Multiple sclerosis in the far north--incidence and prevalence in Nordland County, Norway, 1970-2010

Increasing age of multiple sclerosis onset from 1920 to 2022: a population-based study

OBJECTIVE

To study the age at onset of relapsing-remitting multiple sclerosis (RRMS) during the past century.

METHODS

This is a population-based cohort study of persons diagnosed with RRMS in Hordaland, Møre, and Romsdal counties, Western Norway, from 1920 to 2022. Individual patient data were available and assessed from previously conducted prevalence and incidence studies in addition to hospital records up until October 31, 2022. Participants were categorized according to onset period and analyzed for temporal trends in age at onset, time from onset to diagnosis, and distribution of onset over time.

RESULTS

We identified 3364 persons with confirmed RRMS. The mean age at onset significantly increased (p < 0.001) throughout the study period, despite a decrease in time from symptom onset to diagnosis (p < 0.001). The proportion of persons with MS onset after 50 years of age increased from 2.6% before 1970 to 11.9% after 2010. We also found a trend toward a bimodal distribution of age at onset that peaked at around 30 years and 40-45 years of age in the latest period.

CONCLUSION

Age at onset of MS significantly increased throughout the study period. This was mainly due to an increasing number of persons with MS, predominantly female, experiencing onset after 40-45 years of age. This bimodal distribution could indicate different susceptibility periods of MS or changes in exposure to risk factors during the observation period.

Molecular insights into the pathogenic impact of vitamin D deficiency in neurological disorders

Neurological disorders are the major cause of disability, leading to a decrease in quality of life by impairing cognitive, sensorimotor, and motor functioning. Several factors have been proposed in the pathogenesis of neurobehavioral changes, including nutritional, environmental, and genetic predisposition. Vitamin D (VD) is an environmental and nutritional factor that is widely distributed in the central nervous system's subcortical grey matter, neurons of the substantia nigra, hippocampus, thalamus, and hypothalamus. It is implicated in the regulation of several brain functions by preserving neuronal structures. It is a hormone rather than a nutritional vitamin that exerts a regulatory role in the pathophysiology of several neurological disorders, including Alzheimer's disease, Parkinson's disease, epilepsy, and multiple sclerosis. A growing body of epidemiological evidence suggests that VD is critical in neuronal development and shows neuroprotective effects by influencing the production and release of neurotrophins, antioxidants, immunomodulatory, regulation of intracellular calcium balance, and direct effect on the growth and differentiation of nerve cells. This review provides up-to-date and comprehensive information on vitamin D deficiency, risk factors, and clinical and preclinical evidence on its relationship with neurological disorders. Furthermore, this review provides mechanistic insight into the implications of vitamin D and its deficiency on the pathogenesis of neurological disorders. Thus, an understanding of the crucial role of vitamin D in the neurobiology of neurodegenerative disorders can assist in the better management of vitamin D-deficient individuals.

Reply to the Letter to the Editor by Sipila, Jussi

This a Reply to the Letter to the Editor by Sipila, Jussi regarding our article titled: James LM, Georgopoulos AP. High Correlations Among Worldwide Prevalences of Dementias, Parkinson’s Disease, Multiple Sclerosis, and Motor Neuron Diseases Indicate Common Causative Factors. Neurosci Insights. 2022 Aug 8;17:26331055221117598. doi: 10.1177/26331055221117598.

Autoreactive lymphocytes in multiple sclerosis: Pathogenesis and treatment target

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) characterized by destruction of the myelin sheath structure. The loss of myelin leads to damage of a neuron’s axon and cell body, which is identified as brain lesions on magnetic resonance image (MRI). The pathogenesis of MS remains largely unknown. However, immune mechanisms, especially those linked to the aberrant lymphocyte activity, are mainly responsible for neuronal damage. Th1 and Th17 populations of lymphocytes were primarily associated with MS pathogenesis. These lymphocytes are essential for differentiation of encephalitogenic CD8⁺ T cell and Th17 lymphocyte crossing the blood brain barrier and targeting myelin sheath in the CNS. B-lymphocytes could also contribute to MS pathogenesis by producing anti-myelin basic protein antibodies. In later studies, aberrant function of Treg and Th9 cells was identified as contributing to MS. This review summarizes the aberrant function and count of lymphocyte, and the contributions of these cell to the mechanisms of MS. Additionally, we have outlined the novel MS therapeutics aimed to amend the aberrant function or counts of these lymphocytes.

