Seasonal patterns in optic neuritis and multiple sclerosis: a meta-analysis

Detecting seasonal trends in optic neuritis within the Ottawa region

OBJECTIVE

In this study we aim to determine seasonal patterns underlying optic neuritis (ON) onset that may provide valuable epidemiologic information and help delineate causative or protective factors.

DESIGN

Single-centre retrospective chart review.

METHODS

A database search of centralized electronic health records was completed using diagnostic codes employed at the Ottawa Eye Institute for data collection. Charts were reviewed for documentation supporting a diagnosis of ON falling into the following categories: multiple sclerosis ON and clinically isolated syndrome ON, myelin oligodendrocyte glycoprotein ON, neuromyelitis optica ON, and idiopathic ON. Date of onset, biological sex, and age were extracted from each chart. Data were analyzed for calculation of frequency by season and overall pooled seasonal trends of all cases of ON.

RESULTS

From the 218 included patients with ON, there was no statistically significant seasonal correlation. The overall trend of ON was lowest in winter and spring (22% and 23%, respectively) and highest in summer and fall (28% and 27% respective). Divided further, multiple sclerosis ON or clinically isolated syndrome ON rates (n = 144) were lowest in the spring (21%) and highest in fall (29%); myelin oligodendrocyte glycoprotein ON rates (n = 25) were lowest in winter (16%) and highest in summer and fall (both at 32%); neuromyelitis optica ON rates (n = 16) were lowest in fall (12.5%) and highest in winter and summer (both at 31.25%); and idiopathic ON rates (n = 33) were lowest in fall (18%) and highest in spring (33%).

CONCLUSIONS

The overall ON seasonal trend appears to have a predilection for the summer and fall months, which may be explained by warmer weather and viral infections as risk factors for multiple sclerosis relapse during those seasons.

Seasonal Variation in Neurologic Hospitalizations in the United States

OBJECTIVE

Certain neurologic diseases have been noted to vary by season, and this is important for understanding disease mechanisms and risk factors, but seasonality has not been systematically examined across the spectrum of neurologic disease, and methodologic guidance is also lacking.

METHODS

Using nationally representative data from the National Inpatient Sample, a stratified 20% sample of all non-federal acute care hospitalizations in the United States, we calculated the monthly rate of hospitalization for 14 neurologic diseases from 2016 to 2018. For each disease, we assessed seasonality of hospitalization using chi-squared, Edward, and Walter-Elwood tests and seasonal time series regression models. Statistical tests were adjusted for multiple hypothesis testing using Bonferroni correction.

RESULTS

Meningitis, encephalitis, ischemic stroke, intracerebral hemorrhage, Guillain-Barre syndrome, and multiple sclerosis had statistically significant seasonality according to multiple methods of testing. Subarachnoid hemorrhage, status epilepticus, myasthenia gravis, and epilepsy had significant seasonality according to Edwards and Walter-Elwood tests but not chi-square tests. Seasonal time series regression illustrated seasonal variation in all 14 diseases of interest, but statistical testing for seasonality within these models using the Kruskal-Wallis test only achieved statistical significance for meningitis.

INTERPRETATION

Seasonal variation is present across the spectrum of acute neurologic disease, including some conditions for which seasonality has not previously been described, and can be examined using multiple different methods. ANN NEUROL 2023;93:743-751.

Seasonal and monthly variation in multiple sclerosis relapses: a systematic review and meta-analysis

BACKGROUND

Multiple Sclerosis (MS) relapses are episodes of transient disease exacerbation. There are contradictory findings regarding seasonal variation in MS relapses. In this systematic review and meta-analysis, we aimed to investigate the seasonal and monthly variation in relapse rates among patients with MS.

METHODS

We systematically queried PubMed, Scopus, and Web of Science for published papers until February 30, 2022.

RESULTS

A total of 24 studies were included in this systematic review and meta-analysis with a total of 29,106 patients with MS. We found that the relapse rate was significantly lower in fall compared to the average relapse rate in other seasons with a risk ratio (RR) of 0.97 (95% CI 0.95-0.98). Furthermore, patients with MS experienced a higher number of relapses in April (RR: 1.06, 95% CI 1.01-1.11) and March (RR: 1.08, 95% CI 1.00-1.16) compared to other months. Also, the risk of relapse was lower in August (RR: 0.92, 95% CI.85-0.98), September (RR: 0.97, 95% CI.94-0.99), October (RR: 0.92, 95% CI.89-0.96), and November (RR: 0.93, 95% CI.89-0.97).

CONCLUSION

Our systematic review and meta-analysis confirm the temporal fluctuations in the relapse of MS through a comprehensive review of the existing literature, with a lower relapse rate during late summer and fall and a higher relapse rate during early spring.

Melatonin and multiple sclerosis: antioxidant, anti-inflammatory and immunomodulator mechanism of action

BACKGROUND

Melatonin is an indole hormone secreted primarily by the pineal gland that showing anti-oxidant, anti-inflammatory and anti-apoptotic capacity. It can play an important role in the pathophysiological mechanisms of various diseases. In this regard, different studies have shown that there is a relationship between Melatonin and Multiple Sclerosis (MS). MS is a chronic immune-mediated disease of the Central Nervous System.

AIM

The objective of this review was to evaluate the mechanisms of action of melatonin on oxidative stress, inflammation and intestinal dysbiosis caused by MS, as well as its interaction with different hormones and factors that can influence the pathophysiology of the disease.

RESULTS

Melatonin causes a significant increase in the levels of catalase, superoxide dismutase, glutathione peroxidase, glutathione and can counteract and inhibit the effects of the NLRP3 inflammasome, which would also be beneficial during SARS-CoV-2 infection. In addition, melatonin increases antimicrobial peptides, especially Reg3β, which could be useful in controlling the microbiota.

CONCLUSION

Melatonin could exert a beneficial effect in people suffering from MS, running as a promising candidate for the treatment of this disease. However, more research in human is needed to help understand the possible interaction between melatonin and certain sex hormones, such as estrogens, to know the potential therapeutic efficacy in both men and women.

