Obesity and outcomes in patients hospitalized with pneumonia.

Studies suggest obesity is paradoxically associated with better outcomes for patients with pneumonia. Therefore, we examined the impact of obesity on short-term mortality in patients hospitalized with pneumonia. For 2 years clinical and radiographic data were prospectively collected on all consecutive adults admitted with pneumonia to six hospitals in Edmonton, Alberta, Canada. We identified 907 patients who also had body mass index (BMI, kg/m(2)) collected and categorized them as underweight (BMI < 18.5), normal (18.5 to <25), overweight (25 to <30) and obese (>30). Overall, 65% were >65 years, 52% were female, and 15% reported recent weight loss. Eighty-four (9%) were underweight, 358 (39%) normal, 228 (25%) overweight, and 237 (26%) obese. Two-thirds had severe pneumonia (63% PSI Class IV/V) and 79 (9%) patients died. In-hospital mortality was greatest among those that were underweight (12 [14%]) compared with normal (36 [10%]), overweight (21 [9%]) or obese (10 [4%], p <0.001 for trend). Compared with those of normal weight, obese patients had significantly lower rates of in-hospital mortality in multivariable logistic regression analyses: adjusted odds ratio (OR), 0.46; 95% CI, 0.22-0.97; p 0.04. However, compared with patients with normal weight, neither underweight (adjusted OR, 1.13; 95% CI, 0.54-2.4; p 0.7) nor overweight (adjusted OR, 0.94; 95% CI, 0.52-1.69; p 0.8) were associated with in-hospital mortality. In conclusion, in patients hospitalized with pneumonia, obesity was independently associated with lower short-term mortality, while neither being underweight nor overweight were. This suggests a protective influence of BMIs > 30 kg/m(2) that requires better mechanistic understanding.