Explain What Good Sleep Hygiene Actually Requires and Why

Sleep hygiene advice is largely correct and largely ignored, partly because the rules come without the mechanism. Understanding why screens disrupt sleep, what temperature does to sleep architecture, and which recommendations have solid evidence versus which are more speculative produces a much more targeted approach to a specific sleep problem. This explains the biology first and then identifies the most important single change for a specific issue.

Explain sleep hygiene in a way that goes beyond the standard checklist. I have read the advice about screens, temperature, and consistency. What I want to understand is:

1. The underlying biology: why these recommendations work at a physiological level, not just that they work
2. Which recommendations have the strongest evidence and which are more speculative or individual
3. The most important single change for someone whose primary problem is {SLEEP_PROBLEM}
4. What the research says about how long it typically takes to see improvement after making consistent changes

Write for someone who is analytically sceptical of wellness advice and wants to understand the mechanism, not just follow the rule.