Determinant of factors associated with water requirement measured using the doubly labelled water method among older Japanese adults

Objective: Water is an essential nutrient for all organisms and is important for maintaining life and health. We aimed to develop a biomarker-calibrated equation for predicting water turnover (WT) and pre-formed water (PW) using the doubly labelled water (DLW) method.

Design: Cross-sectional study.

Setting: General older population from the Kyoto-Kameoka Study, Japan.

Participants: The 141 participants aged ≥ 65 years were divided into a model developing (n 71) and a validation cohort group (n 70) using a random number generation. WT and PW was measured using the DLW method in May-June of 2012. In developing the cohort, equations for predicting WT and PW were developed by multivariate stepwise regression using all data from the questionnaires in the Kyoto-Kameoka study (including factors such as dietary intake and personal characteristics). WT and PW measured using the DLW method were compared with the estimates from the regression equations developed using the Wilcoxon signed-rank test and correlation analysis in validation cohort.

Results: The median WT and PW for 141 participants were 2·81 and 2·28 l/d, respectively. In the multivariate model, WT (R² = 0·652) and PW (R² = 0·623) were moderately predicted using variables, such as height, weight and fluid intake from beverages based on questionnaire data. WT (r = 0·527) and PW (r = 0·477) predicted that using this model was positively correlated with the values measured by the DLW method.

Conclusions: Our results showed factors associated with water requirement and indicated a methodological approach of calibrating the self-reported dietary intake data using biomarkers of water consumption.