Apparent changes in the epidemiology and severity of multiple sclerosis

Multiple sclerosis (MS) is an immunological disease that causes acute inflammatory lesions and chronic inflammation in the CNS, leading to tissue damage and disability. As awareness of MS has increased and options for therapy have come into use, a large amount of epidemiological data have been collected, enabling studies of changes in incidence and disease course over time. Overall, these data seem to indicate that the incidence of MS has increased, but the course of the disease has become milder, particularly in the 25 years since the first disease-modifying therapies (DMTs) became available. A clear understanding of these trends and the reasons for them is important for understanding the factors that influence the development and progression of MS, and for clinical management with respect to prevention and treatment decisions. In this Review, we consider the evidence for changes in the epidemiology of MS, focusing on trends in the incidence of the disease over time and trends in the disease severity. In addition, we discuss the factors influencing these trends, including refinement of diagnostic criteria and improvements in health-care systems that have increased diagnosis in people with mild disease, and the introduction and improvement of DMT.

Temporal trends of incidence and prevalence of multiple sclerosis in Razavi Khorasan Province, Northeast Iran

OBJECTIVES

The prevalence of multiple sclerosis (MS) in the Persian Gulf countries has been significantly increasing during the past decades. This study was conducted for investigating the prevalence and incidence of MS in Northeast Iran (Khorasan Razavi province).

METHODS

This cross-sectional study was conducted during 1 January 1988 and 23 September 2018. All patients with a clinically definite diagnosis of MS according to the McDonald criteria (2005) and MRI along with the medical diagnosis, recorded in the Khorasan MS society, were considered for calculation of crude and age-standardized prevalence, and incidence rates of MS. The periodic incidence rates were calculated based on the year of onset of MS. Also, we calculated gender ratios for prevalence and incidence rates.

RESULTS

The mean age-standardized prevalence and incidence rates of MS in the Khorasan Razavi were 8.69 (95% CI 8.05-9.41) per 100,000 (3.99 (95% CI 3.39-4.74) for males, 13.49 (95% CI 12.37-14.76) for females). Age-standardized prevalence was 48.87 (95% CI 48.37-49.35) per 100,000 (22.47 (95% CI 22.01-22.93) for males, 75.65 (95% CI 74.80-76.51) for females). Also, the mean incidence and prevalence for Mashhad County as capital of province were 11.38 and 59.09 per 100,000 populations, respectively. The female/male ratio was 3.33 for all age groups.

CONCLUSION

Our results showed that this region is a high-risk area for MS like central region of Iran. Our results revealed that the prevalence and incidence of MS in the study area have increased during the recent decades with a sharp slope.

Nordic clues for uncovering the aetiology of Multiple Sclerosis

Our understanding of the etiology of multiple sclerosis (MS) is inadequate to effectively combat the increasing incidence and prevalence of the disease. Environmental factors are of crucial importance but more information about them is needed. Recent results of incidence trends over several decades in Denmark, Norway and Finland provide suggestions for further studies on the subject. Since incidence trends show marked differences by region and sex taking these factors into account when investigating birth cohort exposures could provide important new insights. Exposures during the first 15 years of life should be prioritized. International and multidisciplinary co-operation is needed.

Geography of hospital admissions for multiple sclerosis in Greece

BACKGROUND

Multiple sclerosis (MS) is the 2^nd most common, disability causing neurological disorder in young adults, known for its differences in prevalence according to geographical position. Data on MS epidemiology is lacking in Greece. In this study, we aimed to examine the pattern of MS related hospital admissions in Greece and analyze their spatial distribution. Data for hospital admissions due to MS was obtained from the Hellenic Statistical Authority (ELSTAT) database and they were available from 1999 to 2012.

