Associations between body hydration status and serum markers of apoptosis in elderly persons.

Healthy humans are well able to regulate their daily water balance despite exposures to stressors on hydration status. Older individuals have a higher risk of developing dehydration than younger adults. The enhanced risk is related to decreased thirstsensation with aging and reduction of muscular mass, which is hydrated and contains 73% of body water [1]. Increasing evidence suggests that mild dehydration plays a role in the development of various morbidities. Dehydration is often linked to infection in elderly people, and is associated with chronic diseases, such as urolithiasis, venous thromboembolism, exercise asthma, and hyperglycemia in diabetic ketoacidosis [2]. Determination of whole body bioimpedance is a non-invasive and reproducible method to monitor hydration status. Using segmental bioimpedance measurements, it is possible to obtain information about the fluid changes in each body compartment [3]. Urine concentration can be determined by measurement of urine specific gravity (USG), and the USG can serve as an index of hydration status. The Fas molecule is an important membrane death receptor that is involved in the induction of apoptosis [4]. Triggering of Fas by its ligand results in rapid induction of apoptosis in susceptible cells. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is capable of inducing apoptosis in tumor cell lines and TRAIL has key roles in tumor suppression and immune cell homeostasis [5]. Few studies have examined the associations of serum soluble Fas (sFas) and TRAIL concentrations in relation to body hydration status. The present study investigated whether the ratio of extracellular fluid to total body water (ECF/TBW ratio), evaluated in conjunction with USG, is significantly related to serum sFas and TRAIL levels in elderly persons.