Crowded facilities are more likely to experience larger and deadlier COVID-19 outbreaks, according to a study of approximately 600 nursing homes in Ontario. There, 60% of nursing home residents live in shared rooms, according to the authors. 

The population-based cohort study followed COVID-19 cases and deaths among more than 78,000 residents between March 29 and May 20. Researchers tracked the cumulative incidence of cases as confirmed by a validated molecular test and mortality per 100 residents. Crowding was defined as the mean number of residents per bedroom and bathroom.

Infections were unevenly distributed, with 86% of diagnosed cases occurring in 10% of facilities, investigators found. Homes with low crowding also had less than half the COVID-19 mortality than crowded homes. In less-crowded homes, 578 of 46,028 residents died (1.3%). And in homes with more shared rooms, 874 of 32,579 residents died (2.7%).

The findings relate to another recent study of the same cohort that showed for-profit nursing homes experiencing larger COVID-19 outbreaks and more resident deaths. The new study suggests that this finding may have been linked to the older design standards of these homes, wrote Nathan Stall, M.D., of the University of Toronto, and colleagues.

In the United States, congressional legislation has been proposed that would require multiple federal agencies to develop best practices for designing senior housing facilities to reduce the spread of contagious disease, McKnight’s has reported.

The study was published Monday in JAMA Internal Medicine.