The headline is a little misleading. The word "hygiene" means more than just "cleanliness", although the two are frequently used interchangeably. In this case

The headline is a little misleading. The word "hygiene" means more than just "cleanliness", although the two are frequently used interchangeably. In this case, it refers specifically to "sleep hygiene", which is a medical term for sleep-related behaviors conducive to health (setting a regular sleep schedule, getting enough sleep, not consuming food/caffeine/alcohol too close to bedtime, etc.). http://en.wikipedia.org/wiki/Sleep_hygiene http://en.wikipedia.org/wiki/Sleep_hygiene