Risk factors for outbreaks of COVID-19 in care homes following hospital discharge: A national cohort analysis

Abstract

Background: The population of adult residential care homes has been shown to have high morbidity and mortality in relation to COVID-19.

Methods: We examined 3115 hospital discharges to a national cohort of 1068 adult care homes and subsequent outbreaks of COVID-19 occurring between 22 February and 27 June 2020. A Cox proportional hazards regression model was used to assess the impact of time-dependent exposure to hospital discharge on incidence of the first known outbreak, over a window of 7-21 days after discharge, and adjusted for care home characteristics, including size and type of provision.

Results: A total of 330 homes experienced an outbreak, and 544 homes received a discharge over the study period. Exposure to hospital discharge was not associated with a significant increase in the risk of a new outbreak (hazard ratio 1.15, 95% CI 0.89, 1.47, P = .29) after adjusting for care home characteristics. Care home size was the most significant predictor. Hazard ratios (95% CI) in comparison with homes of <10 residents were as follows: 3.40 (1.99, 5.80) for 10-24 residents; 8.25 (4.93, 13.81) for 25-49 residents; and 17.35 (9.65, 31.19) for 50+ residents. When stratified for care home size, the outbreak rates were similar for periods when homes were exposed to a hospital discharge, in comparison with periods when homes were unexposed.

Conclusion: Our analyses showed that large homes were at considerably greater risk of outbreaks throughout the epidemic, and after adjusting for care home size, a discharge from hospital was not associated with a significant increase in risk.

Keywords: COVID-19 pandemic; care homes; hospital discharge; long-term care; outbreak; time-dependent Cox regression.

FIGURE 1

Study period analysis timeline with risk period interaction scenarios. Scenarios: (A) Two non‐overlapping exposure periods, no outbreak; (B) No exposure to hospital discharge, outbreak occurs; (C) Two overlapping periods of exposure, outbreak occurs later when not exposed; (D) Two non‐overlapping periods of exposure, outbreak occurs during the second discharge period

FIGURE 2

Hospital discharges and outbreaks (first positive SARS‐CoV‐2 tests in resident), care homes in Wales, 22 February to 27 June 2020