A timing-of-birth effect on multiple sclerosis clinical phenotype

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.

Seasonal patterns of relapse and disability in Danish MS patients: A population-based cohort study

BACKGROUND

The importance of environmental risk factors in the onset of multiple sclerosis (MS) has been studied extensively. Similarly, a growing number of studies address the importance of environmental factors, including seasonality, for ongoing activity of established disease. Specifically, past research demonstrates higher rates of relapse activity in summer months among individuals with MS. Our study adds to the existing literature on seasonality of disease relapse by analysing a large population-based and virtually complete cohort of patient with relapsing and remitting MS (RRMS) in an area of temperate climate.

METHODS

The Danish Multiple Sclerosis Registry includes follow-up for all patients receiving disease modifying treatment from 1996-2020, with near-complete registration of all relapses and their dates. We compared the observed and expected numbers of relapses for each calendar month and calculated month-specific annualized relapse rates (ARR) using Poisson regression. In addition, we analysed seasonal variation in disability as measured by the Expanded Disability Status Scale (EDSS).

RESULTS

From 1996 to 2020 we followed 13,575 MS patients treated with disease modifying therapy (4165 men and 9410 women) for a total of 82,187 person years and 134,593 control visits. The mean age at entry was 41.1 years with standard deviation 10.9 years. We recorded 16,083 relapses throughout the observation period, and for 15,728 of the relapses the date of onset was known. Relapses were unevenly distributed by calendar month (p < 0.00001). The most prominent deviation was a paucity of relapses in July in which the ARR was 0.166 compared with mean of 0.191 for the whole year. Otherwise, the ARR formed a plateau slightly above mean during the spring months. Mean EDSS was slightly higher in autumn (2.78) than in spring (2.74), but there was no difference between winter and summer; p < 0.0001.

CONCLUSION

In contrast with previous studies, we observed a nadir of relapses in July among Danish patients with RRMS. This finding may be related to increased exposure to sunlight in the summer, particularly during vacation when outdoor recreational activities are more frequent and potential exposure to infections is decreased. Confirmation of this in future studies is warranted.

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.

The epidemiology of multiple sclerosis: insights to a causal cascade

MS-pathogenesis involves both genetic-susceptibility and environmental determinants. Three (or more) sequential environmental-factors are implicated. The first acts near birth, the second acts during childhood/adolescence, and the third acts subsequently. Two candidate factors (vitamin D deficiency and Epstein-Barr viral infection) seem particularly well-suited to the first two environmental-events but other factors (e.g., obesity and smoking behavior) seem also to be involved in the causal scheme. MS-pathogenesis can be modeled by incorporating both the environmental and genetic-factors into a causal scheme, which can then help to explain some of the changes in MS-epidemiology (e.g., increasing disease-prevalence, changing sex-ratio, and regional-variations in monozygotic-twin-concordance-rates), which have been taking place recently. This model suggests that genetic-susceptibility is overwhelmingly the most important determinant of MS and that, at least, 92.5% of individuals (and likely much more) are, essentially, incapable of developing MS, regardless of their specific environmental-exposures. Nevertheless, the genetics is complex and the contribution of any specific gene to MS-susceptibility seems to be quite modest. Thus, even for the DRB1*1501 allele (the strongest known MS-susceptibility marker), most carriers are not in the genetically-susceptible group. Moreover, 45-50% of individuals with MS lack this allele entirely and some of the haplotypes that carry this allele don't also confer any disease-risk. Finally, because the prevalence of genetic-susceptibility seems to be so similar throughout North America and Europe, and despite the crucial importance of a person's genetic make-up to disease pathogenesis, it is the environmental-factors, which largely responsible for the observed regional variations in disease-characteristics. Thus, despite MS being more common in women, men are more likely to be genetically-susceptible. This apparent paradox seems to relate to the fact that women are much more responsive than men to the recent changes in environmental-exposure (whatever these have been). These gender-differences may help to explain changes in the sex-ratio and the increasing disease-prevalence, which have both been observed recently. The potential importance of these conclusions regarding the role of environment in MS-pathogenesis is that they open the door to the possibility of pursuing strategies for primary primary disease prevention in the future.