METHODS

We used the proportional hospitalization ratio (PHR) which was age and sex adjusted according to hospitalizations of Greek population, in order to calculate the ratio between hospitalizations in each regional unit (RU) and hospitalizations of national population. PHR was calculated for each RU, which is categorized as level 3 based on the Nomenclature of Territorial Units for Statistics (NUTS level 3). The classification of MS was based on International Classification of Diseases, Ninth Revision (ICD-9), code 340. Descriptive analysis was conducted to understand the epidemiological characteristics and time series analysis was used to investigate the trend of annual PHR's values during the study period. Global spatial autocorrelation analysis was conducted to assess spatial homogeneity of MS across the country. Moreover, local spatial autocorrelation analysis was performed using the LISA statistic to detect any potential clusters of similar values. Finally, multiple linear regression was conducted to examine correlations between PHR and latitude.

RESULTS

Over the 14-year period the number of hospitalizations increased while the proportion of hospitalizations remained higher for females compared to males, as well as for the 25-44 year age group. RUs that appeared to be most affected included Evros with a sex- and age- adjusted PHR of 2.00 (95%CI: 1.89-2.10), Larisa with a PHR of 1.74 (95%CI: 1.67-1.81) and Chios with a PHR of 1.77 (95%CI: 1.60-1.95). The least affected RU was Arkadia with a PHR of 0.29 (95%CI: 0.24-0.36).

CONCLUSION

In this study we present a rise in hospital admissions related to MS over a 14-year period, possibly indicating a parallel rise in incidence. A combinational analysis of the number of hospitalizations along with incidence studies could be further performed to be used to design public health interventions.

Prevalence of multiple sclerosis in rural and urban districts in Telemark county, Norway

OBJECTIVE

To explore the trends in prevalence and incidence of multiple sclerosis (MS) in Telemark, Norway (latitude 58.7-60.3˚N), over the past two decades, with focus on differences between rural and urban areas.

METHODS

Data from all patients with a confirmed diagnosis of MS in Telemark since 1993 were prospectively recorded and collected in a retrospective chart review. Prevalence estimates on January 1^st 1999, 2009 and 2019, and incidence rates at five-year intervals between 1999 and 2018 were calculated and all results were adjusted to the European Standard Population. The study population was divided into urban and rural residency using a Norwegian governmental index.

RESULTS

We registered 579 patients with MS in Telemark between 1999 and 2019. The adjusted prevalence estimates for January 1^st 1999, 2009 and 2019 were 105.8/10⁵, 177.1/10⁵ and 260.6/10⁵, respectively. In 2019, the prevalence estimates were 250.4/10⁵ in urban and 316.2 /10⁵ in rural areas. Between 1999 and 2018, the yearly incidence increased from 8.4/10⁵ to 14.4/10⁵.

CONCLUSIONS

The prevalence of MS in Telemark is among the highest ever reported in Norway, consistent with an increasing incidence in the county over the past twenty years. The even higher prevalence in the rural areas is unlikely to be explained by possible risk factors like latitude, exposure to sunlight and diet. Further studies on differences between urban and rural areas are required to reveal possible new risk factors.

High incidence and prevalence of MS in Møre and Romsdal County, Norway, 1950-2018

Objective

To determine prevalence and longitudinal trends in incidence of MS in Møre and Romsdal County, Western Norway, from 1950 to 2018.

Methods

Retrospective longitudinal population-based observational study. All patients diagnosed, or living, with MS in Møre and Romsdal were identified as incident or prevalent cases from local, regional, and national sources. We compiled the data in the Norwegian Multiple Sclerosis Registry and Biobank and used the aggregated data set to calculate incidence and prevalence rates using population measures obtained from Statistics Norway.

Results

On January 1, 2018, the estimated prevalence was 335.8 (95% CI, 314.1–358.5) per 100,000 inhabitants, with a female:male ratio of 2.3. From 1950 through 2017, we observed a considerable (p < 0.001) increase in average annual incidence rates from 2.1 (95% CI, 1.3–3.3) to 14.4 (95% CI, 11.9–17.3) per 100,000. From 2005 through 2017, the incidence among women increased from 17.1 (95% CI, 14.0–20.7) to 23.2 (95% CI, 18.7–28.5) per 100,000, whereas the incidence among men declined from 10.3 (95% CI, 7.9–13.2) to 5.9 (95% CI, 3.4–8.8) per 100,000.

