Gender and autoimmune comorbidity in multiple sclerosis

Comorbid autoimmune disorders in people with multiple sclerosis: A retrospective cohort study

Most autoimmune disorders, including multiple sclerosis (MS), are influenced by shared genetic and environmental factors. We conducted a cohort study of people with MS to calculate the frequency of comorbid autoimmune disorders and characterize this cohort. Autoimmune diseases were present in 30 (8.6%) of 349 patients. The most prevalent diagnoses were autoimmune thyroiditis, type 1 diabetes mellitus, psoriasis, and inflammatory bowel disease. We found no association with demographic or clinical factors. In our cohort, autoimmune disorders were not uncommon. Identifying such comorbidities in people with MS can be determinant for understanding disease mechanisms, treatment decisions and disease management.

Recent progress in epidemiology, clinical features, and therapy of multiple sclerosis in China

Multiple sclerosis (MS) is a demyelinating disease of the central nervous system characterized by inflammation, demyelination, and neurodegeneration. It mainly affects young adults, imposing a heavy burden on families and society. The epidemiology, clinical features, and management of MS are distinct among different countries. Although MS is a rare disease in China, there are 1.4 billion people in China, so the total number of MS patients is not small. Because of the lack of specific diagnostic biomarkers for MS, there is a high misdiagnosis rate in China, as in other regions. Due to different genetic backgrounds, the clinical manifestations of MS in Chinese are different from those in the West. Herein, this review aims to summarize the disease comprehensively, including clinical profile and the status of disease-modifying therapies in China based on published population-based observation and cohort studies, and also to compare with data from other countries and regions, thus providing help to develop diagnostic guideline and the novel therapeutic drugs. Meanwhile, we also discuss the problems and challenges we face, specifically for the diagnosis and treatment of MS in the middle- and low-income countries.

Therapeutic consequences in patients with both inflammatory rheumatic diseases and multiple sclerosis

Dealing with patients with both multiple sclerosis (MS) and inflammatory rheumatic disorders (IRDs) is not uncommon for a rheumatologist, as there is a statistical association between SpA and MS. As several CNS demyelinating events have been reported in patients treated with TNF inhibitor (TNFi), the pre-existing demyelinating disease was considered a contraindication for TNFi. However, this contraindication is mainly based on a randomized controlled trial in MS and not on large epidemiological studies. According to the last epidemiological studies, TNFi might not be an inducer of MS. Moreover, there are no clear recommendations on the use of the other DMARDs in patients suffering from an IRD and MS. In this review, we summarize the link between MS and IRDs and the impact of DMARDs on MS, especially TNFi. We also look at the impact of disease-modifying drugs for adults with MS and IRDs.

Autologous hematopoietic stem cell transplantation of patients with aggressive relapsing-remitting multiple sclerosis: Danish nation-wide experience

BACKGROUND

Autologous hematopoietic stem cell treatment (AHSCT) is considered an effective treatment option for patients with aggressive relapsing-remitting multiple sclerosis (RRMS). Still there are few randomized and controlled studies of AHSCT to shed light on the safety and efficacy of the treatment, and therefore experiences from single centers are important.

AIM

To describe the Danish experience with AHSCT regarding patient characteristics, safety, and efficacy.

METHOD

Nationwide retrospective single center study of patients with multiple sclerosis (MS) treated with AHSCT.

RESULTS

A total of 32 patients were treated with AHSCT from May 2011 to May 2021. Seven were treated with carmustine, etoposide, cytarabine arabinoside, and melphalan (BEAM) as well as antithymocyte globulin (ATG). Twenty-five patients were treated with cyclophosphamide (CY) and ATG. In the whole cohort, relapse-free survival (RFS) was 77% (95% CI: 64-94%), worsening-free survival (WFS) was 79% (95% CI: 66-96%), MRI event-free survival (MFS) was 93% (95% CI: 85-100%), and no evidence of disease (NEDA-3) was 69% (95% CI: 54-89%) at the end of year two post-AHSCT. We had no treatment related mortality and only few severe adverse events (AEs).

CONCLUSION

AHSCT of patients with aggressive RRMS was an effective and relatively safe treatment with few serious AEs and no mortality in Danish patients.

Prevalence of comorbidities in patients with multiple sclerosis using administrative data from 2007 to 2016 in Iran

BACKGROUND

Research interest in the impact of comorbidities in MS has been expanding. Based on studies, certain comorbidities are more prevalent in MS population such as depression, anxiety, hypertension and hypercholesterolemia, diabetes, and hypothyroidism.

