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dc.contributor.authorTorkildsen, Øivind Fredvik
dc.contributor.authorAarseth, Jan Harald
dc.contributor.authorBenjaminsen, Espen
dc.contributor.authorCelius, Elisabeth Gulowsen
dc.contributor.authorHolmøy, Trygve
dc.contributor.authorKampman, Margitta Theodora
dc.contributor.authorLøken-Amsrud, Kristin Ingeleiv
dc.contributor.authorMidgard, Rune
dc.contributor.authorMyhr, Kjell-Morten
dc.contributor.authorRiise, Trond
dc.contributor.authorTorkildsen, Nina Agnethe Grytten
dc.date.accessioned2015-03-05T10:39:15Z
dc.date.available2015-03-05T10:39:15Z
dc.date.issued2014
dc.description.abstractA month of birth effect on multiple sclerosis (MS) risk has been reported from different countries. Recent critics have suggested that this finding is caused by confounding and that adequately adjusting for year and place of birth would markedly reduce this effect. All inhabitants in Norway are registered in the Norwegian Population Registry (Statistics Norway), making this an ideal area for performing adjusted analyses. Using the entire Norwegian population born between 1930 and 1979 (n = 2,899,260), we calculated the excess between observed and expected number of births for each month for 6649 Norwegian MS patients, 5711 mothers, 5247 fathers, and 8956 unaffected siblings. The analyses were adjusted for year of birth and place of birth according to the 19 counties in Norway. An unadjusted analysis revealed 13% fewer MS births than expected in February (P = 0.0015; Bonferroni corrected P = 0.018), 10% more in April (P = 0.0083; Bonferroni corrected P = 0.0996) and 15% more in December (P = 0.00058; Bonferroni corrected P = 0.007). Adjustments for both year and place of birth significantly altered our results for February and December, but even after these adjustments there were still 10% more MS births than expected in April (P = 0.00796; Bonferroni corrected P = 0.096). MS patients had a higher incidence of April births than their siblings (Fisher-exact test; P = 0.011), mothers (Fisher-exact test; P = 0.004), and fathers (Fisher-exact test; P = 0.011) without MS. Adjustments for confounding significantly affected our results. However, even after adjustments, there appears to be a persistent higher than expected frequency of April births in the MS population.en_US
dc.identifier.citationAnnals of clinical and translational neurology 1(2014) nr. 2 s. 141-144en_US
dc.identifier.cristinIDFRIDAID 1220659
dc.identifier.doi10.1002/acn3.37
dc.identifier.issn2328-9503
dc.identifier.urihttps://hdl.handle.net/10037/7342
dc.identifier.urnURN:NBN:no-uit_munin_6942
dc.language.isoengen_US
dc.publisherWiley Open Accessen_US
dc.rights.accessRightsopenAccess
dc.subjectVDP::Medisinske Fag: 700::Helsefag: 800::Epidemiologi medisinsk og odontologisk statistikk: 803en_US
dc.subjectVDP::Medical disciplines: 700::Health sciences: 800::Epidemiology medical and dental statistics: 803en_US
dc.titleMonth of birth and risk of multiple sclerosis: confounding and adjustmentsen_US
dc.typeJournal articleen_US
dc.typeTidsskriftartikkelen_US
dc.typePeer revieweden_US


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