title: Do new cases of rheumatoid arthritis cluster in time or in space?
abstract: OBJECTIVE
  To examine for evidence of clustering in time, in space and in space/time in the occurrence of rheumatoid arthritis (RA).
  
  
  METHODS
  A population-based incidence register of RA in the East Anglian region of the UK: population size 413,000.
  
  
  METHODS
  In all 687 new cases of inflammatory joint disease registered between 1 January 1990 and 31 December 1994 were studied. Population data were obtained from postcode areas by age and sex.
  
  
  METHODS
  Time trend analysis was conducted over the first 36 months and observed and expected distributions compared. Spatial clustering was based on comparison of observed distribution using map grid references to random expectation based on simulation. A similar procedure was undertaken for time/space clustering.
  
  
  RESULTS
  There was no evidence of a time trend. There was only modest evidence of spatial clustering with non-random distribution observed in one area but there was no evidence of time/space clustering.
  
  
  CONCLUSIONS
  Although a viral aetiology is the strongest candidate for RA, no evidence of a localized event in time was associated with disease development in this population.
authors.affiliation: ARC Epidemiology Research Unit, University of Manchester, UK.
authors.forename: A
authors.initials: A
authors.lastname: Silman
authors.forename: C
authors.initials: C
authors.lastname: Bankhead
authors.forename: B
authors.initials: B
authors.lastname: Rowlingson
authors.forename: P
authors.initials: P
authors.lastname: Brennan
authors.forename: D
authors.initials: D
authors.lastname: Symmons
authors.forename: A
authors.initials: A
authors.lastname: Gatrell
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001168:Arthritis / Q000145:classification / Q000453:epidemiology; D001172:Arthritis, Rheumatoid / Q000453:epidemiology* / Q000209:etiology; D003198:Computer Simulation; D003430:Cross-Sectional Studies; D004739:England / Q000453:epidemiology; D005194:Family Practice / Q000706:statistics & numerical data; D005260:Female; D006306:Health Surveys; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012042:Registries; D013029:Space-Time Clustering; D013269:Stochastic Processes