I tracked 177 nights of sleep and the biggest lever I found was going to bed earlier (but there are others)

Over the last ~7 months, I’ve been tracking my sleep quality alongside Apple Health metrics to answer a simple question:

What actually improves my sleep the most?

I ended up with 177 nights of data and 39 variables. This is obviously N=1, and my sleep quality score includes some subjective judgment, so I’m not claiming causation. But a few patterns came through pretty clearly:

• Earlier bedtime was the strongest lever
• Sleep duration had a sweet spot for me, roughly 6.5–7.3 hours
• Higher pre-bed heart rate usually meant worse sleep
• REM share trended positively
• Weekends were slightly worse than weekdays
• Previous-night effects were weak, so same-night behavior seems to matter more than carryover

A few concrete numbers:

• Earlier bedtime: +0.89 quality points for earliest vs latest bedtime quartile
• Duration sweet spot: +0.84 points for the best duration range vs the shortest-sleep quartile
• Lower pre-bed HR: +0.58 points vs high pre-bed HR
• REM share: +0.60 points best vs worst quartile
• Weekend penalty: about -0.31 points

My main takeaway: for me, bedtime timing beat almost everything else. Not supplements, not some complicated hack, just getting to sleep earlier.