OBJECTIVE

This study aims to describe the prevalence of comorbidities in MS population based on the health insurance claims data.

METHOD

This retrospective database analysis was conducted using patient-level medicinal and pharmacy claims data from a leading insurance group (Iranian health insurance) in 2007-2016. MS population was identified based on their Disease Modifying Therapies prescribed by a neurologist (qualified to diagnose MS). Comorbidities in MS and non-MS population were assessed by their prescriptions. Crude and age-standardized prevalence rate (ASPR) of coverage of comorbidities in different age and sex groups and their odds ratio versus non-MS population were assessed.

RESULTS

The most common comorbidities were depression (15.50%) and anxiety (10.1%). Hypercholesterolemia, diabetes, hypertension, and hypothyroidism were prevalent in 6%, 3.6%, 3.5%, and 2.7% respectively. Anxiety and depression were more prevalent in middle age group (45-65 years old). But other comorbidities were more prevalent in older age groups. All comorbidities were more prevalent in female except hypertension in patients ≥45 years old. The odds of all comorbidities were higher for male patients with MS rather than their parallel age group in non-MS patients. These also applied for female patients with MS 18-44 years old (except hypertension).

CONCLUSION

Using claims data, the prevalence of taking treatment for selected comorbidities in MS population and their association with sex and age, can guide patients, healthcare providers, and policy makers to help improve MS patients' wellbeing.

Multiple Sclerosis in Mongolia; the First Study Exploring Predictors of Disability and Depression in Mongolian MS Patients

Mongolia is located at 45° north latitude in the center of the Asian continent, and about 80% of the territory is at 1000 m above sea level. Epidemiologically, multiple sclerosis (MS) has not been investigated in Mongolia, although there have been a few MS case reports. We investigated the characteristics of MS in Mongolia for the first time, focusing on the association between MS-related parameters and depression levels. We initiated cross-sectional analyses, using data from 27 MS patients aged 20 to 60 years in Ulaanbaatar, Mongolia. The patients completed a questionnaire on their lifestyles and clinical information. We classified the MS patients on the basis of disability levels using the expanded disability status scale (EDSS) scores: 11.1% mild disability and 88.9% moderate to severe disability (median EDSS score, 5.5). We also classified the patients on the basis of depression levels using the 9-item patient health questionnaire (PHQ-9) scores: 44.4% mild depression, 40.7% moderate depression, and 14.8% severe depression (mean PHQ-9's score, 9.96 ± 5.05). We used multivariate logistical regression analyses to identify predictors of EDSS or PHQ-9 scores. Disability levels were associated with vision and balance problems. Depression levels were associated with corticosteroid treatment; no patients were treated with disease-modifying drugs (DMDs). The odds ratios for disease onset age and treatment duration were associated with EDSS scores. In conclusion, MS onset age and treatment duration were independent predicting factors influencing the level of disability. Appropriate DMD treatment would lower the disability and depression levels.

Sex bias in lymphocytes: Implications for autoimmune diseases

Autoimmune diseases are characterized by a significant sex dimorphism, with women showing increased susceptibility to disease. This is, at least in part, due to sex-dependent differences in the immune system that are influenced by the complex interplay between sex hormones and sex chromosomes, with contribution from sociological factors, diet and gut microbiota. Sex differences are evident in the number and function of lymphocyte populations. Women mount a stronger pro-inflammatory response than males, with increased lymphocyte proliferation, activation and pro-inflammatory cytokine production, whereas men display expanded regulatory cell subsets. Ageing alters the immune landscape of men and women in differing ways, resulting in changes in autoimmune disease susceptibility. Here we review the current literature on sex differences in lymphocyte function, the factors that influence this, and the implications for autoimmune disease. We propose that improved understanding of sex bias in lymphocyte function can provide sex-specific tailoring of treatment strategies for better management of autoimmune diseases.

Demyelinating Events Following Anti-tumor necrosis factor alpha therapy; rare but challenging to treat

BACKGROUND

Demyelinating events are listed as adverse events with tumor necrosis factor alpha inhibitors (TNFi), but epidemiological studies have provided partly conflicting risk estimates. Furthermore, studies examine long term outcomes of demyelinating events associated with TNF inhibitors are rare.

METHODS

Retrospective, observational study comprising validation and tracking of long-term outcomes in patients referred to a tertiary neurology referral center for suspected neurological complications associated with TNFi.

