Take note that what sleep researchers count as hours of sleep is not the same as what we colloquially count as sleep.
Let's say you get in bed, lights off, at 11 PM and wake up at 7 AM. Most people would call that an eight hour night of sleep. But in reality it takes the average person 20-30 minutes before actually falling into sleep. The average person also wakes up four or more times a night, sometimes for ten minutes or longer. Often we don't even remember all the times we get up. A lot of people also awaken before their scheduled wakeup times, and spend 20+ minutes in pre-dawn twilight.
Add it altogether and an "eight hour night" may actually only constitute 6.5 hours of actual physiological sleep. The only way to know for sure how much sleep you get is to use a device specifically designed for the purpose.
Normally I would be inclined to agree with you but the article specifically says: "The research has some important limitations including ... the subjective measure of sleep being based on time spent in bed rather being asleep per se"
According to the study 9 hrs of sleep is bad for your health (too much sleep). But that 9 hrs may actually constitute 8 hrs of actual physiological sleep. So 8 hrs of actual sleep is too much and is bad?
I try to be in bed for 9 hours every night which actually logs 8 hours of time asleep. Not always but keeping my weekly average around that amount +/- %5. I'm sure the tracker is off by some amount but it seems fairly accurate.
This right here is why I schedule myself for about 8 hours, but also have my alarm set with a snooze feature of 30 minutes. If I wake up but I don't feel done, I'll allow myself to snooze a few times before actually getting up.
It's simple, but surprisingly effective. I figure, all the studies in the world are nice, but listening to the signals my body gives me is probably the best approach. 30 minutes is about the length of one more REM cycle, and I tend to find that I dream most vividly during those snooze sessions, and wake up remarkably refreshed by the end of them.
I've used (a) the Beddit touch-sensitive mat, (b) the Fitbit watch, and (c) the Oura ring. Beddit claimed I never slept more than 2 hours a night, which was something of an exaggeration. Fitbit was better, but I still caught it a couple of times claiming that I was asleep when I was actually lying awake reading for an hour. I've been using the Oura ring for maybe 6 months and I haven't caught it in any known mistakes so far; there was one weird thing where if you had multiple sleep periods separated by several hours, it'd show only one of them in the cloud view, but I've not hit that recently.
I would recommend the Oura ring with few reservations.
I have a Xiaomi fitness band 2. As far as I can tell, the sleep metrics it reports are pretty good. I wouldn't attempt to compare its accuracy to an Apple watch, but the Xiaomi's battery charge lasts about a week and it cost $30.
I'm really impressed with Mi Band 2 sleep tracking. It correctly matches the time I go to bed, and get up. Also gets each time I wake up during the night, or when I'm reading before sleep. I'm not sure about the "deep sleep" recording, and maybe I'm being suggested, but in nights with low deep sleep I fell terrible. Just monitoring my sleep I improved it. Sorry that it does not have a smart alarm neither an alarm to go to bed.
Withings (ex Nokia) is selling mats that you put under your sheets and where you lie on. I think Apple does, too, but only in America.
That's probably the best device for home-use. But sleep labs are using EEGs, cameras, microphones and puls oxymeters for a reason. Don't expect medical-grade results from a home-use device.
Less accurate are several kinds of fitness trackers/smart watches, very inaccurate are smartphone apps.
I wish the Withings mat would have the option to wake me up when optimal time comes. I had a fitness tracker that did that but it was very subtle and started working after a few weeks.
Are you thinking of the Pebble watch? Maybe in combination with some Android app? I had this setup years ago and I do miss it. I'll have to see whether it can be replicated with my current Fitbit, last I checked it couldn't but it was a while ago.
Let's say you get in bed, lights off, at 11 PM and wake up at 7 AM. Most people would call that an eight hour night of sleep. But in reality it takes the average person 20-30 minutes before actually falling into sleep. The average person also wakes up four or more times a night, sometimes for ten minutes or longer. Often we don't even remember all the times we get up. A lot of people also awaken before their scheduled wakeup times, and spend 20+ minutes in pre-dawn twilight.
Add it altogether and an "eight hour night" may actually only constitute 6.5 hours of actual physiological sleep. The only way to know for sure how much sleep you get is to use a device specifically designed for the purpose.