One thing I have noticed about rich people is that they are insomniacs. If money never sleeps, why should they?

Billionaire Lynn Tilton, who I profiled last month, rarely gets more than a few hours sleep a night. John D. Rockefeller was famous for his brief nighttime naps. Donald Trump says he only gets three hours a night, while Martha Stewart says she only needs four.

What we dont know is whether sleep deprivation is a cause or a consequence of wealth.

A new study suggests it may be a cause.

According to a survey of more than 1,400 people around the world with an average net worth of $2 million, the wealthiest respondents in the sample had 80% more energy than those at the bottom of the sample.