Effect of Seasonal Variation on Relapse Rate in Patients With Relapsing-Remitting Multiple Sclerosis in Saudi Arabia

Multiple sclerosis (MS) is becoming a global subject of study in which some demographic variations are thought to be correlated with its activity. Relapsing-remitting multiple sclerosis (RRMS) is the most common demyelinating disorder, characterized by periods of exacerbating attacks, followed by partial or complete remission. Several factors might play a role in disease progression and relapse frequency, such as vitamin D, ultraviolet B radiation, estrogen levels, smoking, obesity, and unhealthy lifestyles. In this study, we identified the relationship between seasonal variation and relapse rate and correlated the latter with sex, age, and vitamin D levels in patients with RRMS in Jeddah, Saudi Arabia. We retrospectively collected data from 182 RRMS patients between 2016 and 2021. A total of 219 relapses were documented in 106 patients (58.2 %). The relapse per patient ratio showed a sinusoidal pattern, peaking in January at a rate of 0.49 and troughed in June at a rate of 0.18. There was no difference in relapse rates between men and women (p =0.280). There was a significant negative correlation between vitamin D levels and relapse rate (r = −0.312, p =0.024). Therefore, the relapse rate was higher during the winter and was correlated with low vitamin D levels. However, relapses are likely multifactorial, and more population-based studies are needed to understand the role of environmental variables in MS exacerbation. A better understanding of this relationship will allow for improved treatment and possibly better prevention of relapse.

Ambient air pollution and multiple sclerosis: a systematic review

OBJECTIVES

Some studies have shown that environmental risk factors, including air pollution, might be related to the incidence or recurrence of multiple sclerosis (MS). This systematic review was conducted to investigate the relation between air pollution and MS.

METHODS

A systematic search was conducted in PubMed, Scopus, Science Direct, Embase, and Web of Science; until January 2020 with no restrictions. The search strategy was conducted with air pollution key words such as CO, PM_2.5, PM₁₀, SO₂, and NO₂, for exposure and the key word "Multiple sclerosis" as the outcome.

RESULTS

Eventually, after applying the inclusion and exclusion criteria, 17 articles were included. The methodologies and outcomes reported were heterogeneous and different metrics had been used in the results; therefore conducting a meta-analysis was not possible. Eight studies had analyzed the relation between particulate matter (PM) and the prevalence or relapse of MS and had observed a significant relation. NO₂ and NOx were associated with recurrence or prevalence of MS in three studies. But, in three cohort studies, no association was observed between air pollution and recurrence or occurrence of MS.

CONCLUSIONS

The results of this systematic review show that outdoor air pollution, especially PM and nitrogen oxides might be related to the prevalence or relapse of MS.

Seasonal variation in attacks of neuromyelitis optica spectrum disorders and multiple sclerosis: Evaluation of 794 attacks from a nationwide registry in Argentina

BACKGROUND

Identification of triggers that potentially instigate attacks in neuromyelitis optica spectrum disorders (NMOSD) and multiple sclerosis (MS) has remained challenging. We aimed to analyze the seasonality of NMOSD and MS attacks in an Argentinean cohort seeking differences between the two disorders.

METHODS

A retrospective study was conducted in a cohort of NMOSD and MS patients followed in specialized centers from Argentina and enrolled in RelevarEM, a nationwide, longitudinal, observational, non-mandatory registry of MS/NMOSD patients. Patients with complete relapse data (date, month and year) at onset and during follow-up were included. Attack counts were analyzed by month using a Poisson regression model with the median monthly attack count used as reference.

RESULTS

A total of 551 patients (431 MS and 120 NMOSD), experiencing 236 NMOSD-related attacks and 558 MS-related attacks were enrolled. The mean age at disease onset in NMOSD was 39.5 ± 5.8 vs. 31.2 ± 9.6 years in MS (p < 0.01). Mean follow-up time was 6.1 ± 3.0 vs. 7.4 ± 2.4 years (p < 0.01), respectively. Most of the included patients were female in both groups (79% vs. 60%, p < 0.01). We found a peak of number of attacks in June (NMOSD: 28 attacks (11.8%) vs MS: 33 attacks (5.9%), incidence rate ratio 1.82, 95%CI 1.15-2.12, p = 0.03), but no differences were found across the months in both disorders when evaluated separately. Strikingly, we observed a significant difference in the incidence rate ratio of attacks during the winter season when comparing NMOSD vs. MS (NMOSD: 75 attacks (31.7%) vs MS: 96 attacks (17.2%), incidence rate ratio 1.82, 95%CI 1.21-2.01, p = 0.02) after applying Poisson regression model. Similar results were observed when comparing the seropositive NMOSD (n = 75) subgroup vs. MS.

CONCLUSIONS

Lack of seasonal variation in MS and NMOSD attacks was observed when evaluated separately. Future epidemiological studies about the effect of different environmental factors on MS and NMOSD attacks should be evaluated prospectively in Latin America population.

Seasonal variation in autoimmune encephalitis: A multi-center retrospective study

OBJECTIVE

The aim of this study was to examine the seasonal distribution in clinical onset of autoimmune encephalitis (AE) in a multi-center cohort in China.

METHODS

This retrospective study consecutively recruited patients with new-onset definite neuronal surface antibody-associated AE between January 2015 and December 2020 from 3 tertiary hospitals. Demographic and clinical characteristics of the participants were comprehensively collected. Statistical analyses were performed using R.

RESULTS

Of the 184 patients of AE in our database, 149 (81.0%) were included in the final analysis. The median age of onset was 40.0 years, and 66 (44.3%) patients were female. AE predominantly started in autumn (47, 31.5%) and summer (43, 28.9%) months. Summer-autumn predominance of the clinical onsets was also present in the anti-N-methyl-d-aspartate receptor (NMDAR) encephalitis group (54, 60.0%) and anti-leucine-rich glioma inactivated 1 (LGI1) encephalitis group (20, 76.9%). No obvious seasonal variations were observed among gender, onset age, disease duration, prodromal symptoms, clinical type of initial symptoms, and disease severity by the time of admission.

CONCLUSION

This study suggested summer-autumn predominance of the clinical onsets in patients with AE, especially anti-NMDAR and anti-LGI1 encephalitis. Therefore, clinicians should have a high index of suspicion for AE in encephalopathy patients in summer and autumn period.

