title: Incidence of adult Huntington's disease in the UK: a UK-based primary care study and a systematic review.
abstract: OBJECTIVE
  The prevalence of Huntington's disease (HD) recorded in the UK primary care records has increased twofold between 1990 and 2010. This investigation was undertaken to assess whether this might be due to an increased incidence. We have also undertaken a systematic review of published estimates of the incidence of HD.
  
  
  METHODS
  Incident patients with a new diagnosis of HD were identified from the primary care records of the Clinical Practice Research Datalink (CPRD). The systematic review included all published estimates of the incidence of HD in defined populations.
  
  
  METHODS
  A total of 393 incident cases of HD were identified from the CPRD database between 1990 and 2010 from a total population of 9,282,126 persons.
  
  
  METHODS
  The incidence of HD per million person-years was estimated. From the systematic review, the extent of heterogeneity of published estimates of the incidence of HD was examined using the I(2) statistic.
  
  
  RESULTS
  The data showed that the incidence of HD has remained constant between 1990 and 2010 with an overall rate of 7.2 (95% CI 6.5 to 7.9) per million person-years. The systematic review identified 14 independent estimates of incidence with substantial heterogeneity and consistently lower rates reported in studies from East Asia compared with those from Australia, North America and some--though not all--those from Europe. Differences in incidence estimates did not appear to be explained solely by differences in case ascertainment or diagnostic methods.
  
  
  CONCLUSIONS
  The rise in the prevalence of diagnosed HD in the UK, between 1990 and 2010, cannot be attributed to an increase in incidence. Globally, estimates of the incidence of HD show evidence of substantial heterogeneity with consistently lower rates in East Asia and parts of Europe. Modifiers may play an important role in determining the vulnerability of different populations to expansions of the HD allele.
authors.affiliation: Department of Neurology and Psychiatry, Columbia University, New York, New York, USA Hereditary Disease Foundation, New York, New York, USA.
authors.forename: Nancy S
authors.initials: NS
authors.lastname: Wexler
authors.affiliation: Department of Medical Statistics, London School of Hygiene and Tropical Medicine, London, UK.
authors.forename: Laura
authors.initials: L
authors.lastname: Collett
authors.affiliation: Hereditary Disease Foundation, New York, New York, USA.
authors.forename: Alice R
authors.initials: AR
authors.lastname: Wexler
authors.affiliation: Department of Non-Communicable Disease Epidemiology, London School of Hygiene and Tropical Medicine, London, UK.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Rawlins
authors.affiliation: Department of Neurodegenerative Diseases, Institute of Neurology, University College London, London, UK.
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Tabrizi
authors.affiliation: Department of Non-Communicable Disease Epidemiology, London School of Hygiene and Tropical Medicine, London, UK.
authors.forename: Ian
authors.initials: I
authors.lastname: Douglas
authors.affiliation: Department of Non-Communicable Disease Epidemiology, London School of Hygiene and Tropical Medicine, London, UK.
authors.forename: Liam
authors.initials: L
authors.lastname: Smeeth
authors.affiliation: Department of Medical Statistics, London School of Hygiene and Tropical Medicine, London, UK.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Evans
mesh_terms: D000328:Adult; D017668:Age of Onset; D057286:Electronic Health Records; D006801:Humans; D006816:Huntington Disease / Q000453:epidemiology*; D015994:Incidence; D008875:Middle Aged; D015995:Prevalence; D011320:Primary Health Care; D006113:United Kingdom / Q000453:epidemiology
keywords: EPIDEMIOLOGY; GENETICS