The National Resident Assessment Instrument was introduced a quarter century ago, was fully operational by October 1991, and appeared to reduce the prevalence of dehydration from 2% to 1% in nursing home residents. 1 Fries B.E. Hawes C. Morris J.N. Phillips C.D. Mor V. Park P.S. Effect of the National Resident Assessment Instrument on selected health conditions and problems. J Am Geriatr Soc. 1997; 45: 994-1001 Crossref PubMed Scopus (126) Google Scholar Despite this, Marra and colleagues 2 Marra M.V. Simmons S.F. Shotwell M.S. et al. 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. J Acad Nutr Diet. 2016; 116: 828-836 Abstract Full Text Full Text PDF PubMed Scopus (25) Google Scholar found that 38% of long-term-care residents are dehydrated (assessed using serum osmolality), and a further 30% have impending dehydration. The 132 long-term residents of eight long-term-care facilities in Nashville, TN, who were studied had a blood sample and a written order for caloric supplementation, but were not receiving hospice care, enteral nutrition, or parenteral nutrition. The mean age of the 247 adults included in the study (not all had a blood sample) was 83±11 years, mean body mass index (BMI) was 25±5, and 79% were women. 2 Marra M.V. Simmons S.F. Shotwell M.S. et al. 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. J Acad Nutr Diet. 2016; 116: 828-836 Abstract Full Text Full Text PDF PubMed Scopus (25) Google Scholar Hydration status was measured using serum osmolality (directly measured by freezing point depression). A resident was determined to be dehydrated when serum osmolality was >300 mOsm/kg, impending dehydration was defined as serum osmolality between 295 and 300 mOsm/kg, and normal hydration was defined as serum osmolality below 295 mOsm/kg. 3 Thomas D.R. Cote T.R. Lawhorne L. et al. Understanding clinical dehydration and its treatment. J Am Med Dir Assoc. 2008; 9: 292-301 Abstract Full Text Full Text PDF PubMed Scopus (210) Google Scholar , 4 Institute of Medicine, Food and Nutrition BoardPanel on Dietary Reference Intakes for Electrolytes and Water. Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate. The National Academies Press, Washington, DC2004 Google Scholar L. Hooper is a reader in research synthesis, nutrition, and hydration, Norwich Medical School, University of East Anglia, Norwich, UK. 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 IndexJournal of the Academy of Nutrition and DieteticsVol. 116Issue 5PreviewDehydration 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. Full-Text PDF