Impact of malnutrition on the relationship between obesity and mortality in patients with atrial fibrillation

Abstract

Abstract Introduction A protective effect of obesity has been previously reported in patients with atrial fibrillation (AF) – the so-called `obesity paradox”. Nutritional status could behave as a confounding factor, but there are no studies that analyze the interaction of malnutrition in the relationship between obesity and mortality in AF patients. Aim The objective of this study was to determine the impact of nutritional status on the relationship between body mass index (BMI) and mortality in AF patients. Methods A retrospective, multicenter, population-based cohort study of patients with diagnosis of AF from January 1, 2014 to December 31, 2017, in Vigo, Spain, was conducted. We created three separate groups according to BMI (normal-weight, overweight, and obesity) and three separate cohorts based on nutritional status according to CONUT score (good nutrition, mild malnutrition, and moderate-severe malnutrition). The primary outcome was all-cause mortality. Secondary outcomes included embolic events (systemic embolism and stroke) and major bleeding. A combined endpoint of mortality, embolic and haemorrhagic events was assessed (clinical net outcome). Results A total of 14,849 AF patients aged ≥75 years (75.6±10.3 years, 50.9% women) were followed-up during 44.4±1.8 years. Overweight and obesity was observed in 42.6% and 46.0%, respectively, whereas malnutrition was observed in 34.3%. Malnutrition rates were lower as BMI increased: from 48.1% in patients with underweight, to 36.8%, 35.1% and 33.0% in patients with normal weight, overweight, and obesity, respectively (p-value <0.001 for the trend). BMI was inversely associated with mortality (HR 0.96, 95% CI 0.95–0.97; p<0.001) in the univariate analysis; however, this association was lost when adjusted analysis by nutritional status was performed (HR 0.99, 95% CI 0.99–1.00; p=0.285). Thus, neither overweight nor obesity were predictors of mortality nor net outcome when we adjusted by nutritional status: after stratifying for presence of malnutrition, survival of patients with a BMI>25 kg/m2 was similar to that of patients with BMI ≤25 kg/m2. Regarding to nutritional status, both mild and moderate-severe malnutrition were associated with higher rates of mortality, stroke/systemic embolism and bleeding in all BMI groups (normal-weight, overweight and obesity). In this real-world observational study, we have assessed the interaction of nutritional status in the association between BMI and prognosis of AF patients. We concluded that 1) Malnutrition is common in AF patients, even among patients with overweight and obesity; 2) Malnutrition is a strong predictor of mortality in patients with AF; and 3) BMI was not associated with worse prognosis after adjusting for nutritional status. Conclusion The analysis of a large population of AF patients showed that the association between improved mortality and obesity/overweight is confounded by malnutrition status. Funding Acknowledgement Type of funding sources: None. Impact of nutrition status and weightClinical outcomes in different groups