Characterization of the Increase in Narcolepsy following the 2009 H1N1 Pandemic in Sweden.

(1) Background: In the context of the H1N1 pandemic and the Pandemrix vaccination campaign, an increased number of narcolepsy cases were noted in several countries. In Sweden, this phenomenon was attributed to the effect of the Pandemrix vaccination in the first place. Studies from China indicated that narcolepsy could occur as a consequence of the H1N1 infection itself. We performed an analysis of the increase, with a specific interest in age and sex distribution. We also aimed to validate the origin of the excess cases, post hoc. (2) Methods: Data for narcolepsy patients (ICD code G 47.4, both type 1 and type 2) distributed by sex and age at 5-year intervals, annually between 2005 and 2017, were retrieved from the National Patient Register. Information on the total population was collected from the Swedish Population Register. (3) Results: The number of narcolepsy cases increased markedly from 2009 to 2014 compared to the period before 2009. A particular increase in 2011 among children and teenagers was observed. The sex ratio did not change significantly during the study period. (4) Conclusions: Our results support an association between the increased prevalence of narcolepsy cases and Pandemrix vaccination, but the effect of the virus itself cannot be ruled out as a contributing factor.

Narcolepsy treatment in Sweden: An observational study.

OBJECTIVES: To describe the pharmacological treatments (2005-2017) and the healthcare utilization (1997-2016) for patients with narcolepsy in Sweden in order to create a framework for future organizational and economic analyses. MATERIAL & METHODS: Patients of all ages with a diagnosis of narcolepsy registered in the National Patient Registry in specialist care in Sweden were included and information on treatments for narcolepsy was retrieved from The Swedish Prescribed Drug Register. RESULTS: We collected 2508 patients with narcolepsy, 43,3% men and 56,7% women and 47,9% were prescribed modafenil, 33,8% metylphenidate and 26,2% amphetamine. In total, 3817 treatments were initiated. Patients treated with amphetamine had a higher mean age. More women than men used modafinil, methylphenidate, amphetamine and antidepressants. The narcolepsy population had more outpatient than inpatient healthcare. Patients treated with sodium oxybate had more outpatient visits than other narcolepsy patients, before and during treatment (p = .00). CONCLUSIONS: This study gives valuable information on pharmaceutical treatments and healthcare utilization for patients with narcolepsy and can be used to estimate the healthcare cost in the future. Patients with sodium oxybate treatment had more outpatient visits than other patients before and during treatment which may be due to the need to monitor potentially severe side-effects or may indicate that patients with sodium oxybate treatment have a severe disease. The number of included patients was less than expected; however, this may depend on patients escaping our collection of data, which does not contain information from primary care.

Validating the diagnosis of multiple sclerosis using Swedish administrative data in Värmland County.

OBJECTIVES: Multiple sclerosis (MS) is a chronic neurodegenerative disease of the central nervous system. Identifying MS at the population level is important for disease surveillance and allocation of resources. The Swedish National Patient Registry (NPR) has been used to study the epidemiology of MS, but the accuracy of this resource is not known. We aimed to validate a definition of MS using the Swedish NPR in Värmland County using a longitudinal cohort design. MATERIALS AND METHODS: Data were extracted from the NPR, the Total Population Register, the Swedish MS Register, and medical records for the years 2001-2013. Fifteen algorithms of hospitalizations and clinic visits for MS were developed and compared with findings in medical records, which acted as the "gold standard" definition. Sensitivity, specificity, and positive and negative predictive values (PPV, NPV) were estimated. RESULTS: Of 805 eligible persons identified in the NPR, 763 had MS (94.8%) according to medical records. Of these, 544 (71.3%) were also registered in the SMSreg. The case definition that had a well-balanced sensitivity and specificity required three or more clinic or hospital visits for MS (sensitivity of 85.3% (95% CI: 82.6-87.8) and specificity of 81.0% (95%CI: 65.9-91.4). CONCLUSIONS: Multiple case definitions with high sensitivity and moderate specificity were found, suggesting that the NPR can be used to accurately identify persons with MS.

Multiple sclerosis and COVID-19: The Swedish experience.

