title: Do ethnic patterns in cryptorchidism reflect those found in testicular cancer?
abstract: OBJECTIVE
  There are established variations in testicular cancer incidence between ethnic groups within countries. It is currently unclear whether the occurrence of cryptorchidism-a known risk factor for testicular cancer-follows similar patterns. In New Zealand Māori have unusually high rates of testicular cancer compared to individuals of European ancestry. We hypothesized that ethnic trends in the incidence of cryptorchidism would reflect those for testicular cancer in this setting.
  
  
  METHODS
  We followed 318,441 eligible male neonates born in New Zealand between 2000 and 2010 for the incidence of orchiopexy confirmed cryptorchidism and the incidence of known risk factors for cryptorchidism (low birth weight, short gestation, small size for gestational age) using routine maternity, hospitalization and mortality records. Logistic regression was used to calculate odds ratios for the presence of known risk factors for cryptorchidism by ethnic group. Poisson regression was used to calculate relative risk of cryptorchidism by ethnicity, adjusted for risk factors.
  
  
  RESULTS
  Ethnic patterns of cryptorchidism incidence in New Zealand closely mirrored those previously observed for testicular cancer. Māori had higher rates of cryptorchidism than all other ethnic groups (adjusted RR 1.2 [95% CI 1.11-1.3]), with Pacific (0.89 [0.8-0.99]) and Asian groups (0.68 [0.59-0.79]) having the lowest rates (European/other, referent).
  
  
  CONCLUSIONS
  Since the principal risk factors for cryptorchidism are present in utero, the results of the current study strengthen the likelihood that the ethnic patterning of testicular cancer is at least partly due to prenatal risk factors.
authors.affiliation: Department of Public Health, University of Otago, Wellington, and Capital and Coast District Health Board, Wellington Hospital (RS), Newtown, Wellington, New Zealand. Electronic address: jason.gurney@otago.ac.nz.
authors.forename: Jason
authors.initials: J
authors.lastname: Gurney
authors.forename: Diana
authors.initials: D
authors.lastname: Sarfati
authors.forename: James
authors.initials: J
authors.lastname: Stanley
authors.forename: Rodney
authors.initials: R
authors.lastname: Studd
mesh_terms: D002648:Child; D002675:Child, Preschool; D003456:Cryptorchidism / Q000453:epidemiology*; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D009520:New Zealand / Q000453:epidemiology; D012307:Risk Factors; D013736:Testicular Neoplasms / Q000453:epidemiology*
keywords: MAT; Maternity Data Collection; PY; cryptorchidism; orchiopexy; person-year; testicular neoplasms; testis