Background Previous evidence of an association between body mass index (BMI) and mortality in patients with diabetes was inconsistent. The BMI–mortality association with normal fasting glucose (NFG), impaired fasting glucose (IFG) and prevalent diabetes is still unclear in the Chinese population.
Methods We analysed data for 17 252 adults from the Rural Chinese Cohort Study during 2007–2008 and followed for mortality during 2013–2014. Participants were classified with NFG, IFG and diabetes according to baseline measurement values of fasting glucose and self-reported diabetes. Multivariable Cox proportional hazard models were used to calculate HRs and 95% CIs across BMI categories by glycemic status.
Results During the 6-year follow-up, 1109 participants died (563/10 181 with NFG, 349/5572 with IFG and 197/1499 with diabetes). The BMI–mortality association was curvilinear, with low BMI (even in normal range) associated with increased mortality regardless of glycemic status. In adjusted Cox models, risk of mortality showed a decreasing trend with BMI≤18 kg/m2, 18<BMI≤20 kg/m2 and 20<BMI≤22 kg/m2 vs 22<BMI≤24 kg/m2: HR 2.83 (95% CI 1.78 to 4.51), 2.05 (1.46 to 2.87) and 1.45 (1.10 to 1.90), respectively, for NFG; 2.53 (1.25 to 5.14), 1.36 (0.86 to 2.14) and 1.09 (0.76 to 1.57), respectively, for IFG; and 4.03 (1.42 to 11.50), 2.00 (1.05 to 3.80) and 1.52 (0.88 to 2.60), respectively, for diabetes. The risk of mortality was lower for patients with diabetes who were overweight or obese versus normal weight.
Conclusions Low BMI was associated with increased mortality regardless of glycemic status. Future studies are needed to explain the ‘obesity paradox’ in patients with diabetes.
- body mass index
- cohort study
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Contributors YZ, YL, HS, DH and MZ substantially contributed to the design and drafting of the study and the analysis and interpretation of the data. XS, ZY, HL, YR, BW, DZ, XL, DL, RZ, FL, XC, LL, CC and QZ revised it critically for important intellectual content. All authors were involved in the collection of data and approved the final version of the manuscript.
Funding This study was supported by the National Natural Science Foundation of China (grant nos 81373074, 81402752 and 81673260); the Natural Science Foundation of Guangdong Province (grant no 2017A030313452); the Medical Research Foundation of Guangdong Province (grant no A2017181); and the Science and Technology Development Foundation of Shenzhen (grant nos JCYJ20140418091413562, JCYJ20160307155707264, JCYJ20170302143855721 and JCYJ20170412110537191).
Competing interests None declared.
Patient consent Obtained.
Ethics approval The study was approved by the Medical Ethics Committee of Shenzhen University.
Provenance and peer review Not commissioned; externally peer reviewed.
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