title: Age- and sex-specific incidence of childhood leukemia by immunophenotype in the Nordic countries.
abstract: BACKGROUND
  Studies from various countries have found an increasing incidence of childhood leukemia in recent decades. To characterize time trends in the age- and sex-specific incidence of childhood acute leukemia during the last 20 years in the Nordic countries, we analyzed a large set of population-based data from the Nordic Society of Paediatric Haematology and Oncology (NOPHO) in their acute leukemia database covering a population of approximately 5 million children aged 0-14 years.
  
  
  METHODS
  Temporal trends in acute myeloid leukemia and acute lymphoblastic leukemia incidence rates overall and for acute lymphoblastic leukemia immunophenotypes and for specific age groups were analyzed by Poisson regression adjusting for age, sex, and country. All statistical tests were two-sided.
  
  
  RESULTS
  We identified 1595 girls and 1859 boys diagnosed with acute lymphoblastic leukemia between January 1, 1982, and December 31, 2001, and 260 girls and 224 boys diagnosed with de novo acute myeloid leukemia between January 1, 1985, and December 31, 2001. No statistically significant change was seen in the overall incidence rate for acute lymphoblastic leukemia during the 20-year study (annual change = 0.22%, 95% confidence interval [CI] = -0.36% to 0.80%). The incidence rate of B-precursor acute lymphoblastic leukemia remained unchanged (annual change = 0.30%, 95% CI = -0.57% to 1.18%) from January 1, 1986, through December 31, 2001. A somewhat lower incidence in the first years of the study period indicated an early increasing incidence of B-precursor acute lymphoblastic leukemia that corresponded to a simultaneous decreasing incidence of unclassified acute lymphoblastic leukemia. Incidences of T-cell acute lymphoblastic leukemia (annual change = 1.55%, 95% CI = -1.14% to 4.31%) and acute myeloid leukemia (annual change = 0.58%, 95% CI = -1.24% to 2.44%) were stable during the study period.
  
  
  CONCLUSIONS
  Incidences of acute myeloid leukemia overall, acute lymphoblastic leukemia overall, and specific acute lymphoblastic leukemia immunophenotypes have been stable in the Nordic countries over the past two decades.
authors.affiliation: Department of Epidemiology Research, Danish Epidemiology Science Centre, Statens Serum Institut, Copenhagen, Denmark. lih@ssi.dk
authors.forename: Lisa Lyngsie
authors.initials: LL
authors.lastname: Hjalgrim
authors.forename: Klaus
authors.initials: K
authors.lastname: Rostgaard
authors.forename: Kjeld
authors.initials: K
authors.lastname: Schmiegelow
authors.forename: Stefan
authors.initials: S
authors.lastname: Söderhäll
authors.forename: Svein
authors.initials: S
authors.lastname: Kolmannskog
authors.forename: Kim
authors.initials: K
authors.lastname: Vettenranta
authors.forename: Jon
authors.initials: J
authors.lastname: Kristinsson
authors.forename: Niels
authors.initials: N
authors.lastname: Clausen
authors.forename: Mads
authors.initials: M
authors.lastname: Melbye
authors.forename: Henrik
authors.initials: H
authors.lastname: Hjalgrim
authors.forename: Göran
authors.initials: G
authors.lastname: Gustafsson
mesh_terms: D000293:Adolescent; D017677:Age Distribution; D002648:Child; D002675:Child, Preschool; D005260:Female; D005387:Finland / Q000453:epidemiology; D006801:Humans; D007055:Iceland / Q000453:epidemiology; D016130:Immunophenotyping; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D015470:Leukemia, Myeloid, Acute / Q000453:epidemiology* / Q000235:genetics; D008297:Male; D016012:Poisson Distribution; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000453:epidemiology* / Q000235:genetics; D012537:Scandinavian and Nordic Countries / Q000453:epidemiology; D017678:Sex Distribution