Using standardized incidence ratios to compare rates of pre-existing conditions among 7,162 people seeking care for COVID-19 at US hospitals from 2/12 - 3/28/2020

Abstract

Background/Aim: Protecting people at higher risk of severe COVID-19 by keeping them away from front-line jobs requires data on the risks associated with pre-existing conditions (PEC). We derived standardized incidence ratios (SIR) for “never smokers” and seven PEC for which the Centers for Disease Control (CDC) reported only unadjusted numbers in a study of 7,162 people treated for COVID-19 at U.S. hospitals in 50 states, 4 territories and Washington DC.Methods: For each PEC, we calculated the SIR overall—and for emergency departments (ED), intensive care units (ICU) and non-intensive care (non-ICU)—by dividing the observed rates that CDC reported by estimates of their prevalence among US adults. We used CDC estimates for chronic diseases of kidney (CKD), liver (CLD), and lung, diabetes mellitus (DM), cardiovascular and immunocompromised conditions, pregnancy (PRG), and current (CS) and former smoking (FS). We also added three categories for never smokers: with PEC (NS+), without (NS-), and combined (NS=).Results: Of 48 SIR, 43 were statistically significant at p<0.001. Overall, more cases than expected were NS+[SIR=1.93], NS=[1.48], NS-[1.31], PRG [1.72], CKD [1.35] or DM [1.15]. Only NS+ and NS= also were over-represented in all care settings, with highest NS+[3.97] in ICU, second only to CKD [5.57]. Only CS and FS were under-represented overall [0.10 and 0.11] and in all care settings [CS:0.08-0.15, FS:0.07-0.34]. The difference between CS and NS+ was greatest in ICU, where NS+ SIR was 50.1 times that of CS.Conclusions: At highest risk of seeking care for COVID-19—and most in need of protection—are NS+, PRG, CKD, and DM. At lowest risk are CS and, to a lesser degree, FS, making them better suited for front-line jobs. These findings are consistent with French and Chinese COVID-19 studies and literature showing both exogenous and endogenous carbon monoxide protect against infection.