Not everything is well thought-out: can you say "a proxy for race?" Also notice that "There is a consensus" drops in without any reasons why.
ON THE QUESTION of how to explain the black-white sleep gap itself, researchers have a number of related theories. (There is a consensus that innate biological differences between blacks and whites are not a factor.) The stress caused by discrimination is one strong possibility. In the San Diego sleep study, Tomfohr’s team knew, going in, that slow-wave sleep is very sensitive to stress—which is, in turn, our body’s signal to remain vigilant against perceived threats, including discrimination. “That was our thought: If people are feeling really discriminated against, then of course they are not going to want to get into a really deep stage of sleep,” she says.
On the grimmer side of things, sleep apnea is more common, 12.8 vs 7.4% This is comparable to the obesity rate difference, and might be due to it, but it seems to be less frequently treated than among whites--and sleep apnea leads to lots of problems.