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.

Risk factors associated with the onset of relapsing-remitting and primary progressive multiple sclerosis: a systematic review

Multiple sclerosis (MS) is a chronic central nervous system disease with a highly heterogeneous course. The aetiology of MS is not well understood but is likely a combination of both genetic and environmental factors. Approximately 85% of patients present with relapsing-remitting MS (RRMS), while 10–15% present with primary progressive MS (PPMS). PPMS is associated with an older onset age, a different sex ratio, and a considerably more rapid disease progression relative to RRMS. We systematically reviewed the literature to identify modifiable risk factors that may be associated with these different clinical courses. We performed a search of six databases and integrated twenty observational studies into a descriptive review. Exposure to Epstein-Barr virus (EBV) appeared to increase the risk of RRMS, but its association with PPMS was less clear. Other infections, such as human herpesvirus-6 and chlamydia pneumoniae, were not consistently associated with a specific disease course nor was cigarette smoking. Despite the vast literature examining risk factors for the development of MS, relatively few studies reported findings by disease course. This review exposes a gap in our understanding of the risk factors associated with the onset of PPMS, our current knowledge being predominated by relapsing-onset MS.

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.

The epidemiology of multiple sclerosis: insights to disease pathogenesis

The purpose of studying the epidemiology of multiple sclerosis (MS) is twofold. First, it is important to understand clearly the natural history of the illness in order to assist patients in making decisions about their future with respect to issues such as family planning, the importance of securing lifelong healthcare, their ability to get and maintain employment, and making appropriate choices of therapy for their particular circumstances. This is not to suggest that, even with the best possible information, the ultimate prognosis for any individual can be predicted with absolute accuracy. It cannot. Nevertheless, accurate information can be very helpful both to reassure patients that many individuals with MS do remarkably well in the long term (perhaps, especially, with current and future therapies) and also to empower individuals with respect to their ability to make their own life choices. Second, and arguably the more important purpose for studying the epidemiology of MS, is to gain insights to the underlying causes of the disease. Indeed, if the principal mechanisms of disease pathogenesis were to be understood clearly, then it might be possible to entertain notions of either a cure for existing disease or the primary prevention of future disease. Much of our current understanding of disease pathogenesis, as discussed in other chapters of this volume, has been derived from basic science investigations of animal models of MS such as experimental autoimmune encephalomyelitis (EAE), and these models have provided considerable insight both to the complexity of the mammalian immune system and to the mechanisms underlying its dysfunction in inflammatory autoimmune conditions. Nevertheless, MS is a disease of humans without any known, naturally occurring, counterpart in any nonhuman species. For this reason, the clues to disease pathogenesis provided by a study of basic epidemiologic facts regarding MS (and by a systematic consideration of their implications) are essential to a comprehensive understanding of the human illness we call MS.

Genetics of primary progressive multiple sclerosis

Multiple sclerosis (MS) patients are classified as either having relapsing onset or progressive onset disease, also known as primary progressive MS (PPMS). Relative to relapsing onset patients, PPMS patients are older at disease onset, are equally likely to be men or women, and have more rapid accumulation of disability that does not respond well to treatments used in relapsing onset MS. Although estimates vary, 5-15% of all MS patients have a PPMS disease course. Genetic variance is a proposed determinant of MS disease course. If distinct genes associated with PPMS were identified study of these genes might lead to an understanding of the biology underlying disease progression and neural degeneration that are the hallmarks of PPMS. These genes and their biological pathways might also represent therapeutic targets. This chapter systematically reviews the PPMS genetic literature. Despite the intuitively appealing notion that differences between PPMS and relapsing onset MS are due to genetics, definite differences associated with these phenotypes at the major histocompatibility complex or elsewhere in the genome have not been found. Recent large-scale genome wide screens identified multiple genes associated with MS susceptibility outside the MHC. The genetic variants identified thus far make only weak individual contributions to MS susceptibility. If the genetic effects that contribute to the differences between PPMS and relapsing MS are similar in magnitude to those that distinguish MS from healthy controls then, given the relative scarcity of the PPMS phenotype, very large datasets will be needed to identify PPMS associated genes. International collaborative efforts could provide the means to identify such genes. Alternately, it is possible that factors other than genetics underlie the differences between these clinical phenotypes.

