RT Journal Article
SR Electronic
T1 Spatial cluster analysis of population amyotrophic lateral sclerosis risk in Ireland
JF Neurology
JO Neurology
FD Lippincott Williams & Wilkins
SP 1537
OP 1544
DO 10.1212/WNL.0000000000001477
VO 84
IS 15
A1 Rooney, James
A1 Vajda, Alice
A1 Heverin, Mark
A1 Elamin, Marwa
A1 Crampsie, Arlene
A1 McLaughlin, Russell
A1 Staines, Anthony
A1 Hardiman, Orla
YR 2015
UL http://n.neurology.org/content/84/15/1537.abstract
AB 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.ALS=amyotrophic lateral sclerosis; ASCII=American Standard Code for Information Interchange; BMAA=β-methylamino-l-alanine; ED=electoral division; INLA=Integrated Nested Laplace Approximation; RR=relative risk