking dependence.

Results

In our sample, 67.5% were women, and the mean age was 48.1 years. The patients had a median Expanded Disability Status Scale of 3.0 at a median disease duration of 10 years. Patients with MS with severe smoking dependence had on average a significantly higher neuroticism score in the NEO-FFI compared to those with mild or moderate smoking dependence. Patients with MS and polypharmacy had significantly higher neuroticism scores than those without. In the extraversion scale of the NEO-FFI, patients with MS and polypharmacy had significantly lower scores on average. Significant differences were also found when analysing the TCI-R in patients with MS and heavy smoking dependence, with higher scores for harm avoidance (HA) and lower scores for reward dependence, self-directedness (S-D) and cooperativeness (CO) in various subscales. Polypharmacy in patients with MS was associated with higher scores for HA and self-transcendence. Furthermore, patients with polypharmacy showed lower values than patients without polypharmacy in individual subscales of the dimensions of persistence, S-D and CO.

Conclusion

Using the NEO-FFI, we were able to show that neuroticism is a detrimental trait and extraversion a protective trait in patients with MS in relation to nicotine dependence and polypharmacy. In addition, the evaluation of the TCI-R showed that high HA as well as low S-D and CO scores were more common in patients with MS and nicotine dependence or polypharmacy. With this knowledge, the risk of polypharmacy and smoking can be understood in the context of personality characteristics and targeted treatment and counselling can be provided.

Multiple sclerosis: economic burden, therapeutic advances, and future forecasts in the Middle East and North Africa region

INTRODUCTION

Multiple sclerosis (MS) is a persistent condition characterized by immune-mediated processes in the central nervous system, affecting around 2.8 million individuals globally. While historically less prevalent in the Middle East and North Africa (MENA) region, recent trends mirror the global rise in MS.

AREA COVERED

The impact of MS is substantial, particularly in the MENA region, with costs per patient surpassing nominal GDP per capita in certain countries. Disease-modifying therapies aim to alleviate MS effects, but challenges persist, especially in managing progressive MS as it shifts from inflammatory to neurodegenerative phases. Limited resources in the MENA region hinder care delivery, though awareness initiatives and multidisciplinary centers are emerging. Contrary to global projections of a decline in the MS market, the MENA region is poised for growth due to increased prevalence, healthcare expenditures, and infrastructure investments.

EXPERT OPINION

This review underscores the urgent necessity for effective treatments, robust disease management, and early diagnosis in tackling MS's repercussions in the MENA region. Bolstering resources tailored to MS patients and elevating the quality of care stand as pivotal strategies for enhancing health outcomes in this context. Taking decisive action holds the key to enhancing the overall well-being of individuals grappling with MS.

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, 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 the title/abstract and then by their full text. Extraction of data was performed for relevant studies. Odds ratios (ORs) 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 3,087 individuals, among which there were 1,135 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.

Head trauma results in manyfold increased risk of multiple sclerosis in genetically susceptible individuals

BACKGROUND

Large register-based studies have reported an association between head trauma and increased risk of multiple sclerosis (MS). We aimed to investigate possible interactions between head trauma and MS-associated HLA genes in relation to MS risk.

METHODS

We used a Swedish population-based case-control study (2807 incident cases, 5950 matched controls with HLA genotypes available for 2057 cases, 2887 controls). Subjects with and without a history of self-reported head trauma were compared regarding MS risk, by calculating ORs with 95% CIs using logistic regression models. Additive interaction between head trauma, HLA-DRB1*1501 and absence of HLA-A*0201, was assessed by calculating the attributable proportion (AP) due to interaction.

RESULTS

A history of head trauma was associated with a 30% increased risk of subsequently developing MS (OR 1.34, 95% CI 1.17 to 1.53), with a trend showing increased risk of MS with increasing number of head impacts (p=0.03). We observed synergistic effects between recent head trauma and HLA-DRB1*15:01 as well as absence of HLA*02:01 in relation to MS risk (each AP 0.40, 95% CI 0.1 to 0.7). Recent head trauma in individuals with both genetic risk factors rendered an 18-fold increased risk of MS, compared with those with neither the genetic risk factors nor a history of head trauma (OR 17.7, 95% CI 7.13 to 44.1).

