Respiratory Threat Matrix Model of Chronic Insomnia

In my book Sound Sleep, Sound Mind, I first described the ”Respiratory Threat Matrix Model of Chronic Insomnia,” where I theorized that the threat (subconsciously experienced) of suffering a breathing event is enough to prevent a person from falling asleep.

We know from past research that sleep breathing problems awaken an individual during the night, but thereafter, the sleeper still must find a way to fall asleep again. Thus, whether at bedtime or in the middle of the night, the respiratory threat matrix model implies that falling asleep would be difficult for anyone who on a subconscious level knows danger lies ahead in the form of apneas, choking, or flow limitation events of UARS; overall, we often use the term mini-suffocations to convey this idea to patients. And, as part of the model, the repetitive experiences of night time sleep breathing disruption adds fuel to the fire by teaching the patient, again subconsciously, that sleep is a risky venture.

On an intellectual level, when discussing the threat matrix model with patients as well as sleep specialists and mental health professionals interested in insomnia, I have encountered a strong, intuitive curiosity about this theory. Insomniacs often are perplexed about the etiology of their sleeplessness, which no doubt contributes to their interest in a newer theory. Still, this model alone may not push the patient toward treatment unless he or she is either fairly desperate to solve the problem or is clearly frustrated in trying to find better answers to explain it.

Among healthcare professionals, even for those interested in insomnia, the theory has not spread very far, arguably because it would be very difficult to prove the subconscious mind is triggering racing thoughts. Rather, it might be easier to prove PAP therapy decreases racing thoughts in patients with co-occurring insomnia and OSA/UARS while not necessarily explaining how PAP produced such results.

In sum, then, trying to put forward this theory to patients or professionals has not been a smooth process for many of the same reasons that new ideas often require years and much experimentation and experience before they are accepted. Now, 17 years later since first developing the theory, I still believe it is worthwhile to share some of the discussion points we use when explaining these ideas to patients, because I believe this information engages some insomniacs to consider moving forward with treatment. Moreover, as the theory spreads as more research proves its validity, i.e. racing thoughts abate with treatment of sleep-disordered breathing, it will open more minds to the idea of physiological as opposed to psychological interventions as an additional and key therapy for chronic insomnia.

With that backdrop, I will briefly review some of the discussions we have with patients in clinic.

First, for any insomniac, we will always ask when do you recall first suffering the problem and why do you think you developed insomnia, to which more than 80 to 90% of patients respond with a specific time of a stressful life event (e.g. car accident, crime victim, divorce, death of loved one, etc.). But surprisingly, many insomniacs do not necessarily see these events causing the insomnia. Rather, they are more likely to mention the close timing of the events and insomnia without connecting the Zzzots. Nonetheless, it only takes a brief discussion to point out that if one suffers from sleep problems soon after a death in the family and these sleep problems persist, then it would not be unreasonable to surmise the trauma is the primary or at least initial cause of the insomnia. Most people get this point even though they themselves have not been thinking along such lines previously.

Next, there is usually a discussion about psychological theories of insomnia involving models based on learned behaviors. As we discussed previously there are many psychological strategies for resolving insomnia. However, at this point in the conversation, I will also ask the patients to tell me a good working theory on why they wake up at night. At this point in the dialogue I can help patients to change their mindset to realize that all along there was a missing link in how to understand their insomnia. After the patient often gives no definitive explanation for why he or she awakens from sleep, I have the chance to fill the vacuum and start by asking how do you feel right after the awakening? Do you feel wired and wide awake or do you feel drowsy and ready to return to sleep? Most patients report both experiences, after which we begin to focus on the more alerting state.

By the way, to become fully alert shortly after arousing from sleep is a very abnormal process, notwithstanding some actual disturbance in the home that awakens you and which immediately affects your sense of security. Threats get our attention and rapidly so! But, when I ask patients who experience these very wide awake feelings following arousal from sleep, none of them report a threat or disturbance beforehand. They just report being wide awake for no good reason.

Then, I remind them of the normal experience of gradually awakening from sleep such that some drowsy feelings linger. This train of thought allows me to ask: if it is abnormal to abruptly feel wide awake, then something must have occurred just before the awakening to trigger these feelings. We go down the pathways of what could cause an abrupt change in one’s body to provoke this experience, which might lead some patients to say their heart seemed to be beating faster. I applaud them on their insight and then ask what could cause the heart to beat faster? Bottom line, in just a few minutes these insomniacs realize that a sensation of choking while awake clearly would cause anyone to become more alert and suffer a rapid heartbeat. At this point, the insomniac realizes and usually accepts that something else is happening in their bodies when this alerting experience surfaces into consciousness from the depths of slumber in the middle of the night.

