Predictors of dehydration in older people living in UK residential care

Introduction
Dehydration is common in frail older people and associated with increased mortality, disability and morbidity. We explored factors associated with dehydration in older people living in residential care.

Methods
DRIE (Dehydration Recognition In our Elders, http://driestudy.appspot.com/) recruited people aged ≥65 years living in UK residential care without cardiac or renal failure. Blood samples were taken, serum osmolality >300mOsm/kg defined dehydration. Assessments included Mini-Mental State Exam (MMSE), sitting and standing blood pressure (BP) and nutritional status. Staff were asked about functional status (Barthel Index), chronic illness, health-professional contacts, continence, dementia stage and medications. We used univariate logistic regression to determine factors associated with dehydration, then multivariate stepwise backwards logistic regression, including statistically significant univariate factors, removing factors with the highest p-value one by one until all remaining factors were statistically significant.

Results
Analyses included 188 participants (66% women, mean age 85.7 years, range 65-105, mean MMSE 21 range 0-30, 31% needed consultee consent, 20% dehydrated). In univariate analyses a wide range of factors predicted dehydration. In the multivariate model, adjusting for age and all other factors at once, moderate or severe dementia, using diabetic medication, swollen feet, poor renal function, higher numbers of prescription medications and health professional contacts, and lower standing blood pressure were all associated with greater odds of dehydration (Table).

Conclusions
A range of diverse factors are moderate predictors of dehydration in care home residents, including markers of cognitive and physical frailty. We need to find ways of identifying individuals becoming dehydrated.