High prevalence of multiple sclerosis in the Swedish county of Värmland

Abstract

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.

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

“…This finding, i.e. the great variation of MS rates within the county, was detected by us before and was interpreted as an indication of diffusion [20,31].…”

“…The MS prevalence 1925-1934 [18] and in 2002 [20], and the annual age-and gender-adjusted MS mortality 1952-1992 [19], were correlated with industry in 14 sectors in 1913 [24]. These were shown in the form of maps in the original data source.…”

“…The three population-based investigations on MS frequency in Värm-land [18][19][20] were used to make an ecological study on the correlation of MS with density of specific industries, as an indicator of environmental pollution. The MS prevalence 1925-1934 [18] and in 2002 [20], and the annual age-and gender-adjusted MS mortality 1952-1992 [19], were correlated with industry in 14 sectors in 1913 [24].…”

“…Corresponding data for the judicial district in Värmland 1925-1934 is shown in Table 2 and data from the mortality study of Värmland in 1952-1992 is shown in Table 3. A third study of MS, an investigation on prevalence in the county of Värmland, was made in 2002 [20]. The prevalence was 170 per 100,000 inhabitants.…”

“…Rates and percentages ranges versus the total rate of 170.07 for Värmland are shown for each municipality. Reprinted from Boström et al[20] with permission from SAGE Publications Ltd.…”