Activity ID



November 13, 2023

Format Type


CME Credit




CME Provider: JAMA Internal Medicine

Description of CME Course

Nursing home residents have been disproportionately affected by coronavirus disease 2019 (COVID-19). Prevention recommendations emphasize frequent testing of health care personnel and residents, but additional strategies are needed.

To develop a reproducible index of nursing home crowding and determine whether crowding was associated with COVID-19 cases and mortality in the first months of the COVID-19 epidemic.

Design, Setting, and Participants:
This population-based retrospective cohort study included more than 78?000 residents across more than 600 nursing homes in Ontario, Canada, and was conducted from March 29 to May 20, 2020.

The nursing home crowding index equaled the mean number of residents per bedroom and bathroom.

Main Outcomes and Measures:
The cumulative incidence of COVID-19 cases confirmed by a validated nucleic acid amplification assay and mortality per 100 residents; the introduction of COVID-19 into a home (=1 resident case) was a negative tracer.

Of 623 homes in Ontario, we obtained complete information on 618 homes (99%) housing 78?607 residents (women, 54?160 [68.9%]; age =85 years, 42?919 [54.6%]). A total of 5218 residents (6.6%) developed COVID-19 infection, and 1452 (1.8%) died of COVID-19 infection as of May 20, 2020. COVID-19 infection was distributed unevenly across nursing homes; 4496 infections (86%) occurred in 63 homes (10%). The crowding index ranged across homes from 1.3 (mainly single-occupancy rooms) to 4.0 (exclusively quadruple occupancy rooms); 308 homes (50%) had a high crowding index (=2). Incidence in high crowding index homes was 9.7% vs 4.5% in low crowding index homes (P? In this cohort of Canadian nursing homes, crowding was common and crowded homes were more likely to experience larger and deadlier COVID-19 outbreaks.


1. This activity is accredited by the American Medical Association.
2. This activity is free to AMA members.

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Educational Objectives

To identify the key insights or developments described in this article


Infection Control, Infectious Diseases, Public Health, Geriatrics, Coronavirus (COVID19)


Medical Knowledge

CME Credit Type

AMA PRA Category 1 Credit



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