Obesity linked to hospitalisation and ICUs for Covid-19 patients

People with high BMI at greater risk of severe coronavirus illness, UCD analysts find

Extremely obese people with Covid-19 are 17 times more likely to require admission to intensive care in Ireland than cases with no underlying condition, a new analysis shows.

While 1.4 per cent of patients who have contracted the virus in Ireland were categorised as extremely obese (a body mass index – BMI – greater than or equal to 40), almost half of them required hospitalisation, according to the analysis of official figures by scientists at UCD.

Those who were extremely obese were 3.5 times more likely to require hospitalisation. Only people with cancer, heart disease and kidney disease had a higher risk of needing to go to hospital.

Hospital Report

Among those with high BMI, risk of severe outcomes from a Covid infection is not confined to the extremely obese. A BMI greater than 25 (overweight) is "bad news, with increased severity and death" for those affected, according to Prof Francis Finucane, consultant endocrinologist at Galway University Hospital.


International evidence points to a linear relationship between BMI and the risk of severe Covid-19 illness, Prof Finucane says.

In response to rising evidence of the link between obesity and serious Covid-19 illness, the Health Service Executive is to widen its monitoring of this underlying condition.

Triage and treatment

Currently, surveillance of the disease looks at people with a BMI of 40 or over. The categorisation, traditionally used in flu surveillance, was applied this year to the monitoring of Covid-19.

The HSE told The Irish Times it now planned to collect data on the weight of all ICU patients with the virus – categorised into those with a BMI of under 30, those with a BMI of 30-40 and those above.

Mark Roe, a postdoctoral researcher at UCD specialising in injury risk management, carried out the risk analysis of underlying conditions using figures from the Health Protection Surveillance Centre. He said the information could help inform doctors' decisions in relation to the triage and treatment of patients.

“It’s a small but important piece in the puzzle and, given Covid-19 is going to be around for some time, it shows the need for interventions to reduce people’s risk – even simple, cheap ones such as exercising and eating healthily.”

Prof Finucane said the link between Covid-19 severity and obesity “transcends the weighing scales”.

Metabolic vs mechanical

“It’s really about metabolic rather than mechanical problems. While obesity is associated with poor diet, this doesn’t in itself cause the problem of severe Covid.

“Rather this is due to abnormal blood clotting, inflammation and blood vessel damage in the lungs. This makes Covid a circulatory rather than a ventilatory problem for patients and their carers. It has implications for how we might tackle the problem.”

Obese cases tend to have other underlying conditions that place them at higher risk of severe infection, including diabetes. Non-white ethnicity is also linked to more severe outcomes.

“Rather than looking at it as an excess-fat problem, we need to see it in terms of excess calories. It’s not about how bulky someone is, it’s about their metabolism.”

Dr Roe’s analysis shows cases with chronic neurological disease have the highest Covid-related death risk of any underlying condition, more than eight times higher than cases with no underlying condition.

Paul Cullen

Paul Cullen

Paul Cullen is Health Editor of The Irish Times