Most people who contract COVID-19 get better in a few weeks, but some are in it for the long haul.

Months after clearing the virus, roughly 10 percent of patients are still struggling to recover. Some of the most common lingering symptoms include body aches, unrefreshing sleep, shortness of breath, fatigue after exertion, cardiac issues, and brain fog.

While most of these complaints significantly improve with time, preliminary research suggests a cloudy consciousness is harder to shake.

In a couple of questionnaires, 278 long-haulers were asked to compare their symptoms during the first two weeks of their illness to their symptoms now, an average of 22 weeks later.

During that elapsed time, the authors found most physical problems improved, including post-exertional fatigue and unrefreshing sleep.

On the other hand, five symptoms got worse: trouble forming words, trouble focusing, absent-mindedness, sensitivity to alcohol, and loss of hair.

The findings match other initial reports, suggesting long haulers struggle the most with cognitive problems.

Why that is remains a mystery, but complaints of brain fog are also a key feature of chronic fatigue syndrome (CFS), or myalgic encephalomyelitis (ME).

ME/CFS is a perplexing disease with no known cause, but some evidence suggests the disease is due to an overactive immune system. It's thought some cases can even be triggered by a viral infection.

Interestingly, long-haul symptoms from COVID-19 show many similarities to ME/CFS, which is why researchers are keen to compare the two.

When 502 patients diagnosed with ME/CFS were given the same symptom questionnaires outlined above, researchers found some key similarities across various health domains, including gastrointestinal issues, immune issues, sleep issues, neurocognitive issues, and blood pressure issues.

That said, those with ME/CFS reported more severe symptoms overall, especially when it came to cognitive issues like brain fog and immune issues like sore throats and lymph nodes.

In fact, the only long COVID symptoms that were worse than ME/CFS had to do with blood pressure, such as irregular heartbeats, chest pain, and shortness of breath.

The findings are intriguing and hint at some sort of central nervous system pathology across post-viral infections.

However, this initial comparison between ME/CFS and long COVID is somewhat limited.

Most people in the ME/CFS group had been ill for over two years, while long haulers in the study had been experiencing persistent symptoms for only a few months.

"It is possible that some in the COVID-19 group will continue to improve over time, whereas some might persist in their symptoms or get worse, and those that persist or get worse might over time more closely match the symptoms of the ME/CFS group," the authors suggest.

The team hopes their initial findings will reassure long haulers and the medical community that most lingering symptoms seem to get better with time. On the other hand, circulatory and cognitive issues can get worse and should be closely monitored.

The study was published in Fatigue: Biomedicine, Health & Behavior.