Risk of relapse in patients with neuromyelitis optica spectrum disorder: Recognition and preventive strategy

Neuromyelitis optica spectrum disorder (NMOSD) is a rare autoimmune inflammatory disorder of the central nervous system (CNS) that is mainly associated with serum autoantibodies against aquaporin-4 (AQP4) in astrocytes. The relapsing clinical course of NMOSD, which can be blinding and disabling due to severe visual impairment, spinal cord lesions and a group of brain syndromes, suggests the importance of accurately evaluating the likelihood and severity of relapse at an early stage of the disease. To date, many risk factors have been revealed in association with relapse, and only some of them are supported by substantial evidence. Furthermore, while the clinical use of conventional immunosuppressants is mostly empirical, an increasing number of emerging therapies for monoclonal antibodies have been confirmed by several randomized placebo-controlled trials to be effective and safe for relapse prevention. In this review, we summarize the reported risk factors that may influence the frequency, symptoms, severity and prognosis of relapse in NMOSD, as well as the efficacy and safety of emerging therapies for relapse prevention. All of these results enable us to better recognize patients who are at higher risk of relapse and suggest more effective monoclonal antibody therapies for use in these patients.

Seasonal distribution of attacks in aquaporin-4 antibody disease and myelin-oligodendrocyte antibody disease

BACKGROUND

Seasonal variation in incidence and exacerbations has been reported for neuroinflammatory conditions such as multiple sclerosis and acute disseminated encephalomyelitis (ADEM). It is unknown whether seasonality also influences aquaporin-4 antibody (AQP4-Ab) disease and myelin-oligodendrocyte antibody (MOG-Ab) disease.

OBJECTIVE

We examined the seasonal distribution of attacks in AQP4-Ab disease and MOG-Ab disease.

METHODS

Observational study using data prospectively recorded from three cohorts in the United Kingdom.

RESULTS

There was no clear seasonal variation in AQP4-Ab or MOG-Ab attacks for either the onset attack nor subsequent relapses. In both groups, the proportion of attacks manifesting with each of the main phenotypes (optic neuritis, transverse myelitis, ADEM/ADEM-like) appeared stable across the year. This study is the first to examine seasonal distribution of MOG-Ab attacks and the largest in AQP4-Ab disease so far.

CONCLUSION

Lack of seasonal distribution in AQP4-Ab and MOG-Ab disease may argue against environment factors playing a role in the aetiopathogenesis of these conditions.

Management of Multiple Sclerosis Relapses

PURPOSE OF REVIEW

This article provides an overview of the clinical and pathologic features of multiple sclerosis (MS) relapses and reviews evidence-based approaches to their treatment.

RECENT FINDINGS

Despite the increasing number and potency of MS treatments, relapses remain one of the more unpredictable and disconcerting disease aspects for many patients with MS, making their accurate recognition and treatment an essential component of good clinical care. The expanding range of relapse treatments now includes oral corticosteroids, comparable in efficacy to IV methylprednisolone at a fraction of the cost. While this development improves access to prompt treatment, it also underscores the importance of recognizing mimics of MS relapses to reduce corticosteroid overuse and its attendant risks.

SUMMARY

Like MS itself, MS relapse remains primarily a clinical diagnosis. The treatment options for MS relapse include corticosteroids, adrenocorticotropic hormone (ACTH), plasma exchange, and rehabilitation, used singly or sequentially, with the goal of limiting the duration and impact of associated disability. Even when treated promptly and effectively, clinical or subclinical sequelae of MS relapses frequently remain.

Respiratory viral infections and the risk of rheumatoid arthritis

Background

We aimed to investigate the effects of ambient respiratory viral infections in the general population on rheumatoid arthritis (RA) development.

Methods

Data of weekly incident RA (2012–2013) were obtained from the Korean National Health Insurance claims database, and those of weekly observations on eight respiratory viral infections were obtained from the Korea Centers for Disease Control and Prevention database. We estimated the percentage change in incident RA associated with ambient mean respiratory viral infections using a generalized linear model, after adjusting for time trend, air pollution, and meteorological data.

Results

A total of 24,117 cases of incident RA (mean age 54.7 years, 18,688 [77.5%] women) were analyzed. Ambient respiratory viral infections in the population were associated with a higher number of incident RA over time, and its effect peaked 6 or 7 weeks after exposure. Among the 8 viruses, parainfluenza virus (4.8% for 1% respiratory viral infection increase, 95% CI 1.6 to 8.1, P = .003), coronavirus (9.2%, 3.9 to 14.8, P < .001), and metapneumovirus (44%, 2.0 to 103.4, P = .038) were associated with increased number of incident RA. The impact of these respiratory viral infections remained significant in women (3.8%, 12.1%, and 67.4%, respectively, P < .05) and in older patients (10.7%, 14.6%, and 118.2%, respectively, P < .05).

Conclusions

Ambient respiratory viral infections in the population were associated with an increased number of incident RA, especially in women and older patients, suggesting that respiratory viral infections can be a novel environmental risk factor for the development of RA.

Electronic supplementary material

The online version of this article (10.1186/s13075-019-1977-9) contains supplementary material, which is available to authorized users.

The clinical spectrum and prognosis of idiopathic acute optic neuritis: A longitudinal study in Southern Finland

BACKGROUND

To analyse in a population-based setting the clinical features, prognostic factors, and seasonality of patients diagnosed with acute idiopathic optic neuritis (ON).

METHODS

Retrospective analysis of ophthalmological records, laboratory parameters, and magnetic resonance imaging (MRI) of patients with symptoms suggestive of ON referred to the Helsinki University Hospital (serving a population of 1.53 million in Southern Finland) were analysed between May 1, 2008 and April 14, 2012.

RESULTS

Of the 291 patients with suspected ON, 184 (63%) were diagnosed with ON (mean age 34 years, 76% females). Intravenous methylprednisolone treatment was administered in 131 (71%) patients. First ON was diagnosed in 123 patients (67%), 55 (30%) had a previous diagnosis of multiple sclerosis (MS) and two patients with their first ON were diagnosed with neuromyelitis optica. Evolution of best corrected visual acuity (BCVA) was analysed in 132 (72%) patients, who were reviewed median of 38 days after onset. Median and mean BCVAs in these reviewed patients were 0.4 and 0.2 at the time of diagnosis and 1.0 and 0.5 at the time of the review. Recovery was relatively good in the majority of patients; 82% (n = 108) had reached BCVA of ≥0.5 and 70% (n = 92) and BCVA of ≥0.8 at the time of the review, while thirteen (10%) had poor prognosis, BCVA ≤0.1 at review. Accessory clinical features included optic disc swelling (21%), colour vision impairment (75%), and pain with eye movements (65%). Relative afferent pupillary defect was abnormal in 76% of the patients with their first ON. Baseline visual acuity was most strongly associated with visual outcome at review (P < 0.001, linear regression). Optic disc swelling and the presence of lesions in the optic nerve on MRI had a more modest association with poorer recovery (P = 0.033 and P = 0.049, respectively), while age, sex, previous history of ON, and previous diagnosis of multiple sclerosis were not associated with outcome at review. Incidence of ON showed a clear seasonal pattern; there were two times more cases in April to June versus October to December (P = 0.03), confirming previous results from Sweden.