CONCLUSIONS

Our findings align with previous observations of a dose-dependent association between head trauma and increased risk of MS and add a novel aspect of this association by revealing synergistic effects between recent head trauma and MS-associated HLA genes.

Health behaviors of people with multiple sclerosis and its associations with MS related outcomes: a German clinical cohort

Background

Health behaviors in persons with multiple sclerosis (pwMS) have been associated with MS-related disease outcomes.

Objective

The aim of the study was to gain knowledge about current patient health behaviors in a convenience sample representative for pwMS presenting to a large university-based outpatient clinic and to investigate associations between modifiable risk factors with physical impairment, quality of life (QoL) and cardiovascular comorbidities.

Methods

A questionnaire was administered at the MS Outpatient Clinic of the University Medical Center Hamburg Eppendorf asking for health behaviors regarding dietary habits assessed with the German adaptation of the validated Spanish short Diet Quality Screener (sDQS), level of physical activity assessed with the Godin Leisure Time Questionnaire (GLTEQ) and tobacco smoking. Participants were asked to report cardiovascular comorbidities using items from the Self-Report Comorbidity Questionnaire for Multiple Sclerosis. Additionally, cardiovascular risk factors like blood pressure, height and weight (to calculate BMI) and waist circumference were measured. MS specific clinical data, e.g., disease course, duration, disability and MS-specific QoL were collected from the clinical database. Descriptive analyses were performed and multivariate regression analyses for complete cases were carried out for each of the three outcome variables including all mentioned modifiable risk factors (dietary behavior, smoking, physical activity and BMI) as independent variables.

Results

In this sample of 399 pwMS the mean age was 42 years (SD 12.8) with a mean disease duration since diagnosis of 7.4 years (SD 8.4) and a mean EDSS of 2.8 (SD 1.9). 24% were current smokers, 44% were insufficiently physically active and 54% did not follow a healthy dietary pattern. 49% of this relatively young clinical population was overweight and 27% reported one or more cardiovascular comorbidities. Most modifiable risk factors showed no convincing associations with MS-related disease outcomes in the multiple regression analyses.

Conclusion

This clinical cohort of pwMS shows a high prevalence of critical health behaviors and comorbidities and emphasizes the need for monitoring, education and assistance for behavior change in this population.

The effects of different types of smoking on recovery from attack in hospitalized multiple sclerosis patients

BACKGROUND

Several studies demonstrated the association between tobacco smoking and higher risk and increased progression of multiple sclerosis (MS). Data about the effect of smoking during the recovery from MS attacks is limited. Furthermore, different types of tobacco exposures such as water pipe and passive smoking are not well assessed separately. So this study evaluated the effect of different types of smokes, cigarette and water pipe as well as passive smoking on the function recovery of relapsing-remitting MS (RRMS) attacks METHODS: This cohort study evaluated the adult patients with RRMS and Expanded Disability Status Scale (EDSS) < 5 in the attack phase. Patients were divided into two groups: smokers and non-smokers. The smokers included those who use cigarette, water pipe as well as passive smokers as subgroups for more analyses later. EDSS was monitored after relapse and two months after relapse. Change of EDSS considered as the criteria for functional recovery. The correlation between the amount of consumption and disability level was assessed among smokers by Pearson's correlation test. While, the difference of EDSS between smoker and non-smoker were assessed by Independent samples T-test.

RESULTS

142 patients were evaluated. 79 (55.6%) were smokers (43% male) while 63 (44.4%) were non-smokers (36.5% male). There was a statistically significant difference in change of EDSS between smoker and non-smoker groups, which change of EDSS was higher in non-smoker (-2.62 ± 0.90 non-smoker vs. -1.75 ± 0.76 smoker, P < 0.001). Also, only there was a significantly lesser decline in EDSS after two months in the cigarette smokers in subgroups analyses (P < 0.001). A correlation analysis revealed a significant positive correlation between the number per day of cigarette smoking and EDSS after relapse (r = 0.3, P = 0.03) and a significant positive correlation between minutes per month of smoking of water pipe and EDSS two months after relapse (r = ‎0.6‎‎, P > 0.001).

