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Table 3 Bone mineral density and prevalence of osteoporosis evaluated at the distal radius in three cohorts of women measured in 1970-74, 1987-93 and 1998-99.

From: Prevalence of osteoporosis and incidence of hip fracture in women - secular trends over 30 years

Measurementsa Cohort 1970-74 Cohort 1987-93 Cohort 1998-99 P- value
  n = 106 n = 175 n = 178  
Bone mineral density (mg/cm2)b     
   Non-adjusted 438 (422, 454) 453 (439, 468) 461 (446, 477) 0.15d
   Age-adjusted 444 (430, 458) 460 (449, 471) 451 (440, 461) 0.17e
Prevalence of osteoporosis c     
   Non-adjusted 15.1 (8.2, 22.0) 15.1 (9.7, 20.5) 14.9 (9.5, 20.2) 1.00f
   Age-adjusted 13.6 (6.1, 21.2) 14.7 (8.9, 20.5) 11.0 (8.4, 13.6) 1.00 g
  1. a The bone mineral density in the forearm was measured at a site 6 cm (distal radius) proximal to the styloid process of the ulna by single-photon absorptiometry.
  2. b Values are mean (95 percent confidence interval).
  3. c Values are percentages of valid measurements (95 percent confidence interval). Osteoporosis denotes a bone mineral density 2.5 SD below the bone mineral density in young healthy women.
  4. d Comparing all three cohorts by analysis of variance.
  5. e Comparing all three cohorts by analysis of covariance with adjustment for age.
  6. f Comparing all three cohorts by chi-squared test.
  7. g Comparing all three cohorts, with direct standardisation for age, by logistic regression.