Sleep types

...even middle-schoolers would know the brain is nowhere near the wrist, and there is no circuit for brain waves to travel down to the wrist to be measured there.

Indeed. But we all know that the heart is nowhere near the wrist, either, and yet we accept that it is possible to measure, or at least estimate, heart rate from a wrist measurement. It isn't much of a leap to assume that there's a way to measure brain activity there also; and probably there is some connection between accelerometer activity and conscious state, although how well they correlate, I really have no idea. It might make an interesting PhD project, if it hasn't been done already. Still, if one doesn't have medical training, I can see how it would be very easy to over-estimate the validity of Garmin's data.

It concerns me that Garmin is presenting what seems to be clinical data, using methods that I'm not convinced would stand much clinical scrutiny. It's not just sleep -- we are given data about stress, fitness level, Calorie consumption, etc., presented in such a way that it appears to be authoritative. I think it would be very easy to be convinced.

I own a finger-mounted pulse oximeter. It's not a medical-grade device -- I bought it from a high-street supermarket. But it comes with a booklet that explains how it works, how it was calibrated, and what limits of accuracy might be expected. This kind of information is completely missing from Garmin's product descriptions and advertising. If you're going to inform people, for example, about Calorie consumption, and people are going to rely on that information, then I think you have an ethical duty to explain how much trust can be placed in the information you present.

Sorry, I guess I've wandered off topic here.

It concerns me that Garmin is presenting what seems to be clinical data, using methods that I'm not convinced would stand much clinical scrutiny. It's not just sleep -- we are given data about stress, fitness level, Calorie consumption, etc., presented in such a way that it appears to be authoritative.

The pages at ">://www.garmin.com/en-AU/legal/atdisclaimer">http://www.garmin.com/en-AU/legal/atdisclaimer, ">://www.garmin.com/en-GB/legal/atdisclaimer">http://www.garmin.com/en-GB/legal/atdisclaimer and ">://www.garmin.com/en-US/legal/atdisclaimer">http://www.garmin.com/en-US/legal/atdisclaimer uniformly state:

Activity Tracking Accuracy
Garmin activity trackers are intended to be tools to provide you with information to encourage an active and healthy lifestyle. Garmin activity trackers rely on sensors that track your movement and other metrics. The data and information provided by these devices is intended to be a close estimation of your activity and metrics tracked, but may not be completely accurate, including step, sleep, distance, heart rate and calorie data. Garmin activity trackers are not medical devices, and the data provided by them is not intended to be utilized for medical purposes and is not intended to diagnose, treat, cure, or prevent any disease.

I can't help but suspect a large part of the issue is that you (and some other users) want the Garmin devices to be better and/or offer more than that, and may even rationalise that want on the basis of the asking prices of specific device models, and then insist on interpreting the content of Garmin's marketing collateral in such light.

probably there is some connection between accelerometer activity and conscious state, although how well they correlate, I really have no idea. It might make an interesting PhD project, if it hasn't been done already.

It's been done very thoroughly. Here's a link to get you started:
https://en.wikipedia.org/wiki/Actigraphy

It concerns me that Garmin is presenting what seems to be clinical data,

Garmin never said that data collected by it's wearables is medical-grade. Garmin actually discourages you to use it for medical purposes. Have a look here: https://www.garmin.com/en-US/legal/atdisclaimer
It is you who perceive it as clinical data.

, presented in such a way that it appears to be authoritative. I think it would be very easy to be convinced.

What way of data presentation would convince you that it is not authoritative?

I own a finger-mounted pulse oximeter. It's not a medical-grade device -- I bought it from a high-street supermarket.

"Medical grade" does not depend on where it was bought, but rather what kind of certification process it underwent - depending on local regulations. It is not impossible for a cheap and easily obtainable device to be "medical grade". Garmin wearables - nonetheless - are not.

Sorry, I guess I've wandered off topic here.

No biggie.

I can't help but suspect a large part of the issue is that you (and some other users) want the Garmin devices to be better and/or offer more than that, and may even rationalise that want on the basis of the asking prices of specific device models, and then insist on interpreting the content of Garmin's marketing collateral in such light.

There's probably some truth in this. These devices are not cheap, and I certainly did have a hope (although no particular expectation) that measures of things like Calorie consumption would be more reliable than I think they are. At least I would like to know what the limits of estimation are; and this at least doesn't seem to be an unreasonable hope, for a device as expensive as a VA3.

You're right that Garmin doesn't recommend the use of its gadgets for diagnosing disease, and I don't think anybody would try to use them this way. Nevertheless, I suspect people are using them for making health-related decisions, even it these amount only to whether it's OK to eat a piece of pie after an hour in the gym. But even that decision cannot be made safely, unless we have some kind of idea what limits of accuracy apply to the data on which we are basing the decision.

