Impact of Roommate Cognitive Health on Nursing Home Mortality: Evidence of Peer Effects

This study investigates how patient peer effects in nursing homes influence mortality, using administrative data from 2.6 million stays across 7,200 U.S. facilities between 2000 and 2010. By leveraging exogenous roommate assignments through unique room identifiers, the researchers found that patients placed with roommates diagnosed with Alzheimer’s disease (AD) or Alzheimer’s disease-related dementias (ADRD) faced a 2.1 percentage point higher 90-day mortality rate compared to those in private rooms, equivalent to the effect of a nursing home one standard deviation worse in quality. The impact varies by patient type: patients with AD/ADRD benefit significantly from cognitively healthy roommates, indicating that peer support and monitoring play a critical role, while private rooms do not provide the same advantage. Conversely, patients without AD/ADRD experience lower mortality in private rooms, with roommate cognitive health having little effect. Implementing an assignment strategy that considers these differences could reduce overall mortality by 0.8 percentage points without extra resources.

Cheng, A., & Hackmann, M. B. (2025). Patient peer effects: Evidence from nursing home room assignments (NBER Working Paper No. 34538). National Bureau of Economic Research. https://doi.org/10.3386/w34538