Sleep Data Tracking: 10-Week Follow-Up

Back in January, I kicked off an experiment to track my sleep with my Apple Watch Series 10, hoping to improve my rest and boost my deep sleep - the stage that is supposed to leave you feeling rejuvenated. My first night’s data (6 hours 52 minutes, 24.76% REM, 64.32% core, 8.74% deep, 2.18% awake) set the baseline, and I planned to check my progress after three months. Battery issues cut my tracking short at 10 weeks, but the data still revealed patterns I never would’ve noticed otherwise. Here’s what I learned about my sleep quality, how illness threw a curveball, and what the Apple Watch experience taught me.

My Sleep Data: Weekly Averages

I tracked from January 20 to March 30, 2025, logging total sleep time and stages (REM, core, deep, awake) each week. Below are my weekly averages, showing both duration and sleep stage percentages compared to the optimal ratios (20-25% REM, 50-60% core, 15-20% deep, <10% awake).

Note: Optimal ratios are from health guidelines like those from the NHS and Harvard (sources at the bottom).

Did My Sleep Quality Improve?

My goal was to sleep better, not just longer, with a focus on boosting deep sleep (15-20% ideal) to feel more restored. My first night showed a decent REM (24.76%) but too much core (64.32%) and too little deep (8.74%). Here’s how the 10 weeks stacked up:

• REM Sleep (20-25%): Stayed pretty solid at 20-25%, averaging 22-23%. Even during my shortest week (6h 1m, Mar 17-23), REM held at 22%, matching my first night’s 24.76%. This was great - REM is key for memory and dreaming, so my brain was getting its share. I can confirm this is true, I dream a lot.
• Core Sleep (50-60%): Consistently high at 60-64%, like my first night’s 64.32%. It dipped to 60% in Mar 10-16, but mostly hovered around 63-64%. This suggests I was stuck in lighter sleep, possibly crowding out deeper stages.
• Deep Sleep (15-20%): My weak spot. It averaged 11-12%, ranging from 8% (Feb 24-Mar 2) to 14% (Mar 10-16). Compared to 8.74% on night one, I saw slight gains—hitting 13-14% some weeks—but it stayed below the ideal, explaining why I didn’t always wake up energised.
• Awake Time (<10%): Mostly low at 2-5%, a bit higher than my first night’s 2.18% but still solid. A 7% spike in Mar 17-23 (6h 1m week) hinted at restlessness, maybe from stress.

Overall, my total sleep averaged 7 hours 3 minutes, a tad better than my first night’s 6h 52m but short of my 7.5-hour target. Deep sleep improved slightly (e.g., 14% in Mar 10-16), and awake time stayed minimal, showing decent sleep continuity. But high core sleep and low deep sleep persisted, meaning my rest wasn’t as restorative as I’d hoped.

Illness and Biometric Insights

My ski holiday in February (Feb 10-16) disrupted a lot. One night, I only slept 2h 39m due to an early flight, and I came back sick - likely the flu. My watch picked up on it: my wrist temperature spiked to +0.31°C above baseline (vs. 0°C the week before), and my respiratory rate jumped to 9-26 breaths per minute (vs. 7.5-17 normally). Deep sleep tanked to 8% the following week (Feb 24-Mar 2), and I definitely felt weaker.

By mid-March (Mar 10-16), things turned around. Deep sleep hit 14%, my temperature dropped to -0.09°C, and my respiratory rate normalised. This matched my recovery—I was feeling almost normal again. Seeing the watch confirm my symptoms (and recovery) was actually very insightful.

The Apple Watch Experience

Beyond sleep, the Apple Watch Series 10 shaped my daily habits. The activity rings - tracking movement, exercise, and standing made me more aware of how much I was walking or working out. On my ski trip, I loved using it to log runs and felt safer with the SOS features in the mountains (though I didn’t need them). Subconsciously, the watch nudged me to stay active. I synced it with Strava to share activities with friends, and the integration with my iPhone 15 Pro was seamless. I also found it very helpful around the course, using it with the Golfshot app to track my shots and find my distances from the pin.

But it’s not perfect. The push to “close your rings” can feel a bit exhausting some days, you just need to rest, and the watch doesn’t always like that. You can tweak calorie or exercise goals, but the accountability can stress you out if you get affected by that. Battery life was another small issue. Using it for sleep tracking drained it faster, and since I charged it overnight before, I had to change this. The quick charge (30 minutes for near-full in the morning) saved me, but the overall battery dying and having to send it back for repairs near the end of my experiment was frustrating.

Sleep tracking itself was smooth, but the wristband caused minor skin irritation after wearing it 24/7. I tried switching wrists, but that disabled wrist detection, so my morning alarm didn’t work unless I manually updated settings which is a bad design oversight from Apple. A dedicated sleep mode that ignores wrist preference would be a game-changer.

Lessons Learned and Next Steps

This experiment taught me that sleep quality matters as much as quantity. While I inched closer to 7 hours on average, my deep sleep stayed low, likely why I didn’t always feel refreshed. Stable REM and minimal awake time were wins, but I need to dial back core sleep and boost deep sleep to hit that 15-20% sweet spot. Avoiding YouTube before bed helped but I suspect stress and late nights held back deeper rest.

The Apple Watch was solid, despite battery problems. It made me more active and gave me health insights I wouldn’t have caught, like how my temperature spiked when sick. Once it’s repaired, I’ll keep tracking, focusing on earlier workouts and winding down better to balance my sleep stages. I might also try a comfier band for 24/7 wear.

If you’re thinking about sleep tracking, start simple. Notice your habits, like screen time or bedtime consistency, and don’t stress about perfect numbers. Small changes add up.

Sources

For more on sleep health, check out these resources:

• NHS: How to get to sleep, fight tiredness & tips
• Mind: Sleep Problems - How sleep affects mental health
• The Sleep Charity: Sleep Advice, hygiene, disorders etc.
• Harvard Medical School’s Division of Sleep Medicine: Harvard sleep & health education gateway