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.
| 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 |
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.
b Values are mean (95 percent confidence interval).
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.
d Comparing all three cohorts by analysis of variance.
e Comparing all three cohorts by analysis of covariance with adjustment for age.
f Comparing all three cohorts by chi-squared test.
g Comparing all three cohorts, with direct standardisation for age, by logistic regression.