Panzetta Giovanni, Abaterusso Cataldo
S.C. di Nefrologia e Dialisi, Azienda Ospedaliero-Universitaria, Trieste, Italy.
G Ital Nefrol. 2010 Nov-Dec;27(6):629-38.
About 50% of patients who undergo dialysis are overweight or obese. Rather than being a disadvantage, the extra weight is associated with improved survival in this patient group. However, the relationship between weight and outcome is complex among dialysis patients. In the general population obesity constitutes a clear cardiovascular risk factor. By contrast, in obese dialysis patients the nutritional status may be better, and obesity thus provides, at least in the short term, some protection against malnutrition and the associated morbidity. On the other hand, some studies suggest that mortality in the long term is directly correlated with excess weight and obesity, which indicates that fat represents a risk factor also in uremia. In the elderly, particularly those affected by end-stage renal disease, endocrine and metabolic effects on the nitrogen balance cause the loss of muscle mass despite an excess of adipose tissue, which is a condition known as sarcopenic obesity. While a good nutritional state is found in some obese dialysis patients, which probably accounts for the improved survival of the obese group as a whole, there is a sizable proportion of sarcopenic obese, which is probably increasing. Sarcopenic obesity is not only characterized by the reduction of muscle mass but also by the accumulation of fat surrounding the abdominal viscera (visceral fat syndrome), which may be associated with a greater degree of metabolic and atherosclerotic disease. Several studies have shown that malnutrition associated with obesity, including sarcopenic obesity, is the risk factor most closely correlated with morbidity and mortality both in dialysis patients and the general population. The timely identification of this condition has therefore become necessary in the dialysis population now dominated by the elderly and very elderly. Body mass index is inadequate as a measure of sarcopenic obesity since it cannot define muscle mass nor indicate the localization of the fat in the visceral compartment. Other indices must be developed and validated in well performed clinical trials to identify fat localization and the presence of sarcopenia.
接受透析治疗的患者中约50%超重或肥胖。在这一患者群体中，额外的体重并非劣势，而是与生存率提高相关。然而，透析患者体重与预后之间的关系较为复杂。在普通人群中，肥胖是明确的心血管危险因素。相比之下，肥胖的透析患者营养状况可能较好，因此肥胖至少在短期内能为营养不良及相关发病情况提供一定保护。另一方面，一些研究表明，长期死亡率与超重和肥胖直接相关，这表明脂肪在尿毒症中也是一个危险因素。在老年人中，尤其是那些受终末期肾病影响的老年人，内分泌和代谢对氮平衡的影响会导致肌肉量减少，尽管脂肪组织过多，这种情况被称为肌少症性肥胖。虽然一些肥胖的透析患者营养状况良好，这可能是肥胖组整体生存率提高的原因，但仍有相当一部分肌少症性肥胖患者，且这一比例可能在增加。肌少症性肥胖不仅表现为肌肉量减少，还表现为腹部内脏周围脂肪堆积（内脏脂肪综合征），这可能与更高程度的代谢和动脉粥样硬化疾病相关。多项研究表明，与肥胖相关的营养不良，包括肌少症性肥胖，是透析患者和普通人群中与发病率和死亡率最密切相关的危险因素。因此，在如今以老年人和高龄老年人为主的透析人群中，及时识别这种情况变得十分必要。体重指数不足以衡量肌少症性肥胖，因为它既无法界定肌肉量，也无法表明内脏脂肪的分布位置。必须开发其他指标，并在完善的临床试验中进行验证，以识别脂肪分布位置和肌少症的存在。
