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• Posted January 29, 2025

Long COVID Severity Linked to White Blood Cell Count

A simple blood test might determine which patients are at risk for long COVID, a new study says.

Higher levels of leukocytes – a form of white blood cell – are associated with more severe symptoms of long COVID among older women, researchers reported in a new study published Jan. 29 in the journal Menopause.

“Our findings suggest that leukocyte count, a well-standardized, stable, widely available, and inexpensive clinical marker of inflammation, is an independent predictor of future (long COVID) severity in postmenopausal women,” the research team led by Ted Ng, an assistant professor with the Rush Institute for Healthy Aging at Rush University Medical Center in Chicago, concluded.

For the study, researchers analyzed blood samples taken from more than 1,200 women who participated in a COVID study between June 2021 and February 2022.

More than a third (36%) of the women suffered from long COVID symptoms, including memory problems (13%), “brain fog” (12%), or confusion or difficulty thinking or concentrating (11%), results show.

Of those women, 75% had two or more long COVID symptoms, researchers added.

Women with higher leukocyte counts tended to have more of these symptoms, and their symptoms tended to be more severe, researchers found.

“These findings are consistent with evidence showing that elevated inflammatory markers during or after COVID-19 infection are associated with subsequent (long COVID) severity and (long COVID)-associated symptoms,” researchers wrote.

One theory of long COVID is that a person’s initial infection causes heavy inflammation that does long-term damage to tissues and organs, resulting in lasting symptoms, researchers noted.

However, these results also might mean that the women were suffering from low-level inflammation prior to their COVID infection, researchers said. That existing inflammation could have made the disease even worse.

Further study is needed to better tease out the connections between long COVID and inflammation, and to verify the link between white blood cell counts and long COVID risk, researchers said.

Long COVID “significantly affects quality of life, often leading to severe disability,” Dr. Monica Christmas, associate medical director for The Menopause Society, said in a news release.

“This effect is particularly pronounced in women, who already experience higher rates of cognitive impairment after menopause,” added Christmas, who was not involved in the initial study. “By understanding underlying factors, we can better address these challenges and work to mitigate the cascade of symptoms that follow.” 

More information

The U.S. Centers for Disease Control and Prevention has more about long COVID.

SOURCE: The Menopause Society, news release, Jan. 29, 2025