Obesity's strong link to severe COVID outcomes, especially in under-40s and Black people

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A study of 6.9m English patients found that people with excess weight, especially for younger adults and Black people, are at substantially increased risk of admission to hospital and ICU and death due to COVID-19, even without other comorbidities, reports MedicalBrief. A Mexico study found that obesity alone almost tripled the risk of death, while comorbidities increased that risk even further.

In the first study, University of Oxford researchers extracted data from the QResearch database for nearly 7m English patients 20 years and older with available body mass index (BMI) values registered at an eligible general practice from 24 January to 30 April, 2020. The UK study noted the highest hospitalisation rate in young adults.

It is the largest study to date assessing body weight and COVID outcomes.

Of 6,910,695 eligible patients with a mean BMI of 26.8 kg/m2, 0.20% were hospitalised, 0.02% were admitted to an intensive care unit (ICU), and 0.08% died after they were diagnosed as having COVID-19. Roughly one third of patients with severe coronavirus outcomes had type 2 diabetes, and most were 60 years or older.

Starting at 23 kg/m2, BMI was associated with coronavirus-related hospitalisation (adjusted hazard ratio [aHR], 1.05) and, starting at 28 kg/m2, death (aHR, 1.04). There was a linear association across the entire BMI range for ICU admission (aHR, 1.10).

According to the US Centres for Disease Control and Prevention, a BMI of 23 kg/m2 is considered normal, but 28 kg/m2 is considered overweight.

The researchers found a significant link between BMI and age, with higher HRs for hospitalisation above a BMI of 23 kg/m2 for patients 20 to 39 years old (aHR, 1.09), compared with no association for those 80 to 100 (aHR, 1.01). Similarly, Black patients had a higher risk of hospitalisation than White patients (aHR, 1.07 vs 1.04).

The risk of COVID-19–hospitalisation and ICU admission tied to increasing BMI was slightly lower in patients with type 2 diabetes, high blood pressure, and cardiovascular disease than in those with no underlying medical conditions.

The authors noted that even a small increase in BMI over 23 kg/m2 increased the risk of poor COVID-19 outcomes. "People with excess weight, even without other comorbidities, are at substantially increased risk of admission to hospital and ICU and death due to COVID-19, especially for younger adults and Black people," they wrote.

"Excess weight is a modifiable risk factor, and investment in the treatment of overweight and obesity and long-term preventive strategies could help reduce the severity of COVID-19 disease."

Co-senior author Dr Paul Aveyard said: "We don't yet know that weight loss specifically reduces the risk of severe COVID-19 outcomes, but it is highly plausible, and will certainly bring other health benefits."

In a commentary Dr Krishnan Bhaskaran, of the London School of Hygiene & Tropical Medicine, said that BMI is now being used in risk-prediction tools that inform vaccine prioritisation, underscoring the importance of understanding the link between BMI and COVID-19 outcomes in informing public policy.

"Key future research priorities will be to establish whether BMI affects vaccine efficacy, and to understand whether people outside the BMI range considered to be healthy (18.5–24.9 kg/m2) are at increased risk of post-COVID-19 sequelae," he wrote.

"Further careful epidemiological study of these and other emerging questions will inform the ongoing public health response to this new disease that is likely here to stay."

In a commentary, Dr Naveed Sattar, of the University of Glasgow, said of the study, "These data add to the overwhelming evidence from other sources (several hundred studies now in many parts of the world) that support excess body weight are an important, causal risk factor for more severe COVID-19 outcomes."

The second study was led by researchers at the Instituto Nacional de Ciencias Medicas y Nutricion and the Instituto Nacional de Cardiologia Ignacio Chavez in Mexico City. The national observational study involved analysing data from 15,529 COVID-19 inpatients and outpatients in Mexico's 32 states from the National COVID-19 Epidemiological Surveillance Study between 24 February and 26 April, 2020.

The case-fatality rate was 9.2%, and 21% of hospitalised patients died. Obesity alone almost tripled the risk of death (aHR, 2.7), while obesity combined with other underlying illnesses increased the risk of death and other severe outcomes even further (diabetes HR, 2.79; immunosuppression HR, 5.06; high blood pressure HR, 2.30).

Of all COVID-19 patients, 47.8% were 41 to 60 years old, which the researchers said shows that many younger Mexican patients were infected early in the pandemic.

The authors observed that Mexicans are metabolically distinct from Asians and Europeans in that they are more likely to have early-onset overweight or obesity. In addition, overeating, especially of highly processed foods, has led to an obesity epidemic in Mexico in recent decades, with 75.2% of the population older than 20 years either overweight (39.1%) or obese (36.1%).

"Thus, the toll of COVID-19 could be higher in Mexico by affecting younger people compared to populations with a lesser burden of disease among young adults," they wrote.

Of all underlying illnesses, obesity was most strongly tied to COVID-19 infection in Mexicans with mostly symptomatic illness. "Obesity alone and in combination with other comorbidities was a significant risk factor for secondary outcomes (pneumonia, hospitalisation, [invasive mechanical ventilation], and ICU admission) in patients positive for SARS-CoV-2," the researchers concluded. "The risk conferred by obesity increases when it is present alongside other comorbidities, particularly, [diabetes], hypertension, and immunosuppression."


