title: Incidence rates of progressive childhood encephalopathy in Oslo, Norway: a population based study.
abstract: BACKGROUND
  Progressive encephalopathy (PE) in children is a heterogeneous group of diseases mainly composed of metabolic diseases, but it consists also of neurodegenerative disorders where neither metabolic nor other causes are found. We wanted to estimate the incidence rate and aetiology of PE, as well as the age of onset of the disease.
  
  
  METHODS
  We included PE cases born between 1985 and 2003, living in Oslo, and registered the number presenting annually between 1985 and 2004. Person-years at risk between 0 and 15 years were based on the number of live births during the observation period which was divided into four 5-year intervals. We calculated incidence rates according to age at onset which was classified as neonatal (0-4 weeks), infantile (1-12 months), late infantile (1-5 years), and juvenile (6-12 years).
  
  
  RESULTS
  We found 84 PE cases representing 28 diagnoses among 1,305,997 person years, giving an incidence rate of 6.43 per 100,000 person years. The age-specific incidence rates per 100,000 were: 79.89 (<1 year), 8.64 (1-2 years), 1.90 (2-5 years), and 0.65 (>5 years). 66% (55/84) of the cases were metabolic, 32% (27/54) were neurodegenerative, and 2% (2/84) had HIV encephalopathy. 71% (60/84) of the cases presented at < 1 year, 24% (20/84) were late infantile presentations, and 5% (4/84) were juvenile presentations. Neonatal onset was more common in the metabolic (46%) (25/55) compared to the neurodegenerative group (7%) (2/27). 20% (17/84) of all cases were classified as unspecified neurodegenerative disease.
  
  
  CONCLUSIONS
  The overall incidence rate of PE was 6.43 per 100,000 person years. There was a strong reduction in incidence rates with increasing age. Two-thirds of the cases were metabolic, of which almost half presented in the neonatal period.
authors.affiliation: Department of Pediatrics, Ullevål University Hospital and Faculty of Medicine, University of Oslo, Norway. petter.stromme@medisin.uio.no
authors.forename: Petter
authors.initials: P
authors.lastname: Stromme
authors.forename: Oivind Juris
authors.initials: OJ
authors.lastname: Kanavin
authors.forename: Michael
authors.initials: M
authors.lastname: Abdelnoor
authors.forename: Berit
authors.initials: B
authors.lastname: Woldseth
authors.forename: Terje
authors.initials: T
authors.lastname: Rootwelt
authors.forename: Jorgen
authors.initials: J
authors.lastname: Diderichsen
authors.forename: Bjorn
authors.initials: B
authors.lastname: Bjurulf
authors.forename: Finn
authors.initials: F
authors.lastname: Sommer
authors.forename: Per
authors.initials: P
authors.lastname: Magnus
mesh_terms: D015526:AIDS Dementia Complex / Q000453:epidemiology*; D000293:Adolescent; D017677:Age Distribution; D001928:Brain Diseases, Metabolic / Q000453:epidemiology*; D002648:Child; D002675:Child, Preschool; D018450:Disease Progression; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D019636:Neurodegenerative Diseases / Q000453:epidemiology*; D009664:Norway / Q000453:epidemiology; D011159:Population Surveillance; D012189:Retrospective Studies; D012307:Risk Factors; D017678:Sex Distribution; D014505:Urban Population