De Laet C, Kanis J A, Odén A, Johanson H, Johnell O, Delmas P, Eisman J A, Kroger H, Fujiwara S, Garnero P, McCloskey E V, Mellstrom D, Melton L J, Meunier P J, Pols H A P, Reeve J, Silman A, Tenenhouse A
Scientific Institute of Public Health, Brussels, Belgium.
Osteoporos Int. 2005 Nov;16(11):1330-8. doi: 10.1007/s00198-005-1863-y. Epub 2005 Jun 1.
Low body mass index (BMI) is a well-documented risk factor for future fracture. The aim of this study was to quantify this effect and to explore the association of BMI with fracture risk in relation to age, gender and bone mineral density (BMD) from an international perspective using worldwide data. We studied individual participant data from almost 60,000 men and women from 12 prospective population-based cohorts comprising Rotterdam, EVOS/EPOS, CaMos, Rochester, Sheffield, Dubbo, EPIDOS, OFELY, Kuopio, Hiroshima, and two cohorts from Gothenburg, with a total follow-up of over 250,000 person years. The effects of BMI, BMD, age and gender on the risk of any fracture, any osteoporotic fracture, and hip fracture alone was examined using a Poisson regression model in each cohort separately. The results of the different studies were then merged. Without information on BMD, the age-adjusted risk for any type of fracture increased significantly with lower BMI. Overall, the risk ratio (RR) per unit higher BMI was 0.98 (95% confidence interval [CI], 0.97-0.99) for any fracture, 0.97 (95% CI, 0.96-0.98) for osteoporotic fracture and 0.93 (95% CI, 0.91-0.94) for hip fracture (all p <0.001). The RR per unit change in BMI was very similar in men and women ( p >0.30). After adjusting for BMD, these RR became 1 for any fracture or osteoporotic fracture and 0.98 for hip fracture (significant in women). The gradient of fracture risk without adjustment for BMD was not linearly distributed across values for BMI. Instead, the contribution to fracture risk was much more marked at low values of BMI than at values above the median. This nonlinear relation of risk with BMI was most evident for hip fracture risk. When compared with a BMI of 25 kg/m(2), a BMI of 20 kg/m(2) was associated with a nearly twofold increase in risk ratio (RR=1.95; 95% CI, 1.71-2.22) for hip fracture. In contrast, a BMI of 30 kg/m(2), when compared with a BMI of 25 kg/m(2), was associated with only a 17% reduction in hip fracture risk (RR=0.83; 95% CI, 0.69-0.99). We conclude that low BMI confers a risk of substantial importance for all fractures that is largely independent of age and sex, but dependent on BMD. The significance of BMI as a risk factor varies according to the level of BMI. Its validation on an international basis permits the use of this risk factor in case-finding strategies.
低体重指数（BMI）是未来发生骨折的一个有充分文献记载的风险因素。本研究的目的是量化这种影响，并从国际视角利用全球数据探讨BMI与骨折风险在年龄、性别和骨密度（BMD）方面的关联。我们研究了来自12个基于人群的前瞻性队列的近60000名男性和女性的个体参与者数据，这些队列包括鹿特丹队列、EVOS/EPOS队列、CaMos队列、罗切斯特队列、谢菲尔德队列、达博队列、EPIDOS队列、OFELY队列、库奥皮奥队列、广岛队列以及哥德堡的两个队列，总随访时间超过250000人年。在每个队列中分别使用泊松回归模型研究BMI、BMD、年龄和性别对任何骨折、任何骨质疏松性骨折以及单纯髋部骨折风险的影响。然后将不同研究的结果合并。在没有BMD信息的情况下，任何类型骨折的年龄调整风险随着BMI降低而显著增加。总体而言，BMI每升高一个单位，任何骨折的风险比（RR）为0.98（95%置信区间[CI]，0.97 - 0.99），骨质疏松性骨折的RR为0.97（95%CI，0.96 - 0.98），髋部骨折的RR为0.93（95%CI，0.91 - 0.94）（所有p<0.001）。BMI每单位变化的RR在男性和女性中非常相似（p>0.30）。在调整BMD后，任何骨折或骨质疏松性骨折的这些RR变为1，髋部骨折的RR变为0.98（在女性中显著）。未调整BMD时骨折风险的梯度在BMI值上并非呈线性分布。相反，在低BMI值时对骨折风险的影响比在中位数以上的值时更为显著。这种风险与BMI的非线性关系在髋部骨折风险中最为明显。与BMI为25kg/m²相比，BMI为20kg/m²与髋部骨折风险比增加近两倍相关（RR = 1.95；95%CI，1.71 - 2.22）。相比之下，与BMI为25kg/m²相比，BMI为30kg/m²仅与髋部骨折风险降低17%相关（RR = 0.83；95%CI，0.69 - 0.99）。我们得出结论，低BMI对所有骨折都具有至关重要的风险，这在很大程度上独立于年龄和性别，但依赖于BMD。BMI作为风险因素的重要性根据BMI水平而有所不同。其在国际范围内的验证使得该风险因素可用于病例发现策略。
