It’s likely that, over the course of their lifetimes, white students have slept hundreds of hours more than black students, reports The Washington Post.

According to a forthcoming paper by Tiffany Yip, a psychology professor at Fordham University, the sleep gap between white and nonwhite students begins with children as young as 2 years old — and it grows from there. What starts as a 15 minutes-a-day sleep deficit in childhood eventually becomes almost an hour a night in adulthood.

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