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.

Inflammatory demyelinating central nervous system diseases in childhood: clinical and paraclinical profiles in 133 patients

In a retrospective review of patients with acquired demyelinating disorders of the central nervous system, 133 patients (5.6%) whose diseases started in childhood, were selected from 2369 patients, who had medical records in the Neurology Department of Dokuz Eylul University. Out of 133, 98 had relapsing remitting multiple sclerosis, 21 had secondary progressive multiple sclerosis, 8 had clinically isolated syndrome, 3 had neuromyelitis optica, 2 had Marburg disease, and 1 had radiologically isolated syndrome. In 55 patients (41.3%), disease onset was before age 16. Polysymptomatic presentation (22.6%) was the most common initial feature. The EDSS scores ranged from 0 to 9 with a median of 2.0 (2.22 ± 1.88) for 126 patients. MRI records of 111 patients were obtained. 97 patients had clinically definite multiple sclerosis. 11 MS patients (11.3%) did not initially present the diagnostic MRI features. All of the remaining multiple sclerosis patients fulfilled Barkhof-Tintore criteria (100%) and 88.7% fulfilled KIDMUS criteria. Cranial MRI of NMO patients was normal. Our findings demonstrate some important clinical and paraclinical features that can help the literature on acquired demyelinating disorders of childhood by utilizing data from Western Turkey.

Month of birth as a latitude-dependent risk factor for multiple sclerosis in Norway

OBJECTIVE

We aimed to determine if the risk of Multiple Sclerosis (MS) is associated with month of birth in Norway and to explore a possible latitudinal gradient.

METHODS

All patients with MS born between 1930 and 1979 registered in the Norwegian MS Registry or ascertained in Norwegian prevalence studies were included (n = 6649). The latitude gradient was divided in Southern, Middle and Northern Norway, according to the estimated regional yearly mean vitamin D effective UV dose.

RESULTS

Risk of MS was 11% higher for those born in April (p = 0.045), and 5% higher for those born in May (p = 0.229), 5% lower for those born in November (p = 0.302) and 12% lower for those born in February (p = 0.053) compared with the corresponding population, unaffected mothers and siblings. In Southern Norway the odds ratio of MS births in April and May was 1.05 (0.98-1.24), in Middle Norway 1.11 (0.97-1.27) and in Northern Norway 1.28 (1.0-1.63) compared with the other months.

CONCLUSIONS

This study confirms previous reports of increased MS births in spring and decreased MS births in the winter months. This could support the role of decreased sunlight exposure during pregnancy and vitamin D deficiency in prenatal life in MS.

An integrated approach to design novel therapeutic interventions for demyelinating disorders

Therapeutic strategies are often based on two general principles: interference with the pathogenic process and repair of the damaged tissues. Recent studies, however, have suggested that several pathological conditions may result from the interplay between genetic susceptibility traits and environmental influences that, by modulating the epigenome, also affect disease onset and progression. Based on lessons from neural development, it is conceivable that new lines of preventive and possibly therapeutic intervention might be developed to modulate disease onset or decrease the severity of the symptoms. This review will discuss these concepts within the context of multiple sclerosis, the most common demyelinating disease of the central nervous system, and the leading cause of progressive neurological disability in young adults.

[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.

Month of birth, vitamin D and risk of immune-mediated disease: a case control study

BACKGROUND

A season of birth effect in immune-mediated diseases (ID) such as multiple sclerosis and type 1 diabetes has been consistently reported. We aimed to investigate whether season of birth influences the risk of rheumatoid arthritis, Crohn's disease, ulcerative colitis and systemic lupus erythematosus in addition to multiple sclerosis, and to explore the correlation between the risk of ID and predicted ultraviolet B (UVB) light exposure and vitamin D status during gestation.