Conclusion

Møre and Romsdal County in Western Norway has the highest prevalence of MS reported in Norway. The incidence has steadily increased since 1950, and during the latest 15 years, we observed opposing trends in sex-specific incidence rates.

A systematic review of oral health in people with multiple sclerosis

OBJECTIVES

Despite more than 25 years of research focused on this topic, it remains unclear whether people with multiple sclerosis are more likely to present with oral health problems. The aim of this study was to provide the first systematic review of this literature.

METHODS

A literature search for studies focused on oral health and multiple sclerosis was conducted using PRISMA guidelines. Electronic databases (PubMed, Scopus, Web of Science, MEDLINE and CINAHL) were searched up until February 2019. Two independent coders extracted data, and study quality graded using the Newcastle-Ottawa Scale (NOS).

RESULTS

From 1281 articles identified, 17 met all the eligibility criteria. Of the seventeen studies, more than half included a nonclinical control group, and the majority were observational studies. The included studies were of poor to moderate quality. Taken together, the results provided only very limited evidence that people with multiple sclerosis are more likely to present with dental caries and gingival disease. There was suggestive evidence that people with multiple sclerosis may be at higher risk of periodontal disease and present with poorer oral hygiene, and moderate evidence for an association between multiple sclerosis and temporomandibular disorders.

CONCLUSIONS

This systematic review provides evidence of an association between multiple sclerosis and at least some oral health problems. When temporomandibular disorders and periodontal status specifically have been assessed, most studies provide evidence of an association with multiple sclerosis. However, this review also clearly highlights the need for further, high-quality studies in this area.

Validation of the multiple sclerosis diagnosis in the Norwegian Patient Registry

BACKGROUND

Health registries may yield important data for epidemiological studies. However, in order to be a valuable source for information, the registered data have to be correct.

OBJECTIVES

The aim of the study was to validate data from the Norwegian Patient Registry (NPR) regarding multiple sclerosis (MS).

MATERIALS AND METHODS

We obtained data on individuals residing in Nordland County and registered with a MS diagnosis in the NPR or in local hospital records. The NPR data included a unique 11-digit personal identity number that made it possible to identify the individuals medical records. For each individual registered with MS in the NPR, the hospital record was scrutinized in order to confirm or rule out the diagnosis.

RESULTS

In Nordland County, 657 individuals had MS 1 January 2017. Of these, 637 were recorded with a correct diagnosis of MS in the NPR, while 59 were recorded incorrectly. Incorrect registration was due to a diagnosis that did not fulfill the diagnostic criteria, later investigation had ruled out MS or it was an error in the diagnostic code registration process. Twenty individuals were not registered with MS in the NPR. These were patients who received their diagnosis before data in the NPR were person identifiable (before 2008), and who later had no MS-registered contact with public specialist healthcare services. The sensitivity is 0.97, and the positive predictive value is 0.92.

CONCLUSION

Data from the NPR gave a good estimate of the occurrence of MS, but nearly one in 10 registered diagnoses was not correct.

The Interaction between Viral and Environmental Risk Factors in the Pathogenesis of Multiple Sclerosis

Multiple sclerosis (MS) is a chronic debilitating inflammatory disease of unknown ethology targeting the central nervous system (CNS). MS has a polysymptomatic onset and is usually first diagnosed between the ages of 20–40 years. The pathology of the disease is characterized by immune mediated demyelination in the CNS. Although there is no clinical finding unique to MS, characteristic symptoms include sensory symptoms visual and motor impairment. No definitive trigger for the development of MS has been identified but large-scale population studies have described several epidemiological risk factors for the disease. This list is a confusing one including latitude, vitamin D (vitD) levels, genetics, infection with Epstein Barr Virus (EBV) and endogenous retrovirus (ERV) reactivation. This review will look at the evidence for each of these and the potential links between these disparate risk factors and the known molecular disease pathogenesis to describe potential hypotheses for the triggering of MS pathology.

