Assessing the Impact of the COVID ‐19 Pandemic on Relative Incidence Rates in United States Claims Data

Background Differential COVID‐19‐pandemic‐related changes to healthcare‐seeking behavior across patient groups could contribute to biased estimates of disease incidence. Objective Assess the impact of the pandemic on the incidence of female breast cancer (BC), myocardial infarction (MI), and heart failure (HF) in an asthma versus general population. Method Optum's de‐identified Clinformatics Data Mart Database was used to estimate incidence rates (IRs) and ratios (IRRs) of BC, MI, and HF among adults with asthma versus general population referents during pre‐pandemic (January 2017–March 2020), early pandemic (April–May 2020), and later pandemic (June 2020–May 2023). Results During the early pandemic, IRs dropped substantially compared to pre‐pandemic levels across all outcomes: BC by ~55%, MI by 31%–37%, and HF by ~55%. In the later pandemic period, BC IRs were restored to pre‐pandemic levels, whereas MI and HF IRs remained lower than pre‐pandemic (MI: ~10% lower; HF: 13%–25% lower). Comparing asthma versus referents, BC incidence was similar throughout all periods (pre‐pandemic IRR 0.97, 95% CI 0.91–1.03; early pandemic: 1.03, 0.73–1.45; later pandemic: 1.03, 0.98–1.08). MI incidence was slightly higher in asthma versus referents pre‐pandemic (IRR 1.07, 1.02–1.12), became similar during early pandemic (0.97, 0.79–1.20), and increased again in later pandemic (1.14, 1.09–1.19). HF incidence was consistently higher in asthma versus referents, with the difference magnifying over time (IRR pre‐pandemic 1.33, 1.21–1.46; early pandemic 1.30, 0.77–2.19; later pandemic 1.55, 1.42–1.70). Conclusions Claims‐based time trend or comparative incidence studies could be biased due to the pandemic depending on the underlying population and outcome of interest.