Obesity does not confer benefit in community-acquired pneumonia
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Among patients hospitalized with community-acquired pneumonia, those with obesity did not experience an improved time to clinical stability compared with their normal-weight counterparts, according to study data.
Angel N. Borisov, MBBS, of the department of internal medicine in the division of endocrinology, diabetes and metabolism at the University of Basel Hospital, Switzerland, and colleagues conducted the randomized clinical trial to test the so-called obesity paradox — the beneficial outcome observed in acute medical conditions for patients with obesity — in patients hospitalized with community-acquired pneumonia (CAP).
Researchers stratified 773 patients into four groups depending on baseline BMI: underweight (< 18.5 kg/m2), normal weight (18.5-25 kg/m2), overweight (25-30 kg/m2) and obesity (> 30 kg/m2).
Time to clinical stability served as the primary endpoint, with 30-day mortality, ICU admission rate, CAP complications and duration of antibiotic treatment serving as secondary endpoints.
Results revealed a U-shaped association between BMI and time to clinical stability, with shortest time to clinical stability found for patients with a BMI of 28 kg/m2 (HR = 1.01). Compared with patients with normal weight, those with obesity had a trend toward longer time to reach clinical stability (HR = 0.82; 95% CI, 0.67-1.02; P = .07).
By day 1, the underweight BMI group had a prolonged time to clinical stability (HR = 0.63; 95% CI, 0.45-0.89; P = .008). The underweight group also had a prolonged total duration of antibiotic treatment by 2.5 days (95% CI, 0.88-4.2; P = .003), with no difference in antibiotic treatment duration observed among patients with obesity.
Moreover, researchers found no statistically significant difference in mortality or ICU admission rates between BMI groups.
“Our study cannot confirm an ‘obesity paradox,’ while it underlines that underweight may aggravate the course of disease in patients hospitalized with CAP,” the researchers concluded. “Despite a nadir in time to clinical stability and length of hospital stay for overweight within our multivariable fractional polynomials interaction graphs, our multivariate regression analysis did not reveal an advantage in clinical outcome. To unveil whether patients with overweight enjoy any benefit, future studies should include more clinical aspects such as waist circumference, hip-to-waist ratio or fat mass in order to better reflect the metabolic status than BMI alone. Furthermore, mechanistic studies in this field are warranted investigating underlying mechanisms of obesity, immunometabolism and acute systemic infections.”
Perspective
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The central hypothesis of the “obesity paradox” is that obesity can confer health advantages in situations where it is counterintuitive. This has been described for longevity in elderly individuals with obesity and in patients with various chronic illnesses who have better outcomes if they also have obesity compared to their lean counterparts. This hypothesis has generally merited criticism based on the principle of “reverse causality,” which holds that lower ranges of BMI can be due to processes that produce adverse outcomes leading to the false appearance that higher BMI levels are protective.
Borisov and colleagues have examined whether the obesity paradox applies to CAP. These authors conducted a secondary analyses of data from a multicentered study addressing the adjunct use of corticosteroids in hospitalized patients with CAP. Their analysis featured careful adjustments for multiple relevant covariables that could pertain to reverse causality, including cigarette smoking, cancer, diabetes, COPD, renal insufficiency and others. The data demonstrated that obesity was progressively associated with increased time to clinical stability, 30-day mortality, ICU admission rate, pneumonia complications and duration of antibiotic treatment. Thus, these authors were able to rebut previous studies that did demonstrate an obesity paradox in patients with CAP, and in particular, a 2014 meta-analysis (Nie W, et al. BMC Med. 2014;doi:10.1186/1741-7015-12-61) showing a progressive decline in CAP-associated mortality with increments in BMI even up to BMI levels as high as 40 kg/m2.
The outcomes assessed by Borisov and colleagues exhibited a U-shaped curve as a function of BMI with low and high BMI values associated with poorer outcomes. The nadir occurred within the midrange of overweight (BMI, 25-29.9 kg/m2) with risk for adverse events increasing as BMI rose above the high overweight range into greater degrees of obesity (BMI ≥ 30 kg/m2). The data are consistent with more aggressive treatment of overweight/obesity in patients with BMI of at least 27 kg/m2. Incidentally, this is the BMI threshold when obesity medications become indicated for treatment of overweight/obesity. Patients with obesity are at increased risk for CAP, and the prevention and treatment of pneumonia add to a long list justifying a complications-centric approach to the treatment of obesity — as espoused by the American Association of Clinical Endocrinology obesity treatment guidelines — and the new diagnostic term, adiposity-based chronic disease.
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