Background Vertebral fractures are a hallmark of postmenopausal osteoporosis and an important end point in trials of osteoporosis treatment, but the clinical significance of prevalent fractures remains uncertain.

Objectives To examine the associations of prevalent vertebral fractures and other characteristics with physical functioning among 589 Japanese women ages 40 to 90 years.

Methods Lateral spine radiographs were obtained and radiographic vertebral fractures were assessed by quantitative morphometry, defined as vertebral heights more than 3 SD below the normal mean. A self-administered questionnaire was used to survey participants about difficulty in performing selected basic and instrumental activities of daily living (ADL).

Results The prevalence of vertebral fractures increased significantly with age. Half of women ages 80 and over had vertebral fractures. Impaired function was defined as difficulty performing 3 or more ADLs. Each vertebral fracture increased the odds of impaired function by 1.4 times (95% CI: 1.1, 1.8) in an age-adjusted logistic regression model. The number of vertebral  fractures remained a significant predictor independent of age, number of painful joints, and BMI in multiple variable logistic regression models; the odds ratio of impairment for number of vertebral fractures was 1.5 (CI: 1.2, 2.0). Additional adjustment for back pain did not alter these findings.

Conclusion The number of prevalent vertebral fractures contributed significantly to impaired function. The association was independent of age, back pain and the number of painful joints. The results also suggest that vertebral fractures may impair physical function even when back pain is not present.