Women are more than twice as likely as men to suffer from long Covid, according to the largest study of the condition to date, which found a history of autoimmune disease or depression also increased the likelihood of experiencing symptoms.
The study by genetic testing company 23andMe surveyed more than 100,000 people who had Covid-19, about a quarter of whom reported having experienced long Covid — where symptoms such as breathing problems, fatigue and brain fog last for more than 12 weeks. Some 7,000 of these had been formally diagnosed.
Researchers found that women who developed Covid-19 disproportionately suffered from long Covid, despite other studies showing men are more likely to be infected and more likely to die from the disease. About half of the women with long Covid suffered symptoms for six months or more.
Catherine Weldon, associate scientist at 23andMe, and Stella Aslibekyan, genetic epidemiologist, wrote that the higher case rate among women may be due to hormonal differences.
“Scientists know there are similar differences for other kinds of conditions. For example, women are much more likely than men to develop autoimmune conditions such as lupus or multiple sclerosis,” they wrote.
They added that women typically have two copies of the X chromosome, which has the largest number of immune-related genes, which means that different immune responses are more pronounced in women.
The results from the study — which could be less reliable than other research because participants reported their own conditions — support smaller scientific studies that have found females are more likely to develop long Covid than males, including a paper published earlier this month in the Journal of Women’s Health and a UK study focused on patients discharged from hospital.
The 23andMe study also showed that about a third of people with long Covid had a history of autoimmune disease, and more than half had a history of depression, anxiety or cardiometabolic disease such as heart attacks or diabetes. Patients who were admitted to hospital with Covid-19 were 10 times more likely to develop long Covid.
The study found that a year after infection about a quarter of female long Covid sufferers were experiencing disruptions to their menstrual cycle.
Estimates on how many people may suffer from long Covid vary, but one prominent study from Penn State university suggested more than 100mn patients worldwide could have the condition. In the UK, an official survey found more than 1mn Britons reported symptoms at least four weeks after a Covid-19 infection.