Like most mass-media writeups of scientific studies, there's no science here. The sample size is absolutely tiny, and it's poorly designed on top of that.<p>Here are some problems with it:<p>- The sample size is absolutely insignificant. For studies that we want to generalize to all humans, a sample of at least 100,000 is ideal.<p>- This is not longitudinal or experimental data. We have no idea if we're just seeing a random correlation or not. There are simply too many variables to control for, especially with such a small population.<p>- Only people 47 to 59 were studied, and the questionnaire was administered in the present. We don't know what their sleep patterns have been in the past.<p>- The groups were self-reported, which likely caused problems. What if you're a morning person on weekdays, but not on weekends?<p>- Correlated health issues, like obesity or diabetes, might be the cause rather than the effect.<p>- They're presumably all Korean. I don't know how this might influence the study, but it very well might.