Obesity not only worsens COVID-19 outcomes but also significantly increases susceptibility to infection after exposure to SARS-CoV-2, emphasizing the need for heightened prevention efforts among at-risk populations.

Study: Obesity and age are transmission risk factors for SARS-CoV-2 infection among exposed individuals. Image Credit: Studio Romantic / Shutterstock.com

Obesity has been shown to worsen morbidity and mortality outcomes among people infected with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In a recent study published in PNAS Nexus, researchers reveal that obesity also increases the risk of contracting the coronavirus disease 2019 (COVID-19) following exposure to SARS-CoV-2.

Does obesity increase susceptibility?

The COVID-19 pandemic, which was caused by the spread of SARS-CoV-2, caused millions of deaths and hundreds of millions of hospitalizations throughout the world.

Throughout the pandemic, personal protective equipment, hygiene measures, and social distancing were advised by most public health authorities to restrict the transmission of SARS-CoV-2. Despite the widespread distribution of COVID-19 vaccines, continuous mutation of SARS-CoV-2, combined the inability to achieve universal vaccination and variability in the protective effects of available vaccines, have limited their efficacy.

Early in the pandemic, about 5% of hospitalized COVID-19 patients in New York were obese. Since then, several studies have reported the increased risk of severe illness and mortality from COVID-19 in obese patients. Despite these observations, it remains unclear how obesity may impact the risk of testing positive for COVID-19 following exposure to an infected individual.

About the study

Data were obtained from the Massachusetts General Brigham’s (MGB) electronic medical records (EMR) for the current case-control study. A total of 72,613 individuals with a history of exposure to SARS-CoV-2 or were diagnosed with COVID-19 were included in the study, about 97% of whom were adults, 72% were White, and 59% female.

The aim of the current study was to examine susceptibility, which was defined as the risk of testing positive for COVID-19 following suspected exposure. The study period was between March 1, 2020, to January 25, 2021, which ensured that vaccine immunity did not influence the results, as less than 1% of the population of Massachusetts was vaccinated during this period.

Obesity increases susceptibility

Of the 72,613 suspected exposures, 18,477 individuals subsequently tested positive for COVID-19, which reflected 25% of the study cohort. The proportion did not vary across age groups nor between the sexes.

Obese individuals comprised 33.7% of the study cohort, which similarly corresponds to the national and state obesity statistics of 42.4% and 23%, respectively. The prevalence of obesity across all age groups was comparable, with middle-aged adults between 40 and 64 years of age most frequently affected by obesity with a prevalence of 39%.

Obesity was found to increase the risk of testing positive for COVID-19 by 34% as compared to non-obese individuals, thus indicating that obesity confers a higher risk of transmission in this population. The increased risk of productive SARS-CoV-2 infection following exposure was consistent across age groups and sex.

Both hypertension and type 2 diabetes mellitus (T2DM) are co-morbidities that are commonly associated with obesity. Since T2DM has been reported to increase the severity and frequency of infections like COVID-19, the researchers were interested in determining whether these clinical factors may contribute to the increased risk of SARS-CoV-2 positivity in this patient population.

When comparing individuals with and without diabetes mellitus, obesity did not increase the risk of SARS-CoV-2 positivity in those with diabetes. An increased risk of contracting SARS-CoV-2 following exposure was observed in obese adults with and without a history of hypertension.

Conclusions

It is important to identify and limit risk factors for SARS-CoV-2 infection to avoid its rapid transmission and evolution. Although external risk factors such as close proximity, poor ventilation, and aerosol production, may be easily recognized and modified, the same is not true of internal risk factors like obesity.

Obesity is not only a risk factor for worsened outcomes but also increases the risk for infection upon exposure. Identifying such populations early will be crucial for curbing the spread of this infectious disease.”

Among the obese, older people, as well as those with hypertension and diabetes, were not found to be at an increased risk of SARS-CoV-2 positivity. This lack of an effect may be attributed to the marked increased risk of infection associated with the comorbidity itself, thereby masking the effect of obesity. For example, the risk of testing positive for COVID-19 is 44% higher in both obese individual and diabetics.

The mechanism of increased risk could be due to inflammation, the ability of adipose tissue to retain SARS-CoV-2, and the dysregulated metabolism in obesity that promotes infection. The rising prevalence of obesity emphasizes the importance for active preventative measures against viral transmission.