title: The effect of bed rest on bone turnover in young women hospitalized for anorexia nervosa: a pilot study.
abstract: BACKGROUND
  Malnourished adolescents with anorexia nervosa (AN) requiring medical hospitalization are at high risk for skeletal insults. Even short-term bed rest may further disrupt normal patterns of bone turnover.
  
  
  OBJECTIVE
  The objective of the study was to determine the effect of relative immobilization on bone turnover in adolescents hospitalized for AN.
  
  
  METHODS
  This was a short-term observational study.
  
  
  METHODS
  The study was conducted at a tertiary care pediatric hospital.
  
  
  METHODS
  Twenty-eight adolescents with AN, aged 13-21 yr with a mean body mass index of 15.9 +/- 1.8 kg/m(2), were enrolled prospectively on admission.
  
  
  METHODS
  As per standard care, all subjects were placed on bed rest and graded nutritional therapy.
  
  
  METHODS
  Markers of bone formation (bone specific alkaline phosphatase), turnover (osteocalcin), and bone resorption (urinary N-telopeptides NTx) were measured.
  
  
  RESULTS
  During the 5 d of hospitalization, serum osteocalcin increased by 0.24 +/- 0.1 ng/ml . d (P = 0.02). Urine N-telopeptides reached a nadir on d 3, declining -6.9 +/- 2.8 nm bone collagen equivalent per millimole creatinine (P = 0.01) but returned to baseline by d 5 (P > 0.05). Bone-specific alkaline phosphatase exhibited a decline that was strongly age dependent, being highly significant for younger subjects only [age 14 yr: -0.42 +/- 0.11 (P = 0.0002); age 18 yr: -0.03 +/- 0.08 (P = 0.68)]. Age had no effect on other outcome measures.
  
  
  CONCLUSIONS
  Limitation of physical activity during hospitalization for patients with AN is associated with suppressed bone formation and resorption and an imbalance of bone turnover. Future interventional studies involving mechanical stimulation and/or weight-bearing activity are needed to determine whether medical protocols prescribing strict bed rest are appropriate.
authors.affiliation: Division of Adolescent Medicine, Children's Hospital Boston, Boston, Massachusetts 02115, USA. amy.divasta@childrens.harvard.edu
authors.forename: Amy D
authors.initials: AD
authors.lastname: DiVasta
authors.forename: Henry A
authors.initials: HA
authors.lastname: Feldman
authors.forename: Ashley E
authors.initials: AE
authors.lastname: Quach
authors.forename: Maria
authors.initials: M
authors.lastname: Balestrino
authors.forename: Catherine M
authors.initials: CM
authors.lastname: Gordon
mesh_terms: D015502:Absorptiometry, Photon; D000293:Adolescent; D000469:Alkaline Phosphatase / Q000378:metabolism; D000568:Amenorrhea / Q000150:complications; D000856:Anorexia Nervosa / Q000378:metabolism* / Q000628:therapy*; D001510:Bed Rest; D015519:Bone Density / Q000502:physiology; D001842:Bone and Bones / Q000378:metabolism*; D002118:Calcium / Q000097:blood; D005260:Female; D006760:Hospitalization; D006801:Humans; D007103:Immobilization; D009752:Nutritional Status; D015675:Osteocalcin / Q000378:metabolism; D010865:Pilot Projects; D013131:Spine / Q000033:anatomy & histology / Q000378:metabolism; D015430:Weight Gain; D055815:Young Adult
chemical_list: D015675:Osteocalcin; D000469:Alkaline Phosphatase; D002118:Calcium