Because nursing homes were closed to visitors for much of last year, staff members were the primary source of residents' COVID-19 exposure. A retrospective cohort study investigated the relationship between the number of unique staff members working daily and COVID-19 outcomes in U.S. nursing homes.

Skilled nursing facilities that were certified by the Centers for Medicare and Medicaid Services and had not had a COVID-19 case among residents as of June 2020 were categorized into quartiles. These categories were based on the number of clinical and nonclinical employees entering and leaving the facility each day.

Facilities that were in the highest quartile of staff size had 92% more resident cases than those in the lowest quartile (11.9 versus 6.2 resident cases per 100 beds, respectively) and 69% more staff cases (11.8 versus 7 staff cases per 100 beds, respectively). Facilities in the highest quartile also had 133% more resident deaths than those in the lowest quartile (2.1 versus 0.9 resident deaths per 100 beds, respectively). After staff size was controlled for, there was no clear relationship between COVID-19 outcomes and more traditional measures of staffing, such as staff-to-resident ratios or the skill mix of direct care hours.

The authors advise that rather than lowering staff-to-resident ratios, nursing homes should aim to maintain direct care hours using fewer unique staff members (that is, more full-time versus part-time staff).

Because of data limitations, the researchers say their measure of staff size may not fully reflect nursing home staffing patterns during the pandemic. They also say they couldn't account for other factors that could be related to staff size and COVID-19 outcomes, including the extent to which employees work in more than one nursing home.