While much of the world is focused on adapting to the new norms of the post-pandemic era, researchers continue to look for clues as to what factors may make a Covid-19 infection more serious for some than for others.
A large-scale genetic study, a collaboration between researchers from the University of Hong Kong (HKU) and the Chinese University of Hong Kong (CUHK), concludes that smoking and being obese are likely to increase the risk of people contracting mild to severe Covid-19.
“Our study confirms the importance of smoking and obesity in increasing the risk of contracting all forms of Covid-19,” said Dr Ryan Au Yeung Shiu-lun, a researcher and assistant professor in the division of epidemiology and biostatistics of HKU’s School of Public Health.
The results, published in the Journal of Medical Virology, also found that targeting a key enzyme the coronavirus uses to infect cells, angiotensin-converting enzyme 2 (ACE2), may help to offset some of the risks obesity presents.
ACE2 is a protein “receptor” found on the surface of many cells in the human body, particularly those in the heart, kidneys and lungs. The enzyme provides a point for the Covid-19 virus to enter and infect the body.
Some Covid-19 patients have been treated with ACE2-modulating medications, and these have been found to effectively control the virus’ entry.
“Our findings will enhance research into several therapeutic targets for Covid-19 treatment,” said Kwok Kin-on, a researcher and assistant professor in the School of Public Health and Primary Care at CUHK.
The Hong Kong-based research team used genome-wide association studies – which help scientists identify gene variants statistically associated with a risk for a particular disease – and extracted genes associated with smoking, obesity and other potential risk factors.
From this process of deduction, the team made some alarming discoveries regarding the link between obesity and Covid-19.
Body mass index (BMI) measures the ratio of your weight to your height. Waist-to-hip ratio measures the ratio of your waist circumference to your hip circumference, to determine how much fat is stored on your waist, hips and buttocks.
The research team found that a high BMI may increase the risk of suffering a severe case of Covid-19 by as much as 81 per cent, increase the risk of hospitalisation from Covid-19 by up to 55 per cent and increase the risk of contracting the virus in the first place by 18 per cent.
The risk of suffering a severe bout of Covid-19 for those with a higher waist-to-hip ratio may be 34 per cent higher.
In 2016, about 13 per cent of the world’s adults were considered obese, with the European Union and United States having obesity rates of 25 per cent and 37 per cent respectively. During the pandemic, rich countries in Europe, and the US, were among the places that suffered high Covid-19 death rates.
Countries such as Japan and South Korea, as well as the island of Taiwan, have much lower obesity levels than many Western countries, but other parts of East Asia such as China and Hong Kong do not.
Fifty per cent of China’s population – well over half a billion people – are overweight, and 16.4 per cent of the population are obese.
The rates are similar in Hong Kong, where the number of overweight kindergarten and primary-school children nearly doubled during the Covid-19 pandemic. For children aged nine to 13, the increase was from 7 per cent to 24 per cent during this period.
Although the proportion of Hong Kong residents who smoke has fallen to 9.5 per cent, vaping has increased by nearly 1.5 times in the past two years.
The team found that lifetime smokers had a 65 per cent higher risk of suffering a severe bout of Covid-19, a 61 per cent higher risk of being admitted to hospital as a result of Covid infection and were 23 per cent more susceptible to the disease in the first place than non-smokers.
The study was one of the largest to date to explore the role of various risk factors in the differing severity of Covid-19 cases. It underscores the dangers of obesity and smoking, which the World Health Organization says are two of the biggest causes of health issues for humans.
“This study highlights the importance of genomics and big data analytics in understanding the causes of diseases,” Kwok said, and showed the value of “enhancing the understanding of the interaction between infectious diseases and non-communicable diseases”.
He said high-risk groups, such as smokers who may have difficulty quitting, and people with a high BMI who may find it hard to lose weight, should be “strongly encouraged” to receive a Covid-19 vaccine booster shot as soon as possible, to mitigate against the potentially severe impact of them being infected with Covid-19.
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