It'd increase them, for sure. Never mind, though, the only cognitive effort required is a focus on gentle breathing. Plus an occasional flick of the duvet to refresh the air!
> CO2 tended to cause poor sleep, headache, and hand tremor before it caused cognitive issues.
If you're concerned about carbon dioxide you can either refresh the air periodically or you can create a small gap in the duvet to allow some exchange of air with the surrounding room (whilst keeping the humidity relatively high).