How does total body water (TBW) change with advancing age?

Total body water (TBW) changes significantly throughout different stages of life, particularly falling under the influence of both gestational and chronological age. In neonates, especially preterm infants, TBW is quite high, making up a large percentage of their body weight, which is essential for various physiological processes. As these infants grow and mature, there is a gradual decrease in the proportion of TBW relative to their body weight.

The decrease in TBW with advancing age can be attributed to several physiological developments. For instance, as children transition from infancy to childhood and into adulthood, body composition changes, with an increase in fat mass and a decrease in the proportion of extracellular fluid, which contributes to a lower percentage of TBW.

Understanding this change is vital in neonatal care as alterations in body water can impact hydration status, medication dosing, and the overall health status of the infant. Maintaining an awareness of how TBW evolves over time allows healthcare providers to offer improved care tailored to the specific needs of the neonate as they grow.