Time of birth, residential solar radiation and age at onset of multiple sclerosis

Adaptive and Innate Immunity Are Key Drivers of Age at Onset of Multiple Sclerosis

Background and Objectives

Multiple sclerosis (MS) age at onset (AAO) is a clinical predictor of long-term disease outcomes, independent of disease duration. Little is known about the genetic and biological mechanisms underlying age of first symptoms. We conducted a genome-wide association study (GWAS) to investigate associations between individual genetic variation and the MS AAO phenotype.

Methods

The study population was comprised participants with MS in 6 clinical trials: ADVANCE (N = 655; relapsing-remitting [RR] MS), ASCEND (N = 555; secondary-progressive [SP] MS), DECIDE (N = 1,017; RRMS), OPERA1 (N = 581; RRMS), OPERA2 (N = 577; RRMS), and ORATORIO (N = 529; primary-progressive [PP] MS). Altogether, 3,905 persons with MS of European ancestry were analyzed. GWAS were conducted for MS AAO in each trial using linear additive models controlling for sex and 10 principal components. Resultant summary statistics across the 6 trials were then meta-analyzed, for a total of 8.3 × 10-6 single nucleotide polymorphisms (SNPs) across all trials after quality control and filtering for heterogeneity. Gene-based tests of associations, pathway enrichment analyses, and Mendelian randomization analyses for select exposures were also performed.

Results

Four lead SNPs within 2 loci were identified (p < 5 × 10-8), including a) 3 SNPs in the major histocompatibility complex and their effects were independent of HLA-DRB1*15:01 and b) a LOC105375167 variant on chromosome 7. At the gene level, the top association was HLA-C (p = 1.2 × 10-7), which plays an important role in antiviral immunity. Functional annotation revealed the enrichment of pathways related to T-cell receptor signaling, autoimmunity, and the complement cascade. Mendelian randomization analyses suggested a link between both earlier age at puberty and shorter telomere length and earlier AAO, while there was no evidence for a role for either body mass index or vitamin D levels.

Discussion

Two genetic loci associated with MS AAO were identified, and functional annotation demonstrated an enrichment of genes involved in adaptive and complement immunity. There was also evidence supporting a link with age at puberty and telomere length. The findings suggest that AAO in MS is multifactorial, and the factors driving onset of symptoms overlap with those influencing MS risk.

Seasonality and clinical characteristics of MS in an equatorial country

BACKGROUND

Month and season of birth have been associated with risk of multiple sclerosis (MS), but there is relatively little evidence regarding their influence on the timing and severity of disease at onset.

OBJECTIVE

To assess whether month and season of birth influence the age and phenotype at onset of MS as well as its severity in a cohort of Colombian patients.

METHODS

This study is an analysis on MS cases only, drawn from a previously published case-control study. MS cases confirmed with current diagnostic criteria cared for at least once in our center were included. We assessed the influence of the month and season of birth in the age at MS onset, MS severity score, and age-related MS severity score using multiple and pairwise comparisons. Age at onset was also studied using Kaplan-Meier survival estimates compared with the log-rank test. The likelihood of progressive MS onset was evaluated with OR estimated from logistic regression models adjusted for age at onset and sex.

RESULTS

668 MS cases were included. No significant differences were found in the age at MS onset according to month of birth or season of birth. Neither month of birth nor season of birth conferred significant differences in MS severity score or age-related MS severity score. No significant association was found between month (ORs ranging from 0.62 to 3.11, none significant) or season of birth (OR 0.91; 95 %CI: 0.46-1.84) with primary progressive MS.

CONCLUSION

The month or season of birth do not appear to influence the age onset and phenotype of MS in our country.

No seasonality in the risk of multiple sclerosis in an equatorial country: A case-control ecological study

BACKGROUND

Multiple sclerosis risk has been shown to have seasonal variations that are more pronounced in higher latitudes. However, this phenomenon has not been adequately studied near the Equator.

OBJECTIVE

To explore the risk of multiple sclerosis associated with month, season of birth, and sunlight exposure variables in Colombia.

METHODS

In this case-control study, 668 multiple sclerosis cases were matched to 2672 controls by sex and age. Association of multiple sclerosis with each month/season of birth and sunlight exposure variables was estimated with multilevel mixed-effects logistic regression and ecological regression models, respectively. Seasonality in the births of multiple sclerosis was assessed with a non-parametric seasonality test.