A Systematic Assessment of Prevalence, Incidence and Regional Distribution of Multiple Sclerosis in Bavaria From 2006 to 2015

Introduction: Worldwide, incidence and prevalence of multiple sclerosis (MS) have increased over the last decades. We present a systematic epidemiological study with recent prevalence and incidence rates of MS in Bavaria. Methods: Incidence and prevalence of MS stratified by gender, age groups and region were analyzed by data records from 2006 to 2015 of more than 10 million people insured by the Bavarian Association of Statutory Health Insurance Physicians. Official statistics of the German Federal Ministry of Health provided the size of the general population. Future prevalence was estimated with a predictive model. Results: From 2006 to 2015 prevalence of MS in Bavaria increased from 171 per 100,000 to 277 per 100,000, while incidence rates remained relatively stable (range 16-18 per 100,000 inhabitants with a female to male ratio between 2.4:1 and 2:1). Incidence and prevalence were higher in urban than urbanized and rural areas. The prevalence is expected to increase to 374 per 100,000 in 2040 with the highest prevalence rates between 50 and 65 years. Conclusion: The prevalence of MS in Bavaria is among the highest worldwide and will further rise over the next two decades. This demonstrates a need to strengthen healthcare provision systems due to the increasing numbers of particularly older patients with MS in the future.

Epidemiology of Multiple Sclerosis in Torbat-e Heydarieh (Northeast of Iran) during 1982-2016

It was believed that the risk of multiple sclerosis (MS) is associated with latitude gradient. Due to the increasing prevalence of MS in some areas around the equator such as Iran, this theory has been criticized in recent years. Since the distribution of MS in Iran is not uniform, this study was designed to describe the prevalence and incidence of MS in the northeastern area of Iran. The patients were registered in the MS center of Torbat-e Heydarieh County and all of them were living in this county during the study period (during 1 January 1982 to 31 December 2016). Data of the patients were extracted from their files in the MS center. Because of the long-term span of this study, we used different diagnosis criteria according to the files of the patients to proven case missing. In addition, population data were obtained from the website of Statistical Centre of Iran. The total number of the MS patients during the study period was 110 cases. The prevalence of the disease at the beginning and end of the research period was 0.33 (95% CI, 0.008-1.85) and 30.48 (95% CI, 25.25-37.03) patients per 100,000 persons, respectively. The incidence of the disease in this 36-year period was 1.41 (95%CI, 1.15-1.69) patients per 100,000 persons. The average age of the patients was 35.01 (95% CI, 33.37-36.65) years and the female to male ratio was 2.8:1. The prevalence of MS has been increased in the 36-year period in Torbat-e Heydarieh, especially for women. More epidemiological studies are needed to determine the factors affecting this increasing trend.

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.

Which Environmental Factor Is Correlated with Long-Term Multiple Sclerosis Incidence Trends: Ultraviolet B Radiation or Geomagnetic Disturbances?

Background

Insufficient received ultraviolet B radiation (UV) is regarded as the main environmental risk factor (RF) for MS in vitamin D deficiency hypothesis. Nevertheless, geomagnetic disturbance (GMD) has also been proposed as a potential trigger for MS in GMD hypothesis. The aim of this study was to investigate which of these mentioned RF is correlated with long-term ultradecadal MS incidence.

Methods

After a systematic search, long-term incidence reports of the United Kingdom (UK), Denmark, Tayside County, Nordland County, the Orkney, and Shetland Islands were selected for this retrospective time-series study. Possible lead-lag relationships between MS incidence, GMD, and UV were evaluated by cross-correlation analysis.

Results

Significant positive correlations between GMD and MS incidence were seen in Tayside County (at lag of 2 years: r_S = 0.38), Denmark (peak correlation at lag of 2 years: r_S = 0.53), and UK (at lag of 1 year: r_S = 0.50). We found a positive correlation between received UV and MS incidences in the Nordland at lag of 1 year (r_S = 0.49).

