title: Quantitative bone ultrasound measurements in young females 14-23 years of age.
abstract: OBJECTIVE
  This study examined how transaxial quantitative ultrasound (QUS) measurements differed in young females between 14 and 23 years of age and if body composition and behavioral factors, namely, oral contraceptive (OC) use, physical activity, and calcium intake, influenced these measurements.
  
  
  METHODS
  Participants (n = 595) were classified as nonusers or users of OC. QUS measurements were performed at the distal radius and midtibia, and the bone speed of sound (SOS) was recorded for each site. Body mass index (BMI) was calculated from body mass and height. Physical activity and dietary calcium intake were assessed using standardized questionnaires.
  
  
  RESULTS
  Bone SOS increased significantly with increasing age (r(2) = 0.28 and 0.20 for radius and tibia, respectively, p < 0.05) but slower after age 18. OC use was not significantly associated with the QUS measurements, yet there was a significant age-by-OC use interaction (p < 0.05) for SOS of the tibia. For the nonusers of OC, age, BMI, and calcium intake were significant predictors of tibia SOS, explaining 24% of the variance in tibial SOS scores, whereas among the OC users, only age and BMI were significant predictors of tibial SOS, explaining 18% of the variance with no other variables entering in the model. Age was the only predictor of radius SOS in both groups. QUS scores increased steadily from 14 to 23 years of age in young females.
  
  
  CONCLUSIONS
  OC use was associated with lower tibial SOS scores in early adulthood but not during adolescence, suggesting that OC use possibly may interfere with the bone development of the tibia. Furthermore, daily calcium intake demonstrated a positive relationship with the tibial SOS only in the nonusers of OC; however, this relationship was reversed for BMI irrespective of OC use.
authors.affiliation: Department of Physical Education and Kinesiology, Brock University, St. Catharines, Ontario, Canada. nklentrou@brocku.ca
authors.forename: Panagiota
authors.initials: P
authors.lastname: Klentrou
authors.forename: Izabella A
authors.initials: IA
authors.lastname: Ludwa
mesh_terms: D000293:Adolescent; D017677:Age Distribution; D015992:Body Mass Index; D015519:Bone Density / Q000187:drug effects / Q000502:physiology*; D001842:Bone and Bones / Q000000981:diagnostic imaging; D002136:Calcium, Dietary / Q000008:administration & dosage; D003276:Contraceptives, Oral / Q000009:adverse effects; D003430:Cross-Sectional Studies; D015444:Exercise; D005260:Female; D006801:Humans; D009043:Motor Activity; D011884:Radius / Q000000981:diagnostic imaging*; D012044:Regression Analysis; D012307:Risk Factors; D012574:Schools; D013334:Students; D011795:Surveys and Questionnaires; D013977:Tibia / Q000000981:diagnostic imaging*; D014463:Ultrasonography; D055815:Young Adult
chemical_list: D002136:Calcium, Dietary; D003276:Contraceptives, Oral