RESULTS

Out of 48 patients evaluated only 14 showed signs of demyelinating disease on magnetic resonance imaging, where six fulfilled criteria for a clinically isolated syndrome (CIS) and eight were diagnosed with multiple sclerosis (MS). However, 13 patients had received an ICD code for MS at some stage. Mean follow-up from referral was 13 and 10.5 years among subjects with MS and CIS, respectively. Continued disease activity was recorded among several of those fulfilling MS criteria and two ultimately underwent autologous hematopoietic stem cell transplantation. In contrast, subjects with CIS showed no progression after cessation of TNFi.

CONCLUSIONS

Our findings suggest that only a minority of those with suspected demyelinating disease following TNFi fulfill diagnostic criteria for MS and that MS diagnoses also among those not fulfilling MS criteria may contribute to inflated epidemiological risk estimates. Nevertheless, in those fulfilling MS criteria, initiation of disease modulating therapy, with escalation as needed, was important to suppress further disease activity.

Identification of common susceptibility genes and drug target genes in multiple sclerosis, systemic lupus erythematosus, and rheumatoid arthritis and its value to guide clinical treatment

BACKGROUND

Multiple sclerosis (MS) is an autoimmune-mediated demyelinating disease of the white matter in the central nervous system (CNS). In clinical practice, it was found that MS is associated with a variety of autoimmune diseases, such as systemic lupus erythematosus (SLE), rheumatoid arthritis (RA). The aim of this study was to identify common susceptibility genes and drug target genes in MS, SLE, and RA and to provide new insights into treatment.

METHODS

The common susceptibility genes of MS, SLE, and RA were obtained by searching the GWAS database and using microarray data to validate. The Genome Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were performed, and the common KEGG pathways were selected. All the genes enriched in the common pathways were obtained and intersected with the susceptibility genes of MS, SLE, and RA to obtain the pathway genes of them respectively, and found the common pathogenesis-related genes of the three diseases. By reviewing the literature and the DrugBank database, the drugs and drug target genes that have been approved for the treatment of the three diseases were obtained. Finally, the DGIdb database was searched to predict potential drugs or molecular compounds that interact with susceptibility genes common to MS, SLE, and RA.

RESULTS

In MS, SLE, and RA, there were 46 common susceptibility genes, of which 23 were significantly differentially expressed in the microarray expression profile. Then, 2117 genes were obtained in the 42 common pathways, among which 17 pathogenesis-related genes were common in MS, SLE, and RA. The Drugbank database was used to obtain 29 drug target genes for MS, 43 drug target genes for RA, and 20 drug target genes for SLE. DHODH is a common drug target gene for MS, SLE, and RA, and its corresponding drugs are Leflunomide and Teriflunomide. A total of 13 genes and 366 potential drugs or molecular compounds were predicted to have interaction relationships after searching the DGIdb database.

CONCLUSION

The common susceptibility genes and drug target genes among MS, SLE, and RA provide a theoretical basis for the co-morbidity phenomenon of the three diseases in clinical practice and may guide the clinical treatment.

The Danish Multiple Sclerosis Registry

OBJECTIVES

The Danish Multiple Sclerosis Registry is the oldest operative and nationwide MS registry. We present The Danish Multiple Sclerosis Registry with its history, data collection, scientific contribution, and national and international research collaboration.

MATERIALS AND METHODS

Detailed description of data collection, completeness, quality optimizing procedures, funding, and legal, ethical and data protection issues are provided.

RESULTS

The total number of registered cases with clinical isolated syndrome and multiple sclerosis since 1956 was by start of May 2020 30,023 of whom 16,515 cases were alive and residing in Denmark, giving a prevalence rate of about 284 per 100,000 population. The mean annual number of new cases receiving an MS diagnosis was 649 per year in the period 2010 to 2019. In total, 7,945 patients (48.1%) are receiving disease modifying therapy at the start of May 2020.

CONCLUSIONS

Multiple Sclerosis registers are becoming increasingly important, not only for epidemiological research but also by quantifying the burden of the disease for the patients and society and helping health care providers and regulators in their decisions. The Danish Multiple Sclerosis Registry has served as data source for a number of scientific publications including epidemiological studies on changes in incidence and mortality, cohort studies investigating risk factors for developing MS, comorbidities and socioeconomic outcomes in the MS population, and observational studies on effectiveness of disease modifying treatments outside the narrow realms of randomized clinical trials.