METHODS

The monthly distribution of births of patients with ID from the UK (n = 115,172) was compared to that of the general population using the Cosinor test. Predicted UVB radiation and vitamin D status in different time windows during pregnancy were calculated for each month of birth and correlated with risk of ID using the Spearman's correlation coefficient.

RESULTS

The distributions of ID births significantly differed from that of the general population (P = 5e-12) with a peak in April (odds ratio = 1.045, 95% confidence interval = 1.024, 1.067, P < 0.0001) and a trough in October (odds ratio = 0.945, 95% confidence interval = 0.925, 0.966, P < 0.0001). Stratification by disease subtype showed seasonality in all ID but Crohn's disease. The risk of ID was inversely correlated with predicted second trimester UVB exposure (Spearman's rho = -0.49, P = 0.00005) and third trimester vitamin D status (Spearman's rho = -0.44, P = 0.0003).

CONCLUSIONS

The risk of different ID in the UK is significantly influenced by the season of birth, suggesting the presence of a shared seasonal risk factor or factors predisposing to ID. Gestational UVB and vitamin D exposure may be implicated in the aetiology of ID.

Viruses and vitamin D in the etiology of type 1 diabetes mellitus and multiple sclerosis

Although specific viruses have been associated with autoimmune diseases, none fulfill Koch's criteria of causation. The etiologies of such diseases appear to be complex and multifactorial. For example, one might propose that the etiology of type 1 diabetes mellitus results from a toxic metabolite of nitrosamines during an enteroviral infection. Multiple sclerosis might result from a cascade of events involving several herpes virus infections activated during periods of vitamin D deficiency. We encourage investigators to consider Rotman's sufficient-component causal model when developing hypotheses for testing for the etiology of chronic diseases. Delineating the web of causation may lead to additional strategies for prevention and treatment of several autoimmune diseases.

Month of birth is associated with multiple sclerosis but not with HLA-DR15 in Finland

BACKGROUND

Spring birth has been found to be associated with increase in the risk of MS. However, this effect is reportedly found particularly in HLA-DR15 positive patients.

OBJECTIVE

Examine the month of birth (MOB) effect in Finnish MS patients and its association with HLA-DR15.

METHODS

Using the national register on hospitalizations during 1979-2004 we identified 8359 MS patients. We used a χ(2)-analysis to compare the distribution of MOB in MS patients versus age-adjusted controls. Patients were subdivided into 10-year birth cohorts to analyse temporal variations in MOB. A subgroup of HLA-typed MS patients (n = 657) and a population sample of healthy donors from the Finnish Bone Marrow Donor Registry (n = 19,805) were included to analyse connections between HLA-DR15 and MOB.

RESULTS

An April birth was associated with a 9.4% increased risk of MS (p = 0.008), whereas November birth was associated with an 11.1% decreased risk (p = 0.004) compared with the expected birth distribution. No temporal clustering in the MOB effect was found during 1900-1988. Both HLA-DR15 positive (34% increase, p = 0.043) and DR15 negative (48% increase, p = 0.0095) MS patients exhibited an increase in spring births (in May). HLA-DR15 in healthy subjects was not associated with MOB.

CONCLUSIONS

We confirm that spring birth increases MS risk. This phenomenon was not associated with HLA-DR15 and there was no evidence of temporal clustering. The MOB effect suggests that early developmental processes may modulate MS risk.

Sunlight exposure and sun sensitivity associated with disability progression in multiple sclerosis

BACKGROUND

Sunlight and vitamin D have been inversely associated with the risk of multiple sclerosis (MS).

OBJECTIVE

We investigated sunlight exposure and sun sensitivity in relation to disability progression in MS.

METHODS

We conducted a survey among persons with MS, registered by the Flemish MS society, Belgium, and stratified data according to relapsing-onset and progressive-onset MS. We used Kaplan-Meier survival and Cox proportional hazard regression analyses with time to Expanded Disability Status Scale (EDSS) 6 as outcome measure. Hazard ratios for the time from onset and from birth were calculated for the potentially predictive variables, adjusting for age at onset, gender and immunomodulatory treatment.

