What does a nationally renowned sleep specialist think about at home sleep trackers? Well, that fact that he’s using one himself is a pretty good indication! Dr. Alejandro D. Chediak is Medical Director of the Miami Sleep Disorders Center and former president of the American Academy of Sleep Medicine, the non-profit group that represents sleep medicine in the United States. During a conversation with Wellocracy, Dr. Chediak points out that an at-home sleep tracker has its shortcomings: It can’t provide as comprehensive a study as a professionally-administered laboratory sleep study, called a polysomnography, or an at-home professional sleep tracker called actigraphy. It can, however, provide good insight on both sleep habits and lifestyle. Below, Dr. Chediak answers some questions on sleep and sleep trackers aimed at the consumer market.

Wellocracy: Which tracker are you using and how did you happen to pick it?

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Dr. Alejandro D. Chediak

Dr. Chediak: I use the Pulse. It’s made by Withings (I have no stock in the company!). I wear it during the day because it also measures daytime activity. I selected the Pulse because I own the Withings scale, and the Withings blood pressure monitor. All three of these devices are integrated into one piece of software, and send my data to a central server in the sky. I love the fact that I can access all of that data in one place on my cell phone.

W: What do you think is the value of wearing a sleep tracker like the Pulse?

Dr. Chediak: One important point first: The Pulse is also a daytime activity tracker, and like other activity trackers that also track sleep, you have to let the device know, “I’m going to bed now” and “I’ve woken up now.” If you’re consistent in doing this, you can get a pretty good idea of your sleep pattern. The most powerful information that medical grade actigraphy gives sleep physicians is the sleep pattern, do you go to bed late and wake up late? Are you going to bed early and waking up early? Or do you just have lots of sleep fragmentation in between. If one consistently tells the sleep tracker when they are going to bed and getting up, sleep patterns can be reproduced with these consumer devices. The pattern of sleep is very important because lack of structure in bedtime and rise time is a common problem in insomnia. In some types of insomnia, inconsistency of bedtime and rise time is either the primary cause or a perpetuating factor.

W: If someone who has difficulty falling asleep notices a pattern of irregular bedtimes and wake-up times, would adopting a more regular sleep/wake schedule help?

Dr. Chediak: Yes, in particular, he should get up at the same time every day. That seems to be the one thing that is consistently beneficial, regardless of whether you slept well the night before. The time you get up and the time you expose your eyes to the natural sunlight is a very important setter of how the day is going to progress. We have a circadian rhythm whose length is predictable. If you start the circadian rhythm at the same time every morning; the tiredness of sleep is going to come around at the same time, more or less, every night. And what sets the circadian rhythm is exposure to sunlight in the morning.

Part II: Making Sense of Your Sleep Data

W: People who start tracking their sleep are often shocked by their data. Specifically, most say, ‘I had no idea how much I woke up at night.’ What’s normal, and when do you have to start to worry?

Dr. Chediak: Normally, people wake up six to 12 times every night, and they just don’t remember most of them. We remember waking up once or twice, maybe three times, but we wake up a lot more; we change our body position and we go right back to sleep. In the morning, one has amnesia of many of these awakenings, it never happened — that’s a normal sleep pattern. What’s not normal is when someone has prolonged awakenings that they remember. That’s when they may need to get help.

W: Some at-home trackers break down sleep data into stages like light sleep or deep sleep; how should users interpret this data?

Dr. Chediak: In sleep medicine, deep sleep has a very specific meaning that is based on measurement of brainwaves recorded by polysomnography. At present, this kind of information from a home sleep tracker is meaningless because it has not been validated against the gold standard of measurement of sleep, polysomnography. Rather than looking at the home sleep tracker data in terms of deep sleep or light sleep, those who use these devices should think of the data in terms of movement or activity. Light sleep reported by home sleep trackers represents parts of the night with some movement/activity and that could be an indication that you’re not sleeping well. On the other hand, portions of the night with very little activity/movement will be labeled as deep sleep, and you might be sleeping better with fewer arousals and fewer movements.

