Why is an AHI below 5.0 considered normal?

jwong wrote:I have 2.3 events per hour. 8 hour sleep that is 16 for the total night. Is that bad, normal, below average?

Your doctor would say that it is very good, and it might be.

The number isn't bad, but you need to determine if you feel good. Have your symptoms stopped? Some people really don't feel better until it is under 2. Also, it is possible to have really long events or clusters that would only be seen by looking at the graphs. And some people have UARS which can still cause major sleep problems but not get flagged as events.

If you are feeling good, and the problems are solved, then great. Don't worry about it or stress over it. If you think your sleep quality could use a bit more improving, then keep at it. You can probably get it a bit lower, and you may feel better.

jwong wrote:I have 2.3 events per hour. 8 hour sleep that is 16 for the total night. Is that bad, normal, below average?

That's less than half what is considered 'treated' so yes that is good, especially if you're getting 8 hours good sleep. Is 2.3 an average AHI? Most of us won't get the same AHI every night, how are you feeling during the day? That's the biggest clue as to how things are going for you.

What is the breakdown of events and how are you sleeping and feeling during the day?

If the events are primarily obstructives or hypopneas then some tweaking of pressure can usually help to reduce these events.

If the events are central or clear airway then not so much.

How one feels and sleep quality are also major factors. I have to admit that for me I can't tell the difference between AHI of 0.4 and 2.4, for example. I have never had it go much higher than that except during times of sickness so then of course things are not usual.

I've also wondered if looking at the AHI number first thing in the morning and seeing a good number sets us up to anticipate a great day ahead, so could it be psychological when people say that they can feel the difference between an AHI of 1 and 2? Just a possibility.

Arlene1963 wrote:I've also wondered if looking at the AHI number first thing in the morning and seeing a good number sets us up to anticipate a great day ahead, so could it be psychological when people say that they can feel the difference between an AHI of 1 and 2? Just a possibility.

I think it can create a self fulfilling prophecy in some people but not necessarily all people. For this reason when I was a newbie to therapy and really into checking the data daily I elected to wait until bedtime to check the prior nights numbers. I had some really crappy days where the AHI was darn near perfect and I had some amazing days where it was fairly high and in fact one of my best days early in therapy followed a night with AHI of 10.2
Go figure that one.

So maybe with some people especially early on in therapy but with cpap veterans I don't know so much. They have long ago learned their own bodies and how the data ends up correlating with how they feel.

For myself I can't really predict how my AHI was last night by how I feel today...I have too many other things messing with sleep that affect how I feel to put all the eggs in the AHI basket. Now maybe if I didn't have those other things muddying up things I would get a better indicator by AHI.
Besides, I can't do much about last night anyway and I won't go making any changes to therapy based on one crappy AHI night anyway.

I think the reason I can't tell the difference is because most of my AHI is sleep wake junk. I so rarely get obstructives or hypopneas and when I do they are not long, so maybe that is another reason I just can't tell the difference between somewhat higher and lower AHI.

I really cannot tell what my AHI is by how I feel. I feel the same whether it is near zero, or over five which it has been a few time since starting treatment. The only thing I can say is I feel much better since starting treatment. I took a few months for me to get to the point where I realized I was feeling better. Prior to treatment, my oxygen was dropping to the dangerous level when I slept. When I was in the hospital for a knee replacement, the nurses noticed my oxygen level was going too low while I slept. The day I came home from the hospital, an oxygen concentrator was delivered to my house. I used supplemental oxygen while sleeping until I could have a sleep study performed and start treatment. During one of my sleep studies, my oxygen level dropped to 63% before the placed me on oxygen and completed my study. Once I was placed on a bi-level machine, my oxygen level returned to normal while sleeping.

Another problem with AHI is that if your AHI is, say, 5, that doesn't necessarily mean that they are nicely spread out over the course of the night. My own specialty is to have an AHI of 5 sometimes but all those events are packed into (for example) one half-hour period of time. When I have nights like that I don't necessarily feel more tired, but my brain struggles, for instance I'll have more trouble with memory.

AMK wrote:Another problem with AHI is that if your AHI is, say, 5, that doesn't necessarily mean that they are nicely spread out over the course of the night. My own specialty is to have an AHI of 5 sometimes but all those events are packed into (for example) one half-hour period of time. When I have nights like that I don't necessarily feel more tired, but my brain struggles, for instance I'll have more trouble with memory.