RESULTS

704 (51.3%) of the 1372 respondents had reached EDSS 6. In relapsing-onset MS, respondents reporting equal or higher levels of sun exposure than persons of the same age in the last 10 years had a decreased risk of reaching EDSS 6. In progressive-onset MS, increased sun sensitivity was associated with an increased hazard of reaching EDSS 6.

CONCLUSION

The association of higher sun exposure with a better outcome in relapsing-onset MS may be explained by either a protective effect or reverse causality. Mechanisms underlying sun sensitivity might influence progression in progressive-onset MS.

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.

Pediatric multiple sclerosis

BACKGROUND

Pediatric multiple sclerosis (MS), once considered a rare childhood illness, has been increasingly identified as an important childhood acquired neurologic disease requiring early recognition and intervention.

SUMMARY

We present a comprehensive review of the current terminology of acquired central nervous system demyelination in children, pertinent investigations, including magnetic resonance imaging and cerebrospinal fluid cerebrospinal fluid studies, and an approach to the differential diagnosis of pediatric onset MS. In addition, the recent studies exploring the epidemiology and pathobiology will be discussed. Finally, we present an algorithm for the treatment of episodes of demyelination along with chronic immunomodulatory therapeutic options in this patient population.

CONCLUSIONS

Although some similarities exist to adult onset MS, MS onset during childhood and adolescence presents unique diagnostic challenges and requires specialized multidisciplinary care for optimal management. National and international collaborative studies are underway to aid in the understanding of the early and ongoing pathogenesis of MS.

Low maternal exposure to ultraviolet radiation in pregnancy, month of birth, and risk of multiple sclerosis in offspring: longitudinal analysis

OBJECTIVES

To investigate the distribution of month of birth in people with multiple sclerosis in Australia. To use the large regional and seasonal variation in ambient ultraviolet radiation in Australia to explore the association between exposure to ultraviolet radiation during pregnancy and subsequent risk of multiple sclerosis in offspring.

DESIGN

Data were gathered on birth month and year (1920-1950), sex, and state of birth for all patients surveyed in 1981 in Queensland, Western Australia, New South Wales (including Australian Capital Territory), South Australia, and Hobart (Tasmania). Population denominators were derived from the 1981 census and supplementary birth registration data. A variable for exposure to ambient ultraviolet radiation "at birth" was generated from monthly averages of daily total ambient ultraviolet radiation for each region. Negative binomial regression models were used to investigate exposure to ambient ultraviolet radiation at birth and at various intervals before birth.

SETTING

Patient data from multiple sclerosis prevalence surveys carried out in 1981; 1981 Australian census (giving the total number of people born in Australia and still alive and living in Australia in 1981 by year of birth 1920-50); supplementary Australian birth registration data covering the same birth years by month and state.

PARTICIPANTS

1524 patients with multiple sclerosis born in Australia 1920-50 from total population of 2 468 779.

MAIN OUTCOME MEASURE

Cumulative incidence rate of multiple sclerosis.

RESULTS

There was a pattern of risk of multiple sclerosis with month of birth (adjusted incidence rate ratio 1.32, 95% confidence interval 1.10 to 1.58, P<0.01, for those born in November-December compared with those born in May-June). This pattern mirrored that previously reported in the northern hemisphere. Region of birth was related to risk. After adjustment for region of birth and other factors, there was an inverse association between ambient ultraviolet radiation in the first trimester and risk of multiple sclerosis (with ≥25 erythemal (skin reddening) dose units as reference (that is, adjusted incidence rate ratio=1.00), the rates were 1.54 (1.10 to 2.16) for 20-<25 units; 1.58 (1.12 to 2.22) for 15-<20 units; 1.65 (1.17 to 2.33) for 10-<15 units; 1.65 (1.18 to 2.29) for 5-<10 units; and 1.67 (1.18 to 2.37) for <5 units). After adjustment for this exposure during early pregnancy, there was no residual association between month of birth and multiple sclerosis.

CONCLUSION

Region of birth and low maternal exposure to ultraviolet radiation in the first trimester are independently associated with subsequent risk of multiple sclerosis in offspring in Australia.

