In the early 20th century, dense population in cities with poor sanitation led to a phenomenon known as the urban mortality penalty. However, improvements in sanitation and increased effectiveness and accessibility to healthcare eventually eliminated this disparity(1). Indeed, mortality rates declined throughout the United States in the 20th century(2). However, in 2008, Cosby et al. identified a new trend, beginning in the 1980s, in which a new rural mortality penalty became evident(3), leading to a host of research on location-based health disparities. Since its initial discovery, the rural mortality penalty has only increased(4). Such population health disparities can have acute impacts during a public health crisis, such as the COVID-19 pandemic that began in 2019. Indeed, many have noted that rural populations in the United States suffered increased mortality due to COVID-19 compared to their urban counterparts(5-7). When it comes to healthcare, a common assumption with rural disparities is that access to care plays a major role(8, 9). Our focus is on the persistence of the rural mortality penalty even in those patients with access to, means for, and willingness to go to a hospital. Therefore, in this work, we studied mortality in a population of patients with COVID-19 following their admission to a hospital, using a large national dataset of approximately a million COVID-19 patients who were admitted to hospitals to determine its drivers.
When viewing rural dwelling as a social determinant of health, it is important to note that other social determinants are associated with excess mortality, such as education, poverty, race, and more(10). In fact, Black Americans experience larger mortality disparities, irrespective of location, than rural populations(11), particularly with respect to the COVID-19 pandemic. Also, it is worth noting that the emergence of the rural mortality penalty has not, for most population groups, been due to increased mortality rates. In many areas, it has been driven by smaller declines in mortality in rural compared to urban populations(3, 4, 12). Nevertheless, although COVID-19 has made the trend harder to analyze, there is evidence to suggest that mortality is increasing in younger and middle-aged adults for certain causes of death (causes related to drugs and alcohol, as well as suicide) and that the group has overall seen smaller declines in mortality due to cardiovascular disease(13).
Others have written about rural/urban mortality disparities from COVID-19. Grome et al. studied county-level mortality data in Tennessee throughout most of 2020 and found an incidence rate ratio of 1.13 for mortality in rural vs. urban counties after controlling for county-level demographics, access to care, and comorbidities(5). Interestingly, they found that the disparity was greater for COVID-19 than for influenza or pneumonia. Iyanda et al. found similar results for a nationwide county-level analysis with a mortality incident rate ratio between 1.24 and 1.26 depending on the county classification(7), which also adjusted for county-level demographic and other factors. However, these studies did not examine COVID-19 mortality in the context of patients who were admitted to a hospital.
Although several studies on hospital outcomes for COVID-19 patients have been done(14-18), most have not evaluated location-based risk. One large national study conducted by Anzalone et al. examined whether the rural mortality penalty is present in COVID-19 patients following hospital admission, using data on approximately one million patients obtained from the National COVID Cohort Collaborative (N3C)(19). A strength of the study is that it analyzed in-hospital risk at the individual level. Indeed, they found an increased risk of in-hospital mortality for rural patients, with an adjusted odds ratio of 1.36. However, the study did not examine patient condition at admission or vaccination status. Therefore, the study was limited in its ability to determine the drivers of the rural mortality penalty with respect to COVID-19 hospital patients.
Several studies have examined factors contributing to hospital outcomes for COVID-19 patients without considering rurality. Two studies found that the effects of race on COVID-19 mortality in hospital patients was largely mitigated after adjusting for admitting hospital(14, 17). A different study found that once admitted to hospitals in New York, Black patients were less likely to die(20). Thus, it appears race as a risk factor for COVID-19 mortality following hospital admission is largely related to where the patient is admitted. Other factors affecting risk of COVID-19 mortality noted by multiple studies were age(14, 17, 21), sex(17, 21), and vital signs at admission(14, 21).
It is important to remember that the rural mortality penalty existed prior to the COVID-19 pandemic. The dramatic increase in mortality due to COVID-19 brought these existing disparities in health outcomes into sharp focus. However, the underlying drivers will remain. Furthermore, rurality, race, and most other social determinants of health are typically not causes of health outcomes. Instead, issues such as access to care, differences in demographics, differences in behavior, lower rates of belief in the efficacy of public health intervention(22-24), and many other factors are the true drivers. Therefore, it is critical to gain understanding of these drivers so we can work to improve the health of the entire population. We hypothesized that the rural mortality penalty in patients hospitalized with COVID-19 is driven by deteriorated patient health in the rural population prior to admission, in combination with increased risk factors in the rural population overall.