The COVID-19 pandemic has brought challenges for healthcare management of patients with multiple sclerosis (MS). Concerns regarding vulnerability to infections and disease-modifying therapies (DMTs) and their complications have been raised. Recent published guidelines on the use of DMTs in relation to COVID-19 in MS patients have been diverse between countries with lack of evidence-based facts. In Sweden, there exists a particular interest in anti-CD20 therapy as a possible risk factor for severe COVID-19 due to the large number of rituximab-treated patients off-label in the country. Rapid responses from the Swedish MS Association (SMSS) and the Swedish MS registry (SMSreg) have resulted in national guidelines on DMT use for MS patients and implementation of a COVID-19 module in the SMSreg. Recently updated guidelines also included recommendations on COVID-19 vaccination with regard to the different DMTs. Social distancing policies forced implementation of telemedicine consultation to replace in-person consultations as part of regular MS health care. Patient-reported outcome measures (PROMs) in SMSreg have been useful in this respect. This paper reports our experiences on the progress of national MS health care during the COVID-19 pandemic, in addition to offering an overview of the present scientific context.

Physical activity is associated with a decreased multiple sclerosis risk: The EnvIMS study.

BACKGROUND: The lifestyle factors smoking and obesity have been associated with the risk of multiple sclerosis (MS). Physical activity (PA) may also be of importance. OBJECTIVE: To examine the association between PA and MS risk in Italy, Norway, and Sweden and to evaluate the possible influence by established risk factors. METHODS: In this case-control study, 1904 cases and 3694 controls were asked to report their average weekly amounts of light and vigorous PA during adolescence on a scale ranging from none to more than 3 hours activity. We used logistic regression to estimate odds ratios (ORs) and 95% confidence intervals (CIs) and adjusted for potential confounders. RESULTS: Vigorous PA was inversely associated with MS risk in the pooled analysis ( p-trend < 0.001) with an age- and sex-adjusted OR of 0.74 (95% CI: 0.63-0.87) when comparing the highest and lowest levels. Adjusting for outdoor activity, infectious mononucleosis, body size, and smoking yielded similar results. The association was present in all countries and was not affected by exclusion of patients with early disease onset. Light PA was not associated with the risk of MS. CONCLUSION: Our findings suggest that vigorous PA can modify the risk of developing MS independent of established risk factors.

Negative interaction between smoking and EBV in the risk of multiple sclerosis: The EnvIMS study.

BACKGROUND: Results from previous studies on a possible interaction between smoking and Epstein-Barr virus (EBV) in the risk of multiple sclerosis (MS) are conflicting. OBJECTIVES: To examine the interaction between smoking and infectious mononucleosis (IM) in the risk of MS. METHODS: Within the case-control study on Environmental Factors In Multiple Sclerosis (EnvIMS), 1904 MS patients and 3694 population-based frequency-matched healthy controls from Norway, Italy, and Sweden reported on prior exposure to smoking and history of IM. We examined the interaction between the two exposures on the additive and multiplicative scale. RESULTS: Smoking and IM were each found to be associated with an increased MS risk in all three countries, and there was a negative multiplicative interaction between the two exposures in each country separately as well as in the pooled analysis ( p = 0.001). Among those who reported IM, there was no increased risk associated with smoking (odds ratio (OR): 0.95, 95% confidence interval (CI): 0.66-1.37). The direction of the estimated interactions on the additive scale was consistent with a negative interaction in all three countries (relative excess risk due to interaction (RERI): -0.98, 95% CI: -2.05-0.15, p = 0.09). CONCLUSION: Our findings indicate competing antagonism, where the two exposures compete to affect the outcome.

New data identify an increasing sex ratio of multiple sclerosis in Sweden.

BACKGROUND: An increasing women-to-men ratio in later birth cohorts of patients with multiple sclerosis (MS) has been observed in several populations and has been hypothesised to be due to one or several environmental factors of importance for disease aetiology. However, in a study based on data from the Swedish MS registry (SMSreg) this ratio was recently reported to be rather stable during the 20(th) century. OBJECTIVE: The purpose of this study was to reinvestigate the women-to-men ratio in Sweden based on data from all available data sources, including deceased patients. METHOD: We combined data from the SMSreg with data from national patient registers. RESULTS: In total we obtained information on 19,510 MS patients born 1931-1985, 13,321 women and 6189 men. The women-to-men ratio increased from 1.70 for patients born in the 1930s to 2.67 for patients born in the 1980s. When comparing the coverage of SMSreg to the full data set, a significantly higher proportion of women born 1931-1935 compared to men born in the same period were found in SMSreg, resulting in a sampling bias hiding the increasing sex ratio in the full material. CONCLUSION: The women-to-men ratio in MS has increased in Sweden during the 20(th) century similarly to observations in other western countries.

Sex ratio of multiple sclerosis in the National Swedish MS Register (SMSreg).

