title: Increased incidence rates but no space-time clustering of childhood astrocytoma in Sweden, 1973-1992: a population-based study of pediatric brain tumors.
abstract: BACKGROUND
  Incidence patterns, trends, and spatial and/or temporal clustering of childhood brain tumors were analyzed in the population-based national cancer registry of Sweden.
  
  
  METHODS
  Temporal trends were analyzed by a logistic regression procedure in which the average annual percentages of change in incidence rates and the corresponding 95% confidence intervals (CIs) were calculated. Spatial and/or temporal clustering were investigated by using a geographic information system and analyzed with a modified version of the Knox test and a spatial scan statistic.
  
  
  RESULTS
  Primary brain tumors in 1223 children ages 0-15 years were registered during 1973-1992. In 80% of cases, the tumor was classified as malignant. Conclusive histopathology was classified in 1142 cases. The age-adjusted incidence rate for all subtypes of brain tumors was 35.9 cases per million children, and for malignant brain tumors 28.6. A statistically significant increasing temporal trend was observed for the group of malignant brain tumors as a whole (P=0.0001) and the astrocytoma subgroup (P=0.0001). The annual average increases were 2.6% (95% CI=1.5-3.8) and 3.0%, respectively (95% CI=1.6-4.4). The increase in astrocytoma cases was significantly larger for girls than for boys (P=0.021) and was most striking for girls ages 6-15 years, with an annual average increase of 4.7%. Rates had not increased for the primitive neuroectodermal tumor (PNET)/medulloblastoma or ependymoma subgroups. The geographic distribution of astrocytoma cases was homogenous. No statistically significant space-time interaction or local clusters in space and/or time were found for astrocytomas only or when astrocytomas were grouped with PNETs/medulloblastomas and ependymomas.
  
  
  CONCLUSIONS
  The results show statistically increased incidence rates of childhood astroglial tumors, predominantly for girls, in Sweden during the period 1973-1992, but no clustering in space or time.
authors.affiliation: Department of Pediatrics, Ostersunds Hospital, Ostersund, Sweden.
authors.forename: U
authors.initials: U
authors.lastname: Hjalmars
authors.forename: M
authors.initials: M
authors.lastname: Kulldorff
authors.forename: Y
authors.initials: Y
authors.lastname: Wahlqvist
authors.forename: B
authors.initials: B
authors.lastname: Lannering
mesh_terms: D000293:Adolescent; D017677:Age Distribution; D001254:Astrocytoma / Q000453:epidemiology*; D001932:Brain Neoplasms / Q000453:epidemiology*; D002648:Child; D002675:Child, Preschool; D004806:Ependymoma / Q000453:epidemiology; D005260:Female; D005909:Glioblastoma / Q000453:epidemiology; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008527:Medulloblastoma / Q000453:epidemiology; D011159:Population Surveillance; D012042:Registries; D017678:Sex Distribution; D013029:Space-Time Clustering; D013548:Sweden / Q000453:epidemiology; D014504:Urban Health