While many who contract COVID-19 have mild symptoms, some people are susceptible to severe illness. Severe disease is defined by outcomes requiring significant medical intervention, such as hospitalization, intensive care, or mechanical ventilation. Understanding the factors that increase the risk for a serious case of COVID-19 is important for making informed health decisions.
Demographic and Genetic Factors
Age is the most significant predictor of severe COVID-19. The risk increases substantially for individuals over 50 and grows exponentially with each subsequent decade. Compared to young adults, the risk of death is 60 times higher for those 65-74 years old and 340 times higher for people 85 and older. This vulnerability is attributed to immunosenescence, the natural, age-related decline in immune system function, which hampers the body’s defense against the virus.
Biological sex also plays a role, with males being at a greater risk of severe illness and death compared to females. This disparity may involve hormonal differences, as research suggests estrogen may have a protective effect on the immune response. Additionally, differences in immunity linked to the X chromosome may contribute to more robust antiviral activity in females.
Specific genetic conditions can predispose an individual to a more severe disease course. One example is Down syndrome, where underlying immune system dysregulation can lead to a delayed viral clearance and an excessive inflammatory response. Other genetic disorders, such as sickle cell disease, also increase risk by compromising organ function and the body’s ability to handle infections.
Chronic Health Conditions Increasing Risk
The presence of one or more chronic health conditions elevates the risk of developing severe COVID-19. The more underlying conditions a person has, the higher their risk of a serious outcome.
Chronic lung diseases like chronic obstructive pulmonary disease (COPD), cystic fibrosis, and moderate-to-severe asthma compromise respiratory function from the outset. This makes it harder for the body to cope with the lung inflammation caused by the virus. Similarly, pre-existing cardiovascular conditions such as heart failure, coronary artery disease, and hypertension mean the heart is more vulnerable to the stress and direct injury the virus can inflict.
Metabolic disorders also create a high-risk environment. Both Type 1 and Type 2 diabetes are associated with severe COVID-19, as high blood sugar can impair immune function. Obesity, particularly a BMI of 30 or higher, is another risk factor linked to chronic inflammation and reduced lung capacity. Chronic kidney and liver diseases also increase risk by impairing the body’s ability to filter waste and maintain balance.
A weakened immune system, or being immunocompromised, leaves a person vulnerable to severe infection. This can result from cancer and its treatments, an organ or stem cell transplant, or a poorly controlled HIV infection. The use of high-dose corticosteroids for autoimmune diseases also dampens the immune response, reducing the body’s ability to fight the virus.
Neurological and mental health conditions are linked to worse COVID-19 outcomes. Dementia and other neurodegenerative disorders like Parkinson’s or Alzheimer’s disease are risk factors. The connection may be related to underlying frailty, chronic inflammation, or a diminished capacity to manage personal health. A history of stroke also indicates underlying vascular issues that can be exacerbated by the virus. Certain mental health disorders, including schizophrenia and mood disorders, are also associated with a higher risk.
Lifestyle Choices and Other Circumstances
Certain lifestyle habits and personal circumstances can also increase the risk of severe COVID-19.
Smoking, both current and former, is a risk factor because it damages lung tissue and cilia, the structures that clear pathogens from the airway. This damage impairs the lungs’ defense mechanisms and fosters chronic inflammation. This makes the respiratory system more susceptible to severe infection.
Physical inactivity is another behavior linked to more severe outcomes. A sedentary lifestyle can negatively impact cardiovascular health and immune system function. In contrast, regular physical activity helps support the body’s overall resilience.
Substance use disorders involving alcohol, opioids, or other drugs can lead to more severe illness. Chronic, excessive alcohol use can damage the liver and suppress immune function. Other drug use can affect respiratory and cardiac health, compounding the potential damage from the virus.
Pregnancy or having recently given birth also places an individual at higher risk. The body undergoes significant changes during pregnancy, including alterations to the immune system and increased strain on the heart and lungs. These changes can make a person more susceptible to severe respiratory infections.
The Role of COVID-19 Vaccination
Vaccination is the most effective tool for preventing severe COVID-19. Being unvaccinated or not up-to-date with recommended boosters is a primary risk factor for hospitalization and death across all age groups. The protection from vaccination fundamentally alters an individual’s risk profile.
COVID-19 vaccines work by preparing the immune system to recognize and fight the SARS-CoV-2 virus without causing illness. They introduce a harmless piece of the virus, like the spike protein, prompting the body to produce protective antibodies and memory cells. This process primes the immune system for a rapid response upon future exposure.
If a vaccinated person gets a breakthrough infection, their prepared immune system can control the virus more quickly. This rapid response helps prevent the virus from replicating extensively and causing widespread damage. As a result, vaccination reduces the likelihood that an infection will progress to severe disease.
While the virus evolves, evidence shows that current vaccines and boosters remain effective at preventing the most serious outcomes. Staying current with COVID-19 vaccinations is a direct action to mitigate the risk of a severe disease course.