CONCLUSIONS

Our data suggest that besides baseline visual acuity, optic disc swelling and lesions in the optic nerve on MRI are associated with poorer prognosis. As in previous studies, we observed that diagnostics of ON is difficult, accessory clinical findings such as pain and RAPD are not always present. Although the diagnosis of ON is clinical, the role of MRI should be considered in differential diagnostics and in defining potential prognostic markers.

Ozone, NO2 and PM10 are associated with the occurrence of multiple sclerosis relapses. Evidence from seasonal multi-pollutant analyses

BACKGROUND

Triggers of multiple sclerosis (MS) relapses are essentially unknown. PM10 exposure has recently been associated with an increased risk of relapses.

OBJECTIVES

We further explore the short-term associations between PM10, NO2, benzene (C6H6), O3, and CO exposures, and the odds of MS relapses' occurrence.

METHODS

Using a case-crossover design, we studied 424 MS patients living in the Strasbourg area, France between 2000 and 2009 (1783 relapses in total). Control days were chosen to be ± 35 days relative to the case (relapse) day. Exposure was modeled through ADMS-Urban software at the census block scale. We consider single-pollutant and multi-pollutant conditional logistic regression models coupled with a distributed-lag linear structure, stratified by season ("hot" vs. "cold"), and adjusted for meteorological parameters, pollen count, influenza-like epidemics, and holidays.

RESULTS

The single-pollutant analyses indicated: 1) significant associations between MS relapse incidence and exposures to NO2, PM10, and O3, and 2) seasonality in these associations. For instance, an interquartile range increase in NO2 (lags 0-3) and PM10 exposure were associated with MS relapse incidence (OR = 1.08; 95%CI: [1.03-1.14] and OR = 1.06; 95%CI: [1.01-1.11], respectively) during the "cold" season (i.e., October-March). We also observed an association with O3 and MS relapse incidence during "hot" season (OR = 1.16; 95%CI: [1.07-1.25]). C6H6 and CO were not significantly related to MS relapse incidence. However, using multi-pollutant models, only O3 remained significantly associated with the odds of relapse triggering during "hot" season.

CONCLUSION

We observed significant single-pollution associations between the occurrence of MS relapses and exposures to NO2, O3 and PM10, only O3 remained significantly associated with occurrence of MS relapses in the multi-pollutant model.

Central nervous system neuroinflammatory disorders in Asian/Pacific regions

PURPOSE OF REVIEW

The discovery of aquaporin-4 (AQP4) antibodies with high specificity for neuromyelitis optica spectrum disorder (NMOSD) has induced tremendous changes in the approach and management of central nervous system (CNS) neuroinflammatory disorders. Owing to the increasing availability of the AQP4 antibody assay and evolution of diagnostic criteria for multiple sclerosis and NMOSD, recent studies have reevaluated CNS neuroinflammatory disorders. This review describes recent advances in the understanding of CNS neuroinflammatory disorders in Asian/Pacific regions.

RECENT FINDINGS

Although multiple sclerosis prevalence is lower in Asian countries than in Western countries, the overall clinical features of multiple sclerosis are comparable between these countries. Hospital-based studies have reported that the frequency of NMOSD is higher in Asian populations (22-42%) than in white populations (2-26%). Despite improvements in the AQP4 antibody assay, AQP4 antibodies are not detected in certain patients with NMOSD. Recently, myelin oligodendrocyte glycoprotein (MOG) antibodies have been identified in AQP4 antibody-negative patients with the NMOSD phenotype, and the clinical features differ slightly between MOG antibody-positive patients and AQP4 antibody-positive patients.

SUMMARY

The understanding of CNS neuroinflammatory disorders in Asian/Pacific regions continues to evolve owing to the discovery of new biological markers and recognition of broader clinical phenotypes.

Seasonality and autoimmune diseases: The contribution of the four seasons to the mosaic of autoimmunity

Autoimmune diseases (ADs) are a heterogeneous groups of diseases that occur as a results of loss of tolerance to self antigens. While the etiopathogeneis remain obscure, different environmental factors were suggested to have a role in the development of autoimmunity, including infections, low vitamin D levels, UV radiation, and melatonin. Interestingly, such factors possess seasonal variation patterns that could influence disease development, severity and progression. Vitamin D levels which reach a nadir during late winter and early spring is correlated with increased disease activity, clinical severity as well as relapse rates in several disease entities including multiple sclerosis (MS), non-cutaneous flares of systemic lupus erythematosus (SLE), psoriasis, and rheumatoid arthritis (RA). Additionally, immunomodulatory actions of melatonin secretion ameliorate the severity of several ADs including MS and SLE. Melatonin levels are lowest during spring, a finding that correlates with the highest exacerbation rates of MS. Further, melatonin is postulated to be involved in the etiopathogenesis of inflammatory bowel diseases (IBD) through it influence on adhesion molecule and therefore transcription factor expression. Moreover, infections can mount to ADs through pro-inflammatory cytokine release and human antigen mimicry. Seasonal patterns of infectious diseases are correlated with the onset and exacerbation of ADs. During the winter, increased incidence of Epstein-Barr virus (EBV) infectious are associated with MS and SLE flares/onset respectively. In addition, higher Rotavirus infections during the winter precedes type 1 diabetes mellitus onset (T1DM). Moreover, Escherichia coli (E. coli) infection prior to primary biliary cirrhosis (PBC) and T1DM disease onset subsequent to Coxachievirus infections are seen to occur during late summer, a finding that correlate with infectious agents' pattern of seasonality. In this review, the effects of seasonality on the onset, relapses and activity of various ADs were discussed. Consideration of seasonal variation patterns of ADs can possibly provide clues to diseases pathogenesis and lead to development of new approaches in treatment and preventative care.

