Comment by andy_ppp

I have tried many masks and they always irritate me when I'm sleeping. I never manage to get to sleep easily with one on so I'm not sure your assumption everyone thinks they sleep better with a mask on is true. If the study used a more transparent material and didn't tell the participants or small holes I would think light was certainly the issue. Why do you think the participants were guessing correctly what the study was observing - it seems likely they were not told and went in without judgment - I certainly wouldn't have noticed if the mask was a bit thin? It seems more likely to be a real difference, we know circadian rhythms are controlled by light and food timing so I don't see why it wouldn't be a correct result.