The findings, published in the journal 'Brain, Behavior and Immunity', highlight the need for special care for populations with these pre-existing conditions during the pandemic.
"We took a hypothesis-free approach and the most statistically significant ones are the cognitive disorders and Type 2 diabetes," said study senior author Kaixiong Ye from the University of Georgia in the US.
"Right now, we don't know the mechanisms behind these associations, we only know these are more common in Covid-19 patients," Ye added.
In a blind study, the researchers analysed data from nearly 1,000 diseases and two specific genes to compare the health profiles of Covid patients with those testing negative, looking for commonalities in the patients.
The study relied on data from UK Biobank, a long-term study of more than 5,00,000 participants investigating the respective contributions of genetic predisposition and environmental exposure to the development of disease.
Analysing the genetic factors that make some individuals at higher risk for severe Covid-19, the team focused on two genes: ACE2 and TPMPRSS2, known to be critical for the virus to enter into human cells.
"In the TMPRSS2 gene, we found that a specific genetic variation is more common in the Covid-19 patients," Ye said, adding that while the discovery was novel at the time, the team knows more data now exists about host genetic factors than even three months ago.
The research team also found that variations in genes related to SARS-CoV-2 infection may be associated with severe Covid-19 that requires hospitalization.
"And we are starting to understand how those genetic variations are making a difference," Ye stressed.
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"Working on one disease, the whole field is converging together, around the world, at the same time. It really showcases the power of science," he said.
"What my group is doing is really just data analysis, large-scale data mining, but from vaccine development to studies in patients, scientists are attacking the disease from different aspects, and that's moving us forward very quickly in combating Covid-19." the study author wrote.