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Mortality higher in diabetes patients with 'normal' weight

Patients with type 2 diabetes who are normal weight have a higher mortality rate than those who are overweight or obese, researchers have found.  

In what has been described as a ‘wake-up call' for the timely prevention and management of all patients with type 2 diabetes, the analysis found adults with the disease who were normal weight experienced higher total and non-cardiovascular mortality compared with those who were overweight or obese.

US researchers said their results showed an ‘obesity paradox' in diabetes. They analysed five studies involving 2,625 adults over the age of 40 and found around 12% of participants had a BMI of 18.5 to 24.99 and were therefore classified as normal weight.

During follow-up, 449 participants had died, 178 from cardiovascular causes and 263 from non-CVD causes.  

The rate of total mortality was 284 per 10,000 person years and non-CVD mortality was 198 per 10,000 person years among normal weight participants, compared to 152 per 10,000 person years and 87.8 per 10,000 person years respectively among overweight and obese participants. 

And after adjusting for blood pressure, lipid levels, waist circumference and smoking status as well as demographic characteristics, the rates of total and non-CVD mortality were still higher in normal weight participants.

The authors of the study said: ‘Mechanisms to explain our findings of higher mortality in adults who are normal weight at the time of incident diabetes are unknown.

‘However previous research suggests that normal weight persons with diabetes have a different genetic profile than overweight or obese persons with diabetes.

‘If the same genetic variants than predispose to diabetes are associated with other illnesses, these individuals may be "genetically loaded" toward experiencing higher mortality.'

Professor Azhar Farooqi, GP in Leicester and honorary senior lecturer at the University of Leicester, said the study highlighted the complexities of type 2 diabetes.

He said: ‘This just shows that type 2 diabetes is complicated and has its own subcategories and different physiologies which mean that thin diabetes patients need insulin earlier on than overweight patients.

‘This study just highlights that this difference may be important in terms of mortality and the risk factors that GPs need to focus on.'

The authors also pointed out that their findings were particularly relevant to older, black and Asian patients with diabetes who were more likely to be of normal weight.

In an accompanying editorial, Professor Hermez Florez, associate professor in medicine at the University of Miami, USA, and Dr Sumaya Castillo-Florez, a post doctoral associate at the University of Miami, USA,  said that the study highlighted the ‘emerging challenge' regarding diabetes and weight status.

They said: ‘This could be a wake-up call for timely prevention and management to reduce adverse outcomes in all patients with type 2 diabetes, particularly in those metabolically obese normal-weight at diagnosis, who may have a false sense of protection because they are not overweight or obese.'

JAMA 2012, online 7 August

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