Women aged 40-55 worldwide are at the highest risk of developing long COVID, according to research published in the Journal of American Medical Association (JAMA).
The peer-reviewed study, led by the University of Texas Health Science Center, observed 12,276 people and found females had a "significantly higher" risk of long-term COVID-19 than males.
Of the people in the study, 95 per cent of females aged between 40-55 were associated with a higher risk of long COVID — between 1.31 and 1.44 times as likely as men.
- Women aged 18 to 39 years old had a lower risk at 1.04 times that of men.
- Women in general were at 1.5 times the risk of getting long COVID than men, in non-pregnant women.
- Among menopausal women, the risk was 1.42 times higher and among non-menopausal women, the risk was 1.45 times that of men.
The findings suggested patients' sex, age and other factors should be taken into account when assessing their risk of long COVID.
The development of long COVID was measured using a self-reported symptom-based questionnaire and scoring guidelines six months after initial infection.
Why are women more at risk?
Medical researchers at the University of New South Wales have been investigating the long-term effects of COVID as part of the ADAPT study at the Kirby Institute.
Gail Matthews from the Kirby Institute, who is one of the lead investigators of the study, said there were several theories about why long COVID affected women more than men.
"It's almost as though the immune response has been turned up but doesn't turn itself off," Professor Mathews said.
So, you have this chronic, aberrant immune response with the body trying to react against something. And that's why people have this ongoing fatigue and viral-type symptoms."
She said another theory related to an auto-immune phenomenon where the COVID-19 virus triggered the autoimmunity, which might also explain why the virus had a female predominance, as women tend to be affected twice as often as men.
"We know that women have a tendency to suffer from autoimmune diseases, so maybe that's the reason why it's common in women. It could be an autoimmune process that is stimulated by the virus," Professor Matthews explained.
What is long COVID?
Worldwide, COVID has infected more than 700 million people, with an estimated 7 million deaths, according to the World Health Organization (WHO).
Although many individuals recover, some experience long-term effects.
The WHO defined long COVID as the continuation or development of new symptoms three months after the initial COVID infection, with symptoms lasting for at least two months with no other explanation.
The symptoms contributing to the long COVID definition included post-exertional malaise, fatigue, brain fog, dizziness, palpitations, loss of or change in smell or taste, thirst, chronic cough, chest pain, shortness of breath, and snoring or sleep apnoea.
A 2022 study by the Australian National University (ANU) of more than 11,000 Australians who tested positive for COVID-19 found almost one in five experienced long COVID three months after their initial diagnosis.
ANU researcher Mulu Abraha Woldegiorgis said the results from the study showed the risk of developing long COVID was higher than previously thought.
"It is more than double the prevalence reported in a review of Australian data from earlier in the pandemic, and higher than similar studies done in the UK and Canada," Dr Woldegiorgis said.
She said the risk of long COVID was also greater for women and people aged 50-69, as well as those with pre-existing health conditions and people who'd had fewer vaccine doses.
What are the most common symptoms of long COVID?
The most frequently reported symptom was tiredness and fatigue.
Seventy per cent of participants in the ANU study reported these symptoms, followed by difficulty thinking or concentrating, or 'brain fog', sleep problems and coughing.
A third of women in the study with long COVID also reported changes in their menstrual cycle.
"More than a third of individuals with persistent long COVID — 38 per cent — had sought medical care in the month prior to the survey," Dr Woldegiorgis said.
"This most frequently involved a visit to a GP, hospitalisations or trips to the emergency department were thankfully less common," she said.
The study found 64 per cent of people with long COVID were able to fully return to work or study within a month of their infection, but 18 per cent reported still not being well enough to do so three months after their infection.
"Further studies could help us better understand the duration and severity of long COVID and identify effective treatments," Dr Woldegiorgis said.