CONCLUSION

Tobacco smoking especially cigarette smoking is associated with a negative effect on recovery from the attack in patients with RRMS.

Association between exposure to combustion-related air pollution and multiple sclerosis risk

BACKGROUND

Smoking and occupational pulmonary irritants contribute to multiple sclerosis (MS) development. We aimed to study the association between ambient air pollution and MS risk and potential interaction with the human leukocyte antigen (HLA)-DRB1*15:01 allele.

METHODS

Exposure to combustion-related air pollution was estimated as outdoor levels of nitrogen oxides (NOx) at the participants' residence locations, by spatially resolved dispersion modelling for the years 1990-18. Using two population-based case-control studies (6635 cases, 8880 controls), NOx levels were associated with MS risk by calculating odds ratios (OR) with 95% confidence intervals (CI) using logistic regression models. Interaction between high NOx levels and the HLA-DRB1*15:01 allele regarding MS risk was calculated by the attributable proportion due to interaction (AP). In addition, a register study was performed comprising all MS cases in Sweden who had received their diagnosis between 1993 and 2018 (n = 22 173), with 10 controls per case randomly selected from the National Population register.

RESULTS

Residential air pollution was associated with MS risk. NOx levels (3-year average) exceeding the 90th percentile (24.6 µg/m3) were associated with an OR of 1.37 (95% CI 1.10-1.76) compared with levels below the 25th percentile (5.9 µg/m3), with a trend of increasing risk of MS with increasing levels of NOx (P <0.0001). A synergistic effect was observed between high NOx levels (exceeding the lower quartile among controls) and the HLA-DRB1*15:01 allele regarding MS risk (AP 0.26, 95% CI 0.13-0.29).

CONCLUSIONS

Our findings indicate that moderate levels of combustion-related ambient air pollution may play a role in MS development.

Smoking habits, awareness and support needs for cessation among people with multiple sclerosis in Australia: findings from an online survey

OBJECTIVES

To assess smoking habits, nicotine use, exposure to passive smoking, awareness of associated harms, and experiences with and preferences for smoking cessation support among people with multiple sclerosis (MS).

DESIGN

Online survey, convenience sampling.

SETTING

Community setting, Australia.

PARTICIPANTS

Adults living in Australia with probable or diagnosed MS were recruited via social media and newsletters to participate in 2020.

RESULTS

Of the 284 participants in our convenience sample, 25.7% were current smokers (n=73) and 38.0% were former smokers (n=108). Awareness of the harms of smoking on MS onset (n=68, 24.3%) and progression (n=116, 41.6%) was low. Almost a quarter (n=67, 23.8%) of participants were regularly exposed to passive smoke, and awareness of associated harm was also low (n=47, 16.8%). Among current smokers, 76.1% (n=54) had tried quitting and 73.2% considered quitting within 6 months (n=52). Many participants reported perceived short-term benefits of smoking, and long-term benefits of quitting, on MS symptoms and general well-being (short-term n=28, 40.0%; long-term n=28, 82.4%). While most participants reported that their neurologist (n=126, 75.4%) or other healthcare providers (n=125, 74.9%) had assessed smoking status, very few neurologists (n=3, 1.8%) or other healthcare providers (n=14, 8.4%) had provided help with quitting. Most current smokers preferred speaking about smoking to a neurologist (n=36, 52.2%) or general practitioner (n=41, 59.4%). Almost 60% of the current smokers wanted additional cessation information specific to MS (n=41, 59.4%), and 45.5% said this information would motivate them to quit smoking (n=30).

CONCLUSIONS

Our convenience sample, which may not be representative, indicated an urgent need for regular evidence-based smoking cessation supports for people with MS. Most participants felt they would benefit from smoking cessation advice. MS clinicians, in collaboration with patient organisations, smoking cessation services and general practitioners, should make smoking cessation promotion with people with MS a priority.

