Also, over eating is bad for health and not eating adequately is also bad for your health.

So, how do we explain fasting? I think there are some people who eat once every 24 hours and still is healthy as a horse.

Although according to your table, the elderly population were supposed to sleep for 7 to 8 hours a day, in reality, they probably slept like 5-6 hours or lesser. Their melatonin production is not that good and they will be unable to resist the effect of cortisol which is a type of hormone that is responsible for waking us up (that's why we felt moody in the morning, our cortisol is high!).

Regarding depression, although sleep disorder is one of the criteria from DSM-V to diagnose depression, it can be either hypersomnia or insomnia. Insomnia can be either it's difficult for them to fall asleep or it's difficult for them to stay asleep thus early awakening. If the article that claimed sleep deprivation is a good way of treating depression, it would be for people who were hypersomnia. However, it would be difficult since, the type of sleeping disorder can sometimes, varies. The best way is to consult a psychiatrist and get a treatment.

What is your opinion regarding sleeping pattern in a day? For example, Nikolas Tesla is well known for his aggressive style of polyphasic sleep. He will sleep for 20-30 minutes for every 4 hours so that he can earn extra hours per day compared to the general population. This sleeping technique was also used by Leonardo Da Vinci. Do you think it is a good idea to distribute your hours of sleep in a day into a few naps which will total up to the same number of hours or less?