RESULTS

We found a higher probability of multiple sclerosis in September (0.25; 95% confidence interval (CI) = 0.21-0.31) and lower in March (0.15; 95% CI = 0.10-0.18), which turned non-significant after a multiple comparisons test. Sunlight exposure variables had no significant effect on the risk of MS, and the tests of seasonality in the births of MS did not show significant results.

CONCLUSION

Our results show no seasonality in the risk of multiple sclerosis near the Equator, supporting the hypothesis that this phenomenon is latitude dependent.

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.

Long-term effects of latitude, ambient temperature, and ultraviolet radiation on the incidence of multiple sclerosis in two cohorts of US women

BACKGROUND

Differences in multiple sclerosis (MS) risk by latitude have been observed worldwide; however, the exposures driving these associations are unknown. Ultraviolet radiation (UV) has been explored as a risk factor, and ambient temperature has been correlated with disease progression. However, no study has examined the impact of all three exposures. We examined the association between these exposures and incidence of MS within two nationwide prospective cohorts of women, the Nurses' Health Study (NHS) and Nurses' Health Study II (NHSII).

METHODS

Both cohorts were followed with biennial questionnaires to ascertain new diagnoses and risk factors. Time-varying exposures to latitude, cumulative average July temperature (°C), and cumulative average July erythemal UV (mW/m2) were predicted at each participant's biennially updated residential addresses. Using Cox proportional hazards models adjusted for MS risk factors, we calculated hazard ratios (HR) and 95% confidence intervals (CIs) within each cohort and pooled via meta-analyses.

RESULTS

In multivariable models, there were suggestions that decreasing latitude (meta-analysis multivariable-adjusted HR = 0.72; 95% CI 0.55, 0.94 for women living <35.73° compared with those ≥42.15°, P-for-trend = 0.007) and increasing cumulative average July temperature (meta-analysis multivariable-adjusted HR = 0.81; 95% CI 0.72, 0.91 for each interquartile range increase [3.91°]) were associated with decreasing risk of MS. There was no evidence of heterogeneity between cohorts. We did not observe consistent associations with cumulative average UV.

CONCLUSION

Our results suggest that adult exposures to decreasing latitude and increasing temperature, but not UV, were associated with reduced MS risk in these two cohorts of women. Studies of MS incidence may want to consider temperature as a risk factor.

Modeling Approaches in Cost-Effectiveness Analysis of Disease-Modifying Therapies for Relapsing-Remitting Multiple Sclerosis: An Updated Systematic Review and Recommendations for Future Economic Evaluations

BACKGROUND

Numerous cost-effectiveness analyses (CEAs) of disease-modifying therapies (DMTs) for relapsing-remitting multiple sclerosis (RRMS) have been published in the last three decades. Literature reviews of the modeling methods and results from these CEAs have also been published. The last literature review that focused on modeling methods, without country or time horizon in the inclusion criteria, included studies published up to 2012. Since then, new DMTs have become available, and new models and data sources have been used to assess their cost effectiveness.

OBJECTIVE

The aim of this systematic review was to provide a detailed and comprehensive description of the relevant aspects of economic models used in CEAs of DMTs for RRMS, to understand how these models have progressed from recommendations provided in past reviews, what new approaches have been developed, what issues remain, and how they could be addressed.

METHODS

EMBASE, MEDLINE, Cochrane Central Register of Controlled Trials (CENTRAL), the National Health System (NHS) Economic Evaluations Database, the Health Technology Assessment (HTA) Database, and EconLit were searched for cost-effectiveness studies of DMTs for RRMS that used decision-analytic models, published in English between 1 January 2012 and 24 December 2017. The inclusion criteria were as follows: being a full economic evaluation, a decision-analytic model was used, the target population concerned adult patients with RRMS, and being available in full-text format. Studies were not excluded based on the methodological quality. The background information of the included studies, as well as specific information on the components of the economic models related to the areas of recommendation from previous reviews were extracted.

RESULTS

Twenty-three studies from ten countries were included. The model structure of these studies has converged over time, characterizing the course of disease progression in terms of changes in disability and the occurrence of relapses over time. Variations were found in model approach; data sources for the natural course of the disease and comparative efficacy between DMTs; number of lines of treatment modeled; long-term efficacy waning and treatment discontinuation assumptions; type of withdrawal; and criteria for selecting adverse events. Main areas for improvement include using long-term time horizons and societal perspective; reporting relevant health outcomes; conducting scenario analyses using different sources of natural history and utility values; and reporting how the model was validated.

