(NEW YORK) -- COVID-19 patients are at least four times more likely to develop chronic fatigue than someone who has not had the virus, a new federal study published Wednesday suggests.

Researchers from the Centers for Disease Control and Prevention (CDC) looked at electronic health records from the University of Washington of more than 4,500 patients with confirmed COVID-19 between February 2020 and February 2021.

They were followed for a median of 11.4 months and their health data was compared with the data of more than 9,000 non-COVID-19 patients with similar characteristics.

Fatigue developed in 9% of the COVID patients, the team found. Among COVID-19 patients, the rate of new cases of fatigue was 10.2 per 100 person-years and the rate of new cases of chronic fatigue was 1.8 per 100 person-years.

Person-years is a type of measurement that multiplies the number of people in a study and the amount of time each person spends in a study. It is useful for evaluating risk.

Compared with non-COVID-19 patients, those who has tested positive were 68% at risk of fatigue and were 4.3 times more likely to develop chronic fatigue in the follow-up period, the study found.

Fatigue following COVID-19 infection was more common among women, older people and those who had other medical conditions including diabetes, chronic obstructive pulmonary disease and a history of mood disorders.

There was no strong evidence of racial or ethnic differences when it came to developing fatigue after COVID-19 except a slightly lower incidence among Black patients, results also showed.

Additionally, researchers found that patients with COVID-19 who developed fatigue after the infection had far worse outcomes such as hospitalization or death than patients without fatigue.

Among 434 COVID-19 patients in whom fatigue developed, 25.6% were hospitalized more than one time during the follow-up period compared to 13.6% of 4,155 patients without fatigue who were hospitalized.

What's more, COVID-19 patients with fatigue were at higher risk of dying. During the follow-up period, 5.3% with fatigue died compared to 2.3% of those without fatigue.

"Our data indicate that COVID-19 is associated with a significant increase in new fatigue diagnoses, and physicians should be aware that fatigue might occur or be newly recognized [more than] one year after acute COVID-19," the authors of the study wrote. "Future study is needed to better understand the possible association between fatigue and clinical outcomes."

The authors added that the high rates of fatigue "reinforce the need for public health actions to prevent infections, to provide clinical care to those in need, and to find effective treatments for post–acute COVID-19 fatigue."

The team said it also hopes that increased awareness of fatigue and other long COVID symptoms helps COVID patients seek early care when needed to reduce their risk.

The results build upon those seen in previous reports including a joint U.S.-U.K. study of electronic health records that found 12.8% of patients received a new fatigue diagnosis within six months of COVID-19 infection.

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