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African Americans sleep on average almost an hour less than do Euro Americans. The two groups have mean sleep times of 6.05 hours and 6.85 hours. This finding has recently been discussed by Brian Resnick in National Journal and by our Steve Sailer.
Researchers reject a genetic explanation: “There is a consensus that innate biological differences between blacks and whites are not a factor.” So what is the cause?
The study is by Tomfohr et al. (2012). It found that duration of deep sleep and duration of Stage 2 of light sleep correlated in African Americans with perceived discrimination, which is defined as “the extent to which an individual believes that members of his or her ethnic group have been discriminated against in society.”
Nonetheless, as the authors note, sleep duration still differs significantly between African and Euro Americans even when the difference is adjusted for the effects of perceived discrimination. So we are left with a curious finding: two separate causes, one genetic and the other environmental, are producing the same pattern of effects. Both are reducing deep sleep and Stage 2 light sleep in African Americans while not affecting Stage 1 light sleep.
Whenever I see this kind of finding, I start looking for confounds. Is one cause a sock puppet for the other? It may be that perceived discrimination increases with African ancestry. Perhaps African Americans who feel conscious of discrimination also tend to be darker-skinned and more visibly African than those who don’t.
Read full, original post: The Missing Hour of Sleep