Women are significantly more likely than men to experience long-term symptoms of COVID-19, a new review suggests.
Researchers from Johnson & Johnson's Office of the Chief Medical Officer for Women's Health analyzed data from studies involving 1.3 million patients.
The results, published Tuesday in the journal Current Medical Research and Opinion, showed females are 22% more likely to develop long COVID than males.
"Knowledge about fundamental sex differences … of COVID-19 is crucial for the identification … of effective therapies and public health interventions that are inclusive of and sensitive to the potential differential treatment needs of both sexes," the authors said in a news release.
Long COVID occurs when patients who have cleared the infection still have symptoms lasting more than four weeks after recovering. In some cases, these symptoms can persist for months, or even years.
Patients can experience a variety of lingering symptoms including fatigue, difficulty breathing, headaches, brain fog, joint and muscle pain, and continued loss of taste and smell, according to the Centers for Disease Control and Prevention.
It's unclear what causes people to develop long COVID but there are several theories among experts including lingering virus in the body, damage to nerve pathways caused by the virus and the immune system remaining active following infection.
The study found the most common symptoms for women within four weeks of testing positive included ear, nose and throat (ENT) issues; muscle aches and pain; shortness of breath and psychiatric or mood disorders such as depression.
Meanwhile, men were more likely to have renal disorders such as acute kidney injury.
Not only were symptoms during COVID-19 infection different among males and females but the symptoms were also different after the development of long COVID.
For women, they had higher rates of long-term symptoms including fatigue; ENT; gastrointestinal; neurological; skin and psychiatric and/or mood disorders.
Women were at least twice as likely to have ENT long-term symptoms and 60% more likely to have gastrointestinal symptoms.
On the other hand, men had higher rates of renal disorders as well as endocrine disorders, including diabetes.
Several studies in the past have looked at differences in hospitalization, ICU admission and death from COVID-19 broken down by sex.
But the researchers noted that, out of more than 600,000 articles analyzed for this study -- published between December 2019 and June 2021 -- only 35 provided data about COVID-19 symptoms and aftereffects in enough detail to understand how males and females may experience the disease differently.
"Unfortunately, most studies did not evaluate or report granular data by sex, which limited sex-specific clinical insights that may be impacting treatment," they wrote.
It's unclear why women are more susceptible to long COVID than men, but the authors said it could be due to differences in how women's immune systems respond to infection compared to those of men.
"Females mount more rapid and robust innate and adaptive immune responses, which can protect them from initial infection and severity," they wrote. "However, this same difference can render females more vulnerable to prolonged autoimmune-related diseases."
Additionally, the team said women may be at greater risk of COVID-19 because certain professions, such as nursing and education, are largely made up of females, which could -- in turn -- make them more likely to develop long COVID.
What's more, "there may be disparities in access to care based on gender that could affect the natural history of the disease, leading to more complications and [aftereffects]," the authors wrote in the release.
The team said it hopes more researchers include detailed data about COVID-19 symptoms and effects broken down by sex in their studies to further study how differently men and women are affected and if different treatments are needed.
Dr. Roberto Herrera contributed to this report.