I agree with this limitation. The NPI-Q nighttime behavior question excludes the ability to identify other types of sleep-wake disorders and even though the score is based on the answer from an informant, there is often a gap between the subjective perception of sleep and objective data via PSG. The question also doesn’t capture sleep behavior or CBT-I attempts. Although CBT-I is moderately effective for insomnia at best, cases where this has been attempted and proved unsuccessful could help point to neurobiological drivers of the SD-MBI-dementia relationship.

Did you consider breaking apart the MBI analysis by category (decreased motivation, emotional dysregulation, impulse dyscontrol, social inappropriateness, abnormal perception/thought) versus using a global MBI score to better see where the relationship between MBI, SD and dementia is strongest (if any)? This could help extrapolate the potential common cause/pathology.

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Typo: "...were CN, 3293 (27.6%) had MCI.." :)