title: No association between soil constituents and amyotrophic lateral sclerosis relative risk in Ireland.
abstract: BACKGROUND
  We have recently mapped ALS spatial risk in Ireland using Bayesian and cluster analysis methods at electoral division (ED) and small area (SA) levels. As a number of metal elements (both minerals and toxins) have been proposed as risk factors for ALS, here we extend this analysis to include soil constituents from the Irish National Soils Database as Bayesian conditional auto-regression covariates to determine associations with small area ALS risk.
  
  
  METHODS
  Data on 45 different soil parameters were obtained under license from National Soils Database (via Irish EPA). We interpolated average values of each soil constituent for each small area using ordinary kriging. All cases of ALS in Ireland from January 1995 to December 2013 were identified from the Irish ALS register and observed and age and gender standardised expected cases were calculated for each SA. Besag-York-Mollié (BYM) models were then built including each parameter from the national soils database in turn as a Bayesian covariate in the BYM model. Models were compared using the deviance information criterion (DIC) and separate models were built for ALS subtypes.
  
  
  RESULTS
  1701 ALS patients were included - 959 (56%) were male, 938 (55%) had limb onset ALS. 315 Bayesian models were built in total. Of the 315 models built, only one resulted in a coefficient that did not overlap zero. For limb onset cases, total magnesium had a mean coefficient of 0.319 (credible interval 0.033-0.607).
  
  
  CONCLUSIONS
  We report the first spatial analysis of potential association between ALS and soil minerals using a population-based dataset collected over 18 years. Our sole non-zero finding is likely a random finding due to the high number of models built. We did not find any evidence to support soil mineral and toxin levels as risk factors for ALS. However as soil parameters are an ecological assessment of exposure in a given area, individual level measures of exposure are required.
authors: Academic Unit of Neurology, Trinity Biomedical Sciences Institute, Trinity College, Dublin 2, Ireland. Electronic address: jrooney@rcsi.ie.
authors: James
authors: J
authors: Rooney
authors: Academic Unit of Neurology, Trinity Biomedical Sciences Institute, Trinity College, Dublin 2, Ireland.
authors: Alice
authors: A
authors: Vajda
authors: Academic Unit of Neurology, Trinity Biomedical Sciences Institute, Trinity College, Dublin 2, Ireland.
authors: Mark
authors: M
authors: Heverin
authors: School of Geography, University College Dublin Belfield, Dublin, Ireland.
authors: Arlene
authors: A
authors: Crampsie
authors: Academic Unit of Neurology, Trinity Biomedical Sciences Institute, Trinity College, Dublin 2, Ireland.
authors: Katy
authors: K
authors: Tobin
authors: Academic Unit of Neurology, Trinity Biomedical Sciences Institute, Trinity College, Dublin 2, Ireland.
authors: Russell
authors: R
authors: McLaughlin
authors: School of Nursing and Human Sciences, Dublin City University, Dublin, Ireland.
authors: Anthony
authors: A
authors: Staines
authors: Academic Unit of Neurology, Trinity Biomedical Sciences Institute, Trinity College, Dublin 2, Ireland; Department of Neurology, Beaumont Hospital, Beaumont, Ireland.
authors: Orla
authors: O
authors: Hardiman
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000690:Amyotrophic Lateral Sclerosis / Q000139:chemically induced / Q000453:epidemiology*; D001499:Bayes Theorem; D004784:Environmental Monitoring; D005260:Female; D006801:Humans; D007494:Ireland / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D008903:Minerals / Q000032:analysis*; D012044:Regression Analysis; D012306:Risk; D012987:Soil / Q000737:chemistry*
chemical_list: D008903:Minerals; D012987:Soil
keywords: Amyotrophic lateral sclerosis; Epidemiology; Soil minerals; Spatial risk