CONCLUSION

The structure of economic models used in CEAs of DMTs for RRMS has converged over time. However, variation remains in terms of model approach, inputs, and assumptions. Though some recommendations from previous reviews have been incorporated in later models, areas for improvement remain.

Modeling month-season of birth as a risk factor in mouse models of chronic disease: from multiple sclerosis to autoimmune encephalomyelitis

Month-season of birth (M-SOB) is a risk factor in multiple chronic diseases, including multiple sclerosis (MS), where the lowest and greatest risk of developing MS coincide with the lowest and highest birth rates, respectively. To determine whether M-SOB effects in such chronic diseases as MS can be experimentally modeled, we examined the effect of M-SOB on susceptibility of C57BL/6J mice to experimental autoimmune encephalomyelitis (EAE). As in MS, mice that were born during the M-SOB with the lowest birth rate were less susceptible to EAE than mice born during the M-SOB with the highest birth rate. We also show that the M-SOB effect on EAE susceptibility is associated with differential production of multiple cytokines/chemokines by neuroantigen-specific T cells that are known to play a role in EAE pathogenesis. Taken together, these results support the existence of an M-SOB effect that may reflect seasonally dependent developmental differences in adaptive immune responses to self-antigens independent of external stimuli, including exposure to sunlight and vitamin D. Moreover, our documentation of an M-SOB effect on EAE susceptibility in mice allows for modeling and detailed analysis of mechanisms that underlie the M-SOB effect in not only MS but in numerous other diseases in which M-SOB impacts susceptibility.-Reynolds, J. D., Case, L. K., Krementsov, D. N., Raza, A., Bartiss, R., Teuscher, C. Modeling month-season of birth as a risk factor in mouse models of chronic disease: from multiple sclerosis to autoimmune encephalomyelitis.

Peginterferon beta-1a versus other self-injectable disease-modifying therapies in the treatment of relapsing-remitting multiple sclerosis in Scotland: a cost-effectiveness analysis

AIMS

Peginterferon beta-1a 125 mcg administered subcutaneously every 2 weeks, a new disease-modifying therapy (DMT) for relapsing-remitting multiple sclerosis (RRMS), was approved in January 2015 by the Scottish Medicines Consortium. This study assesses long-term clinical and economic outcomes of peginterferon beta-1a compared with other self-injectable DMTs (interferon beta-1a [22 mcg, 30 mcg, and 44 mcg], interferon beta-1b, and glatiramer acetate 20 mg) in the treatment of RRMS, from the National Health Service and Personal Social Services perspective in Scotland.

METHODS

A previously published, validated Markov cohort model was adapted for this analysis. The model estimates changes in patient disability, occurrence of relapses, and other adverse events, and translates them into quality-adjusted life years and costs. Natural history data came from the ADVANCE trial of peginterferon beta-1a, the London Ontario (Canada) database, and a large population-based MS survey in the UK. The comparative efficacy of each DMT vs placebo was obtained from a network meta-analysis. Costs (2015 British Pounds) were obtained from public databases and literature. Clinical and economic outcomes were projected over 30 years and discounted at 3.5% per year.

RESULTS

Over 30 years, peginterferon beta-1a was dominant compared with interferon beta-1a (22, 30, and 44 mcg), and interferon beta-1b, and cost-effective compared with glatiramer acetate 20 mg. Results were most sensitive to variations in each DMT's efficacy and acquisition costs. Deterministic and probabilistic sensitivity analyses confirmed the robustness of the results.

LIMITATIONS

The impact of improved adherence with peginterferon beta-1a on clinical and economic outcomes and the impact of subsequent DMTs after treatment discontinuation were not considered. Oral and infused DMTs were not included as comparators. Conclusion Long-term treatment with peginterferon beta-1a improves clinical outcomes, while its cost profile makes it either dominant or cost-effective compared with other self-injectable DMTs for the treatment of RRMS in Scotland.

Birth month and risk of atopic dermatitis: a nationwide population-based study

BACKGROUND

An individual's birth month has been associated with allergic diseases, but little is known about the association between birth month and atopic dermatitis (AD).

OBJECTIVE

The aim of this study was to investigate the risk of AD in children born in various months.