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

BACKGROUNDS/AIM: Gestational and early life events have been suggested to contribute to multiple sclerosis (MS) susceptibility. We assessed the effects of time and place of birth on the age at onset of MS symptoms.

METHODS

We selected a national cohort of 967 veterans from the Multiple Sclerosis Surveillance Registry for whom month and season (time) of birth, and birthplace (city and state) were available. Multiple linear regression analyses were used to examine the association between time of birth, birthplace latitude and solar radiation, and the age at onset of MS symptoms among the study sample.

RESULTS

Patients with a relapsing form of the disease (R-MS), who were born in winter and whose birthplace was in low solar radiation areas, had disease symptom onset on average 2.8 years earlier than those born in seasons other than winter and in medium- and high-solar radiation areas (p = 0.02).

CONCLUSIONS

These results suggest that exposure early in life to geographical and seasonal factors, possibly related to the protective effect of sunlight, and thus vitamin D, is associated with a delay in MS symptom onset. Other larger studies are required to examine the period-specific (from conception to adulthood) environmental factors that are associated with MS susceptibility.

Environmental factors and their timing in adult-onset multiple sclerosis

Multiple sclerosis (MS) is a common, complex neurological disease. Epidemiological data implicate both genetic and environmental factors in the etiology of MS, with various factors interacting with one another. Environmental exposures might occur long before the disease becomes clinically evident, as suggested by the wide range in onset age. In this Review, we examine the key time periods during which the environment might contribute to MS susceptibility, as well as the potential environmental factors involved. Understanding the nature of environmental influences in MS is highly relevant to the development of public health measures that are aimed at preventing this debilitating disease.

Type 1 diabetes mellitus and multiple sclerosis: common etiological features

Type 1 diabetes mellitus and multiple sclerosis have been largely seen as different, organ-specific diseases, which are managed by different medical specialties. Research studies on these diseases have for the most part followed independent tracks. In this Review, we highlight the latest epidemiological and genetic findings, which have identified many features common to both disorders. Experts consider it increasingly likely that the environment contributes substantially to this overlap. However, although genetic elements that are distinct to each disease probably determine the ultimate form of autoimmunity that is manifested, strikingly broad parallels are seen between the components of genetic risk of type 1 diabetes mellitus and multiple sclerosis. Similarities and differences between these two diseases draw attention to shared disease pathways but insights into each disorder are providing mutual illumination of their pathogenesis.

An overview of gene-epigenetic-environmental contributions to MS causation

In this paper we review how environmental factors might interact with genes and epigenetic factors to trigger multiple sclerosis (MS), the latter probably by immune-mediated mechanisms.

Parent-of-origin effect in multiple sclerosis: observations from interracial matings

BACKGROUND

Multiple sclerosis (MS) is a complex neurologic disease with a striking geographical distribution. In Canada, prevalence is high in Caucasians of Northern European ancestry and uncommon in North American Aboriginals, many of whom now have Caucasian admixture.

METHODS

The population-based Canadian Collaborative Project on the Genetic Susceptibility to MS provided the characteristics of 58 individuals with 1 Caucasian and 1 North American Aboriginal parent from a database of 30,000 MS index cases.

RESULTS

We found that MS index cases with a Caucasian mother and a North American Aboriginal father had a higher sib recurrence risk and greater F:M sex ratio (p = 0.043) than patients with a North American Aboriginal mother and Caucasian father.

CONCLUSIONS

Maternal parent-of-origin effects in multiple sclerosis disease etiology previously seen in studies of half-siblings and avuncular pairs are also seen in Caucasian-North American Aboriginal admixture matings and warrant further investigation. A differential influence of maternal risk transmission on the sex ratio of affected offspring is implied. The method of analysis used may have broader implications for detection of parent-of-origin effects in admixture cohorts.

The causal cascade to multiple sclerosis: a model for MS pathogenesis

BACKGROUND

MS pathogenesis seems to involve both genetic susceptibility and environmental risk factors. Three sequential factors are implicated in the environmental risk. The first acts near birth, the second acts during childhood, and the third acts long thereafter. Two candidate factors (vitamin D deficiency and Epstein-Barr viral infection) seem well suited to the first two environmental events.

