title: Mortality trends of amyotrophic lateral sclerosis in Norway 1951-2014: an age-period-cohort study.
abstract: Recent studies suggest that the incidence and mortality of amyotrophic lateral sclerosis (ALS) are increasing. Changing environmental factors could influence disease risk differently throughout life span, and also between genders, birth cohorts, and seasons of birth. We aimed at describing long-term ALS mortality trends in Norway between 1951 and 2014 using age-period-cohort analysis. The Norwegian Cause of Death Registry provided ALS mortality data that were age- and sex-adjusted through direct standardization. Poisson regression analyses were used for identification of mortality trends and potential month of birth effects. We identified 5345 ALS cases, of which 54.7 % were men. ALS mortality increased throughout the whole period (p < 0.001), with a mean annual increase of 1.14 %. The increase was confined to those older than 60 years, but rates consistently dropped amongst the absolute oldest. The increase was mainly driven by birth cohort effects that increased from 1860 until 1934 (p < 0.001). No month of birth effect or change in sex ratio was found. The continuous increase in ALS mortality since 1951 is best explained by the long-term changes in exposure to risk factors or in case ascertainment, affecting men and women equally in the generations born since 1860 and at least into 1934.
authors: Institute of Clinical Medicine, Campus Ahus, University of Oslo, Oslo, Norway. ola.nakken@medisin.uio.no.|Department of Neurology, Akershus University Hospital, Lørenskog, Norway. ola.nakken@medisin.uio.no.
authors: Ola
authors: http://orcid.org/0000-0003-4765-0636
authors: O
authors: Nakken
authors: Institute of Clinical Medicine, Campus Ahus, University of Oslo, Oslo, Norway.|Helse Sør-Øst Health Services Research Centre, Akershus University Hospital, Lørenskog, Norway.
authors: Jonas Christoffer
authors: JC
authors: Lindstrøm
authors: Department of Clinical Medicine, University of Bergen, Bergen, Norway.|Department of Neurology, Haukeland University Hospital, Bergen, Norway.
authors: Ole-Bjørn
authors: OB
authors: Tysnes
authors: Institute of Clinical Medicine, Campus Ahus, University of Oslo, Oslo, Norway.|Department of Neurology, Akershus University Hospital, Lørenskog, Norway.
authors: Trygve
authors: T
authors: Holmøy
mesh_terms: D017677:Age Distribution; D000367:Age Factors; D000690:Amyotrophic Lateral Sclerosis / Q000453:epidemiology* / Q000401:mortality*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D009664:Norway / Q000453:epidemiology; D012044:Regression Analysis; D012737:Sex Factors
keywords: ALS; Age–period–cohort model; MND; Mortality; Neuro-epidemiology; Neurodegenerative disorders