In some cases, I must ask more details to get this point across. For example, I will ask if you have ever experienced any type of near drowning episode, or ever had someone stuff pillows over you when you were young, or ever got shut in a closet for a short time? All these experiences might lead someone to develop claustrophobia, a very natural reaction to restricted breathing. Regardless, if an insomniac can remember such episodes, then he or she can more easily remember the feelings associated with real or imagined insufficient air. Whereas most people do not report repeated episodes of choking in their lives, most do report at least one episode, and as you would imagine one episode of choking is all too memorable. 

Having reached this stage in the conversation, insomniacs are somewhat astonished these breathing disruptions could be occurring without their knowledge, but in the face of no other plausible explanation, most insomniacs find the information quite interesting, almost appealing in that it quickly permits them the opportunity to speculate that sleeplessness is not psychologically-driven; rather it is a physical problem. Since so many insomniacs suffer from mental health issues, it may prove to be quite a relief to learn this physical process is a major causal factor. Of course, patients with the highest levels of anxiety can react in the reverse fashion and start catastrophizing about the possibility of dying in their sleep from choking to death. These patients are rare and can usually hear and accept that the brain is wired to reinitiate breathing automatically and very quickly.

At this point, insomniacs feel a strong sense of comprehension about sleep maintenance insomnia, the problem of nighttime awakenings.   But, at the outset of the post, we also described patients who report difficulty falling asleep or sleep onset insomnia. How then does the respiratory threat matrix model apply to this problem? For the sleep maintenance problem, it is easy to see that if you are wide awake following the awakening, then that feeling alone makes it difficult to fall back asleep. But, what about the beginning of the night, at bedtime, when you might feel somewhat drowsy when you lie down, but then become more alert for no apparent reason.

In psychological terms, this form of arousal is called psychophysiological conditioning, that is, you are so used to suffering a problem at sleep onset that as soon as your head hits the pillow instead of falling asleep, your body and mind remember that you often cannot fall asleep. This memory then, often on a subconscious level, triggers alerting behavior including racing thoughts and ruminations. Thus, we state that beyond the initial cause of your insomnia, you have learned to suffer insomnia so it flares up as soon as you hop into bed.

The above is the standard explanation given to most sleep onset insomniacs. The “Respiratory Threat Matrix of Chronic Insomnia” offers a different explanation, albeit it still relates to the concept of learned behaviors. To explain this point to a patient, I use fairly graphic examples. I almost always start with this question: what is the most fearful thing you could experience that would make you feel you might die? Because we have already been talking about sleep breathing issues, most people respond quickly to say the feelings of suffocation.

Surprisingly or not, some people are unsure, so I ask them to imagine two situations. First, someone is pointing a gun at you and states you will be shot and killed. Second, someone has both hands around your throat and is choking you to the point you cannot breathe. Everyone understands the distinction between the first example, which we would call the threat of dying versus the second example, in which you would actually feel and believe you were about to die from the absence of air.

The last step in the discussion is fairly straightforward: if you knew on a subconscious level that every night you were going to experience repetitive episodes of mini-suffocations, would you be so inclined as to let yourself fall asleep or would you find some way to prevent sleep, which would then prevent the feelings of choking or gasping for air? The answer comes rapidly from most patients: find a way to stay awake. I then ask what is the most reliable way to stay awake when you hop into bed? Nearly everyone responds with some variation of activating one’s mind. I then conclude that the single most common experience reported by insomniacs about their inability to fall asleep is the vexing problem of racing thoughts and other ruminations at bedtime, either just before hopping into bed or just after lying down and trying to initiate sleep.

So, racing thoughts are actually your survival mechanism, so to speak, that protect you from experiencing gasping or choking or related mini-suffocation experiences from sleep-disordered breathing—experiences that you would most likely suffer soon after you entered sleep.

With this background, I explain to patients that racing thoughts often dissipate after starting treatment for OSA/UARS, and this change frequently occurs even in the most severe insomniacs. To be sure, some patients still suffer from the psychophysiological conditioning described above, so they may continue to be plagued by racing thoughts for that particular set of conditions. Still, it is a continuous source of amazement at our center to observe so many patients declaring their racing thoughts disappeared once they started PAP therapy.  

Barry Krakow MD


Dr Krakow’s 27 years of sleep research have focused on the complex relationship between physiological and psychological sleep disorders. Dr Krakow currently operates private sleep medical center, Maimonides Sleep Arts & Sciences, Ltd., and serves as Classic SleepCare’s paid Medical Director.

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