This study provides the first national update on phase angle (PhA) as a biomarker of body composition, nutritional status, and health outcomes in Korean adults. Using data from 5,035 adults aged 20–80 years from the 2023 Korea National Health and Nutrition Examination Survey (KNHANES), we analyzed age-related variations in PhA, body composition, metabolic diseases, and nutrient intake. The mean PhA declined from 5.57° in participants aged 20–39 to 4.23° in those aged 80+, corresponding with decreases in height and weight. Individuals with higher PhA exhibited significantly greater lean body mass and lower body fat; for example, among those aged 20–39, the high PhA group showed 56.02 kg of lean mass versus 40.71 kg in the low group (p < 0.001) and total body water of 41.07 L versus 29.84 L (p < 0.001). Regarding metabolic diseases, 35.2% of the high PhA group aged 20–39 had grade 1 obesity compared with 17.4% in the low group, with similar associations observed for diabetes and hypertension across age groups. Nutritional intake was also higher in the high PhA group, with mean energy intake of 2,180.84 versus 1,710.16 kcal (p < 0.001). Overall, PhA was positively associated with favorable body composition, nutritional intake, and metabolic profiles across all age groups, suggesting its potential as a comprehensive biomarker for assessing physiological health and guiding nutritional interventions in the Korean population.
Malnutrition is common in the critically ill patients and known to cause a variety of negative clinical outcomes. However, various conventional methods for nutrition assessment have several limitations. We hypothesized that body composition data, as measured using bioelectrical impedance analysis (BIA), may have a significant role in evaluating nutritional status and predicting clinical outcomes in critically ill patients. We gathered clinical, biochemical, and BIA data from 66 critically ill patients admitted to an intensive care unit. Patients were divided into three nutritional status groups according to their serum albumin level and total lymphocyte counts. The BIA results, conventional indicators of nutrition status, and clinical outcomes were compared and analyzed retrospectively. Results showed that the BIA indices including phase angle (PhA), extracellular water (ECW), and ECW/total body water (TBW) were significantly associated with the severity of nutritional status. Particularly, PhA, an indicator of the health of the cell membrane, was higher in the well-nourished patient group, whereas the edema index (ECW/TBW) was higher in the severely malnourished patient group. PhA was positively associated with albumin and ECW/TBW was negatively associated with serum albumin, hemoglobin, and duration of mechanical ventilation. In non-survivors, PhA was significantly lower and both ECW/TBW and %TBW/fat free mass were higher than in survivors. In conclusion, several BIA indexes including PhA and ECW/TBW may be useful for nutritional assessment and represent significant prognostic factors in the care of critically ill patients.
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