Effects of cigarette smoke exposure on a mouse model of multiple sclerosis

Multiple sclerosis (MS) is an inflammatory autoimmune disease associated with genetic and environmental factors. Cigarette smoking is harmful to health and may be one of the risk factors for MS. However, there have been no systematic investigations under controlled experimental conditions linking cigarette smoke (CS) and MS. The present study is the first inhalation study to correlate the pre-clinical and pathological manifestations affected by different doses of CS exposure in a mouse experimental autoimmune encephalomyelitis (EAE) model. Female C57BL/6 mice were whole-body exposed to either fresh air (sham) or three concentrations of CS from a reference cigarette (3R4F) for 2 weeks before and 4 weeks after EAE induction. The effects of exposure on body weight, clinical symptoms, spinal cord pathology, and serum biochemicals were then assessed. Exposure to low and medium concentrations of CS exacerbated the severity of symptoms and spinal cord pathology, while the high concentration had no effect relative to sham exposure in mice with EAE. Interestingly, the clinical chemistry parameters for metabolic profile as well as liver and renal function (e.g. triglycerides and creatinine levels, alkaline phosphatase activity) were lower in these mice than in naïve controls. Although the mouse EAE model does not fully recapitulate the pathology or symptoms of MS in humans, these findings largely corroborate previous epidemiological findings that exposure to CS can worsen the symptoms and pathology of MS. Furthermore, the study newly highlights the possible correlation of clinical chemistry findings such as metabolism and liver and renal function between MS patients and EAE mice.

Factors affecting the risk of relapsing-onset and progressive-onset multiple sclerosis

OBJECTIVE

It has been debated whether the different clinical disease courses in multiple sclerosis (MS) are the consequence of different pathogenic mechanisms, with distinct risk factors, or if all MS clinical phenotypes are variations of similar underlying disease mechanisms. We aimed to study environmental risk factors and their interactions with human leucocyte antigen DRB1*15:01 with regards to relapsing-onset and progressive-onset MS.

METHODS

We used two Swedish population-based case-control studies, including 7520 relapsing-onset cases, 540 progressive-onset cases and 11 386 controls matched by age, sex and residential area. Logistic regression was used to estimate ORs with 95% CIs for associations between the different MS phenotypes and a number of environmental and lifestyle factors. Interaction between the DRB1*15:01 allele and environmental risk factors was evaluated on the additive scale.

RESULTS

All environmental and lifestyle factors associated with risk of developing MS apply to both relapsing-onset and progressive-onset disease. Smoking, obesity and Epstein-Barr virus nuclear antigen-1 (EBNA-1) antibody levels were associated with increased risk of both MS phenotypes, whereas snuff use, alcohol consumption and sun exposure were associated with reduced risk. Additive interactions between DRB1*15:01 and smoking, obesity, EBNA-1 antibody levels and sun exposure, respectively, occurred to increase MS risk regardless of the clinical phenotype.

INTERPRETATION

Our finding that the same environmental and lifestyle factors affect both relapsing-onset and progressive-onset MS supports the notion that the different clinical phenotypes share common underlying disease mechanisms.

Improving smoking cessation support for people with multiple sclerosis: A qualitative analysis of clinicians' views and current practice

Introduction Smoking is a key modifiable risk factor in multiple sclerosis (MS). MS healthcare providers have a central role informing people of the deleterious effects of smoking on MS progression and promote smoking cessation, yet there is limited information about smoking cessation and support provided by these providers. This study aimed to gain an understanding of MS healthcare providers current practices, barriers and facilitators related to providing smoking cessation support for people with MS. Methods A total of 13 MS nurses and 6 neurologists working in public and private MS clinics across Australia were recruited through professional networks and MS organisations. Telephone interviews were conducted, transcribed and evaluated using framework analysis. Results MS nurses and neurologists reported that they routinely assess smoking status of people with MS at initial appointments and less regularly also at follow-up appointments. Clinicians considered it important to provide information about smoking impact on MS health outcomes and advise to cease smoking, but the content and delivery varies. Beyond this, some clinicians offer referral for smoking cessation support, while others stated this was not their responsibility, especially in light of competing priorities. Many were unsure about referral pathways and options, requiring more information, training and resources. Conclusion Results of this research indicate that there is potential to improve support for MS clinicians to promote smoking cessation among people with MS. Smoking cessation support may include tailored patient resources, clinician training and stronger collaboration with smoking cessation service providers.