METHODOLOGY/PRINCIPAL FINDINGS

A mathematical Model for MS pathogenesis is developed, incorporating these environmental and genetic factors into a causal scheme that can explain some of the recent changes in MS-epidemiology (e.g., increasing disease prevalence, a changing sex-ratio, and regional variations in monozygotic twin concordance rates).

CONCLUSIONS/SIGNIFICANCE

This Model suggests that genetic susceptibility is overwhelmingly the most important determinant of MS pathogenesis. Indeed, over 99% of individuals seem genetically incapable of developing MS, regardless of what environmental exposures they experience. Nevertheless, the contribution of specific genes to MS-susceptibility seems only modest. Thus, despite HLA DRB1*1501 being the most consistently identified genetic marker of MS-susceptibility (being present in over 50% of northern MS patient populations), only about 1% of individuals with this allele are even genetically susceptible to getting MS. Moreover, because genetic susceptibility seems so similar throughout North America and Europe, environmental differences principally determine the regional variations in disease characteristics. Additionally, despite 75% of MS-patients being women, men are 60% more likely to be genetically-susceptible than women. Also, men develop MS at lower levels of environmental exposure than women. Nevertheless, women are more responsive to the recent changes in environmental-exposure (whatever these have been). This explains both the changing sex-ratio and the increasing disease prevalence (which has increased by a minimum of 32% in Canada over the past 35 years). As noted, environmental risk seems to result from three sequential components of environmental exposure. The potential importance of this Model for MS pathogenesis is that, if correct, a therapeutic strategy, designed to interrupt one or more of these sequential factors, has the potential to markedly reduce or eliminate disease prevalence in the future.

Human responses to the geophysical daily, annual and lunar cycles

Collectively the daily, seasonal, lunar and tidal geophysical cycles regulate much of the temporal biology of life on Earth. The increasing isolation of human societies from these geophysical cycles, as a result of improved living conditions, high-quality nutrition and 24/7 working practices, have led many to believe that human biology functions independently of them. Yet recent studies have highlighted the dominant role that our circadian clock plays in the organisation of 24 hour patterns of behaviour and physiology. Preferred wake and sleep times are to a large extent driven by an endogenous temporal program that uses sunlight as an entraining cue. The alarm clock can drive human activity rhythms but has little direct effect on our endogenous 24 hour physiology. In many situations, our biology and our society appear to be in serious opposition, and the damaging consequences to our health under these circumstances are increasingly recognised. The seasons dominate the lives of non-equatorial species, and until recently, they also had a marked influence on much of human biology. Despite human isolation from seasonal changes in temperature, food and photoperiod in the industrialised nations, the seasons still appear to have a small, but significant, impact upon when individuals are born and many aspects of health. The seasonal changes that modulate our biology, and how these factors might interact with the social and metabolic status of the individual to drive seasonal effects, are still poorly understood. Lunar cycles had, and continue to have, an influence upon human culture, though despite a persistent belief that our mental health and other behaviours are modulated by the phase of the moon, there is no solid evidence that human biology is in any way regulated by the lunar cycle.

Multiple sclerosis: immunopathogenesis and controversies in defining the cause

PURPOSE OF REVIEW

Multiple sclerosis is a major cause of neurological disability in Western societies. The most important reason for the limited success obtained in the treatment and prevention so far is most likely related to the limited knowledge about its cause and pathogenesis. This paper discusses recent progress and controversies in the understanding of the pathogenesis and cause of multiple sclerosis.

RECENT FINDINGS

Both T helper cells type 1 (Th1 cells), Th17 cells, cytotoxic T cells, B cells and regulatory T cells are involved in the inflammatory process. Axonal loss seems to be driven by inflammation during the early stages of disease but may become independent of inflammation at later stages. The target antigen of the immune response has not been identified. Weak genetic association has been established in two cytokine receptors, whereas increasing female: male ratio support the importance of environmental risk factors. A substantial proportion of intrathecal B cells are infected with Epstein-Barr virus.