Comorbidity in Multiple Sclerosis

Comorbidities in patients with multiple sclerosis (MS) has become an area of increasing interest in the recent years. A comorbidity is defined as any additional disease that coexists in an individual with a given index disease and that is not an obvious complication of the index disease. The aim of this review is to describe the current evidence regarding the range of comorbidities in the population with MS reported in different countries and the current knowledge about the influence of comorbidities on the clinical features and therapeutic challenges in MS. Certain comorbidities are more prevalent in people with MS such as depression, anxiety, cerebro- and cardiovascular diseases, and certain autoimmune disorders such as diabetes, thyroid disease, and inflammatory bowel disease. A previous perception of a trend toward a lower overall risk of cancer in patients with MS appears to be challenged, but there is no evidence on any higher occurrence of malignancies in the population with MS. Comorbidities may modify the clinical presentation of MS, and have implications for treatment choice, adherence, and outcome. Several comorbid conditions are associated with increased disability progression, including diabetes, hypertension, and chronic obstructive pulmonary disease. Comorbidities are common in MS from the time of diagnosis and may account for some of the heterogeneity observed in MS, including diagnostic delay, clinical presentation, degree of disability progression, rate of health care utilization, working ability, employment status, and quality of life. Coexisting diseases and polypharmacy increase the complexity of patient management and poses major challenges, particularly with the increasing number of immunosuppressive disease-modifying therapies.

Pregnancy and Motherhood Concerns Surrounding Women with Multiple Sclerosis: A Qualitative Content Analysis

Background

There is a high prevalence of multiple sclerosis (MS) among Iranian women of reproductive age. However, very few studies have been conducted in Iran to assess the experiences with and concerns about pregnancy and motherhood of such patients. The present study was conducted to better understand the experiences and concerns of women with MS about pregnancy and motherhood.

Methods

The present qualitative study was conducted from August 2016 to January 2017 among Iranian women with MS visiting the Iran MS Society in Tehran, Iran. The purposive sampling method was used to recruit the participants and the sampling was continued until data saturation. Based on the inclusion criteria, a total of 25 women with MS were recruited in the study. The data were collected by in-depth semi-structured face-to-face interviews and analyzed using the MAXQDA 10 software.

Results

The analysis of the interview data resulted in four main categories, namely "Pregnancy concerns", "Fear of failing as a parent", "Feeling of threatened fertility", and "Lack of social support". The results showed that Iranian women with MS avoided pregnancy due to the negative effects of the disease on their physical abilities and on life in general. They were also concerned about possible infertility, the effect of MS medications on their menstrual cycle, and the limitations of infertility treatments due to the presence of MS. These concerns led them to postpone pregnancy and lose time or opt for voluntary childlessness and consequently miss out on the experience of motherhood.

Conclusion

MS poses a serious challenge to women who consider getting pregnant and wish to experience motherhood. Health care professionals should support such patients to overcome their concerns and indecisiveness by providing appropriate information and counseling.

Biological characteristics of transcription factor RelB in different immune cell types: implications for the treatment of multiple sclerosis

Transcription factor RelB is a member of the nuclear factror-kappa B (NF-κB) family, which plays a crucial role in mediating immune responses. Plenty of studies have demonstrated that RelB actively contributes to lymphoid organ development, dendritic cells maturation and function and T cells differentiation, as well as B cell development and survival. RelB deficiency may cause a variety of immunological disorders in both mice and humans. Multiple sclerosis (MS) is an inflammatory and demyelinating disease of the central nervous system which involves a board of immune cell populations. Thereby, RelB may exert an impact on MS by modulating the functions of dendritic cells and the differentiation of T cells and B cells. Despite intensive research, the role of RelB in MS and its animal model, experimental autoimmune encephalomyelitis, is still unclear. Herein, we give an overview of the biological characters of RelB, summarize the updated knowledge regarding the role of RelB in different cell types that contribute to MS pathogenesis and discuss the potential RelB-targeted therapeutic implications for MS.

