The absence of evidence that 6 is much worse than 8 hours is not evidence that 6 is not much worse than 8 hours. If sleep studies show that 6-hour sleepers do

The absence of evidence that 6 is much worse than 8 hours is not evidence that 6 is not much worse than 8 hours. If sleep studies show that 6-hour sleepers do better than 8-hour sleepers on a variety of metrics... that definitely counts as evidence. It doesn't matter that much in this case because we already agree that it's worse The parent comment literally cites a study that suggests 8 is worse than 6.