Recent study shows fast walkers may be at lower risk for severe Covid-19, milder coronavirus infections generate fewer antibodies

How quickly people generally walk may be linked to their risk of developing severe Covid-19, a new study suggested. Researchers analyzed data on more than 400,000 participants in the UK Biobank, a British registry that closely tracks people's health over many years. Overall, 973 participants developed a coronavirus infection severe enough to require hospitalization.

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Compared to normal-weight individuals, people with obesity had a 49% higher risk for severe Covid-19. But slow walkers had the highest risk of severe Covid-19 regardless of obesity status. For example, normal-weight people who usually walked at a slow pace - less than 3 miles per hour (4.8 km per hour) - had more than double the odds of developing severe Covid-19 compared to normal-weight people who typically walked more briskly - more than 4 miles per hour (6.4 km per hour). People with slow walking speed often have other underlying conditions that contribute to poor health.

Gait speed is often used to test the physical capacity of adults and to predict risk of future disease, disability and death. "Self-reported walking pace, a simple measure of functional fitness, appears to be a risk factor for severe Covid-19 that is independent of obesity," the authors of the current study wrote in a paper posted on Saturday on medRxiv, ahead of peer review.

Covid-19 inflammatory syndrome now seen in adults

A rare and life-threatening condition seen in some children and young adults after exposure to the novel coronavirus is being reported in older adults now as well. The condition, known as Multisystem Inflammatory Syndrome in Children (MIS-C), can attack multiple organs, impair heart function and weaken heart arteries.

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Children initially experience fever, rash, conjunctivitis, lower-limb swelling, pain in arms and legs, and significant gastrointestinal symptoms. Doctors at New York University, in a report on Saturday in the Lancet medical journal, reported a similar case in a 45-year-old man. Doctors at Maimonides Medical Center in Brooklyn reported last month in the American Journal of Emergency Medicine a case in a 36-year-old woman. While both research teams cautioned against drawing conclusions from these isolated cases, they said they want to "heighten awareness" of the possibility that the syndrome can occur in adults.

London hospital reports rise in stillbirths during pandemic

The number of stillbirths at one large London hospital has jumped significantly during the pandemic. In the four months preceding the pandemic, there were roughly two stillbirths among every 1,000 births at St George's University Hospital.

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From February through mid-June, there were roughly nine stillbirths per 1,000 births. The research appeared on Friday in the Journal of the American Medical Association. None of the women with stillbirths during the pandemic period had been diagnosed with Covid-19, the researchers said. But they noted that the coronavirus still may have been responsible given that previous research showed that up to 90% of infected pregnant women in Britain had no symptoms and therefore could not get tested for the virus. The increase in stillbirths also may be an indirect effect of the pandemic, they said.

If women avoided visiting a doctor or hospital for fear of infection, serious problems might have been missed such as reduced fetal movements or dangerous pregnancy-related high blood pressure.

Milder coronavirus infections generate fewer antibodies

Any immunity to coronavirus reinfection among people who already have had Covid-19 might wane after a few months, particularly if their infection was mild, two studies suggest. Researchers at Kings College London tracked 65 Covid-19 patients for up to 94 days.

All but two developed neutralizing antibodies that defend against future virus attacks, the researchers reported on Saturday on the website medRxiv in advance of peer review. People with more severe infections had more neutralizing antibodies, but in everyone, levels of such antibodies peaked after three to four weeks and then declined. Antibodies are protective proteins generated by the immune system in response to an invading pathogen. "If the person had a high peak antibody level, then the neutralizing antibody level was still high after two to three months," study leader Katie Doores told Reuters.

But in people with milder infections, who developed fewer neutralizing antibodies, those antibodies started to disappear after two to three months, similar to what is seen in patients who recover from seasonal coronaviruses that cause common colds. "We are not trying to say that immunity is gone after three months. There are still many unknowns that need to be addressed, especially the level of antibody that would be needed for protection from infection," Doores said. "In terms of vaccine, this study suggests that a booster vaccination may be required," Doores added.

In a separate study published on Monday in the journal Nature Medicine, Australian researchers reported that 41 people who had experienced mild to moderate cases of Covid-19 had inconsistent and "generally modest" neutralizing antibody responses. This adds to evidence that milder infections in most people do not provoke a full immune response that might provide some future protection