The influence of institutional care and physical dependency on daily water turnover rates in the elderly

Background: Maintaining water balance is essential for health, but environmental factors, pathology and the ageing process can adversely affect water homeostasis. Objective: This study examined the relationship between physical dependency and daily water turnover rate in an older population. Design: Daily water turnover (DWT) was estimated, using deuterium oxide ((H2O)-H-2) as a tracer for water, over two separate 7-day periods in summer and winter in two older populations. The independent group (N=22) lived in their own homes and were self-caring. The dependent group (N=15) lived in institutional care, and were more physically dependent. None of the subjects had significant mental impairment. Total body water (TBW) and DWT were estimated from the equilibration concentration of ingested 21-120 and its subsequent elimination rate. Results: The independent group had a median (range) age of 75(69-88) y, a mean Barthel Index (BI) of 19.8, and a mean Abbreviated Mental Test (AMT) score of 9.8. The dependent group were older (83(72-93) y), with a mean BI of 13 and a mean AMT of 9.3. Average median (range) DWT in the independent group was similar in summer (2.2(1.3-3.6) I.d(-1)) and winter (2.1(1.4-3.6) I.d(-1)), but faster than in the dependent group (1.5(0.9-2.9) and 1.6(1.0-2.8) I.d(-1), respectively) during the same two periods. Median urine output in the independent group was similar in summer (1.7(0.8-3.3) I.d(-1)) and winter (1.7(0.9-3.2) I.d(-1)), but greater than in the dependent group (1.1(0.6-2.7) and 0.9(0.5-1.6) I.d(-1), respectively). Conclusion: These results show that the water turnover rate of many older people is low, and that intake may be affected especially in those with physical disability.