METHODS

Using Taiwan's National Health Insurance Research Database, we conducted a case-control study that included 31 237 AD cases and 124 948 age- and gender-matched controls without AD. Data regarding sociodemographic factors and coexisting medical conditions were collected and controlled in the multivariate logistic regression to determine the adjusted odds ratios and 95% confidence intervals for AD associated with the participant's birth month.

RESULTS

Compared with people born in May, people born in December had the highest risk of AD (OR 1.17, 95% CI 1.10-1.25), followed by people born in October (OR 1.15, 95% CI 1.08-1.22) and November (OR 1.13, 95% CI 1.06-1.20). Low income (OR 1.28), asthma (OR 1.88), allergic rhinitis (OR 1.70), psoriasis (OR 2.36), vitiligo (OR 1.99), urticaria (OR 2.14), and systemic lupus erythematosus (OR 1.91) were significant coexisting medical conditions associated with AD.

CONCLUSION

Being born in December, October, or November may be associated with an increased risk of AD. Future investigations are needed to evaluate the possible mechanism behind the association between birth month and AD.

Cost-effectiveness analysis of peginterferon beta-1a compared with interferon beta-1a and glatiramer acetate in the treatment of relapsing-remitting multiple sclerosis in the United States

Objective Peginterferon beta-1a 125 mcg, administered subcutaneously (SC) every 2 weeks, a new disease-modifying therapy (DMT) for relapsing-remitting multiple sclerosis (RRMS), was approved by the US Food and Drug Administration in 2014. This study assesses the cost-effectiveness of peginterferon beta-1a vs interferon beta-1a (44 mcg SC 3 times per week) and glatiramer acetate (20 mg SC once-daily) in the treatment of RRMS from the perspective of a US payer over 10 years. Methods A Markov cohort economic model was developed for this analysis. The model predicts disability progression, occurrence of relapses and other adverse events and translates them into quality-adjusted life years (QALYs) and costs. Natural history data were obtained from the placebo arm of the ADVANCE trial of peginterferon beta-1a, the London Ontario (Canada) database and a large population-based MS survey. Comparative efficacy of each DMT vs placebo was obtained from a network meta-analysis. Costs (in 2014 US dollars) were sourced from public databases and literature. Clinical and economic outcomes were discounted at 3% per year. Results Over 10 years, peginterferon beta-1a was dominant (i.e., more effective and less costly), with cost-savings of $22,070 and additional 0.06 QALYs when compared with interferon beta-1a 44 mcg and with cost-savings of $19,163 and 0.07 QALYs gained when compared with glatiramer acetate 20 mg. Results were most sensitive to variations in the treatment effect of each DMT, treatment acquisition costs of each DMT and the time horizon. Probabilistic sensitivity analyses indicated that peginterferon beta-1a remains dominant in >90% of 5,000 replications compared with either DMTs. Conclusion This analysis suggests that long-term treatment with peginterferon beta-1a improves clinical outcomes at reduced costs compared with interferon beta-1a 44 mcg and glatiramer acetate 20 mg and should be a valuable addition to managed care formularies for treating patients with RRMS.

Factors associated with onset, relapses or progression in multiple sclerosis: A systematic review

Multiple sclerosis (MS) is a chronic disease of the central nervous system with an unidentified etiology. We systematically reviewed the literature on the possible risk factors associated with MS disease onset, relapses and progression from 1960 to 2012 by accessing six databases and including relevant systematic reviews, meta-analyses, case-control or cohort studies. The focus was on identifying modifiable risk factors. Fifteen systematic reviews and 169 original articles were quality assessed and integrated into a descriptive review. Best evidence, which included one or more prospective studies, suggested that lower exposure to sunlight and/or lower serum vitamin D levels were associated with an increased risk of developing MS onset and subsequent relapses, but a similar quality of evidence was lacking for disease progression. Prospective studies indicated that cigarette smoking may increase the risk of MS as well as accelerate disease progression, but whether smoking altered the risk of a relapse was largely unknown. Infections were implicated in both risk of developing MS and relapses, but data for progression were lacking. Specifically, exposure to the Epstein-Barr virus, particularly if this manifested as infectious mononucleosis during adolescence, was associated with increased MS risk. Upper respiratory tract infections were most commonly associated with an increase in relapses. Relapse rates typically dropped during pregnancy, but there was no strong evidence to suggest that pregnancy itself altered the risk of MS or affected long-term progression. Emerging research with the greatest potential to impact public health was the suggestion that obesity during adolescence may increase the risk of MS; if confirmed, this would be of major significance.