Seasonal variation in multiple sclerosis relapse

Relapses are a characteristic clinical feature of multiple sclerosis (MS), but an appreciation of factors that cause them remains elusive. In this study, we have examined seasonal variation of relapse in a large population-based MS cohort and correlated observed patterns with age, sex, disease course, and climatic factors. Relapse data were recorded prospectively in 2076 patients between 2005 and 2014. 3902 events were recorded in 1158 patients (range 0-24). There was significant seasonal variation in relapse rates (p < 0.0001) and this was associated with monthly hours of sunshine (odds ratio OR 1.08, p = 0.02). Relapse rates were highest in patients under the age of 30 (OR 1.42, p = 0.0005) and decreased with age. There was no evidence of different relapse rates for males compared to females (OR 0.90, p = 0.19). Identification of potentially modifiable environmental factors associated with temporal variation in relapse rates may allow alteration of risk on a population basis and alteration of outcome of established disease once established. Future epidemiological studies should examine dynamic environmental factors with serial prospective measurements and biological sampling. Significant seasonal differences in relapse rates highlight the importance of environmental factors in disease expression and should be taken into account when planning clinical trials in which relapse frequency is an outcome. In addition, identification of potentially modifiable factors associated with this variation may offer unique opportunities for alteration of risk of relapse and long-term outcome on a population level, and suggest putative biological mechanisms for relapse initiation.

Clinical characteristics of optic neuritis in Hong Kong population: 10-year review

PURPOSE

To review the clinical course of adult patients with acute optic neuritis over 10 years in Hong Kong, and the results were compared with other studies among Asian and Caucasian patients.

METHODS

This study retrospectively analysed the clinical features of 38 adult patients (51 eyes) presented with optic neuritis in a Hong Kong hospital over 10 years (2001-2010).

RESULTS

Optic neuritis had a female predominance (68%). The mean age of presentation was 40 years old. Disc swelling (39%) was more common compared to the optic neuritis treatment trial (ONTT). The recovery time ranged from no recovery to 5 years, with a mean of 6.0 months. However, vision continued to deteriorate despite initial improvement in 45% of patients. Only 11.8% of the eyes attained final visual acuity (VA) of 1.0 or better, while 31.4% had VA 0.1 or worse. Multiple sclerosis or neuromyelitis optica only occurred in 10.4% of patients. Three of our patients who did not receive any treatment showed faster recovery than the average.

CONCLUSIONS

Optic neuritis in Hong Kong is mostly a clinically isolated syndrome. Our patients presented at a later age and showed a worse visual outcome. Corticosteroid according to ONTT protocol remained our mainstay of treatment although it did not benefit our patients as much as ONTT study. More work on the long-term prognosis and treatment strategies is worthwhile among Chinese optic neuritis patients.

Outcome Measures in Clinical Trials for Multiple Sclerosis

Due to the heterogeneous nature of the disease, it is a challenge to capture disease activity of multiple sclerosis (MS) in a reliable and valid way. Therefore, it can be difficult to assess the true efficacy of interventions in clinical trials. In phase III trials in MS, the traditionally used primary clinical outcome measures are the Expanded Disability Status Scale and the relapse rate. Secondary outcome measures in these trials are the number or volume of T2 hyperintense lesions and gadolinium-enhancing T1 lesions on magnetic resonance imaging (MRI) of the brain. These secondary outcome measures are often primary outcome measures in phase II trials in MS. Despite several limitations, the traditional clinical measures are still the mainstay for assessing treatment efficacy. Newer and potentially valuable outcome measures increasingly used or explored in MS trials are, clinically, the MS Functional Composite and patient-reported outcome measures, and on MRI, brain atrophy and the formation of persisting black holes. Several limitations of these measures have been addressed and further improvements will probably be proposed. Major improvements are the coverage of additional functional domains such as cognitive functioning and assessment of the ability to carry out activities of daily living. The development of multidimensional measures is promising because these measures have the potential to cover the full extent of MS activity and progression. In this review, we provide an overview of the historical background and recent developments of outcome measures in MS trials. We discuss the advantages and limitations of various measures, including newer assessments such as optical coherence tomography, biomarkers in body fluids and the concept of 'no evidence of disease activity'.

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.

Melatonin Contributes to the Seasonality of Multiple Sclerosis Relapses

Seasonal changes in disease activity have been observed in multiple sclerosis, an autoimmune disorder that affects the CNS. These epidemiological observations suggest that environmental factors influence the disease course. Here, we report that melatonin levels, whose production is modulated by seasonal variations in night length, negatively correlate with multiple sclerosis activity in humans. Treatment with melatonin ameliorates disease in an experimental model of multiple sclerosis and directly interferes with the differentiation of human and mouse T cells. Melatonin induces the expression of the repressor transcription factor Nfil3, blocking the differentiation of pathogenic Th17 cells and boosts the generation of protective Tr1 cells via Erk1/2 and the transactivation of the IL-10 promoter by ROR-α. These results suggest that melatonin is another example of how environmental-driven cues can impact T cell differentiation and have implications for autoimmune disorders such as multiple sclerosis.

A Method of Trigonometric Modelling of Seasonal Variation Demonstrated with Multiple Sclerosis Relapse Data

This report describes a novel Stata-based application of trigonometric regression modelling to 55 years of multiple sclerosis relapse data from 46 clinical centers across 20 countries located in both hemispheres. Central to the success of this method was the strategic use of plot analysis to guide and corroborate the statistical regression modelling. Initial plot analysis was necessary for establishing realistic hypotheses regarding the presence and structural form of seasonal and latitudinal influences on relapse probability and then testing the performance of the resultant models. Trigonometric regression was then necessary to quantify these relationships, adjust for important confounders and provide a measure of certainty as to how plausible these associations were. Synchronization of graphing techniques with regression modelling permitted a systematic refinement of models until best-fit convergence was achieved, enabling novel inferences to be made regarding the independent influence of both season and latitude in predicting relapse onset timing in MS. These methods have the potential for application across other complex disease and epidemiological phenomena suspected or known to vary systematically with season and/or geographic location.

A spring to summer shift of pro-inflammatory cytokine production in multiple sclerosis patients

Higher MS relapse frequency is observed during warmer months in different regions, but evidence for an underlying immunological variation is lacking. Therefore, we investigated seasonal variations of cytokine production in relapsing-remitting MS patients. Twenty-one patients and eight controls had blood samples drawn in each season, evaluating for IL-10, IL-6, TNF-α and IFN-γ. The lowest levels of cytokine production were observed in spring samples, with a significant increase from spring to summer for most cytokines, and especially IFN-γ and TNF-α. This phenomenon may underlie the higher prevalence of clinical and subclinical MS activity observed in warmer months.

