Predictive value of BMD for hip and other fractures.
The relationship between BMD and fracture risk was estimated in a meta-analysis of data from 12 cohort studies of approximately 39,000 men and women. Low hip BMD was an important predictor of fracture risk. The prediction of hip fracture with hip BMD also depended on age and z score.


BACKGROUND
The aim of this study was to quantify the relationship between BMD and fracture risk and examine the effect of age, sex, time since measurement, and initial BMD value.


METHODS
We studied 9891 men and 29,082 women from 12 cohorts comprising EVOS/EPOS, EPIDOS, OFELY, CaMos, Rochester, Sheffield, Rotterdam, Kuopio, DOES, Hiroshima, and 2 cohorts from Gothenburg. Cohorts were followed for up to 16.3 years and a total of 168,366 person-years. The effect of BMD on fracture risk was examined using a Poisson model in each cohort and each sex separately. Results of the different studies were then merged using weighted coefficients.


RESULTS
BMD measurement at the femoral neck with DXA was a strong predictor of hip fractures both in men and women with a similar predictive ability. At the age of 65 years, risk ratio increased by 2.94 (95% CI = 2.02-4.27) in men and by 2.88 (95% CI = 2.31-3.59) in women for each SD decrease in BMD. However, the effect was dependent on age, with a significantly higher gradient of risk at age 50 years than at age 80 years. Although the gradient of hip fracture risk decreased with age, the absolute risk still rose markedly with age. For any fracture and for any osteoporotic fracture, the gradient of risk was lower than for hip fractures. At the age of 65 years, the risk of osteoporotic fractures increased in men by 1.41 per SD decrease in BMD (95% CI = 1.33-1.51) and in women by 1.38 per SD (95% CI = 1.28-1.48). In contrast with hip fracture risk, the gradient of risk increased with age. For the prediction of any osteoporotic fracture (and any fracture), there was a higher gradient of risk the lower the BMD. At a z score of -4 SD, the risk gradient was 2.10 per SD (95% CI = 1.63-2.71) and at a z score of -1 SD, the risk was 1.73 per SD (95% CI = 1.59-1.89) in men and women combined. A similar but less pronounced and nonsignificant effect was observed for hip fractures. Data for ultrasound and peripheral measurements were available from three cohorts. The predictive ability of these devices was somewhat less than that of DXA measurements at the femoral neck by age, sex, and BMD value.


CONCLUSIONS
We conclude that BMD is a risk factor for fracture of substantial importance and is similar in both sexes. Its validation on an international basis permits its use in case finding strategies. Its use should, however, take account of the variations in predictive value with age and BMD.
Johnell
Olof
O
Department of Orthopaedics, Malmo University Hospital, Malmo, Sweden.
Kanis
John A
JA
Oden
Anders
A
Johansson
Helena
H
De Laet
Chris
C
Delmas
Pierre
P
Eisman
John A
JA
Fujiwara
Seiko
S
Kroger
Heikki
H
Mellstrom
Dan
D
Meunier
Pierre J
PJ
Melton
L Joseph
LJ
O'Neill
Terry
T
Pols
Huibert
H
Reeve
Jonathan
J
Silman
Alan
A
Tenenhouse
Alan
A
D015502:Absorptiometry, Photon; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D015519:Bone Density; D015331:Cohort Studies; D005260:Female; D006615:Hip / Q000000981:diagnostic imaging; D006620:Hip Fractures / Q000000981:diagnostic imaging* / Q000453:epidemiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010024:Osteoporosis / Q000150:complications; D011379:Prognosis; D018570:Risk Assessment; D012307:Risk Factors; D012737:Sex Factors; D014463:Ultrasonography