Eight hours of sleep is a number we all know by heart, and precisely for that reason nobody checks it. According to a neurologist specialising in sleep medicine, the number is not wrong - it is just incomplete. You do not sleep the same if you take those eight hours from 10pm to 6am or from 1am to 9am.

The difference is not in your mood in the morning. The difference is that the body runs on its own schedule, and that schedule does not negotiate with an alarm clock. When you go to bed outside the window in which the body is ready to fall asleep, you get the hours but not the repair that was supposed to come with them.

Melatonin does not wait until it suits you

Artificial light from screens interferes with the secretion of melatonin - the hormone that tells the body it is night. That is not new information, but the way it is usually relayed is wrong. It is not that the phone "ruins your sleep". It is that the phone tells your body it is still daytime, so the body obediently postpones falling asleep.

There are also chronotypes - people who are naturally awake in the morning and people who naturally function in the evening. That is not a character trait and it is not discipline. It is biology, and that biology rarely lines up with office hours.

When the schedule and the body do not match

When your work schedule forces you to live outside your natural sleep window, the effect is similar to flying across time zones - except you have not travelled anywhere. The body keeps trying to return to its own rhythm, and life keeps pushing it back.

The practical part of the advice is disappointingly simple and that is exactly why nobody follows it: go to bed and get up at roughly the same time. Not only on weekdays. The weekend is where most people undo everything they earned during the week - two days of shifting and the body no longer knows where it is.

None of this requires an app, a smartwatch or a supplement. It requires a schedule. And a schedule is the thing that sells worst, because there is no money to be made on it.