Infection as an Environmental Trigger of Multiple Sclerosis Disease Exacerbation

Over the past several decades, significant advances have been made in identifying factors that contribute to the pathogenesis of multiple sclerosis (MS) and have culminated in the approval of some effective therapeutic strategies for disease intervention. However, the mechanisms by which environmental factors, such as infection, contribute to the pathogenesis and/or symptom exacerbation remain to be fully elucidated. Relapse frequency in MS patients contributes to neurological impairment and, in the initial phases of disease, serves as a predictor of poor disease prognosis. The purpose of this review is to examine the evidence that supports a role for peripheral infection in modulating the natural history of this disease. Evidence supporting a role for infection in promoting exacerbation in animal models of MS is also reviewed. Finally, a few mechanisms by which infection may exacerbate symptoms of MS and other neurological diseases are discussed. Those who comprise the majority of MS patients acquire approximately two upper-respiratory infections per year; furthermore, this type of infection doubles the risk for MS relapse, underscoring the contribution of this relationship as being potentially important and particularly detrimental.

Latitude, sun exposure and vitamin D supplementation: associations with quality of life and disease outcomes in a large international cohort of people with multiple sclerosis

BACKGROUND

A growing evidence base implicates vitamin D, sun exposure and latitude in the aetiology of multiple sclerosis (MS), however there are less data on the associations of these variables with disease outcomes.

METHODS

We undertook a cross-sectional survey of over 2000 people with MS recruited through internet platforms, seeking self-reported data on geographical location, intentional sun exposure for health, and supplementation with vitamin D, among other lifestyle variables. We also requested data on health-related quality of life (MSQOL-54), self-reported doctor-diagnosed relapse rate, and disability (Patient Determined Disease Steps). Bivariate and multivariate analyses were used for comparisons, including multiple linear regression modeling.

RESULTS

Of 2301 participants, 82.3 % were female, median age was 45 years (IQR 38-53 years), with a median time since diagnosis of 6 years (IQR 3-12 years), the majority (61.6 %) having relapsing-remitting MS. Nearly two-thirds (64.6 %) lived in the Northern hemisphere, mostly in developed countries. Most (66.8 %) reported deliberate sun exposure to raise their vitamin D level, and the vast majority (81.8 %) took vitamin D supplements, mostly 2000-5000 IU a day on average. Unadjusted regression modeling incorporating deliberate sun exposure, latitude and vitamin D supplementation showed strong associations of sun exposure with HRQOL which disappeared when controlling for gender, age, disability, physical activity, and fish consumption. In contrast, associations between vitamin D supplementation and HRQOL were maintained adjusting for these variables, with a dose-response effect. Only latitude had significant adjusted associations with disability, with an increase of latitude by one degree (further from the equator) predicting increased odds of moderate disability (OR 1.02 (95 % CI 1.01-1.04)) or high disability (OR 1.03 (95 % CI 1.01-1.05)) compared to no/mild disability. Similarly, latitude was related to relapse rate, with increase in latitude of 1 degree associated with increased odds of having more relapses over the previous year (1.01 (1.00-1.02)).

CONCLUSIONS

We detected significant associations between latitude, deliberate sun exposure and vitamin D supplementation and health outcomes of this large group of people with MS. Vitamin D is likely to have a key role in these associations and its role in the health outcomes of people with MS urgently requires further study.

Site-specific clinical disease onset in multiple sclerosis

BACKGROUND AND PURPOSE

Multiple sclerosis is a chronic inflammatory disorder of the central nervous system characterized by acute episodes of neurological dysfunction thought to reflect focal areas of demyelination occurring in clinically eloquent areas. These symptomatic relapses are generally considered to be random clinical events occurring without discernible pattern. The hypothesis that relapses may follow a predetermined sequence and may provide insights into underlying pathological processes was investigated.

METHODS

Employing prospective clinical database data from 1482 patients who had experienced one or more consecutive relapses were analysed. Using regression analysis, site and symptom of index event were compared with those of first relapse.

RESULTS

It is demonstrated that following disease ignition subsequent relapses may not be random events but dependent on characteristics of the index event. All anatomical sites were more likely to be affected in the first relapse if that site had been involved in the index event with a similar association observed when comparing by symptoms.

CONCLUSION

These findings have importance in understanding the evolution of the disease and predicting individual disease progression and may aid with patient counselling and management.

Optic neuritis

Acute optic neuritis is the most common optic neuropathy affecting young adults. Exciting developments have occurred over the past decade in understanding of optic neuritis pathophysiology, and these developments have been translated into treatment trials. In its typical form, optic neuritis presents as an inflammatory demyelinating disorder of the optic nerve, which can be associated with multiple sclerosis. Atypical forms of optic neuritis can occur, either in association with other inflammatory disorders or in isolation. Differential diagnosis includes various optic nerve and retinal disorders. Diagnostic investigations include MRI, visual evoked potentials, and CSF examination. Optical coherence tomography can show retinal axonal loss, which correlates with measures of persistent visual dysfunction. Treatment of typical forms with high-dose corticosteroids shortens the period of acute visual dysfunction but does not affect the final visual outcome. Atypical forms can necessitate prolonged immunosuppressive regimens. Optical coherence tomography and visual evoked potential measures are suitable for detection of neuroaxonal loss and myelin repair after optic neuritis. Clinical trials are underway to identify potential neuroprotective or remyelinating treatments for acutely symptomatic inflammatory demyelinating CNS lesions.

Ribosomal protein S6 mRNA is a biomarker upregulated in multiple sclerosis, downregulated by interferon treatment, and affected by season

Background:

Multiple Sclerosis (MS) is an immune-mediated disease of the central nervous system which responds to therapies targeting circulating immune cells.

Objective:

Our aim was to test if the T-cell activation gene expression pattern (TCAGE) we had previously described from whole blood was replicated in an independent cohort.

Methods:

We used RNA-seq to interrogate the whole blood transcriptomes of 72 individuals (40 healthy controls, 32 untreated MS). A cohort of 862 control individuals from the Brisbane Systems Genetics Study (BSGS) was used to assess heritability and seasonal expression. The effect of interferon beta (IFNB) therapy on expression was evaluated.

Results:

The MS/TCAGE association was replicated and rationalized to a single marker, ribosomal protein S6 (RPS6). Expression of RPS6 was higher in MS than controls ( p<0.0004), and lower in winter than summer ( p<4.6E-06). The seasonal pattern correlated with monthly UV light index ( R=0.82, p<0.002), and was also identified in the BSGS cohort ( p<0.0016). Variation in expression of RPS6 was not strongly heritable. RPS6 expression was reduced by IFNB therapy.

