Higher BMI related to lower mortality in patients with AF

Researchers found that patients from the registry with higher BMI had lower risk for mortality, independent of other risk factors, although patients with higher BMI tended to be younger than patients with lower BMI.

Ambarish Pandey, MD, and colleagues stratified the 9,606 patients (42% women) enrolled in the registry from June 2010 to August 2011 into five BMI categories: normal weight, overweight, class I obese, class II obese and class III obese. Seventy-eight percent of patients were overweight or obese.

They assessed the association between BMI and clinical outcomes, including mortality, during a median 2 years of follow-up.

Compared with those with lower BMI, patients with higher BMI were younger and had a higher rate of diabetes, hypertension and obstructive sleep apnea, Pandey, from the division of cardiology, University of Texas Southwestern Medical Center, Dallas, and colleagues wrote.

Those with higher BMI also were more likely to be using anticoagulation and rhythm control strategies than those with lower BMI, they wrote.

According to the researchers, all-cause mortality rates during follow-up declined in a near-linear fashion with increasing BMI (normal-weight group, 8.28/100 patient-years; class III obese group, 3.81/100 patient-years). When they performed multivariable adjustment, higher BMI was associated with lower risk for mortality and the lowest-risk group was class I obese (HR vs. normal weight = 0.65; 95% CI, 0.54-0.78).

They found that the hazard of mortality was 7% lower for every BMI increase of 5 kg/m² (HR = 0.93; 95% CI, 0.89-0.98).

BMI was not associated with other clinical outcomes such as new-onset HF, progression of AF, first CV hospitalization and first bleeding hospitalization. Higher BMI was associated with lower risk for stroke, transient ischemic attack or noncentral nervous system embolism in an unadjusted analysis (HR for class III obese vs. normal weight = 0.38; 95% CI, 0.23-0.63), but the association disappeared after adjustment for other risk factors, Pandey and colleagues wrote.

“One potential explanation is that while obese patients develop AF secondary to greater left atrial size, normal-weight AF patients have a different pathophysiologic substrate, which could be associated with a worse prognosis,” they wrote. “Also, overweight and obese patients have been shown to have lower increases in plasma renin and angiotensin in response to stress, which may lead to improved outcomes.”

Other possible explanations include higher BMI providing greater metabolic reserve to combat increased catabolic stress, greater use of rhythm control strategies in patients with higher BMI and greater use of beta-blockers and anticoagulants in those with higher BMI, they wrote. – by Erik Swain

Source: www.healio.com