The data supporting the negative effects of sleep deprivation are I think all observational, and most use self-reported sleep quality. I remain very sceptical

The data supporting the negative effects of sleep deprivation are I think all observational, and most use self-reported sleep quality. I remain very sceptical of such analyses due to confounding variables (eg people who sleep less are also less healthy in other ways) and reverse causation (eg dementia causes poor sleep not the other way around). Not to mention the almost useless nature of self reported data. Mendelian randomisation studies are a much better way to look at these questions. I could only find one study and it is far from compelling for a link between sleep and dementia: https://academic.oup.com/ije/article/50/3/817/5956327 https://academic.oup.com/ije/article/50/3/817/5956327