The volume-outcome relationship in nursing home care: an examination of functional decline among long-term care residents.

BACKGROUND: Extensive evidence has demonstrated a relationship between patient volume and improved clinical outcomes in hospital care. This study sought to determine whether a similar association exists between nursing home volume of long-term care residents and rates of decline in physical function.
METHODS: We conducted retrospective analyses on the 2004 and 2005 Minimum Data Set files that contain 605,433 eligible long-term residents in 9336 nursing homes. The outcome was defined following the federal "Nursing Home Compare" measure that captures changes in 4 basic activities of daily living status between 2 consecutive quarters. Both the outcome measure and nursing home volume were defined on the basis of long-term care residents. We estimated random-effects logistic regression models to quantify the independent impact of volume on functional decline.
RESULTS: As volume increased, nursing home's unadjusted rate of functional decline tended to be lower. After multivariate adjustment for baseline resident characteristics and the nesting of residents within facilities, the odds ratio of activities of daily living decline was 0.82 (95% confidence interval: 0.79-0.86, P < 0.000) for residents in high-volume nursing homes (>101 residents/facility), compared with residents in low-volume facilities (30-51 residents/facility).
CONCLUSIONS: High volume of long-term care residents in a nursing home is associated with overall less functional decline. Further studies are needed to test other important nursing home outcomes, and explore various institutional, staffing, and resource attributes that underlie this volume-outcome association for long-term care. Understanding how greater experience of high-volume facilities leads to better resident outcome may help guide quality improvement efforts in nursing homes.