Relationship of aging and nutritional status to innate immunity in tube-fed bedridden patients.

BACKGROUND AND OBJECTIVES Aging and malnutrition are known to influence immune functions. The aim of this study was to investigate the relationship of aging and malnutrition to innate immune functions in tube-fed bedridden patients. METHODS AND STUDY DESIGN A cross-sectional survey was performed in 71 tube-fed bedridden patients aged 50-95 years (mean age±SD, 80.2±8.5 years) with serum albumin concentrations between 2.5 and 3.5 g/dL. We evaluated associations of age and nutritional variables with natural-killer cell activity, neutrophilphagocytic activity, and neutrophil-sterilizing activity. Nutritional variables included body mass index, weightadjusted energy intake, total lymphocyte count, and serum concentrations of albumin, transferrin, prealbumin, total cholesterol, C-reactive protein, and zinc. RESULTS Natural-killer cell activity, neutrophil-phagocytic activity, and neutrophil-sterilizing activity were normal or increased in 67 (94%), 63 (89%), and 69 (97%) patients, respectively. Multiple linear regression analysis with a backward elimination method showed that natural-killer cell activity correlated negatively with aging and lymphocyte counts (p<0.01 for both) but positively with body mass index and transferrin (p<0.01 for both). Neutrophil-phagocytic and neutrophil-sterilizing activities were not associated with any variables. CONCLUSIONS In tube-fed bedridden patients with hypo-albuminemia, natural-killer cell activity may be associated with aging, body mass index, transferrin, and lymphocyte counts.