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In contrast, a quasi-causal analysis (via Mendelian randomization) found no causal effect of sleep duration on Alzheimer's risk. > There was little evidence to

• gumby 5y ago
  There are other forms of dementia than Alzheimer's.
  • carbocation 5y ago
    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
• dmicah 5y ago
  The study you cite isn't really in conflict with the parent study. They note that the number of individuals with Alzheimer's Disease in the study was too small to develop a non-linear model relating sleep duration to AD risk: Pg. 858: "Similarly, short and long sleep duration and poor sleep quality have also been linked with an increased risk of dementia. Although a similar J-shaped association was observed in our observational analysis, we were limited to performing only the linear MR analysis, as the non-linear MR method requires a large number of cases and individual-level data. In our linear MR analysis, we found no clear evidence that an increased sleep duration was associated with a higher risk of all-cause dementia in UK Biobank or with AD in IGAP. This is unsurprising, as the true association might be non-linear and we were limited with only 1343 dementia cases in UK Biobank. Also, IGAP does not capture non-AD dementia types and comprises an older and more heterogeneous population." "Results for risks of dementia and AD are still too imprecise to draw any definitive conclusions. Our findings suggest that, in clinical care, attention should be paid to sleep-duration patterns and improved sleep habits could represent a potential therapeutic target for cognition."
  • carbocation 5y ago
    It doesn't disprove the parent study, but it certainly is not supportive of some of the causal interpretations of the observational study.