Prognostic significance of monthly weight fluctuations among older nursing home residents.

BACKGROUND Although weight change in older persons has proven prognostic significance, it is not known whether monthly weights obtained by the clinical staff in long-term care institutions are reliable enough to be useful in identifying at-risk residents. The objective of this study was to determine whether an association exists between mortality risk and the intraresident variation in weight in long-term care institutions. METHODS For this study, 900 nursing home residents with a recently identified nutritional problem from 96 long-term care facilities in 8 states were randomly selected. At study entry, nutritional, health status, and demographic data were extracted from the nursing home chart or the Minimum Data Set. Weights obtained by the nursing home staff were recorded at baseline and during each of the subsequent 6 months. Cox proportional hazards regression analysis was used to assess relationships between weight parameters and mortality risk during the 7 months of observation. RESULTS During the study, 435 (48%) participants had at least 1 monthly weight that differed from the previous month's weight by > or =5%; 163 (18%) participants had this magnitude of a 1-month weight change more than once. By controlling for the linear trend (i.e., slope) of each residents' weight change between the first to the last weight, the average month-to-month residual variability in the resident's weights was calculated. This residual variability or "average random fluctuation" in weight from 1 month to the next was > or =2% in 229 (25%) participants and > or =3% in 82 (9%) participants. Despite the large random fluctuation in the residents' weights, weight loss was an important prognostic indicator. Those who lost > or =5% in any month had a 10-fold increased risk for death compared with those who gained weight (adjusted relative risk, 10.6; 95% confidence interval, 3.2 to 35.5). The average random fluctuation in weight was associated with an increased risk for death only at the upper 10th percentile for the population. CONCLUSIONS Many nutritionally compromised elderly nursing home residents experience significant bidirectional fluctuations in their weight from month to month. How much of this variability is due to measurement error is not known. However, a weight loss of > or =5% in any month has important prognostic implications.