There is also growing concern that some of these "long-haulers" may get the dementia-related changes earlier than expected, the Strait Times reported.
"Anything that diminishes a person's cognitive reserve and resilience is going to allow neurodegenerative processes to accelerate," Alireza Atri, cognitive disorder neurologist, director of Banner Sun Health Research Institute, was quoted as saying.
This can then cause symptoms of neurological disorders, such as dementia, to show earlier, he added.
Dementia is a general term for the impaired ability to remember, think or make decisions that hinders a person's daily life. It results from diseases such as Alzheimer's and injuries that affect the brain, and mainly affects people 65 and above.
Atri said Covid-19 could aggravate this process and hasten cognitive decline, and then dementia, the report said.
"Let's say I'm in my 50s, and I'm destined to show dementia symptoms in my late 60s, early 70s, and I already have these toxic proteins and some issues going on with it. Covid-19 may come in and really fan these flames," said Atri.
Apart from neurological symptoms associated with Covid-19 like the loss of taste and smell, Atri said those who have long Covid should also be on the lookout for "mental fog, problems with attention and concentration, more effortful mental activities, maybe forgetfulness". There can also be sleep issues and anxiety.
This is another reason why people should be vaccinated, he said.
In a recent study published in the journal Scientific Reports, researchers identified more than 50 long-term effects of Covid-19. Besides hair loss, shortness of breath, headache, and cough they also found a prevalence of neurological symptoms, such as dementia, depression, anxiety and obsessive-compulsive disorders.
One in three people who survived Covid-19 have been diagnosed with anxiety and mood disorders, within six months of infection, according to another study published in the journal The Lancet Psychiatry.
Neurological diagnoses such as stroke and dementia were rarer, but among people admitted to intensive care, 7 per cent had a stroke and almost 2 per cent were diagnosed with dementia.