The Benefits of Nursing Home Air Purification on COVID-19 Outcomes: A Natural Experiment

Abstract

Objectives: Improving indoor air quality is one potential strategy to reduce the transmission of SARS-CoV-2 in any setting, including nursing homes, where staff and residents have been disproportionately and negatively affected by the COVID-19 pandemic.

Design: Single group interrupted time series.

Setting and participants: A total of 81 nursing homes in a multifacility corporation in Florida, Georgia, North Carolina, and South Carolina that installed ultraviolet air purification in their existing heating, ventilation, and air conditioning systems between July 27, 2020,k and September 10, 2020.

Methods: We linked data on the date ultraviolet air purification systems were installed with the Nursing Home COVID-19 Public Health File (weekly data reported by nursing homes on the number of residents with COVID-19 and COVID-19 deaths), public data on data on nursing home characteristics, county-level COVID-19 cases/deaths, and outside air temperature. We used an interrupted time series design and ordinary least squares regression to compare trends in weekly COVID-19 cases and deaths before and after installation of ultraviolet air purification systems. We controlled for county-level COVID-19 cases, death, and heat index.

Results: Compared with pre-installation, weekly COVID-19 cases per 1000 residents (-1.69; 95% CI, -4.32 to 0.95) and the weekly probability of reporting any COVID-19 case (-0.02; 95% CI, -0.04 to 0.00) declined in the post-installation period. We did not find any difference pre- and post-installation in COVID-19-related mortality (0.00; 95% CI, -0.01 to 0.02).

Conclusions and implications: Our findings from this small number of nursing homes in the southern United States demonstrate the potential benefits of air purification in nursing homes on COVID-19 outcomes. Intervening on air quality may have a wide impact without placing significant burden on individuals to modify their behavior. We recommend a stronger, experimental design to estimate the causal effect of installing air purification devices on improving COVID-19 outcomes in nursing homes.

Keywords: COVID-19; Nursing homes; SARS-CoV-2; air purification; indoor air; ultraviolet.

Fig. 1

(A) Distribution of nursing homes' weekly resident COVID-19 cases, pre and post periods. Distribution of COVID-19 cases before and after installation of ultraviolet air purification. (B) Weekly cases per 1000 nursing home residents. Actual (observed) and predicted COVID-19 cases per week before and after installation of ultraviolet air purification.

Fig. 2

(A) Distribution of nursing homes with ≥1 COVID-19 case in the pre and post period. Distribution of nursing homes with ≥1 COVID-19 case before and after installation of ultraviolet air purification. (B). Proportion of nursing homes with ≥1 COVID-19 case per week. Actual (observed) and predicted proportion of nursing homes with ≥1 COVID-19 case per week before and after installation of ultraviolet air purification.

Fig. 3

(A) Distribution of nursing homes with ≥1 death, pre and post period. Distribution of nursing homes with ≥1 COVID-19 death before and after installation of ultraviolet air purification. (B) Proportion of nursing homes with ≥1 COVID-19 death per week. Actual (observed) and predicted proportion of nursing homes with ≥1 COVID-19 death per week before and after installation of ultraviolet air purification.