Effect of the COVID-19 pandemic on asthma exacerbations in New Zealand: An interrupted time series analysis

BACKGROUND: New Zealand (NZ) implemented some of the strictest restrictions during the novel coronavirus pandemic (coronavirus disease 2019 [COVID-19]), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). How this impacted asthma exacerbation rates in NZ is unknown. OBJECTIVE: We sought to explore the effects of the COVID-19 restrictions on asthma exacerbations in NZ during 2020. METHODS: We used a population-based, interrupted time series to examine the impact of the first COVID-19 lockdown in NZ on asthma exacerbation rate. The primary outcome measure was change in the monthly exacerbation rate, defined as hospitalization and/or course of corticosteroids, before and after the first lockdown. In a secondary analysis, we quantified the number of patients with asthma, the actual asthma exacerbation rate from March to December 2019 versus March to December 2020, and the number of asthma hospitalizations. RESULTS: There was a significant drop in the exacerbation rate immediately after lockdown (−3.02; P < .0001) followed by a significant and sustained increasing trend; the rate postlockdown increased relative to that prelockdown (0.27; P < .0001). Similar patterns were observed in all sociodemographic groups. In our secondary analysis, we identified 507,622 people with asthma; this reduced to 458,023 in 2020 postlockdown. The overall asthma exacerbation rate was 33.3% less in 2020 than in 2019 (reduction from 48.6/1000 patients to 32.4/1000 patients). The rate of asthma hospitalizations decreased from 9.5 per 1000 patients in 2019 to 6.2 per 1000 patients in 2020; this decrease was observed across all demographic groups. CONCLUSIONS: The first COVID-19 lockdown in 2020 in NZ significantly reduced asthma exacerbation rates across all sociodemographic groups. Whether these reductions are sustained requires further investigation.