What's the point of presenting data, except that you expect people will act on that data? If nobody will act on the data, you might as well save a heap of time and effort and just display random numbers. And if people do act on your data, are they not entitled to know that it is accurate enough to justify those actions?

What's the point of presenting data, except that you expect people will act on that data?

The point, in the context of the consumer fitness appliances market, is to sell products. Whether users only use the presented data for ‘motivation’ and/or entertainment purposes, or unwisely make potentially impactful decisions on the basis of the data, is beside the point – unless such decisions ultimately steer them into situations, circumstances or conditions that they stop buying products.

If nobody will act on the data, you might as well save a heap of time and effort and just display random numbers.

Nah, that won't do the brand's reputation and sales any good, and it creates more risk of lawsuits and regulatory intervention down the track for the manufacturer.

And if people do act on your data, are they not entitled to know that it is accurate enough to justify those actions?

No, they are not entitled, especially when the manufacturer has effectively warned users, “The data may not be completely accurate. Don't rely on it for anything of significant importance or impact to your health.” The beauty of that kind of lowballing statement is that it becomes irrelevant whether a device model is better than that and could reasonably be relied upon. The user unilaterally decides what to do with or do in response to the presented data, and the user has sole responsibility of justifying those choices to themselves.

Well, in a sense, I don't have a dog in this pile, because I only use my VA3 for heart rate and GPS (well, and telling the time), which it seems to do reasonably well. Whether it can detect my depth of sleep accurately is not of any great concern to me. From discussions on other threads, I get the impression that people who read this forum have a reasonably shrewd idea what a Garmin watch can be expected to do, and what it can't.

And yet... I retain some sort of naive conviction that the folks at Garmin think they are actually making something useful. Sure, the Company has to shift stock, but it's hard to motivate your staff if they know they are producing something of no value. Somebody had to sit down and write the code that distinguishes between "deep" and "light" sleep, and presumably that person felt that it was worth getting out of bed in the morning to do it. He, or she, presumably felt that people would make use of that information, and would feel that it was reasonable to do so.

Or do I just have an under-developed cynicism gland?

And yet... I retain some sort of naive conviction that the folks at Garmin think they are actually making something useful.

I have the impression that people at garmin do it because their competitors do it. To the same effect, by the way.

Somebody had to sit down and write the code that distinguishes between "deep" and "light" sleep, and presumably that person felt that it was worth getting out of bed in the morning to do it. He, or she, presumably felt that people would make use of that information, and would feel that it was reasonable to do so.

As a retired programmer and software team manager I can assure you that this is a really far-fetched assumption.

Fair enough. My mental health depends on being able to believe that we are not, despite appearances to the contrary, living in a Dilbert cartoon. Your signature has a long list of Garmin devices that I presume you own and/or use. Presumably you think they are good for something other than Garmin's stock price?

Or do I just have an under-developed cynicism gland?

After reading your post in several different threads I'd have to say yes to this question. A great deal of your post question the validity of the VA3 or Garmin's capabilities. I'm not trying to get under your skin here, but why did you purchase the VA3 in the first place? Or, at the very least, why haven't you returned it? You've stated in a few threads that your only use is for HR, GPS and for telling time. You also stated that you consider the VA3 an expensive device. Surely, you could have found a different device that fit your needs at a cheaper price.

...but why did you purchase the VA3 in the first place? Or, at the very least, why haven't you returned it? You've stated in a few threads that your only use is for HR, GPS and for telling time. You also stated that you consider the VA3 an expensive device. Surely, you could have found a different device that fit your needs at a cheaper price.

Fair question. My requirements are: HR, GPS, waterproof, looks like a watch. It would be nice to have a credible Calorie count, but I'm not sure that's possible outside the laboratory. I couldn't find anything cheaper from a manufacturer I have any experience of dealing with, although perhaps I didn't look hard enough. I've had plenty of other Garmin devices, and mostly they've done what they (appear to) claim to do.

It's peculiar, really -- if the VA3 had done nothing except HR and GPS and tell the time, and all the other stuff was completely absent, I would probably be quite happy with my purchase. However, seeing the other features on offer -- none of which influenced my purchasing decision, if I'm honest -- I find myself wondering whether they might actually be useful to me. So I asked various questions in this forum, about how these features work, and whether people actually used them. The impression I get is that none of them can really be trusted, in the sense that there is no way to assess the accuracy of the data presented against some established standard.

I find that disappointing although, frankly, I find it hard to articulate why.