A preliminary analysis of people admitted to hospital in
China with COVID-19 symptoms shows that people with non-alcoholic fatty liver
disease (NAFLD) were six times more likely to progress to severe COVID-19 illness than
people without NAFLD and remained potentially infectious for longer, Chinese
researchers report in the Journal of Hepatology.
COVID-19 is the disease caused by SARS-CoV-2, the new coronavirus identified
in China in January 2020. SARS-CoV-2 causes a spectrum of clinical illness
ranging from mild symptoms (cough, fever) to severe pneumonia, lung damage and
death.
People with pre-existing health conditions including chronic kidney disease,
cardiovascular disease and chronic obstructive pulmonary disease are at higher
risk of developing serious illness that requires hospital admission and
ventilation.
Whereas early concerns about the effects of underlying conditions on
COVID-19 outcomes focused on respiratory conditions such as chronic
obstructive pulmonary disease and asthma, attention has shifted to cardiovascular
disease, obesity, diabetes and chronic kidney disease as more is learnt about the interaction
between underlying inflammation, vascular disease and severe COVID-19 illness.
The impact of underlying liver disease on COVID-19 outcomes is still
unclear. Preliminary analysis of Chinese cases published in March 2020 did not
show a high prevalence of liver disease among people admitted to hospital with
COVID-19 symptoms.
But that analysis did not differentiate between causes of liver disease. NAFLD is often accompanied by metabolic syndrome
and obesity and so might lead to worse outcomes than other forms of liver
disease.
It’s also unclear if SARS-CoV-2 causes liver injury in the same way as some
other respiratory viruses, in which virus-specific effector T-cells damage
liver cells.
Researchers at two hospitals designated for care of COVID-19 patients in
Beijing and Fuyang have now reported on liver injury and underlying liver
health in patients admitted to hospital with confirmed SARS-CoV-2 infection
between 20 January and 18 February 2020.
A total of 202 patients had confirmed infection (55% male, median age 44 years, 83%
with moderate symptoms and 14% with severe or critical illness). One hundred and one had liver
injury, defined as ALT > 30 IU/l in men and > 19 IU/l in women, or
elevated liver enzymes and ductular enzymes.
Thirty-seven per cent had NAFLD and 23% had at
least one underlying co-morbidity (hypertension, diabetes, cardiovascular
disease, chronic lung disease or HIV).
Thirty-nine experienced progression of illness after admission to hospital,
defined as one of: increase in respiratory rate above 30 breaths a minute, oxygen
saturation reduced below 93%, worsening lung X-ray findings or PaO2/Fi02<300mmHg.
People with NAFLD, or underlying co-morbidities were significantly more
likely to experience worsening of illness after admission (p < 0.001), as were
older people and people with higher body mass index (p < 0.001). People admitted
with severe symptoms were also more likely to suffer worsening symptoms.
People with NAFLD also had a longer viral shedding period after admission to
hospital (17 vs 12 days), suggesting that the condition increases the duration
of infectiousness.
Multivariate analysis showed that people with NAFLD were at least six times
more likely to progress (odds ratio 6.4, 95% CI 1.5-31.2) and underlying
co-morbidity was associated with a similar increase in risk (OR 6.3, 95% CI
2.3-18.8). Male sex (OR 3.1, 95% CI 1.1-9.4) and age over 60 years (OR 4.8, 95%
CI 1.5-16.2) were also associated with progression.
NAFLD was also associated with a higher frequency of liver injury (abnormal
liver function during hospitalisation) (70% vs 11%), although liver enzyme
increases were mild to moderate. A postmortem liver biopsy in one patient who
died showed no evidence of the cytopathic damage reported in cases of other
respiratory viruses.
The study authors say that NAFLD may promote a pro-inflammatory environment
in the liver, impairing innate immunity and leading to more severe COVID-19
illness.