N. Engl. J. Med 2014 Jan 16;370(3)233-244, DK Tobias, A Pan, CL Jackson, EJ O’Reilly, EL Ding, WC Willett, JE Manson, FB Hu
Research · January 30, 2014
TAKE-HOME MESSAGE
- Some studies have reported an “obesity paradox” whereby being overweight vs being normal or underweight was associated with lower mortality in patients with type 2 diabetes. This study, using data from patients with type 2 diabetes who were enrolled in the Nurses’ Health Study and the Health Professionals Follow-Up Study did not confirm these findings. The results showed the lowest risk of mortality to be associated with normal-weight body mass index (BMI, 22.5–24.9). In never smokers, there was a linear relationship between higher BMI and increased mortality risk. Among ever smokers, a nonlinear association was shown.
- Results of this study did not show a protective effect of overweight or obesity in patients with type 2 diabetes.
Commentary By: Peter Lin MD, CCFP
Does BMI at the time of the diagnosis of diabetes predict future death? This group looked at over 11,000 participants from the Nurses’ Health Study and the Health Professionals Follow-Up Study and correlated their BMI at the time of their diabetes diagnosis to see if there is a relationship with an earlier death.
It turned out, if someone never smoked, there is a linear relationship. As expected, the higher the BMI, the higher the risk of death. However, if someone has smoked before, then there is a J curve relationship, meaning at lower BMI there was no less risk of death. Perhaps one explanation is that smoking by itself pushes the risk a lot, and it is only when the BMI gets really high that the obesity increases that risk further. So, yes; we should get people to lose weight, but, equally important, we should get them to lose the cigarettes too.
ABSTRACT
BACKGROUND
The relation between body weight and mortality among persons with type 2 diabetes remains unresolved, with some studies suggesting decreased mortality among overweight or obese persons as compared with normal-weight persons (an “obesity paradox”).
METHODS
We studied participants with incident diabetes from the Nurses’ Health Study (8970 participants) and Health Professionals Follow-up Study (2457 participants) who were free of cardiovascular disease and cancer at the time of a diagnosis of diabetes. Body weight shortly before diagnosis and height were used to calculate the body-mass index (BMI, the weight in kilograms divided by the square of the height in meters). Multivariable Cox models were used to estimate the hazard ratios and 95% confidence intervals for mortality across BMI categories.
RESULTS
There were 3083 deaths during a mean period of 15.8 years of follow-up. A J-shaped association was observed across BMI categories (18.5 to 22.4, 22.5 to 24.9 [reference], 25.0 to 27.4, 27.5 to 29.9, 30.0 to 34.9, and ≥35.0) for all-cause mortality (hazard ratio, 1.29 [95% confidence interval {CI}, 1.05 to 1.59]; 1.00; 1.12 [95% CI, 0.98 to 1.29]; 1.09 [95% CI, 0.94 to 1.26]; 1.24 [95% CI, 1.08 to 1.42]; and 1.33 [95% CI, 1.14 to 1.55], respectively). This relationship was linear among participants who had never smoked (hazard ratios across BMI categories: 1.12, 1.00, 1.16, 1.21, 1.36, and 1.56, respectively) but was nonlinear among participants who had ever smoked (hazard ratios across BMI categories: 1.32, 1.00, 1.09, 1.04, 1.14, and 1.21) (P=0.04 for interaction). A direct linear trend was observed among participants younger than 65 years of age at the time of a diabetes diagnosis but not among those 65 years of age or older at the time of diagnosis (P<0.001 for interaction).
CONCLUSIONS
We observed a J-shaped association between BMI and mortality among all participants and among those who had ever smoked and a direct linear relationship among those who had never smoked. We found no evidence of lower mortality among patients with diabetes who were overweight or obese at diagnosis, as compared with their normal-weight counterparts, or of an obesity paradox.