[__te__]

    > ... 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.

[88840-8855]

Ok, then we could assume the hypothesis: Either you sleep 8 hours and are productive or you go down to 5.5 because 6 wont increase your efficiency levels either.