Study details
Associations between body-mass index and COVID-19 severity in 6·9 million people in England: a prospective, community-based, cohort study

Min Gao, Carmen Piernas, Nerys M Astbury, Julia Hippisley-Cox, Stephen O'Rahilly, Paul Aveyard, Susan A Jebb

Published in The Lancet Diabetes & Endocrinology on 28 April 2021

Obesity is a major risk factor for adverse outcomes after infection with SARS-CoV-2. We aimed to examine this association, including interactions with demographic and behavioural characteristics, type 2 diabetes, and other health conditions.
In this prospective, community-based, cohort study, we used de-identified patient-level data from the QResearch database of general practices in England, UK. We extracted data for patients aged 20 years and older who were registered at a practice eligible for inclusion in the QResearch database between Jan 24, 2020 (date of the first recorded infection in the UK) and April 30, 2020, and with available data on BMI. Data extracted included demographic, clinical, clinical values linked with Public Health England's database of positive SARS-CoV-2 test results, and death certificates from the Office of National Statistics. Outcomes, as a proxy measure of severe COVID-19, were admission to hospital, admission to an intensive care unit (ICU), and death due to COVID-19. We used Cox proportional hazard models to estimate the risk of severe COVID-19, sequentially adjusting for demographic characteristics, behavioural factors, and comorbidities.
Among 6 910 695 eligible individuals (mean BMI 26·78 kg/m2 [SD 5·59]), 13 503 (0·20%) were admitted to hospital, 1601 (0·02%) to an ICU, and 5479 (0·08%) died after a positive test for SARS-CoV-2. We found J-shaped associations between BMI and admission to hospital due to COVID-19 (adjusted hazard ratio [HR] per kg/m2 from the nadir at BMI of 23 kg/m2 of 1·05 [95% CI 1·05–1·05]) and death (1·04 [1·04–1·05]), and a linear association across the whole BMI range with ICU admission (1·10 [1·09–1·10]). We found a significant interaction between BMI and age and ethnicity, with higher HR per kg/m2 above BMI 23 kg/m2 for younger people (adjusted HR per kg/m2 above BMI 23 kg/m2 for hospital admission 1·09 [95% CI 1·08–1·10] in 20–39 years age group vs 80–100 years group 1·01 [1·00–1·02]) and Black people than White people (1·07 [1·06–1·08] vs 1·04 [1·04–1·05]). The risk of admission to hospital and ICU due to COVID-19 associated with unit increase in BMI was slightly lower in people with type 2 diabetes, hypertension, and cardiovascular disease than in those without these morbidities.
At a BMI of more than 23 kg/m2, we found a linear increase in risk of severe COVID-19 leading to admission to hospital and death, and a linear increase in admission to an ICU across the whole BMI range, which is not attributable to excess risks of related diseases. The relative risk due to increasing BMI is particularly notable people younger than 40 years and of Black ethnicity.
NIHR Oxford Biomedical Research Centre.


Study details (2)

Obesity is a strong risk factor for short-term mortality and adverse outcomes in Mexican patients with COVID-19: A national observational study

JM Vera-Zertuche, J Mancilla-Galindo, M Tlalpa-Prisco, P Aguilar-Alonso, MM Aguirre-García, O Segura-Badilla, M Lazcano-Hernández, HI Rocha-González, AR Navarro-Cruz, A Kammar-García, J de J Vidal-Mayo

Published in Epidemiology & Infection on 29 April 2021

Conflicting results have been obtained through meta-analyses for the role of
obesity as a risk factor for adverse outcomes in patients with COVID-19, possibly
due to the inclusion of predominantly multimorbid patients with severe COVID-19.
Here, we aimed to study obesity alone or in combination with other comorbidities
as a risk factor for short-term all-cause mortality and other adverse outcomes in
Mexican patients evaluated for suspected COVID-19 in ambulatory units and
hospitals in Mexico.
We performed a retrospective observational analysis in a national cohort of 71,103
patients from all 32 states of Mexico from the National COVID-19 Epidemiological
Surveillance Study. Two statistical models were applied through Cox regression to
create survival models and logistic regression models to determine risk of death,
hospitalization, invasive mechanical ventilation, pneumonia, and admission to an
intensive care unit, conferred by obesity and other comorbidities (diabetes mellitus
[DM], chronic obstructive pulmonary disease [COPD], asthma,
immunosuppression, hypertension, cardiovascular disease [CVD], and chronic
kidney disease [CKD]). Models were adjusted for other risk factors.
From February 24 to April 26, 2020, 71,103 patients were evaluated for suspected
COVID-19; 15,529 (21.8%) had a positive test for SARS-CoV-2; 46,960 (66.1%),
negative, and 8,614 (12.1%), pending results. Obesity alone increased adjusted
mortality risk in positive patients (HR=2.7, 95%CI:2.04-2.98), but not in negative
and pending-result patients. Obesity combined with other comorbidities further
increased risk of death (DM: HR=2.79, 95%CI:2.04-3.80; immunosuppression:
HR=5.06, 95%CI:2.26-11.41; hypertension: HR=2.30, 95%CI:1.77-3.01) and other
adverse outcomes.
In conclusion, obesity is a strong risk factor for short-term mortality and critical
illness in Mexican patients with COVID-19; risk increases when obesity is present
with other comorbidities.


CIDRAP material

The Lancet Diabetes & Endocrinology study (Open access)

The Lancet Diabetes & Endocrinology commentary (Open access)

Science Media Centre commentary (Open access)

Epidemiology & Infection study (Open access


See also MedicalBrief archives:

Increasingly a link found between obesity and COVID-19 outcome risk

More evidence that diabetes/overweight tied to severe COVID-19 — Hospital meta-analysis

Overweight or obese patients risk more severe COVID-19 — 11-country analysis

Super-spreaders: Exhale increases with COVID-19 infection, age, and obesity

Relationship between COVID-19 deaths and morbid obesity — large US analysis

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