A recent study published in The Lancet (25/01/24) examined cognitive function in 270 patients with post-COVID conditions (PCC) compared to controls without PCC. The aim was to identify objective cognitive markers for PCC, with a hypothesis that cognitive slowing is a key deficit. Patients were tested months to years after COVID-19 diagnosis.
Two web-based cognitive tests were used – a simple reaction time test (SRT) and a sustained attention test (NVT). PCC patients showed markedly slower response times on the SRT compared to controls, with 53.5% having speeds >2 SD below normal. This demonstrates a high prevalence of cognitive slowing in PCC.
The cognitive slowing in PCC patients was replicated across two separate clinic samples in Germany and the UK. It was not explained by comorbidities like fatigue, depression, anxiety, or sleep disorders. SRT speeds correlated with poorer sustained attention on the NVT.
The study provides robust evidence of pronounced cognitive slowing distinguishing PCC patients from controls without PCC. This suggests cognitive slowing is an important factor in PCC-related cognitive impairments.
A limitation is the lack of pre-COVID baseline cognitive data. However, the slowing was significantly greater than in controls who recovered from COVID without PCC. The simple SRT has potential as an objective cognitive marker in PCC.
Further research should examine if treatments improving cognitive speed also improve broader cognition and functioning in PCC. Larger studies should also clarify if particular PCC subsets are more affected by slowing.
The full study can be read here.