Bigaard Janne, Frederiksen Kirsten, Tjønneland Anne, Thomsen Birthe Lykke, Overvad Kim, Heitmann Berit Lillienthal, Sørensen Thorkild I A
Institute of Cancer Epidemiology, The Danish Cancer Society, Strandboulevarden 49, DK-2100 Copenhagen, Denmark.
Obes Res. 2004 Jul;12(7):1042-9. doi: 10.1038/oby.2004.131.
To investigate whether the association between BMI and all-cause mortality could be disentangled into opposite effects of body fat and fat-free mass (FFM).
All-cause mortality was studied in the Danish follow-up study "Diet, Cancer and Health" with 27,178 men and 29,875 women 50 to 64 years old recruited from 1993 to 1997. By the end of year 2001, the median follow-up was 5.8 years, and 1851 had died. Body composition was assessed by bioelectrical impedance. Cox regression models were used to estimate the relationships among body fat mass index (body fat mass divided by height squared), FFM index (FFM divided by height squared), and mortality. All analyses were adjusted for smoking habits.
Men and women showed similar associations. J-shaped associations were found between body fat mass index and mortality adjusted for FFM and smoking. The mortality rate ratios in the upper part of body fat mass were 1.12 per kg/m2 (95% confidence interval: 1.07, 1.18) in men and 1.06 per kg/m2 (95% confidence interval: 1.02, 1.10) in women. Reversed J-shaped associations were found between FFM index and mortality with a tendency to level off for high values of FFM.
Our findings suggest that BMI represents joint but opposite associations of body fat and FFM with mortality. Both high body fat and low FFM are independent predictors of all-cause mortality.
研究体重指数（BMI）与全因死亡率之间的关联是否可分解为体脂和去脂体重（FFM）的相反作用。
在丹麦的“饮食、癌症与健康”随访研究中，对1993年至1997年招募的27178名50至64岁男性和29875名女性进行全因死亡率研究。到2001年底，中位随访时间为5.8年，1851人死亡。通过生物电阻抗评估身体成分。采用Cox回归模型估计体脂质量指数（体脂质量除以身高平方）、FFM指数（FFM除以身高平方）与死亡率之间的关系。所有分析均对吸烟习惯进行了校正。
男性和女性表现出相似的关联。在根据FFM和吸烟情况校正后，体脂质量指数与死亡率之间呈J形关联。男性体脂质量较高部分的死亡率比值比为每千克/平方米1.12（95%置信区间：1.07，1.18），女性为每千克/平方米1.06（95%置信区间：1.02，1.10）。FFM指数与死亡率之间呈倒J形关联，对于高FFM值有趋于平稳的趋势。
我们的研究结果表明，BMI代表了体脂和FFM与死亡率的联合但相反的关联。高体脂和低FFM都是全因死亡率的独立预测因素。
