SLEとRAの身体組成の比較

SLEとRAの身体組成を比較検討した論文を紹介します。

Santos MJ, Vinagre F, Canas da Silva J, Gil V, Fonseca JE. Body composition phenotypes in systemic lupus erythematosus and rheumatoid arthritis: a comparative study of Caucasian female patients. Clin Exp Rheumatol. 2011 May 31. [Epub ahead of print]

SLEとRAではコントロール（炎症性疾患のない方）と比較して、同じようなBMIにもかかわらず身体組成の異常をより多く認めました。RAでは過脂肪と中心性肥満がより多く、SLEではサルコペニアがより多いという結果でした。

サルコペニア肥満はSLEで6.5％、RAで5.6％に認めましたが、コントロールには認めませんでした。体脂肪率と関連し手痛因子は、SLEでは喫煙、疾患の活動度、CRPで、RAでは教育、疾患の活動度、ステロイドの使用量でした。

SLEやRAのような膠原病ではサルコペニアと肥満を認めやすいですが、その原因の一部は疾患による炎症（悪液質）と治療（ステロイド使用）によるものと考えられました。言い方を変えると加齢や活動（廃用）によるサルコペニアの要素は少ないといえます。栄養によるサルコペニア（飢餓）も少ないのかもしれません。

サルコペニアの診断は、やせている場合には容易ですが、やせていない場合には身体計測のみでは容易ではありません。BIA、DEXA、CT、MRIで筋肉量を評価しないと判断できないこともあります。少なくとも膠原病の方では、やせていなくてもサルコペニアや悪液質の可能性を疑うことが必要だと考えます。

Abstract
OBJECTIVES: The amount and distribution of fat and lean mass have important implications for health and systemic inflammation may represent a risk for altered body composition. The aim of this study was to analyse whether changes in body composition are similarly associated with systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA), two inflammatory conditions of different pathogenesis.

METHODS: Body mass index (BMI), waist circumference, fat mass (FM) and fat-free mass (FFM) were measured in 92 women with SLE, 89 with RA and 107 controls. Results were compared among the 3 groups and correlations of FM percentage were explored within SLE and RA.

RESULTS: Abnormal body composition was more frequent in women with SLE and RA than in non-inflammatory controls, despite having a similar BMI. RA diagnosis was significantly associated with overfat (OR=2.782, 95%CI 1.470-5.264; p=0.002) and central obesity (OR=2.998, 95%CI 1.016-8.841; p=0.04), while sarcopenia was more common among SLE (OR=3.003; 95%CI 1.178-7.676; p=0.01). Sarcopenic obesity, i.e. the coexistence of overfat with sarcopenia, was present in 6.5% of SLE and 5.6% of RA women, but no controls. Independent correlations of FM percentage in women with SLE included smoking, disease activity and CRP. In RA, education, disease activity and cumulative corticosteroid dose were identified as independent predictors of FM percentage.

CONCLUSIONS: Women with SLE or RA diagnosis are more likely to have abnormal body composition phenotype, with some differences existing between these two conditions. Changes in body composition are partly explained by the inflammatory burden of disease and its treatment.