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Comment by runjake | Hacker News Reader

I've tracked sleep using a number of devices and algorithms and I haven't found a single one that regularly aligns with what and how I feel.

I know it's tracking real data, but the conclusions feel completely made up.

What are other people's experience -- especially from those who are more bullish about sleep tracking?

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I use an Android app called "Sleep", it just works by accelerometer with your phone on the corner of your bed. I've found it's not really good with its automatic rating and suggestions, but the activity graph has an extremely reliable wave pattern on the mornings I am well rested. Like an hour and a half of no movement at all, then an hour of restlessness, which repeats through the night. Usually the hour of restlessness even has the same pattern each time it happens. But any other pattern and I generally feel tired the whole morning.

Originally I got this app for its alarm, it tries to go off in the half hour before the alarm time when you're already partially awake. The sleep tracking was just a bonus.

I find Garmin's sleep tracking "accurate" in that it typically matches how I feel the next day, but that also makes it not terribly useful because I don't really need a gadget to tell me when I feel tired. Mostly I wear the watch to sleep out of inertia and in case I need a flashlight in the middle of the night.

But there have been three aspects of sleep tracking that have been mildly useful:

1. A few times my heart rate variability went haywire and the sleep scores didn't match how I felt, and it turned out I was sick and had not yet noticed any symptoms. Since then it has been mildly useful to have a heads up when I'm probably coming down with something before symptoms show up.

2. You can use their Lifestyle Logging to track how things like caffeine, alcohol, and various nighttime routines affect your sleep. I mean, I haven't discovered anything that's not already common knowledge, but somehow having hard data makes it more compelling. I suppose if I was going to trial any sleep aids then Garmin's correlation would be convenient and save me from having to maintain my own spreadsheet.

3. It alters the suggested workouts if you haven't been sleeping well. Trivial to do manually, but it's a convenient reminder not to overextend.

I track sleep and energy levels with a galaxy watch and there's a strong correlation with how I feel on a given day. Sometimes it surprises me, and day where I wake up thinking I slept well but after an hour or two I'll realize my energy level isn't great, and sure enough I'll check the app and see it's low, with a warning about my sleeping HRV or resting heart rate being away from my norm.

It's not perfect - there are definitely days when it's wrong. But overall I have a target of keeping my sleep and energy scores in the 90s and it's helpful. I think the most important thing is to keep in mind that it's an imperfect measurements but it's still the best one most of us have for now.

Garmin’s body battery is very close to how I physically feel

Yep, can confirm. It's surprisingly accurate to the subjective feeling.

There are a number of studies comparing these devices with clinical sleep tracking. Just search for sleep tracking on google scholar. My take is that consumer devices have gotten pretty good at detecting when you are sleeping, but are not really good at detecting your sleep phases

Your devices are tracking sleep time, which makes about as much sense as measuring your diet based on how much time you spend chewing.

Time in deep sleep is not a direct marker of slow-wave delta power, which is just one of the measures of repair and glymphatic flush which occurs during deep sleep.

If slow-wave activity is slightly impaired, your brain can try to make up for that reduction by increasing time in deep sleep.

However, larger impairments mean your brain will struggle to stay in deep sleep.

This is why our work at https://affectablesleep.com focuses directly on enhancing the Neural Function of Sleep (and specifically deep sleep) rather than focusing on time.

it's a lot of work, but something you could do is track how you feel (manually or some other way) and do a similar statistical analysis. chess elo was just convenient and aligned for me.

Yeah, I didn't mean to discount your article. Pretty clearly, it's working out for you.

I do have an iOS shortcut that tracks my mood with janky emojis. I use it at least once daily.

I’m surprised people need this data. Are they not aware if they had a good night sleep? Always had been obvious to me.

I think it’s more a way to explore the effects certain other behaviours can have on your sleep quality; for instance does a magnesium supplement help you get more deep sleep, what about workout timing does it effect how long it takes to fall asleep or interruptions and so on.

I don’t trust the raw numbers at all, really, but since i’m wearing the same sensor i can use it to spot trends at least.

Or that’s what i tell myself anyway…

How did you know it was magnesium supplement? There is no control and n=1.

by tracking sleep, what exactly do you mean by that? sleep phases, sleep score, sleep duration?

Yes to all.

Wrist based sleep tracking is worse than finger.

Oura for measuring sleep. Garmin for tracking physical exercise. Oura always reflected the timings and my feeling much closer than Garmin (Enduro), which basically always told me I had bad sleep (started late after my last woken moments and ended an hour early).

My own thought, it's honestly best not to track sleep unless you feel you have an underlying issue. It causes more anxiety than it solves. If you're tired, go to bed earlier, adjust tech use and food consumption before bed.

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