Validated questionnaire to assess the hydration status in a healthy adult Spanish population: a cross sectional study.

Introduction: adequate hydration status is crucial in most physiological functions; conversely, its assessment is hindered by the limited availability of research tools. Objective: to develop and validate a novel questionnaire that evaluates the hydration status of a healthy adult Spanish population. Method: a novel questionnaire was designed and validated relying on biochemical parameters related to blood, urine, and body water content. The study involved 39 healthy subjects aged between 18 and 39 years. Food and beverage consumption were assessed by the novel questionnaire and through a three-day dietary record. Physical activity was assessed using both: accelerometers and the Short International Physical Activity Questionnaire (IPAQ). Validity was determined by correlation of the aforementioned parameters with the water balance and water intake obtained by the novel questionnaire. The questionnaire was administered twice over the course of 28 days to evaluate its reliability. Results: water balance and total water intake were correlated with specific gravity, and urine color. Water intake obtained by the novel questionnaire was correlated with water intake results from the three-day dietary record. Intraclass correlation coefficient indicated moderate concordance between both recordings, and the Cronbach's alpha revealed high consistency. Finally, the Bland and Altman method indicated that the limits of agreement were acceptable to reveal the reliability of the estimated measures. Conclusions: the questionnaire designed is a new valid and reliable screening tool to estimate hydration status of adult populations in dietary and nutritional assessment.