W: Is there an optimal amount of time to sleep?

Dr. Chediak: Turns out it’s about eight to 8.5 hours of sleep per night. But, the question may be better asked the other way around. Rather than how many hours sleep do you need, the question should be how many hours of sustained wakefulness can you endure before performance lapses occur. That’s really how we determine sleep need, we test how many hours of sustained wakefulness one can tolerate before you start having performance lapses. Most of the studies will curtail the opportunity to sleep, starting off with maybe eight to nine hours of opportunity to sleep and then do performance testing. They will then reduce the opportunity to sleep to six hours for two weeks, and repeat performance testing sequentially during those weeks, and so on. You’ll see that once you go from eight hours to six hours; you already start seeing performance lapses. Once you go from six hours to four hours, we see even more performance lapses, and of course at zero hours you see terrible performance lapses. And the performance lapses get progressively worse in those subjects as time goes by.

Part III: Sleep, Performance and Health

W: What do you say to people who say, I can do great on practically no sleep?

Dr. Chediak: Sleep deprived people are poor judges of how well they perform; that’s why we don’t always trust what patients tell us, especially those in high risk occupations like pilots or truck drivers. In studies on sleep loss, when we significantly reduce sleep opportunity, if you ask a subject how well he/she thinks that they are performing, on day one they’ll say maybe not as good as usual, on day two, they’ll say maybe not as good as day one, but by days four, five, six and seven they’ll say they’re not at their best, but are no worse than they were day four. And that’s not true. The performance lapses measured are getting worse. So you develop a kind of “brain numbness” if you will, to your ability to perceive that your performance is deteriorating.

W: In recent years, there have been numerous stories in the media on studies linking lack of sleep to an increased risk for obesity and Type 2 diabetes.

Dr. Chediak: When you link two conditions that seem to parallel each other in some sort of systemic way, there is often an intermediary third condition that’s really the one that causes the other two. If a study finds that people who sleep between seven to eight hours per night tend to be thinner than people who are sleeping four to six hours, there may be another reason why they’re thinner, and it may not be because of sleep. It may be because people who are sleeping eight hours have a lifestyle that is healthier overall; they exercise more, they eat healthier, etc. If they’re sleeping six hours, perhaps it’s because they’re working two shifts and they don’t have the time to exercise and they eat whatever is available in the cafeteria and it may not be the healthiest food. It’s hard to say that there is a direct relationship between weight and sleep.

There is scientific evidence that in normal humans when sleep is deprived, metabolism changes, in a way that promotes weight gain. And again, this occurs when people sleep six or fewer hours a night. So short sleep may facilitate obesity, but then again, in a given individual, you have to consider the cause of short sleep before concluding that insufficient sleep is a cause of weight gain.

W: When do you know it’s time to stop trying to fix the problem yourself, and see a sleep specialist?

Dr. Chediak: Consumer home sleep trackers are simply tools that, when used properly, display sleep patterns. But sleep patterns are not the entire picture when it comes to the evaluation of sleep. Daytime problems like sleepiness and fatigue or feeling that sleep is difficult to achieve, sustain or non-restorative are good reasons to seek advice from a board certified sleep disorders medicine expert.

W: What do you see as the future of at-home sleep tracking devices?

Dr. Chediak: Consumer home sleep trackers, if used appropriately, can display sleep patterns. However, home sleep trackers cannot yet interpret the data they collect in a way that allows the user to make meaningful changes in sleep patterns. Manufacturers should look at professional actigraphy and display the data from their sleep trackers to resemble actigraphy data reports.

Since changes in sleep occur in response to stress and disease, consumer sleep trackers may be of value to monitor general health status. These devices are already useful to the individual and with enhancements in technology, the ability to track sleep and other bodily functions at night will certainly improve. I look forward to the day when a consumer home sleep-tracking device can capably supply actionable data to help us all sleep better and improve general health.