The phenotype and genotype of adult obstructive sleep apnoea/hypopnoea syndrome.

Obstructive sleep apnoea/hypopnoea syndrome (OSAHS) is a common condition affecting approximately 2-4% of the middle-aged population. A hereditary component to the condition has long been recognised but its genetic basis has been difficult to elucidate. Progress in determining the genotype of OSAHS is hampered by the lack of a consistent definition of phenotype and the large environmental influences on its expression. "Intermediate phenotypes", such as craniofacial structure, obesity and upper airway control, have been utilised. Multiple gene polymorphisms have been explored in association with the latter, as well as with the sequelae of OSAHS, such as hypertension and increased insulin resistance. To date, two genome-wide scans have identified potential regions that may be of interest in further defining the intermediate phenotypes. The present paper focuses on human studies with an update of the most recent work in the area, including a short discussion on methods of genetic studies.

Intrathoracic pressure variations in obese habitual snorers.

Six obese patients with complaints of snoring and daytime fatigue were monitored with polysomnography (PSG) and continuous recording of esophageal pressure (Pes) during 1 night. Nonapneic episodes in different sleep stages, with and without snoring, were selected and analysed. Peak to peak pressure was found to be significantly increased during snoring in sleep stages 2 and 3/4 with blood gas variations within the limits of normal unobstructed breathing, indicating increased respiratory effort. The present investigation supports the assumption that daytime tiredness in nonapneic patients can be linked to increased respiratory effort during sleep and that continuous esophageal pressure measuring may contribute to assessment of this condition.