This is a good point, Moreover, remember they only count Apnea event's "over 10 seconds" so if you are getting a lot under 10 seconds, that's still not great, but doesn't even count on the sleep study. In addition, I was diagnosed with severe apnea at 52 AHI, whoever I had a cold while tested, so I suspect It's not normally that high. I haven't gotten any colds since getting the machine (unusual for me) but I did get allergies last week and my treated CPAP AHI went up to 3.5 (which is high for me treated). So if It's making you feel better, I'd just go with it, and even if you decide not to use it (which I'm not suggesting) keep the machine around for when your allergies flair up or you get a cold. and Yes, you can get your AHI below 1. Mine averages about .3.

Actually, I think the below 10 second events may be part of what confounds AHI predicting how well you will feel. For instance if you start getting an apnea or even just snoring, and your machine responds by raising pressure you may Never have a "clinical" apnea. But you could be having apnea's that disturb your sleep. In fact, people may sometimes feel better when getting more Apnea's because they actually went into a deeper sleep state (and thus more relaxed causing the apneas), but the sleep state they got into was much needed and ended up making them feel better.

It's true; sometimes I look at my Sleepyhead graph and marvel at the number of events that don't count because the event was "too short," while I can clearly see that I stopped breathing and then lurched back into breathing. Apnea length is definitely another concern.

I searched for an hour on the internet and the forum and have not found any info on sleep studies of normal healthy persons. What is truly normal? My guess is that everyone, to varying degrees, stops breathing at some point in their sleep. Maybe that's why they set the bar at 5 AHI, because everybody has apnea to some extent. Anyone have any insight into this or can point to some studies?

Rob K wrote:I searched for an hour on the internet and the forum and have not found any info on sleep studies of normal healthy persons. What is truly normal? My guess is that everyone, to varying degrees, stops breathing at some point in their sleep.

I'm interested in this information as well. This morning I went onto Google Scholar and found a study that was published in 2015 that deals with the prevalence of sleep disordered breathing in the normal population, not based on folks sent to a sleep lab and suspected of having OSA, in other words, just the general population.

"Between Sept 1, 2009, and June 30, 2013, we did a population-based study (HypnoLaus) in Lausanne, Switzerland. We invited a cohort of 3043 consecutive participants of the CoLaus/PsyCoLaus study to take part. Polysomnography data from 2121 people were included in the final analysis. 1024 (48%) participants were men, with a median age of 57 years (IQR 49–68, range 40–85) and mean body-mass index (BMI) of 25·6 kg/m2

The median apnoea-hypopnoea index was 6·9 events per h (IQR 2·7–14·1) in women and 14·9 per h (7·2–27·1) in men. The prevalence of moderate-to-severe sleep-disordered breathing (≥15 events per h) was 23·4% (95% CI 20·9–26·0) in women and 49·7% (46·6–52·8) in men."

Note, they scored data for this study using the 2012 AASM guidelines for diagnosis.

In their conclusion they state:

"Using the most recent definitions for respiratory events, and diagnostic techniques commonly used in all modern sleep laboratories, we noted that almost every individual had some degree of sleep-disordered breathing. Moreover, an increasing number of apnoea and hypopnoea events per h was associated with augmented comorbidity. This finding reinforces the idea that sleep-disordered breathing should be considered as a disease with a continuous spectrum, rather than as a definite yes or no diagnosis. Individuals at high risk of incident sleep-disordered breathing-related complications should be identified so treatment efforts can be focused on them."

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4404207/

Perfect, I'll see if I can find that study. Interesting that everybody has sleep disorder events to varying degrees. Good to know.

Just realized you posted the link. Thank you.

Interesting that everybody has sleep disorder events to varying degrees.

Everyone can have an occasional apnea event of some sort and it not a problem when they are random and rare.
The problem comes from having a truckload of them or of a quantity as such that our sleep quality gets trashed and/or the potential desats.

xxyzx wrote:

AMK wrote:It's true; sometimes I look at my Sleepyhead graph and marvel at the number of events that don't count because the event was "too short," while I can clearly see that I stopped breathing and then lurched back into breathing. Apnea length is definitely another concern.

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where do you see on sleepy head that you are not breathing

mine shows me with airflow in/out and it still declares hypops at random

DEAD People! Jim