Several animal and human studies have shown that COVID-19 can cause bone loss during acute illness and after the recovery period from the disease.

A January study from Indiana University School of Medicine found that the SARS-CoV-2 virus “can cause rapid and significant bone loss — even when infections appear mild.”

Researchers from the Department of Orthopedic Surgery found that mouse models infected with the coronavirus lost about 25 percent of their bone mass within two weeks.

They also found that mouse models had a 63 percent increase in osteoclasts, the cells that cause the bone to be broken down and reabsorbed.

These changes “were observed even in mice with mild and asymptomatic infections”.

Hamsters mimic the human experience.

Last month, researchers from the University of Hong Kong published their study on the effects of SARS-CoV-2 infection on bone metabolism in Siberian hamsters.

They describe their hamster model as one that “closely mimics Covid-19 in humans”.

Four days after the hamsters were infected with COVID-19, their bone tissues were collected and analyzed using three-dimensional micro-computerized CT scans.

The study found that SARS-CoV-2 infection caused severe bone loss, particularly of the trabecular bone in the long bones and lumbar vertebrae.

The trabecular bone is the softer, spongy, and more flexible bone tissue that acts as a shock absorber at the end of long bones.

Because walking, running, or carrying takes much of the punishment, the cells of trabecular bone have a higher turnover rate, where they are broken down and absorbed into the body.

It is this type of bone that is vulnerable to osteoporosis.

In this case, the researchers said the inflammatory response characteristic of COVID-19 serves to trigger the activation of osteoclasts — the cells responsible for breaking down bone tissue.

Decrease in bone mineral density in patients

In April, researchers from Atatürk Sanatorium Training and Research Hospital, Ankara, published a study on the effects of COVID-19 symptoms and steroid treatment on bone mineral density (BMD) in hospitalized patients.

Chest computed tomography (CT) scans were obtained for clinical management at diagnosis.

Essentially, the doctors assessed the patients for lung damage, but they also measured BMD.

BMD measures minerals, primarily calcium and phosphorus, contained in bone volume.

BMD measurements are used to diagnose osteoporosis and predict bone fracture likelihood.

Surviving patients were rescanned in follow-up visits.

BMD was found to be reduced by an average of 8.6 percent from diagnosis to follow-up.

Follow-up visits took place on average 81 days after hospital discharge.

The researchers report that “BMD decline was significantly greater than expected for age-related annual BMD loss.”

They determined the severity of COVID-19 pneumonia, and the total steroid dose during treatment predicted BMD loss after hospitalization.

They conclude that “the bone health of patients surviving hospitalization with COVID-19 should be closely monitored during follow-up visits to facilitate the prevention and early treatment of osteoporosis complications”.