81.3 thousand people (mainly residents of the UK) took part in the experiment while they passed intelligence tests throughout 2020. The tests within the Great British Intelligence Test program included tasks for planning, reasoning, concentration, memory training and emotional perception. The subjects were also asked if they had been ill with COVID-19 and if they had any symptoms.
12.6 thousand participants reported that they had been ill with COVID-19. Depending on the severity of the disease, they were divided into groups: those who were ill at home, were hospitalized and were connected to a lung ventilator. Taking into account a number of parameters, such as gender, age, level of education and income, the scientists concluded that it was more difficult for those who had the disease to perform tasks than for people from the control group.
Moreover, cognitive impairments were more pronounced in those who were more seriously ill. So, in patients who were connected to a ventilator, the combined intelligence score decreased by a level that approximately corresponds to seven points in IQ tests.
Those who have been ill with COVID-19 have previously reported cognitive impairment — decreased memory, mental performance and nervous exhaustion.