Catathrenia: The Long Groan That Is Not Snoring
A drawn-out moan on the out-breath, night after night, that the person making it never hears. It is not snoring, it is not a nightmare, and it is not dangerous — but its classification as a breathing disorder is genuinely contested.
If your partner draws a breath in and then releases it as a long, tuneless groan — the same sound, repeated, sometimes for minutes at a time — that is probably catathrenia, and it is not snoring.
The distinction is mechanical and it is the fastest way to tell them apart. Snoring happens on the in-breath. Catathrenia happens on the out-breath. Once you know that, you can identify it from the next room.
What it sounds like
A deep inhalation, a pause, then a prolonged vocalised exhalation — a moan, a groan, sometimes closer to a hum or a drone. Episodes cluster, often lasting from a few seconds to well over a minute, and recur in runs through the night.
It is frequently described by partners as eerie rather than merely annoying, which is why people arrive searching for it at two in the morning. It is also almost always news to the person doing it, who sleeps through it entirely — the same filtering that stops snorers hearing themselves. Can you hear yourself snore.
Is it dangerous?
On the available evidence, no. The groaning itself does not obstruct breathing, does not drop oxygen in the way an apnea does, and is not associated with the cardiovascular consequences that drive treatment of obstructive sleep apnea.
What it does reliably do is disturb the person next to you, which is a real problem of its own rather than a trivial one. What partner sleep deprivation actually does.
What the evidence actually says
Here is the honest state of it, and the uncertainty is unusual.
A 2024 systematic review in Sleep and Breathing searched three databases under PRISMA, screened 288 records and included 31 articles, assessing risk of bias with the Joanna Briggs Institute and ROBINS-I tools. Most included studies carried a moderate risk of bias, which sets the ceiling on everything below.
Its findings:
- The International Classification of Sleep Disorders places catathrenia among the respiratory disorders, and the review opens by noting there are genuine doubts about that — about whether episodes belong to REM or non-REM sleep, their duration, and their symptoms
- Episodes split almost evenly: 49.57% in non-REM sleep, 46% in REM
- There is a sex pattern. In 60.34% of females it was more common in non-REM; in 59.26% of males, in REM (p < 0.05)
- Females and people with obesity had shorter episodes (p < 0.05)
- Age was inversely correlated with minimum episode duration (r = −0.34)
- CPAP use was inversely correlated with maximum episode duration (r = −0.48)
- It occurs with similar frequency in both sexes
- The commonest reported symptoms were groaning, awareness of disturbing a bed partner, and daytime sleepiness — and that last one was not confirmed by the Epworth Sleepiness Scale
That final point deserves emphasis. People with catathrenia report feeling sleepy; the standard objective-ish instrument for sleepiness does not back it up. Either the Epworth is the wrong tool here, or the sleepiness is attributable to something else — and the review cannot tell you which.
Evidence tier 2. The phenomenon is well described and benign-looking. Its mechanism, its sleep-stage home, and even its correct diagnostic category are unsettled, and the underlying studies are of moderate quality.
Can it coexist with sleep apnea?
Yes, and this is the reason the article does not end with "ignore it."
A 2023 case report in Sleep Medicine describes catathrenia occurring in severe obstructive sleep apnea, framed by its authors as an entity not previously described. And the systematic review's finding that CPAP use correlates with shorter maximal episodes implies that some proportion of people with catathrenia are on CPAP in the first place — which means they had apnea.
So groaning does not rule apnea out. If the same person also snores on the in-breath, pauses, gasps, or wakes unrefreshed, the groaning is the less important of the two findings. Snoring versus sleep apnea.
What to do about it
Record it. This is the single most useful thing, because the description is what distinguishes catathrenia from snoring, from sleep talking, and from the sounds that accompany apnea. A phone recording of a few episodes does more in a consultation than any description. Capture whether the sound is on the in-breath or the out-breath, and listen for silences followed by gasps. Recording your partner's snoring.
Do not buy anti-snoring products for it. Nasal strips open the nasal valve, mouth tape seals the lips, positional devices move you off your back — none of these act on a vocalised exhalation, because none of them is the mechanism. Spending money here is spending it on the wrong sound.
Protect the partner's sleep in the meantime, which is the actual harm. Earplugs, white noise or, pragmatically, separate rooms on bad nights. Best earplugs for sleeping next to a snorer · Doing separate rooms well.
Get a sleep study if there is any apnea signal. Witnessed pauses, gasping, morning headaches, or unrefreshing sleep all override the groaning as the thing to investigate. A study also settles the coexistence question directly.
And set expectations about treatment. There is no established, well-evidenced treatment for catathrenia on its own. CPAP has the suggestive correlation above and is not prescribed for groaning alone. Anyone offering you a confident cure for this is ahead of the literature.