Preliminary analysis of month of birth in Iranian/Isfahan patients with multiple sclerosis

Background:

Previous publications reported that an individual's month of birth (MOB) might have an important correlation to that consequent risk of multiple sclerosis (MS).

Aim:

The aim of this preliminary study was to investigate the distribution of different MOBs inpatients with MS in Isfahan, Iran.

Materials and Methods:

This investigation was conducted to the Isfahan Neurosciences Research Centre. 1283 patients with MS were studied. Clinical data were recorded in d-Base and analyzed using SPSS (version 18) for Windows.

Results:

Of the total population studied there were 979 females and 304 males. The mean age of all the patients was 34.6 years (range 10-87 years). Within the total population, the MOBs in the 62% of patients were in the season's spring and summer, and in 38% of patients they were in the season's autumn and winter. As the MOB might be recognized to have a bearing on an individual's risk of contracting MS, the highest and lowest correlations seem to be linked with April, September, May (↑), and November (↓), respectively.

Conclusions:

The seasonal relationship between MOBs and MS risk might be pointed toward a potential function for vitamin D throughout pregnancy or the early life of the newborn. Further studies are needed to confirm these correlations.

Photoimmunology and Multiple Sclerosis

The ultraviolet (UV) radiation contained in sunlight is a powerful immune suppressant. While exposure to UV is best known for its ability to cause skin cancer, it is also associated with protection against a range of autoimmune diseases, particularly multiple sclerosis (MS). Although the precise mechanism by which sunlight affords protection from MS remains to be determined, some have hypothesised that UV immunosuppression explains the "latitude-gradient effect" associated with MS. By stimulating the release of soluble factors in exposed skin, UV activates immune suppressive pathways that culminate in the induction of regulatory cells in distant tissues. Each and every one of the immune suppressive cells and molecules activated by UV exposure are potential targets for treating and preventing MS. A thorough understanding of the mechanisms involved is therefore required if we are to realise the therapeutic potential of photoimmunology.

Multiple sclerosis progression is not associated with birth timing in Italy

BACKGROUND

Month of birth has been associated in some studies with the susceptibility to develop Multiple Sclerosis (MS). However, only few studies have evaluated whether birth timing also affects disease progression.

OBJECTIVES

To assess whether season and month of birth are associated with disease progression in a large cohort of Italian patients.

METHODS

Quantile regression was used to analyze the impact of each month and season of birth with all the others combined on the median Multiple Sclerosis Severity Score of 1866 MS patients.

RESULTS

No significant temporal trend was found after adjustment for multiple comparisons.

CONCLUSIONS

Birth timing showed no association with MS progression in Italian patients.

Role of birthplace in chronic disease in adults and very old individuals: national cohorts in the UK and USA, 2009-2010

OBJECTIVES

To understand the role of birthplace in chronic disease in adults and very old individuals.

STUDY DESIGN

Two national and population-based studies (UK Longitudinal Household Survey and US National Health and Nutrition Examination Surveys) in 2009-2010 were included.

METHOD

Information on demographics, lifestyle factors and self-reported chronic diseases was obtained by household interview. Analyses included Chi-squared test, t-test and logistic regression modelling.

RESULTS

In the UK, there were more cases of heart failure and myocardial infarction in adults (aged 20-79 years) born in Scotland, and more cases of coronary heart disease in adults born in Northern Ireland. There were fewer cases of asthma, depression and hypothyroidism in adults born in Northern Ireland and not born in the UK, and fewer cases of cancer, chronic bronchitis and epilepsy in adults not born in the UK. In USA, there were fewer cases of asthma, cancer, chronic bronchitis, heart failure and heart attack, but more cases of liver disease in adults born in Mexico. Similarly, there were fewer cases of asthma, cancer and chronic bronchitis in adults born in other Spanish or non-Spanish countries, although there were more cases of liver disease in other Spanish-born adults and more cases of diabetes in other non-Spanish-born adults. In very old (≥80 years) individuals, there were more cases of chronic bronchitis in those born in Wales, more cases of myocardial infarction in those born in Northern Ireland, and more cases of diabetes and liver disease in those not born in the UK. Overall, diabetes was more common in foreign-born adults, and respiratory illness and cancer were more common in native-born adults.

