title: Importance of participation rate in sampling of data in population based studies, with special reference to bone mass in Sweden.
abstract: OBJECTIVE
  To study the effects of participation rate in sampling on "normative" bone mass data.
  
  
  METHODS
  This was a comparison between two randomly selected samples from the same population. The participation rates in the two samples were 61.9% and 83.6%. Measurements were made of bone mass at different skeletal sites and of muscle strength, as well as an assessment of physical activity.
  
  
  METHODS
  Malmö, Sweden.
  
  
  METHODS
  There were 230 subjects (117 men, 113 women), aged 21 to 42 years.
  
  
  RESULTS
  Many subjects participated in both studies (163). Those who took part only in the study with the higher participation rate (67) almost invariably had higher values for bone mass density at the sites measured (up to 7.6% for men) than participants in the study with the lower participation rate. No differences in muscle strength were recorded.
  
  
  CONCLUSIONS
  A high degree of compliance is important to achieve a reliable result in determining normal values in population based studies.
authors: Department of Orthopaedics, Malmö University Hospital, Sweden.
authors: H
authors: H
authors: Düppe
authors: P
authors: P
authors: Gärdsell
authors: B S
authors: BS
authors: Hanson
authors: O
authors: O
authors: Johnell
authors: B E
authors: BE
authors: Nilsson
mesh_terms: D000328:Adult; D015519:Bone Density; D015444:Exercise; D005260:Female; D006801:Humans; D008297:Male; D009132:Muscles / Q000502:physiology; D011159:Population Surveillance; D018401:Sample Size; D012494:Sampling Studies; D013548:Sweden