Autoimmune Disease in Women: Endocrine Transition and Risk Across the Lifespan

Women have a higher incidence and prevalence of autoimmune diseases than men, and 85% or more patients of multiple autoimmune diseases are female. Women undergo sweeping endocrinological changes at least twice during their lifetime, puberty and menopause, with many women undergoing an additional transition: pregnancy, which may or may not be accompanied by breastfeeding. These endocrinological transitions exert significant effects on the immune system due to interactions between the hormonal milieu, innate, and adaptive immune systems as well as pro- and anti-inflammatory cytokines, and thereby modulate the susceptibility of women to autoimmune diseases. Conversely, pre-existing autoimmune diseases themselves impact endocrine transitions. Concentration-dependent effects of estrogen on the immune system; the role of progesterone, androgens, leptin, oxytocin, and prolactin; and the interplay between Th1 and Th2 immune responses together maintain a delicate balance between host defense, immunological tolerance and autoimmunity. In this review, multiple autoimmune diseases have been analyzed in the context of each of the three endocrinological transitions in women. We provide evidence from human epidemiological data and animal studies that endocrine transitions exert profound impact on the development of autoimmune diseases in women through complex mechanisms. Greater understanding of endocrine transitions and their role in autoimmune diseases could aid in prediction, prevention, and cures of these debilitating diseases in women.

Distinct regional brain atrophy pattern in multiple sclerosis and neuropsychiatric systemic lupus erythematosus patients

Differentiation of systemic lupus erythematosus (SLE) from multiple sclerosis (MS) can be challenging, especially when neuropsychiatric (NP) symptoms are accompanied by white matter lesions in the brain. Given the lack of discriminative power of currently applied tools for their differentiation, there is an unmet need for other measures that can aid in distinguishing between the two autoimmune disorders. In this study we aimed at exploring whether brain atrophy measures could serve as markers differentiating MS and SLE. Thirty-seven relapsing-remitting MS and 38 SLE patients with nervous system manifestations, matched according to age and disease duration, underwent 1.5 Tesla magnetic resonance imaging (MRI), including volumetric sequences, and clinical assessment. Voxelwise analysis was performed using ANTS-SyN elastic registration protocol, FSL Randomise and Gamma methods. Cortical and subcortical segmentation was performed with Freesurfer 5.3 pipeline using T1-weighted MPRAGE sequence data. Using MRI volumetric markers of general and subcortical gray matter atrophy and clinical variables, we built a stepwise multivariable logistic diagnostic model to identify MRI parameters that best differentiate MS and SLE patients. We found that the best volumetric predictors to distinguish them were: fourth ventricle volume (sensitivity 0.86, specificity 0.57, area under the curve, AUC 0.77), posterior corpus callosum (sensitivity 0.81, specificity 0.57, AUC 0.68), and third ventricle to thalamus ratio (sensitivity 0.42, specificity 0.84, AUC 0.65). The same classifiers were identified in a subgroup analysis that included patients with a short disease duration. In MS brain atrophy and lesion load correlated with clinical disability, while in SLE age was the main determinant of brain volume. This study proposes new imaging parameters for differential diagnosis of MS and SLE with central nervous system involvement. We show there is a different pattern of atrophy in MS and SLE, and the key structural volumes that are differentially affected include fourth ventricle and posterior section of corpus callosum, followed by third ventricle to thalamus ratio. Different correlation patterns between volumetric and clinical data may suggest that while in MS atrophy is driven mainly by disease activity, in SLE it is mostly associated with age. However, these results need further replication in a larger cohort.

Male factor infertility and risk of multiple sclerosis: A register-based cohort study

Background:

Gender, possibly due to the influence of gonadal hormones, is presumed to play a role in the pathogenesis of multiple sclerosis (MS), but no studies have evaluated whether male infertility is associated with MS.

Objective:

To study the association between male factor infertility and prevalent as well as incident MS.

Method:

Our cohort was established by linkage of the Danish National in vitro fertilization (IVF) registry to The Danish Multiple Sclerosis Registry and consisted of 51,063 men whose partners had undergone fertility treatment in all public and private fertility clinics in Denmark between 1994 and 2015.

Results:

With a median age of 34 years at baseline, 24,011 men were diagnosed with male factor infertility and 27,052 did not have male factor infertility and made up the reference group. Men diagnosed with male factor infertility had a higher risk of prevalent (odds ratio (OR) = 1.61, 95% confidence interval (95% CI) 1.04–2.51) and incident MS (hazard ratio (HR) = 1.28, 95% CI 0.76–2.17) when compared to the reference group.

Conclusion:

This nationwide cohort study has shown, for the first time, an association between male infertility and MS which may be due to underlying common etiologies such as hypogonadism, shared genetics, or a joint autoimmune component.

