Organ damage persisted in 59 per cent of long COVID patients a year after initial symptoms, even in those not severely affected when first diagnosed with the virus, according to researchers, led by one of an Indian-origin.

The findings, published in the Journal of the Royal Society of Medicine, confirmed that 29 per cent of patients with long COVID had a multi-organ impairment, with persistent symptoms and reduced function at six and 12 months. About 59 per cent of long COVID patients had single organ impairment 12 months after initial diagnosis.

"Symptoms were common at six and 12 months and associated with female gender, younger age and single organ impairment," said senior author Professor Amitava Banerjee, Institute of Health Informatics at University College London.

The study reported a reduction in symptoms between six and 12 months of extreme breathlessness (in 38 per cent to 30 per cent of patients), cognitive dysfunction (48 per cent to 38 per cent) and poor health-related quality of life (57 per cent to 45 per cent).

"Several studies confirm the persistence of symptoms in individuals with long COVID up to one year. We now add that three in five people with long COVID have impairment in at least one organ, and one in four have impairment in two or more organs, in some cases without symptoms," Banerjee said.

The team included 536 long COVID patients in the study of which 331 (62 per cent) were identified with organ impairment six months after their initial diagnosis.

The underlying mechanisms of long COVID remain elusive, said the researchers, who did not find evidence by symptoms, blood investigations or MRI to clearly define long COVID subtypes. They noted that future research must consider associations between symptoms, multi-organ impairment and function in larger cohorts.

"Organ impairment in long COVID has implications for symptoms, quality of life and longer-term health, signalling the need for prevention and integrated care for long COVID patients," Banerjee said.