‘Obesity paradox’ challenged in type 1 diabetes
May 8, 2019
Adults with type 1 diabetes and overweight or obesity may be more susceptible to cardiovascular disease, heart failure and higher mortality risk compared with those of lower weight status, according to findings published in Diabetes Care.
“Recent studies suggest that insulin resistance in overweight or obese individuals with type 1 diabetes may be associated with an increased risk of vascular complications, but few studies have investigated the relationship between BMI in individuals with type 1 diabetes and mortality,
Annika Rosengren, MD, professor of internal medicine at the Sahlgrenska Academy Institute of Medicine at the University of Gothenburg in Sweden, and colleagues wrote. “Phenomena such as the obesity paradox, which suggests that there is an inverse association between BMI and risk of cardiovascular outcomes, have been debated intensely in the past decade.”
Using data from the Swedish National Diabetes Registry, Rosengren and colleagues examined the effects of BMI on CVD, heart failure and mortality risk in a cohort of 26,215 adults (mean age, 33.3 years; 44.5% women) who were clinically diagnosed with type 1 diabetes between 1998 and 2012. A median follow-up period of 10.9 years was reported, with follow-up concluding when an outcome of CVD, heart failure or death was reached. ä
Based on WHO classifications, there were 2,160 participants with obesity defined as BMI of 30 kg/m2 or more (mean age, 34.4 years; 52.2% women), 8,677 participants with overweight defined as BMI of 25 kg/m2 to less than less than 30 kg/m2 (mean age, 34.9 years; 40.8% women) and 15,288 participants with normal weight defined as BMI of 18.5 kg/m2 to less than 25 kg/m2 (mean age, 32.2 years; 45.5% women).
According to the researchers, 1,031 deaths were reported, including 342 that were related to a CV issue. In addition, CVD events were reported 1,460 times and heart failure was reported 580 times.
In terms of mortality and BMI, the researchers observed a “J-shaped association” while noting that those with lower BMI levels were not at higher risk than those with higher levels.
Participants with obesity had a higher all-cause mortality incidence rate (IR = 4.39; 95% CI, 3.54-5.39) than those with overweight (IR = 3.95; 95% CI, 3.55-4.38) or normal weight (IR = 3.83; 95% CI, 3.52-4.15).
In terms of CV mortality, participants with obesity had an elevated incidence rate (IR = 1.67; 95% CI, 1.16-2.32) compared with those with overweight (IR = 1.42; 95% CI, 1.18-1.68) and those with normal weight (IR = 1.18; 95% CI, 1.01-1.36).
The incidence of a major CV event was higher for participants with obesity (IR = 6.94; 95% CI, 5.84-8.18) compared with those with overweight (IR = 6.58; 95% CI, 6.06-7.14) and those with normal weight (IR = 4.99; 95% CI, 4.64-5.36).
Lastly, elevated rates for heart failure hospitalization were found for those with obesity (IR = 2.85; 95% CI, 2.17-3.67) in comparison with those with overweight (IR = 2.72; 95% CI, 2.39-3.08) and those with normal weight (IR = 1.84; 95% CI, 1.63-2.07).
The associations between BMI and all-cause mortality, CV mortality, CVD events and heart failure were strongest in men, and a similar finding was observed for weight change, the researchers wrote.
“Given the plethora of evidence demonstrating the deleterious effects of poor glycemic control, we believe not only that our results may reassure clinicians about the intrinsic value of pursuing ambitious goals for glycemic control, but also that a low weight among otherwise healthy patients with type 1 diabetes does not imply an increased mortality risk,” the researchers wrote, adding that the evidence did not support the obesity paradox theory.
“Hence, our results support health care professionals to encourage patients with type 1 diabetes to maintain a lower BMI through lifestyle changes, if they can, to further lessen their risk of vascular complications,” the researchers wrote.
BMI, Mortality, and Cardiovascular Outcomes in Type 1 Diabetes: Findings Against an Obesity Paradox
Jon Edqvist, Araz Rawshani, Martin Adiels, Lena Björck, Marcus Lind, Ann-Marie Svensson, Sofia Gudbjörnsdottir, Naveed Sattar, Annika Rosengren
Diabetes Care 2019 Apr; dc181446. https://doi.org/10.2337/dc18-1446
OBJECTIVE Low weight has been associated with increased mortality risks in type 1 diabetes. We aimed to investigate the importance of weight and weight gain/loss in the Swedish population diagnosed with type 1 diabetes.
RESEARCH DESIGN AND METHODS Patients with type 1 diabetes (n = 26,125; mean age 33.3 years; 45% women) registered in the Swedish National Diabetes Registry from 1998 to 2012 were followed from the first day of study entry. Cox regression was used to calculate risk of death from cardiovascular disease (CVD), major CVD events, hospitalizations for heart failure (HF), and total deaths.
RESULTS Population mean BMI in patients with type 1 diabetes increased from 24.7 to 25.7 kg/m2 from 1998 to 2012. Over a median follow-up of 10.9 years, there were 1,031 deaths (33.2% from CVD), 1,460 major CVD events, and 580 hospitalizations for HF. After exclusion of smokers, patients with poor metabolic control, and patients with a short follow-up time, there was no increased risk for mortality in those with BMI <25 kg/m2, while BMI >25 kg/m2 was associated with a minor increase in risk of mortality, major CVD, and HF. In women, associations with BMI were largely absent. Weight gain implied an increased risk of mortality and HF, while weight loss was not associated with higher risk.
CONCLUSIONS Risk of major CVD, HF, CVD death, and mortality increased with increasing BMI, with associations more apparent in men than in women. After exclusion of factors associated with reverse causality, there was no evidence of an obesity paradox.
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