Younger adults who are overweight are at a greater risk of severe COVID-19 outcomes, while obesity is not a major contributing factor for severe illness in older people, according to a new study.
The peer-reviewed findings, published in the Lancet Diabetes & Endocrinology journal on Thursday, showed that the risk of hospitalization, intensive care unit (ICU) admission and death due to COVID-19 increased with weight across different age groups.
However, the risks associated with excess weight were greatest for people below the age of 40. Weight had little to no effect on the likelihood of developing severe COVID-19 after the age of 80, the study found.
Researchers at the University of Oxford looked at data on 6.9 million people living in England, including more than 20,000 COVID-19 patients who were hospitalized or died during U.K.’s first wave.
“We knew obesity could play a role in the severity of COVID … and importantly, it is a much, much stronger risk factor for young people,” said Carmen Piernas, lead author of the study and research lecturer at the University of Oxford.
A number of biological factors could be contributing to this association, but more research is needed, Piernas told Global News.
More receptors in the body fat and lungs may potentially cause a higher viral load for younger patients or it could be related to inflammatory pathways in the body, she explained.
However, in older adults who are generally at a higher risk of developing severe forms of COVID-19, a weaker immune system and pre-existing conditions are important factors that contribute to the excess mortality, Piernas said.
Commenting on the study, Rebecca Christensen, a PhD student of epidemiology at the University of Toronto, said it was “surprising” to see that the younger age group was at a higher risk of severe illness based on weight.
She said one explanation could be survival bias, meaning individuals that live longer with excess weight are not as negatively affected by it, whereas younger people might be more likely to die in their 40s, 50s or 60s due to excess weight, Christensen said.
The Public Health Agency of Canada (PHAC) lists people with severe obesity, or a body mass index (BMI) of 40 or higher, as among those at risk of more severe disease or outcomes from COVID-19.
Around the world, numerous studies have shown that people with obesity face a greater risk of severe illness from COVID-19, with one meta-analysis suggesting that individuals with obesity face a 113 per cent increased risk of hospitalization and 48 per cent increase in risk of death.
COVID-19 can cause inflammation in the body and the health risks are only heightened if you already have inflammation due to excess weight, Christensen explained.
In a January study, led by Christensen, high waist circumference was shown as a significant predictor for testing positive for COVID-19 for those aged 65 and above.
Priority for vaccines
According to Statistics Canada data from 2018, more than one in four Canadian adults reported height and weight that classified them as obese (BMI of 30 or more).
Obesity is a leading cause of Type 2 diabetes, high blood pressure, heart disease, stroke, arthritis, cancer and other health problems.
In Canada, as more seniors get vaccinated, there has been a shift in the coronavirus spread with an increasing number of cases among the younger population.
Vaccinations in some provinces have now opened up to people in their 40s.
Ontario, Manitoba and Alberta have explicitly listed severe obesity as among the criteria for vaccine eligibility once their respective programs expand.
Among the younger age groups, Piernas said priority should be given to people with obesity because they are at a higher risk of severe disease if infected.
Christensen agreed.
“I 100 per cent support the idea that individuals with excess weight are prioritized for vaccination,” she said.
“This just makes sense given the fact that we’re seeing that they are at the greatest risk of severity and the first shot of a COVID-19 vaccination primarily decreases an individual’s risk of severe infection.”
— With files from Global News’ Jacquelyn LeBel.