Barriers and motivators for tobacco smoking cessation in people with multiple sclerosis

INTRODUCTION

Smoking is a key modifiable risk factor for health outcomes of people with multiple sclerosis (MS). Little evidence exists on whether the information and support needs of people with MS who smoke are met. This study aimed to explore knowledge, attitudes and beliefs about smoking and quitting, and quitting support needs in Australian people with MS.

METHODS

Current and recent smokers were recruited for phone interviews through social media and newsletters. Interview data were analysed in NVivo using framework analysis.

RESULTS

We interviewed 25 people with MS (20 current and five recent smokers). Many participants had little knowledge about the risks of smoking on MS progression. Some reported perceived benefits from smoking on MS symptoms, while others perceived smoking worsening their symptoms. Similarly, quitting was believed to have health benefits, but concerns about withdrawal symptoms and the impact on MS symptoms and relapses were common. Participants reported ambivalence discussing smoking with clinicians; some wanting more information and support, while also feeling shame or guilt. Many participants were asked about their smoking status by MS clinicians, however, the provision of evidence-based information, and referrals to quitting support services was very infrequent. General practitioners were often found helpful and supportive, but participants gave more weight to quit advice from MS clinicians.

CONCLUSION

Our results are the first to indicate that smoking cessation needs of Australian people with MS are not met. These findings should be confirmed in a larger sample, but there is potential to investigate whether implementing routine provision of brief advice in MS care, as a coordinated effort between MS researchers, practitioners, consumer advocates and behavioural intervention services, may meet these needs. Further, developing targeted resources and training quit counsellors to provide appropriate information and support specific to people with MS may improve smoking cessation success in people with MS.

MAIT Cells and Microbiota in Multiple Sclerosis and Other Autoimmune Diseases

The functions of mucosal-associated invariant T (MAIT) cells in homeostatic conditions include the interaction with the microbiota and its products, the protection of body barriers, and the mounting of a tissue-repair response to injuries or infections. Dysfunction of MAIT cells and dysbiosis occur in common chronic diseases of inflammatory, metabolic, and tumor nature. This review is aimed at analyzing the changes of MAIT cells, as well as of the microbiota, in multiple sclerosis and other autoimmune disorders. Common features of dysbiosis in these conditions are the reduced richness of microbial species and the unbalance between pro-inflammatory and immune regulatory components of the gut microbiota. The literature concerning MAIT cells in these disorders is rather complex, and sometimes not consistent. In multiple sclerosis and other autoimmune conditions, several studies have been done, or are in progress, to find correlations between intestinal permeability, dysbiosis, MAIT cell responses, and clinical biomarkers in treated and treatment-naïve patients. The final aims are to explain what activates MAIT cells in diseases not primarily infective, which interactions with the microbiota are potentially pathogenic, and their dynamics related to disease course and disease-modifying treatments.

Overweight/obesity in young adulthood interacts with aspects of EBV infection in MS etiology

Objective

Because obesity affects the cellular immune response to infections, we aimed to investigate whether high body mass index (BMI) in young adulthood and high Epstein-Barr nuclear antigen 1 (EBNA-1) antibody levels interact with regard to MS risk. We also aimed at exploring potential 3-way interactions between BMI at age 20 years, aspects of Epstein-Barr virus (EBV) infection (high EBNA-1 antibody levels and infectious mononucleosis [IM] history, respectively) and the human leukocyte antigen (HLA)-DRB1*15:01 allele.

Methods

Using Swedish population-based case-control studies (5,460 cases and 7,275 controls), we assessed MS risk in relation to interactions between overweight/obesity at age 20 years, IM history, EBNA-1 levels, and HLA-DRB1*15:01 status by calculating ORs with 95% CIs using logistic regression. Potential interactions were evaluated on the additive scale.

Results

Overweight/obesity, compared with normal weight, interacted significantly with high (>50th percentile) EBNA-1 antibody levels (attributable proportion due to interaction 0.2, 95% CI 0.1–0.4). The strength of the interaction increased with higher category of EBNA-1 antibody levels. Furthermore, 3-way interactions were present between HLA-DRB1*15:01, overweight/obesity at age 20 years, and each aspect of EBV infection.