CONCLUSIONS

It is suggested that future health policy and public health programmes should consider birthplace.

Month of birth as a risk factor for multiple sclerosis: an update

BACKGROUND

Several studies have indicated month of birth as a risk factor for multiple sclerosis (MS) susceptibility and disease progression.

METHODS

We performed a systematic search on PubMed and Medline up to May 2012 using the search string 'multiple sclerosis' and 'month of birth' or 'season of birth'. In addition, congress abstracts and the reference lists of the publications identified were examined for further citations of relevance.

RESULTS

A total of fifteen published studies and two congress abstracts were found on the effect of month or season of birth on MS risk (sixteen in the northern and one in the southern hemisphere). Most studies in the northern hemisphere detected an excess of MS births in spring and a decrease in autumn. In the southern hemisphere, a reverse pattern was detected, with an excess in November and a decrease in April. Only three studies did not report any month of birth effect, all in low-risk areas for MS. Five studies have analysed a possible effect on disease course by month of birth. Of these, two studies reported an association between month of birth and age at onset of relapsing-remitting MS, with a younger disease onset for those born in the winter months. No consistent findings have been detected on the association between month of birth and disease progression.

DISCUSSION

The month of birth effect is consistently found to influence the risk of MS, and the effect seems to be most prominent in high-risk areas of the disease, especially in areas with low sunlight exposure. There seems to be little or no month of birth effects in areas with high sunlight exposure. These findings indicate a possible role for vitamin D concentrations during pregnancy or early life of the newborn. A possible effect of vitamin D supplementation needs to be further investigated.

Fluctuations of MS births and UV-light exposure

BACKGROUND

Patients with multiple sclerosis (MS) are more frequently born in spring when compared to autumn. Fluctuation of UV-light has been hypothesized to drive this phenomenon.

AIM

To assess the correlation between fluctuation of sunlight and birth season in persons with MS.

METHODS

For this record-linkage study, we collected from the international MSBase and the Italian MS iMed-web databases the dates of birth of 11,415 patients with MS from 36 centres from 15 countries worldwide and compared these to dates of live-births from national registries. From all participating sites, we collected data on UV-light fluctuation and assessed its correlation with seasonal fluctuation in MS births.

RESULTS

Compared with the reference cohort, an increased proportion of persons with MS were born in spring and a decreased proportion in autumn (odds ratio (OR) to be born in spring versus autumn = 1.158, χ² = 36.347, P < 0.001). There was no significantly increased fluctuation of MS births with increased quartile of ambient UV-light fluctuation (Ptrend = 0.086).

CONCLUSION

Seasonal fluctuation of MS births as found in this worldwide cohort of patients with MS did not correlate with variation in seasonal fluctuation of UV-light. Most likely, it results from a complex interplay between fluctuation of sunlight, behavioural factors, other environmental factors and (epi)genetic factors.

Contribution of vitamin D insufficiency to the pathogenesis of multiple sclerosis

The contribution of vitamin D insufficiency to the pathogenesis of multiple sclerosis (MS) is reviewed. Among the multiple recently discovered actions of vitamin D, an immunomodulatory role has been documented in experimental autoimmune encephalomyelitis and in humans. This action in the peripheral immune system is currently the main known mechanism through which vitamin D might influence MS, but other types of actions could be involved within the central nervous system. Furthermore, vitamin D insufficiency is widespread in temperate countries and in patients with MS at the earliest stages of the disease, suggesting that the deleterious effects related to vitamin D insufficiency may be exerted in these patients. In fact, many genetic and environmental risk factors appear to interact and contribute to MS. In genetics, several human leukocyte antigen (HLA) alleles (more particularly HLA-DRB1*1501) could favour the disease whereas some others could be protective. Some of the genes involved in vitamin D metabolism (e.g. CYP27B1) also play a significant role. Furthermore, three environmental risk factors have been identified: past Epstein-Barr virus infection, vitamin D insufficiency and cigarette smoking. Interactions between genetic and environmental risk or protective factors may occur during the mother's pregnancy and could continue during childhood and adolescence and until the disease is triggered in adulthood, therefore possibly modulating the MS risk throughout the first decades of life. Furthermore, some clinical findings already strongly suggest that vitamin D status influences the relapse rate and radiological lesions in patients with MS, although the results of adequately powered randomized clinical trials using vitamin D supplementation have not yet been reported. While awaiting these incontrovertible results, which might be long in coming, patients with MS who are currently in vitamin D insufficiency should be supplemented, at least for their general health status, using moderate doses of the vitamin.

