COVID-19 and the impact of social determinants of health.

The novel coronavirus disease 2019 (COVID-19), caused by the pathogen severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), originated in Wuhan, China, and has now spread internationally with over 4·3 million individuals infected and over 297 000 deaths as of May 14, 2020, according to the Johns Hopkins Coronavirus Resource Center. While COVID-19 has been termed a great equaliser, necessitating physical distancing measures across the globe, it is increasingly demonstrable that social inequalities in health are profoundly, and unevenly, impacting COVID-19 morbidity and mortality.

Many social determinants of health—including poverty, physical environment (eg, smoke exposure, homelessness), and race or ethnicity—can have a considerable effect on COVID-19 outcomes. Homeless families are at higher risk of viral transmission because of crowded living spaces and scarce access to COVID-19 screening and testing facilities. In a Boston study of 408 individuals residing in a shelter, 147 (36%) had a positive SARS-CoV-2 PCR test. Smoke exposure and smoking has been linked to adverse outcomes in COVID-19. A systematic review found that current or former smokers were more likely to have severe COVID-19 symptoms than non-smokers (relative risk [RR] 1·4 [95% CI 0·98–2·00]) as well as an increased risk of intensive care unit (ICU) admission, mechanical ventilation, or COVID-19-related mortality (RR 2·4, 1·43–4·04). In the USA, the COVID-19 infection rate is three times higher in predominantly black counties than in predominantly white counties, and the mortality rate is six times higher. In Chicago alone, over 50% of COVID-19 cases and almost 70% of COVID-19 fatalities are disproportionately within the black population, who make up only 30% of the overall Chicago population.

It is also poignant that physical distancing measures, which are necessary to prevent the spread of COVID-19, are substantially more difficult for those with adverse social determinants and might contribute to both short-term and long-term morbidity. School closures increase food insecurity for children living in poverty who participate in school lunch programmes. Malnutrition causes substantial risk to both the physical and mental health of these children, including lowering immune response, which has the potential to increase the risk of infectious disease transmission. People or families who are homeless are at higher risk of infection during physical lockdowns especially if public spaces are closed, resulting in physical crowding that is thought to increase viral transmission and reduce access to care. Being able to physically distance has been dubbed an issue of privilege that is simply not accessible in some communities.

The association of social inequalities and COVID-19 morbidity is further compounded in the context of underlying chronic respiratory conditions, such as asthma, where there is a possible additive, or even multiplicative, effect on COVID-19 morbidity. Several adverse social determinants that impact the risk of COVID-19 morbidity also increase asthma morbidity, including poverty, smoke exposure, and race or ethnicity. Consistent associations have been noted between poverty, smoke exposure, and non-Hispanic black race and measures of asthma morbidity, including poorer asthma control and increased emergency department visits for asthma. The interplay of social determinants, asthma, and COVID-19 might help explain the risk of COVID-19 morbidity imposed by asthma, such as the disproportionate hospitalisations for COVID-19 among adults with asthma living in the USA. The CDC note asthma to be a risk factor for COVID-19 morbidity. Data released from the CDC on hospitalisations in the USA in the month of March, 2020, notes that 12 (27%) of 44 patients aged 18–49 years who were hospitalised with COVID-19 had a history of asthma, in those aged 50–64 years, asthma was present in 7 (13%) of 53 cases, and in those 65 years or older asthma was present in 8 (13%) of 62 cases.

The effect of social determinants of health and COVID-19 morbidity is perhaps underappreciated. Yet, the great public health lesson is that for centuries pandemics disproportionately affect the poor and disadvantaged. Additionally, mitigating social determinants—such as improved housing, reduced overcrowding, and improved nutrition—reduces the effect of infectious diseases, such as tuberculosis, even before the advent of effective medications. It is projected that recurrent wintertime outbreaks of SARS-CoV-2 will likely occur after this initial wave, necessitating ongoing planning over the next few years. Studies are required to measure the effect of COVID-19 on individuals with adverse social determinants and innovative approaches to management are required, and might be different from those of the broader population. The effect of physical distancing measures, particularly among individuals with chronic conditions facing adverse social circumstances, needs to be studied because adverse determinants and physical distancing measures could compound issues, such as asthma medication access and broader access to care. The long-term effect of school closures, among those facing adverse social circumstances, is also in need of study.

Moving forward, as the lessons of COVID-19 are considered, social determinants of health must be included as part of pandemic research priorities, public health goals, and policy implementation. While the relationships between these variables needs elucidating, measures that affect adverse determinants, such as reducing smoke exposure, regular income support to low-income households, access to testing and shelter among the homeless, and improving health-care access in low-income neighbourhoods have the potential to dramatically reduce future pandemic morbidity and mortality, perhaps even more so among individuals with respiratory conditions such as asthma. More broadly, the effects of COVID-19 have shed light on the broad disparities within our society and provides an opportunity to address those disparities moving forward.