1 in 5 people at risk of severe coronavirus infection due to underlying health conditions: Study

Hospitalizations in the US were six times higher and deaths 12 times higher among those with reported underlying conditions

                            1 in 5 people at risk of severe coronavirus infection due to underlying health conditions: Study
(Getty Images)

About one in five individuals worldwide has an underlying condition that could put them at increased risk of severe Covid-19 if infected, ranging from less than 5% of those younger than 20 years to more than 66% of those aged 70 years or older. The modeling study that analyzed data from 188 countries estimates that 1.7 billion people, 22.4% of the world population, have at least one underlying health condition. Researchers also estimate that 23% of the global working age population (15–64 years) have at least one underlying condition. Chronic kidney disease and diabetes are the most common conditions in this age range.

However, for many of these individuals, their condition might not be diagnosed or known to the health system, or their increased risk could be quite modest, says the research team. The team estimates that fewer individuals — about one in 20 — would require hospital admission if infected. This ranges from less than 1% of those younger than 20 years to nearly 20% of people aged 70 years or older, rising to more than 25% in males. Overall, the authors estimate that 349M people of 7.8 billion people — 4% of the global population — are at high risk of severe Covid-19, meaning they would require hospital treatment if infected. In all age groups under 65, around twice the number of men as women would require hospitalization. Above 65 years, the ratio becomes less marked because women are over-represented in older age groups due to longer life expectancy.

"Our estimates are uncertain and focus on underlying conditions rather than other risk factors such as ethnicity, socioeconomic deprivation, and obesity, but provide a starting point for considering the number of individuals that might need to be shielded or vaccinated as the global pandemic unfolds," says the research team in their analysis published in The Lancet Global Health. It includes experts from the London School of Hygiene & Tropical Medicine (LSHTM), University of Washington and Imperial College London, among others. 

In the US, for example, a report on the coronavirus cases as of May 30 shows that hospitalizations were six times higher among patients with a reported underlying condition (45.4%) than those without reported underlying conditions (7.6%). Deaths were 12 times higher among patients with reported underlying conditions (19.5%) compared with those without reported underlying conditions (1.6%), says the study by the US Centers for Disease Control and Prevention (CDC). Among 287,320 (22%) cases with sufficient data on underlying health conditions, the most common were cardiovascular disease (32%), diabetes (30%) and chronic lung disease (18%), says the CDC. 

The study estimates that 349 million people or 4% of the global population are at high risk of severe Covid-19, meaning they would require hospital treatment if infected (Getty Images)

According to the research team of the current study, as lockdown restrictions are eased, governments could use the new estimates to understand how many people should be prioritized for enhanced physical distancing measures. "As countries move out of lockdown, governments are looking for ways to protect the most vulnerable from a virus that is still circulating. We hope our estimates will provide useful starting points for designing measures to protect those at increased risk of severe disease. This might involve advising people with underlying conditions to adopt social distancing measures appropriate to their level of risk, or prioritizing them for vaccination in the future," says associate professor Andrew Clark from LSHTM, UK, in the analysis. 

The authors based their estimates on disease prevalence data from the Global Burden of Diseases, Injuries and Risk Factors Study (GBD) 2017, UN population estimates for 2020, and the list of underlying health conditions relevant to Covid-19, as defined by current guidelines. The authors point out that the GBD prevalence estimates are likely to be higher than those from national databases because they are designed to capture cases that might be undiagnosed or not severe enough to be included in electronic health records. They analyzed the number of people with an underlying condition by age group, sex and country. "Estimates of the number of individuals at increased risk were most sensitive to the prevalence of chronic kidney disease, diabetes, cardiovascular disease, and chronic respiratory disease," says the study.

To help determine the degree of increased risk, the researchers also provided separate estimates of the proportion of all people (with and without underlying conditions) who would require hospitalization if infected. The authors calculated those at high risk using infection hospitalization ratios for Covid-19 and made adjustments for differences between countries.

(The Lancet Global Health)

The analysis suggests that countries and regions with younger populations have fewer people with at least one underlying health condition, while those with older populations have more people with at least one condition. For example, the proportion of the population with one or more health conditions ranges from 16% in Africa (283M people out of 1.3 billion) to 31% in Europe (231M out of 747M). "The share of the population at increased risk of severe Covid-19 is generally lower in Africa than elsewhere due to much younger country populations, but a much higher proportion of severe cases could be fatal in Africa than elsewhere," says Clark. 

Small island nations with high diabetes prevalence, such as Fiji and Mauritius, have among the highest proportion of people with an underlying condition. In Africa, countries with the highest HIV/AIDS prevalence such as Eswatini and Lesotho have a greater proportion of people with an underlying condition than countries with lower prevalence, such as Niger.

Writing in a linked comment, Professor Nina Schwalbe from Columbia University Mailman School of Public Health, US, who was not involved in the study, says that an increased understanding of risk factors, including the effects of social determinants and their interplay, provides an opportunity to target "mitigation strategies and helps to allay the popular misconception that everyone is at equal risk of severe illness". "As the authors note, it is time to evolve from a one-size-fits-all approach to one that centers on those most at risk. This will need to happen at both the individual and community levels. Considering the relevance of social determinants, such an approach requires urgently improving communication about Covid-19; increasing access to health services, including palliative care, for those already socially vulnerable; and providing economic support to cope with the mitigation," says Schwalbe.

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