[Prevention of multiple sclerosis: a realistic goal?]

Multiple sclerosis (MS) is the most frequent source of chronic neurological disability in Western countries, and its incidence and prevalence are increasing. However, it is possible to determine its prodromal phase and the radiological, biological and immunological endophenotypes that are present before the clinical onset of the disease, despite remaining unseen with the naked eye. In this context, greater knowledge of the aetiological factors, both genetic and environmental, may lead the way towards primary prevention strategies for MS in the near future.

Role of vitamin D in multiple sclerosis: implications for disease management

SUMMARY This review discusses the evidence on the role of vitamin D in multiple sclerosis (MS) and whether vitamin D supplementation is effective for the management of MS. People with MS are at high risk of vitamin D deficiency, osteoporosis and fractures. Observational data suggest that higher vitamin D levels are associated with lower relapse risk and there is promising evidence on its effect on MRI measures, disability progression, mental health and fatigue. However, there is currently insufficient randomized controlled trial evidence to recommend vitamin D supplementation with the aim to improve those outcomes. There is sufficient evidence to justify assessing and correcting vitamin D and calcium levels to optimize bone health in people with MS at high absolute risk of fracture.

Vitamin D-gene interactions in multiple sclerosis

Vitamin D has been studied for over a century and its functions related to calcium homeostasis are well established. Over the last 30 years or so it has become increasingly clear that it has a wider role in physiology and, importantly, also in disease. Vitamin D deficiency has been linked to multiple sclerosis (MS); however the molecular mechanisms of this association were poorly understood. Recent technological advances have provided major insights as to how vitamin D may exert its role, particularly through the actions of the vitamin D receptor (VDR). In this review we aim to highlight the importance of the interaction between vitamin D and MS associated genes which provide a biological basis for the association between vitamin D and MS risk.

Sun exposure, vitamin D intake and progression to disability among veterans with progressive multiple sclerosis

BACKGROUND

Early life events have been suggested to influence multiple sclerosis (MS) susceptibility, and to potentially modulate its clinical course. We assessed vitamin D-related exposures from childhood to disease onset and their associations with MS progression.

METHODS

Among veterans in the Multiple Sclerosis Surveillance Registry, 219 reported having the progressive form and met the inclusion criteria. Participants reported their past sun exposure, vitamin D-related intake and age at disability milestones using the Patient-Determined Disease Steps (PDDS). The Cox proportional hazards model was used to examine the association between vitamin D-related exposures and time (years) to disability.

RESULTS

Low average sun exposure in the fall/winter before disease onset was associated with an increased risk of progressing to a PDDS score of 8 (hazard ratio, HR: 2.13, 95% confidence interval, CI: 1.20-3.78), whereas use of cod liver oil during childhood and adolescence was associated with a reduced risk (HR: 0.44, 95% CI: 0.20-0.96).

CONCLUSIONS

These results suggest that exposure to vitamin D before MS onset might slow disease-related neurodegeneration and thus delay progression to disability among patients with the progressive subtype.

Influence of photoperiod on hormones, behavior, and immune function

Photoperiodism is the ability of plants and animals to measure environmental day length to ascertain time of year. Central to the evolution of photoperiodism in animals is the adaptive distribution of energetically challenging activities across the year to optimize reproductive fitness while balancing the energetic tradeoffs necessary for seasonally-appropriate survival strategies. The ability to accurately predict future events requires endogenous mechanisms to permit physiological anticipation of annual conditions. Day length provides a virtually noise free environmental signal to monitor and accurately predict time of the year. In mammals, melatonin provides the hormonal signal transducing day length. Duration of pineal melatonin is inversely related to day length and its secretion drives enduring changes in many physiological systems, including the HPA, HPG, and brain-gut axes, the autonomic nervous system, and the immune system. Thus, melatonin is the fulcrum mediating redistribution of energetic investment among physiological processes to maximize fitness and survival.

