Catathrenia or nocturnal groaning was first reported by Belgium scientists, De Roek and colleagues in 1983. But despite being recently introduced into the International Classification of Sleep Disorders as a parasomnia, it is still a relatively rare condition with actual incidence and prevalence still unknown. The name Catathrenia is derived from the Greek word kata = below, and threnia = to lament.
Catathrenia is described as sleep related groaning, moaning or just 'making funny noises'. It is characterised by repeated episodes of monotonous moaning or groaning sounds in prolonged expiration, preceded by deep inspiration. These episodes last between 2 - 50 seconds and end with a sigh or arousal. There has been no known health consequences reported which is why it is considered to be a social rather than a medical problem. However, this condition often presents with a morose or sexual connotation that can cause a social problem for some patients.
The etiology of Catathrenia is still unclear. Several mechanisms have been proposed, from upper airways obstruction during expiration to impairment of the respiratory centre.
Respiratory dysfunction can lead to prolonged exhalation and an increase in intrathoracic pressure due to lack of expiratory muscle activity. This gives rise to the typical pattern of deep inhalation followed by prolonged exhalation. However, it does not explain the groaning/moaning sounds. It is thought that the sounds may occur due to partial glottic (part of the larynx associated with voice production) closure. This has led some authors to believe catathrenia is a sleep related breathing disorder (SDB) rather than a parasomnia.
The episodes of groaning tend to occur in clusters mainly during the sleep stage of Rapid Eye Movement (REM), although sporadic occurrence in Non-REM sleep has been noted (mainly Stage II). An increase in groaning episodes is often noted during the latter part of the night. This may be explained by the normal sleep cycle of increasing REM sleep towards the end of the night.
The presence of arousal depends on the duration of the groaning. Long duration of groaning is more likely to end in arousal than those of short duration. A number of studies estimate that nearly three quarters of groaning episodes are associated with arousal. Groaning episodes occur with slightly decreased heart rate and blood pressure and changes in respiratory rhythm. Even when episodes last for 50 seconds there is no oxygen desaturation and there is no snoring. The nocturnal groaning is quite distinct from expiratory snoring. This close connection between groaning and arousals raises the question of whether the respiratory change leads to the arousal or whether the arousal itself sets off the groaning.
Due to frequent arousals during the night it might be thought that patients would suffer Excessive Daytime Sleepiness (EDS), unrefreshing sleep and fatigue, but it seems that not all of them do. In some studies 50-80% of patients demonstrated abnormal Epworth Sleepiness Scores (ESS) whilst patients in other studies had completely normal ESS scores.
Onset of Catathrenia is usually during adolescence or early adulthood and affected individuals are often unaware of their condition until noted by a bed partner or family member.
Interestingly, one small study of women found that 43% of them had a history of another parasomnia during childhood such as sleepwalking, sleep terrors and childhood enurisis (bed wetting). All the women in this study were found to have craniofacial abnormalities such as a narrow upper airway, large tongue and small jaw. Video recordings noted that the mouth was always partially open during the expiratory phase and nasal cannula recordings demonstrated substantial nasal flow limitation. The groaning noise was remarkably loud and appeared to be strained. The authors of the study speculated that the groaning was an adaptive behaviour to enhance normal breathing. Once again, this raises the question as to whether this is a respiratory disorder rather than a parasomnia.
As both these conditions are relatively rare catathrenia can easily be mis-scored or mistakenly recognised as CSA. Tracings from PSG (Polysomnography – overnight sleep study), can appear as central sleep apnoeas due to the long cessation of air flow and breathing effort seen in both conditions. However, in contrast to CSA, where the apnoeic pause is preceded by an exhalation, in cathathrenia the breath before the apnoea is a large inhalation. Additionally, activity in the snoring channel during these apnoeic events will indicate sound production and therefore establish that catathrenia is present as opposed to CSA.
Catathrenia seems to be three times more frequent in men than women with the average onset at around 19 years. Although a family history of catathrenia and other sleep disorders has been documented the evidence to date is inconsistent. However, most researchers have found familial sleep disorders such as bruxism, sleep walking, sleep talking and night terrors to be prevalent in more than half of their subjects.
Distress from the social impact of catathrenia rather than health consequences is usually the primary motivation for seeking treatment. This is especially the case where the loud groaning has a conspicuous sexual connotation which is observed by other family members.
Many anti-depressants and the new 'Z' drugs (commonly used for insomnia) have been tried but in most patients have been unsuccessful. Similarly, upper airway surgical procedures have been used without success.
Continuous Positive Airways Pressure (CPAP) is successful in resolving the nocturnal groaning in most cases despite there being no evidence that Obstructive Sleep Apnoea (OSA) is present. The presence of both conditions occurring together would probably be coincidence rather than a causal relationship.
Despite improvements in their condition, patients in one study found that CPAP was the cause of a new sleep disturbance. The nightly disturbance and inconvenience of the treatment led them to seek alternatives.
In the case of patients with craniofacial abnormalities a Mandibular Advancement Device (MAD) was shown to be effective.