Lower BMI for Type 1 Patients Improves CVD Outcomes

Obesity has  been a leading cause of mortality and morbidity of cardiovascular disease; strategies to lower BMI for type 1 patients can help.

Previous studies have found an increased risk of mortality in patients with type 1 diabetes (type 1) who present with low weight, thus leading to the belief in the “obesity paradox” in certain populations. With obesity on the rise, studies have also shown that obesity can increase mortality for various reasons. While patients with type 1 rely on insulin, a potential worrying side effect is weight gain. How does one determine the role of weight management in these patients?

This study intended to determine if there is an association between body mass index (BMI) and cardiovascular outcomes and mortality. Two cohort studies were performed on the Swedish population, using The Swedish National Diabetes Registry (NDR). Data was looked at from 1998 until 2013. Registration of new patients was allowed from 1998 until 2002, to allow for a 10 year follow up, ending the first cohort in 2012. The follow-up cohort was a 1-year follow-up in 2013. Exclusions, such as previous cardiovascular history, renal dialysis, no documentation of BMI, and patients with no identification of type 1 diabetes, were made to reduce the influence of reverse causality.

After exclusions, 26,125 patients were in the first cohort and 18,979 patients were in the follow-up cohort. The researchers were able to collect the BMI of each patient from the database to document the long-term trends. A mixed model was used to describe the trends in BMI due to repeated measures. They also followed patients from their registration in the system until an occurrence was documented, matching either hospitalization for heart failure, a major cardiovascular event (fatal/nonfatal AMI or stroke), cardiovascular mortality (CHF or stroke), or death of any cause. To analyze the data, Cox regression was used, with a BMI reference of 25 kg/m2.

Patients were split into 3 groups based on their baseline BMI. The largest group were patients with BMI 18.5 to < 25 kg/m2, the second largest with BMI 25 to < 30 kg/m2, and the last with BMI > 30 kg/m2. Throughout the cohort, there was a general increase in mean BMI. The data determined that there was no significantly increased risk associated with low BMI for any outcomes, but from the hazard ratios, determined there was a J-shaped association between BMI and mortality in patients who were male. This association also had a positive association between major cardiovascular disease and heart failure.

The authors acknowledged that intensive glycemic control may add to weight gain, which may be undesirable, but feel that they have support for patients with type 1 to maintain normal weight and good glycemic control for optimal long-term benefits. It was noted that there was no available insulin dosing documented, meaning the intensity of glycemic therapy was unknown. While the study was performed on the Swedish population, the researchers believe that their data can still represent many Western countries that have health insurance. While this study only determines the positive association between BMI and the risk of mortality, future randomized trials should be performed, potentially with the use of glucagon-like peptides 1 receptor agonists in obese patients.

Practice Pearls:

• Patients with type 1 diabetes who are obese may have an increased risk of mortality, major CVD, and HF
• This study shows for potential positive, long-term benefits, patients with type 1 should undergo both intensive glycemic therapy and weight control to keep levels of both as close to normal as possible
• Lifestyle changes to obtain normal weight should be a mainstay component of treatment in any patient with diabetes

Edqvist, Jon, et al. BMI, Mortality, and Cardiovascular Outcomes in Type 1 Diabetes: Findings Against an Obesity Paradox. Diabetes Care. 2019 May 2.

Emma Kammerer, L|E|C|O|M Bradenton School of Pharmacy, PharmD Candidate