Conclusion

This study found significant positive correlations between alterations in GMD with alterations in long-term MS incidence in three out of six studied locations and supports the GMD hypothesis. The observed significant correlation between MS and UV is positive; hence it is not supportive for UV related vitamin D deficiency hypothesis.

Vitamin D in the prevention, prediction and treatment of neurodegenerative and neuroinflammatory diseases

Vitamin D research has gained increased attention in recent times due to its roles beyond bone health and calcium homeostasis, such as immunomodulation. In some parts of the brain and on immune cells, vitamin D hydroxylating enzymes and its receptors are located. Epidemiological evidence demonstrates that deficiency of Vitamin D is relevant for disease risk and course in multiple sclerosis (MS) and presumably also in neuromyelitis optica spectrum disorders (NMOSD), Parkinson's disease (PD), and Alzheimer's disease (AD). Although the exact mechanism underlying vitamin D effects in these diseases remains widely unexplored, human and animal studies continue to provide some hints. While the majority of vitamin D researchers so far speculate that vitamin D may be involved in disease pathogenesis, others could not show any association although none have reported that sufficient vitamin D worsens disease progression. The studies presented in this review suggest that whether vitamin D may have beneficial effects in disease course or not, may be dependent on factors such as ethnicity, gender, diet, vitamin D receptor (VDR) polymorphisms and sunlight exposure. We here review the possible role of vitamin D in the pathogenesis and disease course of MS, NMOSD, PD, and AD and potential therapeutic effects of vitamin D supplementation which may be relevant for predictive, preventive, and personalized medicine. We suggest areas to consider in vitamin D research for future studies and recommend the need to supplement patients with low vitamin D levels below 30 ng/ml to at least reach sufficient levels.

High prevalence and increasing incidence of multiple sclerosis in the Norwegian county of Buskerud

OBJECTIVES

The objective was to investigate the incidence of multiple sclerosis (MS) as well as estimate the prevalence as of 1 January 2014 in the southeastern Norwegian county of Buskerud.

MATERIALS AND METHODS

All patients with MS living in Buskerud county in Norway between 01 January 2003 and 01 January 2014 were identified. Point prevalence of MS was identified on 01 January 2014.

RESULTS

We found a prevalence of 213.8 (95% CI 196.4-231.1) per 100 000. The sex ratio was 2.2:1 with a female prevalence of 293.4 (95% CI 264.7-322.2) per 100 000 and a male prevalence of 134.7 (95% CI 115.3-154.2) per 100 000. About 82% of our MS population had a confirmed relapsing-remitting MS at disease onset, while 16.8% had primary progressive MS. The mean annual incidence between 2003 and 2013 was 11.8 (95% CI 10.6-13.1) per 100 000.

CONCLUSION

This study shows a high incidence of MS in Buskerud county in southeastern Norway, and the incidence may still be on the rise. We found a relatively high prevalence of MS in our population, although this does correspond with the recently published national data. Further studies investigating both changes in incidence and possible factors causing the increasing incidence are warranted.

Level of education and multiple sclerosis risk over a 50-year period: Registry-based sibling study

BACKGROUND

The conflicting results from studies on socioeconomic status (SES) and multiple sclerosis (MS) risk might be due to a change in the distribution of environmental exposures over time or to methodological limitations in previous research.

OBJECTIVE

To examine the association between SES and MS risk during 50 years.

METHODS

We included patients registered in Norwegian MS registries and prevalence studies born between 1930 and 1979, and identified their siblings and parents using the Norwegian Population Registry. Information on education was retrieved from the National Education Registry, categorized into four levels (primary, secondary, undergraduate and graduate) and compared in patients and siblings using conditional logistic regression.

RESULTS

A total of 4494 MS patients and 9193 of their siblings were included in the analyses. Level of education was inversely associated with MS risk ( p trend < 0.001) with an odds ratio (OR) of 0.73 (95% confidence interval (CI): 0.59-0.90) when comparing the highest and lowest levels. The effect estimates did not vary markedly between participants born before or after the median year of birth (1958), but we observed a significant effect modification by parental education ( p = 0.047).

CONCLUSION

Level of education was inversely associated with MS risk, and the estimates were similar in the earliest and latest birth cohorts.