4 ms·

Are there causal analyses of sleep on those other forms of dementia?

sixstringtheory 5y ago
I'm not well versed on different kinds of studies... could you explain the differences between "causal analysis" and whatever the study linked in the article is? They mention a longitudinal study and that the "finding was confirmed in analysis using sleep duration measured by an accelerometer." I assume a causal analysis would also determine the direction of the causality, e.g. if it turns out that people predisposed to dementia have more trouble sleeping in middle age. That definitely seems like a tall order and probably not exactly what the linked study can answer.
- eurasiantiger 5y ago
  Accelerometers tell nothing about the actual sleep duration. Is this another one of that quack sleep doctor’s ”everyone needs 8 hours of sleep every night” studies?
- carbocation 5y ago
  Correct, the study design in the original article cannot answer causal questions (although of course it can generate hypotheses). For example, if an omniscience informed us "actually, people lose sleep in middle age as a consequence of the early stages of dementia", that would make sense as well. The best causal analysis is interventional, but many times (such as in this case) it would be both extremely challenging and likely hard to do in any ethical fashion (I can't imagine how it could be done, but perhaps someone could). Short of that, you're left with instrumental variables. Genetics offers a very nice instrumental variable, since the causal arrow largely goes one way if you setup your study design carefully. That is generally performed as Mendelian randomization, which has several assumptions but, if met, has nice properties. https://en.wikipedia.org/wiki/Mendelian_randomization https://en.wikipedia.org/wiki/Mendelian_randomization
gumby 5y ago
Unfortunately such studies are very very hard to conduct and are never well powered

I'm not well versed on different kinds of studies... could you explain the differences between "causal analysis" and whatever the study linked in the article is? They mention a longitudinal study and that the "finding was confirmed in analysis using sleep duration measured by an accelerometer." I assume a causal analysis would also determine the direction of the causality, e.g. if it turns out that people predisposed to dementia have more trouble sleeping in middle age. That definitely seems like a tall order and probably not exactly what the linked study can answer.

eurasiantiger 5y ago
Accelerometers tell nothing about the actual sleep duration. Is this another one of that quack sleep doctor’s ”everyone needs 8 hours of sleep every night” studies?
carbocation 5y ago
Correct, the study design in the original article cannot answer causal questions (although of course it can generate hypotheses). For example, if an omniscience informed us "actually, people lose sleep in middle age as a consequence of the early stages of dementia", that would make sense as well. The best causal analysis is interventional, but many times (such as in this case) it would be both extremely challenging and likely hard to do in any ethical fashion (I can't imagine how it could be done, but perhaps someone could). Short of that, you're left with instrumental variables. Genetics offers a very nice instrumental variable, since the causal arrow largely goes one way if you setup your study design carefully. That is generally performed as Mendelian randomization, which has several assumptions but, if met, has nice properties. https://en.wikipedia.org/wiki/Mendelian_randomization https://en.wikipedia.org/wiki/Mendelian_randomization

gumby 5y ago

Unfortunately such studies are very very hard to conduct and are never well powered