title: Spatial cluster analysis of population amyotrophic lateral sclerosis risk in Ireland.
abstract: OBJECTIVE
  Few spatial cluster analyses of amyotrophic lateral sclerosis (ALS) incidence have been conducted on prospective incident population-based cohorts; we report results of a formal cluster analysis of the Irish ALS cohort from January 1, 1995, to December 31, 2013.
  
  
  METHODS
  We identified 1,684 incident cases from the Irish ALS register. Population data from 4 census years were used to calculate age- and sex-standardized expected ALS cases for 3,355 areas. Spatial cluster analysis was performed to identify high-risk clusters using both SaTScan and FleXScan software. Poisson-based, time period-stratified statistics and time-stratified Bayesian smoothed risk mapping were used to audit completeness of case ascertainment of the register.
  
  
  RESULTS
  No significant high-risk clusters of incident ALS were identified. However, SaTScan revealed 2 significant areas of lower-than-average ALS risk-one centered on County Kilkenny (relative risk 0.53, p = 0.012) and a smaller area in County Clare (relative risk 0.0, p = 0.029). Audit of case ascertainment did not indicate any failure to detect cases in these areas.
  
  
  CONCLUSIONS
  The absence of high-risk ALS clusters in Ireland contrasts with previous studies. Our study has several advantages, notably the use of a long-running prospective ALS register with nationwide case ascertainment. The presence of 2 low-risk areas was unexpected. No obvious ascertainment, demographic, or common environmental factors explain this finding. However, we postulate that historical factors may have led to altered genetic admixture in these regions, possibly contributing to lower rates.
authors.affiliation: From the Academic Unit of Neurology (J.R., A.V., M.H., M.E., R.M., O.H.), Trinity Biomedical Sciences Institute, Trinity College, Dublin; School of Geography, Planning & Environmental Policy (A.C.), University College Dublin Belfield, Dublin; School of Nursing and Human Sciences (A.S.), Dublin City University; and Department of Neurology (O.H.), Beaumont Hospital, Ireland. jrooney@rcsi.ie.
authors.forename: James
authors.initials: J
authors.lastname: Rooney
authors.affiliation: From the Academic Unit of Neurology (J.R., A.V., M.H., M.E., R.M., O.H.), Trinity Biomedical Sciences Institute, Trinity College, Dublin; School of Geography, Planning & Environmental Policy (A.C.), University College Dublin Belfield, Dublin; School of Nursing and Human Sciences (A.S.), Dublin City University; and Department of Neurology (O.H.), Beaumont Hospital, Ireland.
authors.forename: Alice
authors.initials: A
authors.lastname: Vajda
authors.affiliation: From the Academic Unit of Neurology (J.R., A.V., M.H., M.E., R.M., O.H.), Trinity Biomedical Sciences Institute, Trinity College, Dublin; School of Geography, Planning & Environmental Policy (A.C.), University College Dublin Belfield, Dublin; School of Nursing and Human Sciences (A.S.), Dublin City University; and Department of Neurology (O.H.), Beaumont Hospital, Ireland.
authors.forename: Mark
authors.initials: M
authors.lastname: Heverin
authors.affiliation: From the Academic Unit of Neurology (J.R., A.V., M.H., M.E., R.M., O.H.), Trinity Biomedical Sciences Institute, Trinity College, Dublin; School of Geography, Planning & Environmental Policy (A.C.), University College Dublin Belfield, Dublin; School of Nursing and Human Sciences (A.S.), Dublin City University; and Department of Neurology (O.H.), Beaumont Hospital, Ireland.
authors.forename: Marwa
authors.initials: M
authors.lastname: Elamin
authors.affiliation: From the Academic Unit of Neurology (J.R., A.V., M.H., M.E., R.M., O.H.), Trinity Biomedical Sciences Institute, Trinity College, Dublin; School of Geography, Planning & Environmental Policy (A.C.), University College Dublin Belfield, Dublin; School of Nursing and Human Sciences (A.S.), Dublin City University; and Department of Neurology (O.H.), Beaumont Hospital, Ireland.
authors.forename: Arlene
authors.initials: A
authors.lastname: Crampsie
authors.affiliation: From the Academic Unit of Neurology (J.R., A.V., M.H., M.E., R.M., O.H.), Trinity Biomedical Sciences Institute, Trinity College, Dublin; School of Geography, Planning & Environmental Policy (A.C.), University College Dublin Belfield, Dublin; School of Nursing and Human Sciences (A.S.), Dublin City University; and Department of Neurology (O.H.), Beaumont Hospital, Ireland.
authors.forename: Russell
authors.initials: R
authors.lastname: McLaughlin
authors.affiliation: From the Academic Unit of Neurology (J.R., A.V., M.H., M.E., R.M., O.H.), Trinity Biomedical Sciences Institute, Trinity College, Dublin; School of Geography, Planning & Environmental Policy (A.C.), University College Dublin Belfield, Dublin; School of Nursing and Human Sciences (A.S.), Dublin City University; and Department of Neurology (O.H.), Beaumont Hospital, Ireland.
authors.forename: Anthony
authors.initials: A
authors.lastname: Staines
authors.affiliation: From the Academic Unit of Neurology (J.R., A.V., M.H., M.E., R.M., O.H.), Trinity Biomedical Sciences Institute, Trinity College, Dublin; School of Geography, Planning & Environmental Policy (A.C.), University College Dublin Belfield, Dublin; School of Nursing and Human Sciences (A.S.), Dublin City University; and Department of Neurology (O.H.), Beaumont Hospital, Ireland.
authors.forename: Orla
authors.initials: O
authors.lastname: Hardiman
mesh_terms: D000690:Amyotrophic Lateral Sclerosis / Q000453:epidemiology*; D016000:Cluster Analysis; D015331:Cohort Studies; D005260:Female; D006801:Humans; D015994:Incidence; D007494:Ireland / Q000453:epidemiology; D008297:Male; D012042:Registries / Q000706:statistics & numerical data*; D012306:Risk; D062206:Spatial Analysis