> ... only 5.5 hours per night ...
> ... increased sleep duration by 27 minutes per night ...
I'm not surprised. On average, they were still under 6 hours, if barely. And if the sleep problems are interrupt-driven, this study does not appear to account for sleep quality.
If they'd read the whole PDF, they might have seen these bits:
"All six display units (DUs) blanked with a selected instrument approach to a runway with a 270-degree true heading, and all six DUs stayed blank until a different runway was selected."
And:
"An unsafe condition exists that requires the immediate adoption of this AD without providing an opportunity for public comments prior to adoption."
That's pretty serious, and indeed fits exactly with "some Boeing 737s can't land due West."