BACKGROUND: Sex ratio in multiple sclerosis has been reported from several geographical areas. The disease is more common in women. In Europe the female-to-male ratio varies from 1.1 to 3.4. A recent study from Canada has reported a significant increase, with time, in female-to-male ratio in multiple sclerosis over the last 100 years. OBJECTIVE: The aim of this study was to analyse any change in sex ratio in multiple sclerosis in the Swedish population. METHODS: Data from the Swedish MS Register and data from the Swedish National Statistics Office were used to estimate sex ratio by year of birth and year of onset. RESULTS: In the analysis of sex ratio by year of birth there were 8834 patients (6271 women and 2563 men) born between 1931 and 1985. The mean women-to-men ratio was 2.62. No clear trend was noted for the women-to-men ratio by year of birth (Spearman's rho = 0.345, p = 0.298, n = 11). The number of patients analysed by year of onset was 9098 during the time period 1946 until 2005. The mean women-to-men ratio was 2.57. No significant change in women-to-men ratio (Spearman's rho = -0.007, p = 0.983, n = 12) with time was observed. CONCLUSION: There is no evidence for an increasing women-to-men ratio with time amongst Swedish multiple sclerosis patients.

Mortality statistics for multiple sclerosis and amyotrophic lateral sclerosis in Sweden.

BACKGROUND: Multiple sclerosis (MS) and amyotrophic lateral sclerosis (ALS) are chronic neurologic diseases for which distinct explanations of the pathogenesis are lacking. Two large Swedish register studies have rather unexpectedly detected a correlation between MS and ALS. The aim of this study was to investigate if an association between ALS and MS could be demonstrated as has been shown earlier. MATERIAL AND METHODS: Data on mortality from ALS and MS, 1990-2010, were collected from the Swedish National Statistics Office. In all there were 5,696 deaths due to ALS and 3,941 deaths due to MS. Age- and sex-adjusted mortality rates were calculated. RESULTS: There was no correlation between the mortality rates of ALS and MS in the 21 counties of Sweden for the period 1990-2010 (Spearman's rho = -0.052; p = 0.822; n = 21). The national mean mortality rate for ALS throughout the period of 1990-2010 was 2.98 per 100,000 person-years (95% CI 2.87-3.08). For MS the national mean mortality rate was 2.04 per 100,000 person-years (95% CI 1.95-2.12). CONCLUSION: This study did not confirm the previously shown association between MS and ALS in Sweden.

An ecological study of industry in a high-risk region of multiple sclerosis.

The county of Värmland, Sweden, has shown a high frequency of multiple sclerosis in several investigations. It has been presented in three studies; a period prevalence study in 1925-1934, a mortality study during 1952-1992 and a prevalence investigation in 2002. The aim of this study was to investigate the pattern of industry in this high-risk area for multiple sclerosis. The three investigations were correlated with industry in 1913 and in the 1950s, all analyzed by the Kruskall-Wallis test. Select industries from wood-pulp, paper and iron/mechanical sectors were tested also in whole Sweden. The Spearman rank correlation was used for these data and forestry data in Värmland. In Värmland, industrial data from 1913 revealed that large sawmills were associated with the period prevalence in 1925-1934 and there was a possible correlation with the prevalence for 2002. Wood-pulp factories showed a possible association with the prevalence 1925-1934 and the mortality 1952-1992. Some industries in the 1950s were correlated with the prevalence 2002. Wood and paper industries in Sweden 1913 showed an association with the MS mortality 1952-1992. In summary, data on MS prevalence in Värmland and mortality both in Värmland and all Sweden from the past 100 years suggest an association with wood-related industries in 1913 and in the 1950s, whereas no consistent association was found for other industries.

High prevalence of multiple sclerosis in the Swedish county of Värmland.

Previous epidemiological studies have indicated that the county of Värmland in western Sweden may be a high-risk zone for multiple sclerosis (MS). The objective of this study was to determine the prevalence in the area. Hospital and general practice medical files were scrutinized. The diagnostic criteria of Poser were used, with 31 December 2002 as prevalence day. The prevalence was 170.07 per 100,000 inhabitants. The average annual incidence was 6.39 to 6.46 per 100,000 (1991-1995, 1996-2000). Multiple sclerosis was 2.3 times more common among women than men. There was a variation in prevalence among the 16 municipalities, however it was not statistically significant. The rates seemed highest in the southwestern part of the county, roughly similar in location to findings some 70 years earlier. When the prevalence ratios by geographical units for the county in 1933 were applied to the current prevalence, the distribution from these estimated cases differed from homogeneity with very high significance (p < 0.00001 ). In conclusion, this study supports previous reports indicating that Värmland continues to be a high-risk zone for MS and shares in the diffusion of the disease at the county level which we had presented for the country as a whole.