Does the Rambam's recommendation of eight hours of sleep refer only to nighttime sleep?

Greetings,

Sleep during the day can be included in the total number of hours. However, from a health perspective, it is preferable that the hours of sleep be at the end of the night (see Rambam, Hilchot Deot 4:4, and Hanhagot Olam, part 1, page 44).

By the way, the Rambam (there) recommends eight hours of sleep and did not mention six hours. However, the Mishnah Berurah (siman 238, subsection 2) cited the Magen Avraham, who wrote that there is no fixed measure for a person's nighttime sleep; rather, it depends on each individual according to his health and strength, etc. See there. And the Yaavetz, in his siddur (order of Keriat Shema al haMitah), wrote that six hours of sleep are enough for a healthy person and certainly sufficient, and everything depends on what a person accustoms himself to in his youth, for habit becomes a second nature. And Rav Yaakov Kanievsky, zt"l (Karyana De'Igrata, part 1, siman 28), wrote that in our times, as a rule, one needs to sleep about seven hours in a 24-hour period, although there are exceptional cases in which one must sleep eight hours, and there are exceptional cases in which six hours will also suffice.

It should also be noted what the Tiferet Yisrael wrote (Masechet Avot, chapter 6, letter 84): that what the Rambam wrote, that one should sleep eight hours, applies only before the age of fifty; but afterward, when the wear in the body's foundations is not as great as in one's youth, and there is no longer such a need for so much rest, it is enough to sleep five or six hours each night.

With blessings,

Hillel Meirs