Similar birth-cohort patterns in Crohn's disease and multiple sclerosis

BACKGROUND

The etiology of Crohn's disease and multiple sclerosis is unknown. Genetic susceptibility and environmental factors are believed to play a role in both diseases.

OBJECTIVES

To compare the long-term time trends of the two diseases and thus gain insight about their etiology.

METHODS

We analyzed mortality data of Crohn's disease and multiple sclerosis from Canada, England, Italy, the Netherlands, Switzerland, and the United States during the past 60 years. Age-period-cohort (APC) analyses based on logit models served to disentangle the separate influences of age, period, and cohort effects on the overall time trends.

RESULTS

The long-term time trends of Crohn's disease and multiple sclerosis have been shaped by strikingly similar birth-cohort patterns. In both diseases alike, mortality increased in all generations born prior to 1910. It peaked among generations born between 1910 and 1930 and then declined in all subsequent generations. Similar birth-cohort patterns of Crohn's disease and multiple sclerosis were found in each country analyzed separately.

CONCLUSION

The birth-cohort patterns indicate that the development of Crohn's disease and multiple sclerosis is influenced by exposure to environmental risk factors during an early period of life. These environmental risk factors may be similar or even identical in Crohn's disease and multiple sclerosis.

Update on disease-modifying therapies for multiple sclerosis

Multiple sclerosis (MS) is an autoimmune, demyelinating disease of the central nervous system (CNS). It predominantly affects young women and is one of the most common causes of disability in young adults. MS is characterized by formation of white matter lesions in the CNS as a result of inflammation, demyelination, and axonal loss. Treatment has been a focus of neurological research for over 60 years. A number of disease-modifying therapies (DMTs) have become available making MS a treatable disease. These compounds target the inflammatory response in MS. They work by decreasing the chances of relapse, decreasing the chances of new lesion formation seen on MRI of the CNS and slowing the accumulation of disability. The first drugs for MS to be available were interferon-β and glatiramer acetate. These work by modulating the inflammatory response via different mechanisms that are briefly discussed. Newer agents have since become available and have significantly changed the dynamics of MS treatment. These include fingolimod, dimethyl fumarate and teriflunomide, which are oral agents. Other second-line and third-line Food and Drug Administration (FDA) approved medications include natalizumab and alemtuzumab. Natalizumab is considered one of the most potent treatments for relapse prevention. However, the high risk of progressive multifocal leukoencephalopathy (PML), which is caused by JC virus infection in the brain, tempers the more widespread use of this agent; nevertheless, JC virus antibody tests have helped to stratify the risk of PML. Alemtuzumab, which also has a considerable side effect profile, is likewise highly efficacious. Ocrelizumab, a monoclonal antibody to CD20 on B cells, is a highly effective agent for MS that is likely to be approved soon by the FDA. MS is a major contributor to healthcare costs and it is critical that healthcare providers be aware of the availability and benefits of DMTs. It is imperative that prompt and adequate treatment be established on diagnosis. Changes in therapy should be considered when there is evidence of disease activity as well as accumulation of disability or safety or tolerability concerns.

Physical and social environment and the risk of multiple sclerosis

BACKGROUND

The incidence of multiple sclerosis (MS) in Denmark has doubled in women since 1970, whereas it has been almost unchanged in men. The rapid epidemiological changes suggest that environmental factors may modify the risk of MS.

OBJECTIVES

To investigate whether occupational, physical, or social environmental influence the risk of MS differently in women than in men.

METHODS

The cohort consists of all 1403 patients (939 women, 464 men) identified through Danish Multiple Sclerosis Registry aged 1-55 of years at clinical onset between 2000 and 2004, and up to 25 control persons for each case, matched by sex, year of birth and residential municipality. The same cohort was previously used to investigate the influence of the reproductive factors on the risk of MS.

RESULTS

By linkage to Danish population registers we found a slight albeit statistically significant excess for 6 female MS patients who had been employed in agriculture: OR 3.52; 95% CI 1.38-9.00, p=0.008 (0.046 when corrected for multiple significance) and a trend for exposure to outdoor work in 12 : OR 1.94, 95% CI 1.06-3.55, p=0.03 (0.09 when corrected for multiple significance), but the numbers of cases were small, and the effects were not found in men. Educational level, housing conditions in youth, or the presence of children unrelated by blood in the household did not influence the risk of MS.

CONCLUSIONS

Our study did not reveal any additional factors beyond the previously published childbirths which could explain the extent of the MS incidence increase in women.