Long-term risk of incident vertebral fractures.
BACKGROUND
Vertebral fractures are the most common osteoporotic fracture. Women with low bone mineral density (BMD) and prevalent vertebral fractures have a greater risk of incident vertebral fractures over the short-term, but their absolute risk of vertebral fracture over the long-term is uncertain.


OBJECTIVE
To examine the absolute risk of incident vertebral fracture by BMD and prevalent vertebral fracture status over 15 years.


METHODS
A total of 9704 white women were recruited at 4 US clinical centers and enrolled in the Study of Osteoporotic Fractures, a longitudinal cohort study. Of these, 2680 attended a clinic visit an average of 14.9 years after baseline; mean age of 68.8 years at entry and 83.8 years at follow-up. Mean Outcome Measure Incident vertebral fractures identified from lateral spinal radiographs defined as a decrease of at least 20% and 4 mm at any vertebral level. Prevalent vertebral fractures were identified on the baseline radiographs using vertebral morphometry. Bone mineral density was measured at the total hip and lumbar spine using dual-energy x-ray absorptiometry.


RESULTS
Of the 2680 women, 487 (18.2%) had an incident vertebral fracture including 163 of the 394 (41.4%) with a prevalent vertebral fracture at baseline and 324 of the 2286 (14.2%) without a prevalent vertebral fracture at baseline (odds ratio, 4.21; 95% confidence interval, 3.33-5.34). Low BMD was associated with an increased risk of incident vertebral fracture (odds ratio per 1 SD decrease in total hip BMD, 1.78 [95% confidence interval, 1.58-2.00]). The absolute risk of vertebral fracture ranged from 56% among women with total hip BMD T score of -2.5 or less and a prevalent vertebral fracture to 9% in women with normal BMD and no prevalent vertebral fracture.


CONCLUSIONS
Low BMD and prevalent vertebral fractures are independently related to new vertebral fractures over 15 years of follow-up. Women with a prevalent vertebral fracture have a substantially increased absolute risk of an incident fracture, especially if they have osteoporosis diagnosed by BMD.
Cauley
Jane A
JA
Department of Epidemiology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA. jcauley@edc.pitt.edu
Hochberg
Marc C
MC
Lui
Li-Yung
LY
Palermo
Lisa
L
Ensrud
Kristine E
KE
Hillier
Teresa A
TA
Nevitt
Michael C
MC
Cummings
Steven R
SR
D000368:Aged; D000369:Aged, 80 and over; D015519:Bone Density; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D015663:Osteoporosis, Postmenopausal; D012306:Risk; D016103:Spinal Fractures / Q000453:epidemiology*