Conclusions:

These data support investigation of RPS6 as a potential therapeutic target and candidate biomarker for measuring clinical response to IFNB and other MS therapies, and of MS disease heterogeneity.

Incidence of multiple sclerosis among European Economic Area populations, 1985-2009: the framework for monitoring

Background

A debate surrounding multiple sclerosis epidemiology has centred on time-related incidence increases and the need of monitoring. The purpose of this study is to reassess multiple sclerosis incidence in the European Economic Area.

Methods

We conducted a systematic review of literature from 1965 onwards and integrated elements of original research, including requested or completed data by surveys authors and specific analyses.

Results

The review of 5323 documents yielded ten studies for age- and sex-specific analyses, and 21 studies for time-trend analysis of single data sets. After 1985, the incidence of multiple sclerosis ranged from 1.12 to 6.96 per 100,000 population, was higher in females, tripled with latitude, and doubled with study midpoint year. The north registered increasing trends from the 1960s and 1970s, with a historic drop in the Faroe Islands, and fairly stable data in the period 1980-2000; incidence rose in Italian and French populations in the period 1970-2000, in Evros (Greece) in the 1980s, and in the French West Indies in around 2000.

Conclusions

We conclude that the increase in multiple sclerosis incidence is only apparent, and that it is not specific to women. Monitoring of multiple sclerosis incidence might be appropriate for the European Economic Area.

Can we prevent or treat multiple sclerosis by individualised vitamin D supply?

Apart from its principal role in bone metabolism and calcium homeostasis, vitamin D has been attributed additional effects including an immunomodulatory, anti-inflammatory, and possibly even neuroprotective capacity which implicates a possible role of vitamin D in autoimmune diseases like multiple sclerosis (MS). Indeed, several lines of evidence including epidemiologic, preclinical, and clinical data suggest that reduced vitamin D levels and/or dysregulation of vitamin D homeostasis is a risk factor for the development of multiple sclerosis on the one hand, and that vitamin D serum levels are inversely associated with disease activity and progression on the other hand. However, these data are not undisputable, and many questions regarding the preventive and therapeutic capacity of vitamin D in multiple sclerosis remain to be answered. In particular, available clinical data derived from interventional trials using vitamin D supplementation as a therapeutic approach in MS are inconclusive and partly contradictory. In this review, we summarise and critically evaluate the existing data on the possible link between vitamin D and multiple sclerosis in light of the crucial question whether optimization of vitamin D status may impact the risk and/or the course of multiple sclerosis.

Historical changes of seasonal differences in the frequency of multiple sclerosis clinical attacks: a multicenter study

Previous papers show discordant patterns of monthly and seasonal differences in the frequency of multiple sclerosis relapses. Attacks are more often reported in spring and summer, but there are many variations, mainly as to summer peaks. This paper, an MSBase collaboration substudy, reports multiple series of relapses from 1980 to 2010, comparing ultradecennal trends of seasonal frequency of attacks in different countries. The MSBase international database was searched for relapses in series recording patient histories from 1980 up to 2010. The number of relapses by month was stratified by decade (1981-1990, 1991-2000, 2001-2010). Positive spring versus summer peaks were compared by odds ratios; different series were compared by weighted odds ratio (Peto OR). Decade comparison of the 1990s versus 2000s shows inversion of spring-summer peak (2000s = March; 1990s = July), significant in the whole group (Peto odds ratio = 1.31, CI = 1.10-1.56, p = 0.003) and in Salerno series (OR = 1.97, CI = 1.14-1.40). The global significance persisted also excluding Salerno series (Peto odds ratio = 1.25, CI = 1.04-1.50, p = 0.002). Multicentric data confirm a summer peak of relapses in the 1991-2000 decade, significantly different from the spring peak of 2001-2010. Seasonal frequency of relapses shows long-term variations, so that other factors such as viral epidemics might have more relevance than ultraviolet exposure.

Keeping cool: use of air conditioning by australians with multiple sclerosis

Despite the known difficulties many people with MS have with high ambient temperatures, there are no reported studies of air conditioning use and MS. This study systematically examined air conditioner use by Australians with MS. A short survey was sent to all participants in the Australian MS Longitudinal Study cohort with a response rate of 76% (n = 2,385). Questions included hours of air-conditioner use, areas cooled, type and age of equipment, and the personal effects of overheating. Air conditioners were used by 81.9% of respondents, with an additional 9.6% who could not afford an air conditioner. Regional and seasonal variation in air conditioning use was reported, with a national annual mean of 1,557 hours running time. 90.7% reported negative effects from overheating including increased fatigue, an increase in other MS symptoms, reduced household and social activities, and reduced work capacity. Households that include people with MS spend between 4 and 12 times more on keeping cool than average Australian households.

Warmer outdoor temperature is associated with worse cognitive status in multiple sclerosis

OBJECTIVE

Patients with multiple sclerosis (MS) have more clinical exacerbations and T2 lesion activity during warmer weather. The current study is the first to investigate whether outdoor temperature is related to cognitive status across patients with MS (cross-sectional analysis), and whether cognitive status fluctuates with changes in outdoor temperature within patients with MS (longitudinal analysis).

METHODS

For the cross-sectional analysis, 40 patients with MS and 40 healthy control (HC) subjects were recruited throughout the calendar year. Cognitive status (processing speed, memory) and outdoor temperature were recorded for the day of testing. We calculated partial correlations between cognitive status and temperature for patients with MS and HCs, controlling for demographic and disease variables. For the longitudinal analysis, cognitive status and outdoor temperature were recorded at baseline and 6-month follow-up in a separate sample of 45 patients with MS. We calculated the partial correlation between temperature and cognitive status at follow-up, controlling for baseline temperature and cognitive status (i.e., whether temperature changes are related to cognitive changes within patients with MS).

RESULTS

Cross-sectionally, warmer temperature was related to worse cognitive status in patients with MS (r(p) = -0.45, p = 0.006), not in HCs (r(p) = 0.00, p = 0.984). Longitudinally, increased outdoor temperature from baseline to follow-up was related to a decline in cognitive status within patients with MS (r(p) = -0.39, p = 0.010).

CONCLUSIONS

Cognitive status in patients with MS is worse on warmer days, consistent with a previously established link between heat and lesion activity. Our findings have implications for clinical trial planning, treatment, and lifestyle decisions. We discuss cognitive status as a potential marker of quiescent exacerbations.

