Yes, I remember that study. It was pretty confusing because it really only looked at average hours of sleep versus risk of death over a period of time. It didn't distinguish between people who slept a lot because they were ill (and therefore at greater risk of death) versus healthy people who slept a lot. There were other confounding factors. It did not show that sleeping more CAUSED earlier death, but that there was an association between how long you slept and your chances of death.
Without a doubt women need as much as 1.5 hours more sleep than men for optimal health. I'm pretty certain women taking decent amounts of androgens can prolly get by with less sleep and still make decent gains, but otherwise I think that sleep is the MOST important ingredient for muscle growth. I aim for 9 hours, preferably 7.5-8 at night and 1-1.5 nap in the avo. Keep in mind that what is optimal for muscle growth may not be optimal for longevity. I don't think there's enough evidence in to say for sure yet.
If you feel groggy, it may just be from waking up in the middle of one of your ~90 minute sleep cycles. Alarm clocks are an absolute curse when it comes to this, and I agree that it's better to have less (but complete) sleep rather than sleep longer but have it interupted. In other words it's best to wake up naturally. And of course, everyone's sleep needs are different.
If your sleep cycles are normal, back-to-back 90 minute ones, then you may find that 6, 7.5, 9 or 10.5 hours are best (or any multiple of 90 minutes), and that other amouns of sleep (eg 8 hours) leave you feeling less than your best.