Elevated Serum Osmolality and Total Water Deficit Indicate Impaired Hydration Status in Residents of Long-Term Care Facilities Regardless of Low or High Body Mass Index

Abstract

Background: Dehydration is typically associated with underweight and malnutrition in long-term care (LTC) settings. Evidence is lacking regarding the influence of the rising prevalence of overweight and obesity on risk factors, prevalence, and presentation of dehydration.

Objective: The aim of this study was to objectively assess hydration status and the adequacy of total water intake, and determine relationships between hydration status, total water intake, and body mass index (BMI) in LTC residents.

Design: A cross-sectional analysis of baseline data was performed.

Participants and setting: Baseline data from 247 subjects recruited from eight community-based LTC facilities participating in two randomized trials comparing nutrient and cost-efficacy of between-meal snacks vs oral nutrition supplements (ONS).

Main outcomes: Hydration status was assessed by serum osmolality concentration and total water intakes were quantified by weighed food, beverage, water, and ONS intake.

Statistical analyses: Simple and multiple linear regression methods were applied.

Results: Forty-nine (38.3%) subjects were dehydrated (>300 mOsm/kg) and another 39 (30.5%) had impending dehydration (295 to 300 mOsm/kg). The variance in serum osmolality was significantly accounted for by blood urea nitrogen level, mental status score, and having diabetes (R(2)=0.46; P<0.001). Total water intake averaged 1,147.2±433.1 mL/day. Thus, 96% to 100% of subjects did not meet estimated requirements, with a deficit range of 700 to 1,800 mL/day. The variance in total water intake was significantly accounted for by type of liquid beverages (thin vs thick), type of ONS, total energy intake, total activities of daily living dependence, sex, and BMI (R(2)=0.56; P<0.001).

Conclusions: Dehydration and inadequate total water intake is prevalent in LTC residents across all BMI categories. Type of liquid beverages, type of ONS, and type of between-meal snacks are factors that could be targeted for nutrition interventions designed to prevent or reverse dehydration.

Keywords: Elderly; Fluid; Hydration; Long-term care; Older adult.