Catathrenia

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.