Being overweight, but not obese, associated with decreased mortality in type 2 diabetes

1. From a cohort study, overweight patients with type 2 diabetes had a decreased mortality rate when compared to normal weight or obese patients.

2. Overweight and obese patients with type 2 diabetes were associated with an increased risk of cardiovascular disease.

Evidence Rating Level: 2 (Good)       

Study Rundown: The “obesity paradox” refers to evidence that overweight patients with cardiovascular disease may live longer than patients of lower weight, but such a relationship between weight and outcomes in type 2 diabetes has not been explored. This cohort study found that overweight or obese patients had a higher risk of acute coronary syndrome (ACS) and heart failure (HF) than normal weight patients, and the risk for cerebrovascular accident (CVA) was increased in obese patients. In contrast, mortality risk was not higher in overweight or obese patients, and those with lower than normal weight had a higher associated mortality risk. Furthermore, the best survival rate was seen in the overweight category. Limitations to the study include the use of BMI as an indicator of adiposity as opposed to measures of physical fitness or the waist-hip ratio, the use of prevalent cases, and the lack of data for cause of death. Strengths of the study include its use of a large cohort from a single center, long follow-up, and adjustment for comorbidities. Overall, these results suggest that the relationship between type 2 diabetes, cardiovascular disease, and mortality may be much more complicated than previously thought.

Click to read the study, published today in the Annals of Internal Medicine

Relevant Reading: Obesity Paradox Does Exist

In-Depth [prospective cohort]: A total of 10 568 patients with known type 2 diabetes were enrolled and followed for a median of 10.6 years at a single center in England. The primary outcome was all-cause mortality, and secondary outcomes were hospitalizations for cardiovascular events. Overweight and obese patients had higher rates of ACS and HF (HR 1.34, 95%CI 1.08-1.65; and HR 1.64, 95%CI 1.31-2.05, respectively). Obese patients had higher rates of CVA (HR 1.26, 95%CI 1.01-1.59). All-cause mortality was decreased in over-weight patients (HR 0.87; 95%CI 0.79-0.95) and not different in obese patients (HR 0.97; 95%CI 0.87-1.07) compared to normal weight. Underweight patients had increased mortality with a HR of 2.84 (95%CI 1.97-4.10). Logistic regression suggested lower mortality risk developed around age 60. Exclusion of patients who died early in follow-up, replacing BMI with body surface area, and re-analyzing with different follow-up time-points did not change results.

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