Study Finds Obesity Raises COVID Infection Risk by 34%

Obese patients exposed to SARS-CoV-2 are 34% more likely to be infected than their non-obese counterparts, indicating that obesity is an important risk factor for COVID-19 disease and transmission, a study of more than 72,000 patients seen at Brigham and Women's Hospital suggests.

For the case-control study, the researchers compared the susceptibility to infection of 72,613 obese and non-obese adult and pediatric patients who tested positive for COVID-19 or reported exposure to the virus from March 2020 to January 2021. 

Obesity already tied to severe COVID

The team used the World Health Organization definition of obesity as a body mass index of greater than 30 kilograms per square meter for adults and the US Centers for Disease Control and Prevention's definition of a growth curve greater than the 95th percentile for children.

Participants were predominantly teens and adults (13 to 19 years, 3.5%; 20 to 39, 24.7%; 40 to 64, 9.7%; and older than 64, 30%) but also included children younger than 13 years (2.2%). In total, 58.8% were women, 72.4% were White, 12.3% were Hispanic, 6.7% were Black, and 3.4% were Asian.

The results were published today in PNAS Nexus.

"While the evidence has linked obesity with severe symptoms of COVID-19, the effect of obesity on susceptibility to SARS-CoV-2 infection remains unclear," the investigators wrote. "Identification of intrinsic factors, which increase the likelihood of exposed individuals succumbing to productive SARS-CoV-2 infection could help plan mitigation efforts to curb the illness." 

Identification of at-risk patients

Of all participants, 33.7% were obese, a finding that aligns with the prevalence in the United States (42.2%) and Massachusetts (23.0%). Obesity rates were similarly distributed across age-groups, with the highest rates in middle-aged patients, and sex (34.2% and 32.9% for women and men, respectively). By race, Black and Hispanic participants had the highest obesity rates (46.3% and 43.8%, respectively), while Asians had the lowest (15.4%).

Identification of intrinsic factors, which increase the likelihood of exposed individuals succumbing to productive SARS-CoV-2 infection could help plan mitigation efforts to curb the illness.

During all waves of the pandemic, obese patients were 34% more likely to develop COVID-19 than their healthy-weight peers, regardless of age or sex, a corrected logistic regression model showed.

"The presence of large amounts of adipose tissue in obese individuals could explain the increase in severity and susceptibility to infection," the investigators posited.

The odds ratio for SARS-Co-2 vulnerability in obese patients was lower in older patients and those with diabetes and hypertension. "This variation can be associated with a compromised immune response, thereby increasing vulnerability to infections," the authors wrote. "In such contexts, the impact of obesity on susceptibility is less pronounced due to the influence of these factors."

Expected obesity rates among younger people are expected to reach nearly 50% by 2030, they noted. The findings indicate "that obesity is not only a risk factor for worsened outcomes but also increases the risk for infection upon exposure," the authors wrote. "Identifying such populations early will be crucial for curbing the spread of this infectious disease."

"Future mechanistic studies evaluating shared signaling pathways in obese individuals could lead to the identification of drug targets that can be used to assail the infectivity of SARS-CoV-2," they concluded.

Reference: Matamalas JT, Chelvanambi S, Decano JL, et al. Obesity and age are transmission risk factors for SARS-CoV-2 infection among exposed individuals. Bovell-Benjamin A, ed. PNAS Nexus. 2024;3(8):pgae294. doi: 10.1093/pnasnexus/pgae294

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