SUMMARY

Multiple sclerosis is a complex disease and calls for integrated efforts from immunology, epidemiology, neuroscience and genetics. In particular, the immunological implications of environmental risk factors such as vitamin D desufficiency, smoking and Epstein-Barr virus infection need to be explored.

Genetic epidemiology: the use of old and new tools for multiple sclerosis

We review the practical application of the tools for studying the genetic epidemiology of complex disease. Whole-genome association studies highlight the need to understand the genetic epidemiology. Elucidating the genetic basis of disease anticipated from these studies has been incomplete, and the importance of the environment and its potential interaction with genes cannot be overlooked. Multiple sclerosis yields several key lessons including how epistatic effects might overshadow the small effects of genes identified from whole-genome association studies. We reinterpret twin studies and demonstrate the use and advantages of adoptee, half-sibling and avuncular-pair studies. These show that the environment acts at a population level, strongly indicating epigenetic modifications to germline susceptibility. There is good reason to think that such interactions will be within the major histocompatibility complex, in which strong epistatic effects have already been demonstrated. Family-based data in multiple sclerosis are applicable to other neurological traits.

Timing of birth and disease progression in multiple sclerosis

BACKGROUND

The timing of birth has recently been associated with the risk of developing multiple sclerosis (MS) in later life. Whether the timing of birth also influences the disease course of MS is unknown.

OBJECTIVE

To investigate whether the season or month of birth influences the timing of secondary progression or the time to landmark disability outcomes in MS.

METHODS

To allow confirmation of findings, all analyses were performed in duplicate in two large natural history cohorts from geographically distinct but seasonally similar locations in Europe and North America. Kaplan-Meier survival analyses were used to investigate the influence of month and season of birth on 1) the time to and age at the development of secondary progression in patients with a relapsing disease onset and 2) the time to reach an Expanded Disability Status Scale (EDSS) score of 6.0 in patients with primary progressive and relapsing MS.

RESULTS

No association between the month or season of birth and disease progression could be found, which was reproducible in both natural history cohorts. A seasonal trend was observed for the time to and age at secondary progression in Groningen, with March babies exhibiting a shorter time to and younger age at secondary progression. The birth month affected time to EDSS 6 for those with relapsing MS in British Columbia, with January babies exhibiting a longer time to EDSS 6. Neither finding could be reciprocated in the other natural history cohort.

CONCLUSION

The season or month of birth does not appear to influence disease progression of MS.

Environmental factors and multiple sclerosis

Studies in Canada have provided strong evidence that environmental factors act at a population level to influence the unusual geographical distribution of multiple sclerosis (MS). However, the available data accommodate more than one type of environmental effect. Migration studies show that changes to early environment can greatly affect risk, and there are recent indications that risk can be altered in situ. The rising incidence rates of MS in Canada implied by longitudinal increases in sex ratio place this effect in temporal context and narrow the candidates for mediating the effect of environment. Similarly, geographical patterns in Australia imply that modifiable environmental factors hold the key to preventing some 80% of cases. Genetic epidemiology provides overwhelming evidence that genetic background has an important complementary role. If genetic factors are held constant, the environment sets the disease threshold. Although these could be independent additive risk factors, it seems more likely that susceptibility is mediated by direct interactions between the environment and genes.

Environmental risk factors in multiple sclerosis

OBJECTIVES

Multiple sclerosis (MS) likely results from an interaction between genetic and exogenous factors. While genetics shapes the overall population MS susceptibility, observed epidemiological patterns strongly suggest a role for the environment in disease initiation and modulation.

RESULTS

Findings from studies on seasonality in MS patients' birth, disease onset and exacerbations, as well as apparent temporal trends in incidence and gender ratio support an influential effect of viruses, metabolic and lifestyle factors on MS risk. Epstein-Barr virus, vitamin D status, and smoking are factors that may explain such epidemiological patterns.

CONCLUSIONS

Further epidemiological investigations are encouraged and opportunities to use data from existing cohort studies as well as the design of new studies should be pursued. In particular, the development of new large multicentre population-based case-control studies which incorporate the study of the role of environment and genetics, including epigenetic mechanisms, in determining MS risk is proposed.