The COVID-19 pandemic introduced the world to a new virus, SARS-CoV-2, which can cause a range of symptoms from mild to severe. While anyone can contract COVID-19, certain factors significantly increase the risk of severe illness, potentially leading to hospitalization, intensive care, or death. Understanding these risk factors helps identify individuals who may require closer monitoring and enhanced preventive measures.
Age as a Key Factor
Age is the most prominent risk factor for severe COVID-19 outcomes, with the likelihood of serious illness escalating progressively. The risk begins to rise for adults over 50 and sharpens considerably for those over 65 or 75. For example, compared to individuals aged 18-29, the risk of death is approximately 25 times higher for those aged 50-64, 60 times higher for those 65-74, and 140 times higher for those 75-84.
This heightened vulnerability is largely attributed to immunosenescence, a gradual deterioration of the immune system that occurs with age. This makes the body less effective at fighting off new infections like SARS-CoV-2. Older individuals’ immune systems may produce fewer antibodies and their T cells may respond less effectively, leading to weaker responses to the virus. Even healthy older adults face a higher risk compared to younger individuals due to these age-related immune changes and the increased probability of co-existing health conditions.
Chronic Health Conditions
Many pre-existing chronic medical conditions significantly elevate the risk of severe COVID-19, often due to impaired organ function or chronic inflammation.
Heart Conditions
Heart conditions, including heart failure, coronary artery disease, and cardiomyopathies, increase the risk of complications. COVID-19 can worsen existing heart issues and may lead to inflammation of the heart muscle (myocarditis) or the surrounding membrane (pericarditis), increasing the risk of blood clots and heart attacks.
Chronic Lung Conditions
Chronic lung conditions, such as chronic obstructive pulmonary disease (COPD), asthma, cystic fibrosis, and pulmonary fibrosis, increase susceptibility to severe COVID-19. The virus primarily targets the lungs, and pre-existing lung damage makes it harder for the body to cope, potentially leading to pneumonia or acute respiratory distress syndrome (ARDS). Cystic fibrosis, for example, can increase risk due to decreased lung function and a potentially weakened immune system.
Diabetes
Both Type 1 and Type 2 diabetes significantly increase the risk of severe COVID-19, hospitalization, and death. Uncontrolled blood sugar levels weaken the immune system, making individuals more susceptible to complications like diabetic ketoacidosis (DKA). The virus may also directly harm the pancreas, potentially worsening hyperglycemia.
Chronic Kidney Disease (CKD)
Chronic kidney disease (CKD) at any stage poses a substantial risk for severe COVID-19 outcomes, including hospitalization and mortality. Individuals with CKD, especially those on dialysis or who have received a kidney transplant, often have weakened immune systems. COVID-19 can also worsen kidney function, leading to acute kidney injury (AKI).
Chronic Liver Diseases
Chronic liver diseases, including cirrhosis, hepatocellular carcinoma, nonalcoholic fatty liver disease, and viral hepatitis, are linked to severe COVID-19 and higher mortality. Liver damage is common in severe COVID-19 cases, and pre-existing liver conditions can lead to immune dysfunction.
Neurological Conditions
Neurological conditions, such as dementia, stroke, and Parkinson’s disease, are associated with an increased risk of severe COVID-19. Individuals who tested positive for COVID-19 had a higher likelihood of being diagnosed with Alzheimer’s disease, Parkinson’s disease, or stroke, possibly due to inflammation in the brain.
Down Syndrome
Down Syndrome increases the risk of severe COVID-19 outcomes. Adults with Down Syndrome have a higher risk of hospitalization and death. This heightened vulnerability is likely due to immune dysregulation and specific anatomical airway features.
Sickle Cell Disease and Thalassemia
Sickle cell disease and thalassemia are blood disorders that increase the risk of severe COVID-19 complications. These conditions can affect multiple organs and may impair the immune system, making individuals more susceptible to severe infections. Frequent blood transfusions, common for thalassemia, can also lead to iron overload, linked to poorer outcomes.
Weakened Immune System
Conditions or treatments that compromise the immune system make individuals more vulnerable to severe infections, including COVID-19.
HIV Infection
HIV infection, especially if untreated or advanced, is a significant independent risk factor for severe COVID-19 and in-hospital mortality. People living with HIV often have underlying conditions that further increase their risk, and HIV itself weakens the immune system.
Cancer
Cancer, particularly during active treatment like chemotherapy or radiation, places individuals at higher risk for severe COVID-19 outcomes. Cancer patients often have weakened immune systems due to the disease and anticancer treatments, which can lead to severe and prolonged illness.
Organ or Stem Cell Transplant Recipients
Organ or stem cell transplant recipients are at an elevated risk of severe COVID-19 due to immunosuppressive medications taken to prevent organ rejection. These medications suppress the immune system, leaving the body less capable of mounting a strong defense against the virus.
Primary Immunodeficiencies
Primary immunodeficiencies, rare genetic disorders affecting immune system function, increase susceptibility to severe infections like COVID-19. Individuals with these conditions may experience higher rates of hospitalization, intensive care, and require mechanical ventilation.
Long-Term Immunosuppressive Medications
Long-term use of corticosteroids or other immunosuppressive medications can compromise immune function, increasing the risk of severe COVID-19. These medications reduce inflammation by suppressing immune system activity, which can lead to increased susceptibility to infections and delayed viral clearance. Patients taking moderate to high doses of steroids have shown a higher probability of hospitalization.
Other Important Considerations
Beyond chronic health conditions and weakened immune systems, several other factors contribute to the risk of severe COVID-19.
Obesity
Obesity, defined as a Body Mass Index (BMI) of 30 or higher, is an independent risk factor for severe COVID-19, hospitalization, and death. Severe obesity can triple the risk of hospitalization. Obesity is linked to impaired immune function and can decrease lung capacity, making ventilation more challenging. Metabolic changes like insulin resistance and inflammation further hinder the body’s ability to fight infections.
Pregnancy
Pregnancy increases the risk of severe COVID-19, particularly in the third trimester, and this elevated risk can persist for at least a month after birth. Pregnant individuals experience changes in their immune system, heart, and lungs, making them more susceptible to severe respiratory viruses. Severe COVID-19 during pregnancy can lead to complications such as preterm birth, high blood pressure (preeclampsia), and blood clots.
Current and Former Smoking
Current and former smoking significantly contributes to the risk of severe COVID-19. Smoking damages the lungs and impairs immune function, making individuals more vulnerable to severe respiratory infections. While some studies suggest a lower risk of contracting COVID-19 among smokers, once infected, they face a higher likelihood of developing severe symptoms and worse outcomes, including increased risk for intensive care and death. This is because smoking compromises the lungs’ natural defense mechanisms.