2012年8月7日火曜日

肥満と肺炎入院患者の予後

肥満と肺炎入院患者の予後に関する論文を紹介します。

S. Kahlon, et al. Obesity and Outcomes in Patients Hospitalized with Pneumonia. Clinical Microbiology and Infection, DOI: 10.1111/j.1469-0691.2012.04003.x

肥満患者では肺炎後の予後がよいという先行研究があります。入院期間中の死亡率とBMIの関連を調査しました。907人中、84人が低栄養(BMI18.5未満)、358人が正常体重(BMI18.5-25)、228人が過栄養(BMI25-30)、237人が肥満(BMI30以上)で、79人(9%)が死亡しました。

死亡率は低栄養14%、正常体重10%、過栄養9%、肥満4%で、低栄養で死亡率が高い傾向でした。多変量解析で正常体重と比較した場合、肥満では有意に死亡率が低いという結果でしたが、低栄養と過栄養では統計学的有意差を認めませんでした。肥満では肺炎死亡率が低いという結論です。

肺炎でも慢性臓器不全と同様に、Obesity Paradoxが成立する可能性があります。今回は身体組成を分析していませんが、おそらく筋肉量が多ければ多いほど入院中の肺炎死亡率が低い(より高度の侵襲に耐えることができる)と推測します。体重増加による肥満より筋肉量増加がより重要だと思います。

Abstract

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 6 hospitals in Edmonton, Alberta, Canada. We identified 907 patients who also had body mass index (BMI, kg/m2) collected and categorized them as underweight,  normal, overweight, and obese. Overall, 65% were >65 years, 52% were female, and 15% reported recent weight loss. 84 (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 the underweight (12 [14%]) vs normal (36 [10%]) vs overweight (21 [9%]) vs obese (10 [4%], p<0 .001=".001" p="p">
Compared with 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 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 underweight nor overweight were. This suggests a protective influence for BMIs>30 kg/m2 that requires better mechanistic understanding.

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