Rich people sleep better

I've heard of this before, but now I see an actual study has been published:

There's more to a good night's rest than going to bed early. Sleeping comes easiest and lasts longest for the wealthy, white, and female. Reporting her findings in the June 1 American Journal of Epidemiology, health-studies associate professor Diane Lauderdale, AM'78, AM'81, followed the sleep habits of 669 Americans aged 35 to 50 and found that those with a yearly income of less than $16,000 spend longer in bed than those making $100,000 or more, but they sleep less because their "sleep latency," the amount of time spent lying in bed awake, stretches to nearly an hour.

Using both self-kept sleep logs and wrist-activity monitors, Lauderdale also discovered that people sleep less than they realize: although participants reported averaging nearly seven hours per night, measured sleep was only about six.

So, do rich people worry less? Are they more exhausted by the end of the day? Do they have more comfortable beds? Or do they have better sleeping conditions in their bedrooms, e.g., darkness and silence, with no TV or other people talking?

(Hat-tip: Jonah)