Women were twice as likely as men to experience lingering effects, according to new modeling conducted by the Institute of Health Metrics and Evaluation at the University of Washington's School of Medicine, Bloomberg reported.
The data, compiled for the World Health Organisation's European region, shows that one in three women who were hospitalized risk developing long-COVID.
Lingering symptoms - from chronic fatigue and "brain fog" to breathlessness - are estimated to afflict around 10 to 20 percent of COVID-19 cases.
So far, the condition and its causes have perplexed doctors, prompting calls for more research to find ways to treat and prevent it.
"This data highlights the urgent need for more analysis, more investment, more support, and more solidarity with those who experience this condition," Dr Hans Kluge, the WHO's regional director for Europe, said at a meeting.
The WHO's Europe region includes 53 countries - most of them in Europe but some in central Asia as well.
Long-COVID cases quadrupled in 2021 compared with 2020, the study estimated, based on a definition of the ailment as cases with symptoms lasting at least three months.