Role of vitamin D in immune responses and autoimmune diseases, with emphasis on its role in multiple sclerosis

Vitamin D is a seco-steroid involved in calcium and phosphorus metabolism, and bone formation and mineralization, through binding to a specific nuclear receptor, vitamin D receptor (VDR). Besides its well-established functions on bone health, multiple lines of evidence have indicated the immunomodulatory roles of vitamin D. Vitamin D can affect both innate and adaptive immunity, and prevent autoimmune responses efficiently. Vitamin D regulates the immune responses by suppressing T cell proliferation and modulating macrophage functions. Epidemiological studies have shown that vitamin D deficiency is associated with multiple diseases such as rickets and cancer. Moreover, associations between vitamin D and autoimmune diseases have been confirmed in multiple sclerosis (MS), rheumatoid arthritis (RA), etc. The present review mainly summarized the recent findings on the immunomodulatory role of vitamin D in various disorders, with special focus on its role in MS, an autoimmune disease of the nervous system.

High prevalence of vitamin D deficiency in school-age children in Tehran, 2008: a red alert

OBJECTIVE

To assess the vitamin D status of 9-12-year-old primary-school children in Tehran during autumn and winter 2007-2008.

DESIGN

A descriptive cross-sectional study.

SETTING

Primary schools of Tehran city, Iran.

SUBJECTS

A total of 1111 children aged 9-12 years (573 boys and 538 girls) from sixty primary schools were enrolled in the study. Weight, height, BMI and serum levels of Ca, P, Mg, 25-hydroxyvitamin D (25(OH)D), intact parathyroid hormone (iPTH), osteocalcin and bone-specific alkaline phosphatase of all the participants were assessed. Dietary Ca intake was also evaluated using a quantitative FFQ for a subsample of the study population (n 503). Vitamin D sufficiency was defined on the basis of serum levels of 25(OH)D as either ≥37 nmol/l (criterion 1) or ≥50 nmol/l (criterion 2).

RESULTS

Daily intake of Ca did not differ significantly between boys and girls (929·6 (sd 436·7) mg and 909·5 (sd 465·5) mg, respectively). However, on the basis of the first criterion, approximately 86 % of the children had vitamin D deficiency, with 38·3 % being severely deficient (25(OH)D < 12·5 nmol/l). According to the second criterion, prevalence of vitamin D deficiency rose to 91·7 %. Prevalence of vitamin D deficiency was higher in girls than in boys by either criterion. Serum levels of 25(OH)D inversely correlated with iPTH (r = -0·154, P < 0·001) and BMI (r = -0·092, P = 0·002) but directly correlated with duration of sun exposure (r = 0·115, P < 0·001).

CONCLUSIONS

The high prevalence of vitamin D deficiency among schoolchildren (especially among girls) warrants immediate interventions for proper nutritional support.

Is hypovitaminosis D one of the environmental risk factors for multiple sclerosis?

The role of hypovitaminosis D as a possible risk factor for multiple sclerosis is reviewed. First, it is emphasized that hypovitaminosis D could be only one of the risk factors for multiple sclerosis and that numerous other environmental and genetic risk factors appear to interact and combine to trigger the disease. Secondly, the classical physiological notions about vitamin D have recently been challenged and the main new findings are summarized. This vitamin could have an important immunological role involving a number of organs and pathologies, including autoimmune diseases and multiple sclerosis. Furthermore, human requirements for this vitamin are much higher than previously thought, and in medium- or high-latitude countries, they might not be met in the majority of the general population due to a lack of sunshine and an increasingly urbanized lifestyle. Thereafter, the different types of studies that have helped to implicate hypovitaminosis D as a risk factor for multiple sclerosis are reviewed. In experimental autoimmune encephalomyelitis, vitamin D has been shown to play a significant immunological role. Diverse epidemiological studies suggest that a direct chain of causality exists in the general population between latitude, exposure to the sun, vitamin D status and the risk of multiple sclerosis. New epidemiological analyses from France support the existence of this chain of links. Recently reported immunological findings in patients with multiple sclerosis have consistently shown that vitamin D significantly influences regulatory T lymphocyte cells, whose role is well known in the pathogenesis of the disease. Lastly, in a number of studies on serum levels of vitamin D in multiple sclerosis, an insufficiency was observed in the great majority of patients, including at the earliest stages of the disease. The questionable specificity and significance of such results is detailed here. Based on a final global analysis of the cumulative significance of these different types of findings, it would appear likely that hypovitaminosis D is one of the risk factors for multiple sclerosis.