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High prevalence of multiple sclerosis in the Swedish county of Värmland
Linköping University, Department of Clinical and Experimental Medicine, Neurology. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Clinical and Experimental Medicine, Neurology. Linköping University, Faculty of Health Sciences.
Department of Neurology, Georgetown University, Washington, DC, USA.
Linköping University, Department of Neuroscience and Locomotion, Neurology. Linköping University, Faculty of Health Sciences.
2009 (English)In: Multiple Sclerosis, ISSN 1352-4585, E-ISSN 1477-0970, Vol. 15, no 11, 1253-1262 p.Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
2009. Vol. 15, no 11, 1253-1262 p.
Keyword [en]
epidemiological, risk, aetiological, genetics, environment
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-51888DOI: 10.1177/1352458509345909OAI: oai:DiVA.org:liu-51888DiVA: diva2:278055
Available from: 2009-11-23 Created: 2009-11-23 Last updated: 2012-10-23Bibliographically approved
In thesis
1. Epidemiological Studies of Multiple Sclerosis in Sweden with focus on the County of Värmland
Open this publication in new window or tab >>Epidemiological Studies of Multiple Sclerosis in Sweden with focus on the County of Värmland
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The aim of this thesis was to study the frequency of MS in the suggested high-risk area of Värmland county by investigating the current prevalence and analyzing the development over time; secondly to investigate some aetiological factors – the pattern of industry, both in relation to MS in Värmland and in the whole country, and also to examine the possible relation between the distribution of MS and ALS, as it has previously shown a positive correlation in two studies; finally to analyze the women-to-men ratio of MS in Sweden because of international reports of an increasing ratio.

Clinical data was collected from hospitals and other health care units in the county of Värmland, to calculate the prevalence ratio. The prevalence was 170.07 per 100,000 population on the prevalence day, 31 December 2002. The incidence rates analysed during ten years was 6.46 per 100,000 personyears (1991-1995) and 6.39 (1996-2000).

The ecological study used data from the beginning of the 20th century on industries in Värmland and in all Sweden, which were correlated with the two MS prevalence studies (1925-1934 and 2002), and the mortality study on the time period 1952-1990. There was a statistical significant association between large sawmills and the prevalence 1925-1934 (p = 0.022). For all Sweden, wood-pulp factories and papermills correlated significantly with MS mortality 1952-1990 (p = <0.05).

Collected data from Causes of death Register and from the Total Population Register were used when analysing mortality from ALS and MS. The previously shown correlation between ALS and MS mortality distribution in the Swedish counties was not confirmed in this study. However, the mean MS mortality rate was still highest in the county in Värmland. The mean MS mortality rates for whole Sweden was increased from 1.65 per 100,000 person-years (1952-1992) to 2.04 (1990-2010).

For analysing sex ratio in MS, data from the Swedish Multiple Sclerosis Register and data from Total Population Register of the Swedish Statistics Office were used. These data was analysed by birth day cohort and by year of onset. The sex ratios in Sweden showed a stable women-to-men ratio.

These investigations give indication that Värmland is a high-risk region of multiple sclerosis, and particularly the municipality of Säffle.

We conclude that Värmland is a suitable area for continued epidemiological studies with both an environment and genetic focus.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2012. 52 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1286
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-74177 (URN)978-91-7519-990-0 (ISBN)
Public defence
2012-02-17, Sal Linden, Hälsouniversitetet, Campus US, Linköpings universitet, Linköping, 13:00 (Swedish)
Opponent
Supervisors
Available from: 2012-01-20 Created: 2012-01-20 Last updated: 2012-02-15Bibliographically approved
2. Epidemiological and genetic studies of muliple sclerosis with focus on the Swedish county of Värmland
Open this publication in new window or tab >>Epidemiological and genetic studies of muliple sclerosis with focus on the Swedish county of Värmland
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The aim of this study was to perform detailed investigations of a presumed high-risk area, namely the county of Värmland, to see if previous results from our group indicating a high frequency of multiple sclerosis (MS) could be confirmed. We soon identified an aggregation of MS cases in the parish of Lysvik located in the north of Värmland and initiated epidemiological and genetical analyses of the population. We also extended our genetic research to include studies of a possible association between MS immunopathic trait and the MS susceptibility gene HLA-DR(2)15 type, but in another geographic area.

The onset-adjusted prevalence of MS in Värmland was 170/105 (95% CI: 154-185) in December 2002, which is higher than prevalence previously reported from other Swedish areas. There was a great variation in MS frequency between communities in Värmland. We found a persistently high occurrence of MS in Torsby and Sunne communities. In the community of Årjäng MS frequency had increased substantially since the previous study performed by our group.

Epidemiological analysis of a cluster of MS cases in Lysvik revealed 27 MS patients, of whom 23 were the descendants of a Finnish family originated from a common ancestor born in Savolaks in Finland in the 16th century and 18 had relatives with MS. Since this cluster was most likely to have a genetic basis (located in an area with a high inbreeding rate) the mode of MS inheritance was investigated. The linkage study using the genome-wide transmission disequilibrium test (TDT) provided several regions of interest, especially on chromosome 14q (14q24-31). The linkage peak on chromosome 17q was also confirmed by this study.

The frequency of the HLA-DR(2)15 allele was higher in healthy siblings of MS patients without MS immunopathic trait (MSIT) than in siblings with the trait, which provides further support for the hypothesis that MSIT and MS are two independent, albeit, synergistic conditions.

The prevalence study supports that Värmland County is a high-risk area. Furthermore, the aggregation of MS cases in Lysvik indicates a concentrated risk zone, possibly due to a combination of genetic, environmental and social risk factors. A widely and evenly spread environmental (i.e., infectious) agent together with cultural changes and industrialisation could possibly induce disease in subgroups of genetically more susceptible individuals. The evidence of linkage to chromosome 14 found in this study indicates that further genetic research is required.

Place, publisher, year, edition, pages
Linköping: Institutionen för nervsystem och rörelseorgan, 2006. 60 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 949
Keyword
Inborn genetic diseases, Genetic predisposition to disease, Genetic predisposition to disease, Cluster analysis, Muliple sclerosis, Pedigree
National Category
Medical Genetics
Identifiers
urn:nbn:se:liu:diva-7444 (URN)91-85497-86-X (ISBN)
Public defence
2006-06-01, Elsa Brändströms sal, Södra ingången, plan 10, Campus US, Linköpings Universitet, Linköping, 13:00 (English)
Opponent
Available from: 2006-09-27 Created: 2006-09-27 Last updated: 2012-10-23Bibliographically approved

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Boström, IngerCallander, MargaritaLandtblom, Anne-Marie

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