Multiple sclerosis: long time modifications of seasonal differences in the frequency of clinical attacks

Previous papers show different patterns of seasonal distribution of multiple sclerosis attacks. This paper compares long-time modifications. Salerno MS registry (Southern Italy), was reviewed, including 189 patients, age onset 12-51 years (mean = 29.88, SD = 8.4), disease duration mean = 6.94 years (1-29), attacks mean = 4.5 (2-25, SD = 3.41). Data were stratified by decades. Number of events/month was analyzed by odds ratios and forecast modeling (ARIMA); means by ANOVA and post hoc tests, and correlations by multiple regression. We found 869 relapses: J = 72, F = 48, M = 122, A = 75, M = 68, Jn = 59, Jl = 81, A = 74, S = 63, O = 70, N = 72, D = 65. In 2001-2008 there was one significant peak (March); in 1991-2000 many (greatest = July), and in 1984-1990, one positive (June), one negative (April). Differences between 1990s and 2000s are significant. It is the first study addressing ultradecennal trends, and finding that the season distribution of MS attacks is significantly different: the study confirms frequency peaks in early spring and summer, but they are different in different decades. This significant ultra-decade difference might support hypotheses more linked to infections or toxic substances than to sunlight, UV, or similar.

Monthly variation of multiple sclerosis activity in the southern hemisphere: analysis from 996 relapses in Brazil

BACKGROUND AND PURPOSE

Seasonal variations of multiple sclerosis (MS) activity have been reported, however, most data come from studies in the northern hemisphere.

METHODS

We reviewed medical records of MS patients living in Campinas region, Brazil. The first symptoms' date was defined as the relapse month. Climatic information included UV radiation index, median temperature, rainfall, and humidity.

RESULTS

Two hundred and nine patients were included. The incidence of relapses was highest in January (11.2%) and December (10.4%) and lowest in November (5.7%) and October (7.0%) (P < 0.015). The months with highest incidence of relapses (December-January) had higher UV radiation index and humidity rates (P = 0.032 and 0.040, respectively).

CONCLUSION

Most exacerbations were in the spring/summer transition, which also showed higher UV radiation index and humidity rate. Along with other environmental factors, seasonal fluctuation contributes to MS activity.

Optic neuritis

AIMS

The aim of this study is to provide a clinical update on optic neuritis (ON), its association with multiple sclerosis (MS), and neuromyelitis optica (NMO).

METHODS

This study included a PubMed review of the literature written in the English language.

RESULTS

ON in adults is typically idiopathic or demyelinating, and is characterised by unilateral, subacute, painful loss of vision that is not associated with any systemic or other neurological symptoms. Demyelinating ON is associated with MS, and we review the key studies of ON including the ON treatment trial and several other MS treatment trials and NMO.

CONCLUSION

Acute demyelinating ON can occur in isolation or be associated with MS. Typical ON does not require additional evaluation other than cranial magnetic resonance imaging. NMO is likely a separate disorder from MS and the ON in NMO has a different treatment and prognosis.

METHODOLOGY

The authors conducted an English language search using Pubmed from the years 1964 to 2010 using the search terms 'ON', 'MS' and 'NMO'. The authors included original articles, review articles, and case reports, which revealed new aspects as far as epidemiology, histopathology, clinical manifestations, imaging, genetics, and treatment of ON. Titles were reviewed for topicality and full references were obtained. Letters to the editor, unpublished work, and abstracts were not included in this review.

The human microbiome in multiple sclerosis: pathogenic or protective constituents?

The human microbiome is comprised of commensal and pathogenic microorganisms, which exert diverse effects in close proximity to the site of intection as well as in remote tissues through immune-mediated mechanisms. Multiple infectious agents have been implicated in the pathogenesis of multiple sclerosis (MS) with variable findings depending on the agent, techniques, and disease phenotype. Herein, the contributions of individual infectious agents to MS and their effects on the immune and nervous systems are reviewed, focusing on herpes viruses, coronaviruses, retroviruses, and synchronic infections. While infectious agents are often assumed to be pathogenic, their effects might also be beneficial to the host in the long-term, depending on age and the type of immunogen/pathogen exposure, as proposed by the hygiene hypothesis. The human microbiome has potential impact on future diagnostic and therapeutic issues in MS.

Temporal relationship between environmental influenza A and Epstein-Barr viral infections and high multiple sclerosis relapse occurrence

BACKGROUND

Multiple sclerosis (MS) relapses have been associated with viral and bacterial infection epidemics in MS patients who have not used interferon.

OBJECTIVES

We studied whether environmental viral infections in the general population can be associated with increased MS relapse occurrence using retrospective data from 1986 to 1995 when interferons were not yet available.

METHODS

Logistic regression modelling was used to compare retrospectively the monthly relapse occurrence from 407 MS patients in Turku University hospital archives and data on ten different specifically diagnosed viral infection epidemics in the general population of Southwestern Finland from 1986 to 1995. The outcome was the odds ratio (OR) of very high relapse occurrence versus low relapse occurrence, or moderate versus low relapse occurrence.

RESULTS

After a peak in diagnosed influenza A cases in the general population, the MS relapse occurrence was 6.5 times more likely to be very high (95% CI 1.8-24.0) and 7.1 times more likely to be moderately high (95% CI 1.5-33.2). An increase in MS relapse counts also followed Epstein-Barr virus (EBV) infections (OR 4.4, 95% CI 1.3-15.1), but we found no significant association with adenovirus infections and MS relapses. The MS relapse occurrence was lowest in the summer months July-August (Chi-square test, p<0.01).

CONCLUSIONS

Our findings suggest that influenza A and EBV viral infections in the general population are associated with a higher occurrence of exacerbations in MS patients, and thus environmental infection data should be included in epidemiological models on MS relapses.

Optic neuritis incidence is increased in spring months in patients with asymptomatic demyelinating lesions

Optic neuritis (ON) patients can be divided into two groups based on the presence or absence of asymptomatic demyelinating lesions (ADLs) on brain MRI. The presence of ADLs is associated with an increased risk of progression to clinically definite multiple sclerosis (CDMS). The clinical data and brain MRI of 110 patients with acute unilateral ON were analyzed. Patients with ADLs had a significantly higher incidence of ON in spring months as compared with patients with no ADLs (p = 0.0024). Increased incidence of ON in spring months was seen in patients with ADLs whether or not they were diagnosed with CDMS on follow-up.