Mild obesity tied to increased COVID-19 severity

Even mild obesity (BMI ≥30 kg/m²) may give rise to more severe outcomes in patients hospitalized with COVID-19, results of a single-centre, retrospective study from Italy showed.

UK and US guidelines identifying risk factors for severe COVID-19 include a BMI ≥40 kg/m², said Dr Matteo Rottoli from the Alma Mater Studiorum University of Bologna, Italy, and co-authors.

“Our study showed that any grade of obesity is associated with severe COVID-19 illness and suggests that people with mild obesity should also be identified as a population at risk,” he added.

The researchers analysed 482 consecutive adults (mean age 66.2 years, 62.7 percent male) who were hospitalized at the Sant’Orsola Hospital in Bologna, Italy, with RT-PCR- confirmed COVID-19 between March 1 and April 20, 2020. Of these, 21.6 percent (n=104) were considered obese (BMI ≥30 kg/m²), of whom 4.1 percent (n=20) had a BMI ≥35 kg/m². Patients were followed up for a mean 37.8 days.

Twenty-five percent of patients with obesity required mechanical ventilation, 51.9 percent had respiratory failure, 36.4 percent required intensive care unit (ICU) admission, and 29.8 percent died within 30 days of symptom onset.

Overall, compared with non-obese patients (BMI <30 kg/m²), COVID-19 patients with a BMI ≥30 kg/m² had an increased risk of respiratory failure (odds ratio [OR], 2.48; p=0.001), ICU admission (OR, 5.28; p<0.001), and death (OR, 2.35; p=0.017) within 30 days of symptom onset. [Eur J Endocrinol 2020;doi:10.1530/EJE-20-0541]

Specifically, COVID-19 patients with a BMI of 30–34.9 kg/m² had a significantly increased risk of respiratory failure (OR, 2.32, 95 percent confidence interval [CI], 1.31–4.09; p=0.004) and ICU admission (OR, 4.96, 95 percent CI, 2.53–9.74; p<0.001) compared with individuals with BMI <30 kg/m².

An even higher BMI of ≥35 kg/m² was associated with a further increased risk of respiratory failure (OR, 3.24, 95 percent CI, 1.21–8.68; p=0.019) and ICU admission (OR, 6.58, 95 percent CI, 2.31–18.7; p<0.001), as well as mortality (OR, 12.1, 95 percent CI, 3.25–45.1; p<0.001) vs BMI <30 kg/m².

“[I]n all models, the BMI cut-off determining an increase of risk was 30,” said the researchers, noting that overweight (BMI 25–29.9 kg/m²) was not tied to a significantly increased risk of any of the outcomes compared with normal weight. However, every 1-unit increase in BMI was significantly associated with all outcomes (OR, 1.07; p=0.009; OR, 1.20; p<0.001; and OR, 1.09; p=0.012 for respiratory failure, ICU admission, and death, respectively).

“[T]his finding calls for prevention and treatment strategies to reduce the risk of infection and hospitalization in patients with relevant degrees of obesity, supporting a revision of the BMI cut-off of 40 kg/m²,” they said.

“[This revision is] to ensure we identify everyone at higher risk of serious infection and to avoid underestimating the potential population impact of SARS-CoV-2 infection, particularly in Western countries with higher obesity rates,” said Rottoli.

The mechanism behind the obesity-severe COVID-19 association remains to be seen. “Our hypothesis is that SARS-CoV-2 infection outcomes depend on the metabolic profile of patients and that obesity, interlaced with diabetes and metabolic syndrome are involved too,” said Rottoli.

“[O]bese patients have [also] been proven to have a higher viral load and a longer time of virus shedding as compared to non-obese patients,” the researchers added.  

They noted that the lack of assessment of the role of prediabetes was a limitation, as was the inability to differentiate between metabolically healthy and unhealthy obesity in this study. “This distinction might have allowed to identify subpopulations of patients with obesity at different risks of severe outcomes,” they said.