title: Physical activity from adolescence to young adulthood and bone mineral density in young adults from the 1982 Pelotas (Brazil) Birth Cohort.
abstract: OBJECTIVE
  To evaluate a prospective association between physical activity (PA) and bone mineral density (BMD) in young adults.
  
  
  METHODS
  Total body (TB), lumbar spine (LS) and femoral neck (FN) BMD were measured in participants from the 1982 Pelotas Birth Cohort by dual-energy X-ray absorptiometry at 30 y. PA was evaluated at 15, 18 (males) and 23 y.
  
  
  RESULTS
  3454 young adults were scanned (DXA) at least at one anatomical site. In males, PA at 15 y was associated with LS density (β=0.061 g/cm(2); 95% confidence interval (CI): 0.015; 0.108). A positive dose-response effect was found for the association between PA at 18 y and BMD. Males in the two highest quartiles of PA at 23 y had significantly greater BMD at all anatomical sites than males in the lowest quartile. We observed greater BMD at 30 y in boys who were active at least in one of the assessments (18 or 23 y) compared to inactive boys at both ages. Females in the highest quartile of PA at 23 y showed greater FN density at 30 y (β=0.020; 95%CI: 0.001; 0.039).
  
  
  CONCLUSIONS
  A physically active pattern is important to BMD across the first three decades of life. Potential beneficial effects of PA were not entirely lost with advancing age in male young adults.
authors.affiliation: Post-Graduate Program in Epidemiology, Federal University of Pelotas, Brazil. Electronic address: renatabielemann@hotmail.com.
authors.forename: Renata M
authors.initials: RM
authors.lastname: Bielemann
authors.affiliation: Post-Graduate Program in Physical Education, Federal University of Pelotas, Brazil.
authors.forename: Marlos R
authors.initials: MR
authors.lastname: Domingues
authors.affiliation: Post-Graduate Program in Epidemiology, Federal University of Pelotas, Brazil.
authors.forename: Bernardo L
authors.initials: BL
authors.lastname: Horta
authors.affiliation: Post-Graduate Program in Epidemiology, Federal University of Pelotas, Brazil.
authors.forename: Denise P
authors.initials: DP
authors.lastname: Gigante
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods; D000293:Adolescent; D000328:Adult; D001823:Body Composition; D015992:Body Mass Index; D015519:Bone Density / Q000502:physiology*; D001842:Bone and Bones / Q000000981:diagnostic imaging / Q000502:physiology*; D001938:Brazil; D015331:Cohort Studies; D004305:Dose-Response Relationship, Drug; D015444:Exercise / Q000502:physiology*; D005260:Female; D005272:Femur Neck / Q000000981:diagnostic imaging / Q000502:physiology*; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000502:physiology*; D008297:Male; D011446:Prospective Studies; D012044:Regression Analysis; D012737:Sex Factors; D055815:Young Adult
keywords: Bone density; Cohort studies; Physical activity; Young adults