Conclusions

With regard to MS risk, overweight/obesity in young adulthood acts synergistically with both aspects of EBV infection, predominantly among those with a genetic susceptibility to the disease. The obese state both induces a chronic immune-mediated inflammation and affects the cellular immune response to infections, which may contribute to explain our findings.

Smoking and Epstein-Barr virus infection in multiple sclerosis development

It is unclear whether smoking interacts with different aspects of Epstein-Barr virus (EBV) infection with regard to multiple sclerosis (MS) risk. We aimed to investigate whether smoking acts synergistically with elevated EBNA-1 antibody levels or infectious mononucleosis (IM) history regarding MS risk. Two Swedish population-based case-control studies were used (6,340 cases and 6,219 matched controls). Subjects with different smoking, EBNA-1 and IM status were compared regarding MS risk, by calculating odds ratios (OR) with 95% confidence intervals (CI) employing logistic regression. Potential interaction on the additive scale was evaluated by calculating the attributable proportion due to interaction (AP). Current and past smokers had higher EBNA-1 antibody levels than never smokers (p < 0.0001). There was an additive interaction between current smoking and high EBNA-1 antibody levels (AP 0.3, 95% CI 0.2-0.4), but not between past smoking and high EBNA-1 antibody levels (AP 0.01, 95% CI - 0.1 to 0.1), with regard to MS risk. An interaction also occurred between current smoking and IM history (AP 0.2, 95% CI 0.004-0.4), but not between past smoking and IM history (AP - 0.06, 95% CI - 0.4 to 0.3). Current smoking increases EBNA-1 antibody levels and acts synergistically with both aspects of EBV infection to increase MS risk, indicating that there is at least one pathway to disease in which both risk factors are involved.

Low sun exposure increases multiple sclerosis risk both directly and indirectly

Objective

We aimed to study (1) to what extent the influence of low sun exposure on multiple sclerosis (MS) risk is mediated by low vitamin D levels; (2) whether low sun exposure or vitamin D deficiency act synergistically with HLA-DRB1*15:01 and absence of HLA-A*02:01.

Methods

We used two population-based case–control studies (7069 cases, 6632 matched controls). Subjects with different HLA alleles, sun exposure habits and vitamin D status were compared regarding MS risk, by calculating odds ratios (OR) with 95% confidence intervals (CI) employing logistic regression. Mediation analysis was used to identify the potential mediation effect of vitamin D on the relationship between low sun exposure and MS risk.

Results

Low sun exposure increased MS risk directly as well as indirectly, by affecting vitamin D status. The direct effect, expressed as OR, was 1.26 (95% CI 1.04–1.45) and the indirect effect, mediated by vitamin D deficiency, was 1.10 (95% CI 1.02–1.23). Of the total effect, nearly 30% was mediated by vitamin D deficiency. There was a significant interaction between low sun exposure and vitamin D deficiency (attributable proportion due to interaction 0.3, 95% CI 0.04–0.5) accounting for about 12% of the total effect. Further, both factors interacted with HLA-DRB1*15:01 to increase MS risk.

Interpretation

Our findings indicate that low sun exposure acts both directly on MS risk as well as indirectly, by leading to low vitamin D levels. The protective effect of sun exposure thus seems to involve both vitamin D and non-vitamin D pathways, which is of relevance for prevention, in particular for those with a genetic susceptibility to MS.

Electronic supplementary material

The online version of this article (10.1007/s00415-019-09677-3) contains supplementary material, which is available to authorized users.

Modifiable risk factors for poor health outcomes in multiple sclerosis: The urgent need for research to maximise smoking cessation success

Tobacco smoking is a well-established risk factor for multiple sclerosis (MS) onset, progression and poor health outcomes in people with MS. Despite smoking being a modifiable risk factor, no research has been undertaken to understand how, or who is best placed, to assess or understand smoking behaviour in people with MS, or how healthcare professionals can best assist people with MS to quit. People with MS may have unique motivators to continue smoking, or unique barriers to smoking cessation, that are not addressed by existing cessation tools. Research is urgently needed in this area if the aim is to maximise health outcomes for all people with MS.