It’s become increasingly clear now: there are factors that put some of us at greater risk of severe COVID-19 infection and critical illness. In a comprehensive study involving 72,314 cases, underlying conditions with the highest fatality rates included cardiovascular conditions, diabetes, and high blood pressure. There’s something that connects these risk factors, what could it be? It’s obesity. Hope the title didn’t spoil that surprise.

Worryingly, obesity affects nearly half of all Americans. If that sounds bad, it just so happens that it is - and perhaps especially now. A study at New York University Langone Health looked at how obesity affects those under the age of 60, who are generally considered to be at low risk. They found that among COVID-19 patients younger than 60 years, morbidly obese patients were nearly a staggering 4 times more likely to be admitted to critical care than non-obese patients.

But how can something like obesity make us weaker to COVID-19 by such a huge amount? Obesity affects many aspects of our health, and there are many ways it can affect our response to this virus. For example, obesity can increase airway resistance, impair gas exchange, and decrease lung volume. Just those changes to the respiratory mechanics alone could drastically impact the disease course, transmissibility, and risk of critical illness for those infected with this coronavirus.

Obesity also impacts our metabolic health, and the importance of this to our immune response has become a rapidly developing area of research this past decade. Obesity causes many different metabolic conditions (e.g. diabetes, dyslipidemia, hypertension etc.), and this affects obese patients’ ability to regulate inflammation. This is important in the context of COVID-19, because there’s evidence to suggest that what’s called a “cytokine storm” is involved in multi-organ failure in many severe COVID-19 cases. A “cytokine storm” is when the body produces cytokines (which mediate inflammation and are crucial for normal immune responses), but for whatever reason, the body’s releasing way too much of it, and way too quickly.

Think of it a bit like sugar: a little in my morning coffee can be just what I need to blissfully continue my otherwise uneventful life. But, what if I instead throw self-control out the window and decide to furiously shovel fistfuls of sugar into my mouth faster than a starved 5-year-old on Halloween? Rather than any boost to my mood, I’ll probably quickly find my not-5-year-old self writhing on the floor feeling pain in places I didn’t even know I could feel pain.

Similarly, while inflammation is vital for fighting disease, if it gets out of control it can result in some horrific issues. Dysregulation of inflammation is also associated with the onset and severity of many other conditions such as arthritis, atherosclerosis, and cancer - which obese individuals are also at a higher risk of. In the context of COVID-19, because obese patients have a poor control of inflammation to begin with, it could mean a coronavirus infection is more easily able to illicit an out of control inflammatory response, potentially triggering a “cytokine storm” and exacerbating their disease state and risk of subsequent death.

There are of course many other factors that affect severity of COVID-19 infections. However, with the prevalence of obesity in our society, it’s crucial to get a better understanding of how it can make some of us vulnerable in this pandemic so that the appropriate measures can be placed to combat it. But, there’s still so much we don’t know.

Everyday, COVID-19 continues to kill more and more people, and everyday, researchers and clinicians continue to fight this pandemic. But it’s not just up to them. How we choose to act outside our hospitals and labs will directly impact what happens inside them. COVID-19 is showing little promise of slowing down here in the US. While we continue to support our clinicians and researchers to do everything they can, it’s our responsibility to do everything we can. Wear a mask. Practice social distancing. The pandemic is still here, and we’ll all need to do our part to get through this together.

References:

Wu Z, McGoogan JM. Characteristics of and Important Lessons From the Coronavirus Disease 2019 (COVID-19) Outbreak in China: Summary of a Report of 72 314 Cases From the Chinese Center for Disease Control and Prevention. JAMA. 2020 Apr 7;323(13):1239–42.

Hales CM. Prevalence of Obesity and Severe Obesity Among Adults: United States, 2017–2018. 2020;(360):8.

Petrilli CM, Jones SA, Yang J, Rajagopalan H, O’Donnell LF, Chernyak Y, et al. Factors associated with hospitalization and critical illness among 4,103 patients with COVID-19 disease in New York City [Internet]. Intensive Care and Critical Care Medicine; 2020 Apr [cited 2020 May 20]. Available from: http://medrxiv.org/lookup/doi/10.1101/2020.04.08.20057794

Lighter J, Phillips M, Hochman S, Sterling S, Johnson D, Francois F, et al. Obesity in Patients Younger Than 60 Years Is a Risk Factor for COVID-19 Hospital Admission. Clinical Infectious Diseases. 2020 Apr 9;ciaa415.

Tzelepis GE, Dennis McCool F. Nonmuscular Diseases of the Chest Wall. In: Grippi MA, Elias JA, Fishman JA, Kotloff RM, Pack AI, Senior RM, et al., editors. Fishman’s Pulmonary Diseases and Disorders [Internet]. 5th ed. New York, NY: McGraw-Hill Education; 2015 [cited 2020 May 29]. Available from: accessmedicine.mhmedical.com/content.aspx?aid=1122363991

Stefan N, Birkenfeld AL, Schulze MB, Ludwig DS. Obesity and impaired metabolic health in patients with COVID-19. Nat Rev Endocrinol. 2020 Jul;16(7):341–2.

Chen X, Zhao B, Qu Y, Chen Y, Xiong J, Feng Y, et al. Detectable serum SARS-CoV-2 viral load (RNAaemia) is closely associated with drastically elevated interleukin 6 (IL-6) level in critically ill COVID-19 patients. medRxiv. 2020 Mar 3;2020.02.29.20029520.

COVID-19 Map [Internet]. Johns Hopkins Coronavirus Resource Center. [cited 2020 Jul 2]. Available from: https://coronavirus.jhu.edu/map.html