The impact of pharyngeal fat tissue on the pathogenesis of obstructive sleep apnea

• Published in: Sleep & breathing Vol. 18; no. 2; pp. 275 - 282
• Main Authors: Pahkala, R., Seppä, J., Ikonen, A., Smirnov, G., Tuomilehto, H.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-05-2014; Springer; Springer Nature B.V
• Subjects: Adipose Tissue - pathology; Adult; Biological and medical sciences; Body fat; Cross-Sectional Studies; Dentistry; Disorders of higher nervous function. Focal brain diseases. Central vestibular syndrome and deafness. Brain stem syndromes; Female; Follow-Up Studies; Fundamental and applied biological sciences. Psychology; Humans; Hyoid Bone - pathology; Hypopharynx - pathology; Internal Medicine; Life Style; Male; Medical sciences; Medicine; Medicine & Public Health; Metabolic diseases; Middle Aged; Multidetector Computed Tomography; Nasopharynx - pathology; Nervous system (semeiology, syndromes); Neurology; Obesity; Original Article; Oropharynx - pathology; Otorhinolaryngology; Overweight - pathology; Pediatrics; Pharynx - pathology; Pneumology; Pneumology/Respiratory System; Polysomnography; Respiratory system : syndromes and miscellaneous diseases; Sleep apnea; Sleep Apnea, Obstructive - pathology; Sleep. Vigilance; Snoring - pathology; Throat; Tomography; Vertebrates: nervous system and sense organs; Weight Loss - physiology; Obesity; Computed tomography; Pharyngeal fat; Obstructive sleep apnea; Weight loss; Nervous system diseases; Sleep apnea syndrome; Radiodiagnosis; Respiratory disease; Pathogenesis; Nutrition disorder; Sleep disorder; Sleep; Medical imagery; Computerized axial tomography; Sleep wake cycle; Neurological disorder; Nutritional status
• ISSN: 1520-9512; 1522-1709
• DOI: 10.1007/s11325-013-0878-4

Purpose
Obesity is the most important risk factor for obstructive sleep apnea (OSA); however, the exact underlying mechanisms are still not fully understood. The aim of this study was to examine the morphology of upper airways in overweight habitual snorers and in mild OSA patients. Furthermore, the associations between weight loss, parapharyngeal fat pad area and OSA were assessed in a 1-year randomised, controlled follow-up study originally conducted to determine the effects of lifestyle changes with weight reduction as a treatment of OSA.
Methods
Thirty-six overweight adult patients with mild OSA [apnea–hypopnea index (AHI) 5–15 events/h] and 24 weight-matched habitual snorers (AHI < 5 events/h) were included in the study. All patients underwent nocturnal cardiorespiratory recordings and multislice computed tomography (CT) of parapharyngeal fat pad area, the smallest diameter and area in naso-, oro- and hypopharynx, the smallest diameter and area of the whole pharyngeal airway, the distance from the hyoid bone to the mandibular plane and to cervical tangent as well as the distance between mandibular symphysis and cervical spine. In addition, OSA patients were further randomised to receive either an active 1-year lifestyle intervention with an early weight loss programme or routine lifestyle counselling. After 1 year, the cardiorespiratory recordings and CT scans were repeated.
Results
The pharyngeal fat pad area was significantly larger, and the distance from the hyoid bone to cervical spine was longer in patients with OSA than in habitual snorers (
p
 = 0.002 and
p
 = 0.018, respectively). The multiple regression analysis showed that besides a large pharyngeal fat pad area and a long distance from the cervical spine to hyoid bone, also a short distance from the mandibular symphysis to cervical tangent increased a risk to OSA. During the 1-year follow-up in OSA patients, the pharyngeal fat pad area and AHI decreased significantly in the intervention group (
p
 = 0.003 and
p
 < 0.001, respectively).
Conclusions
In the early stages of OSA, the pharyngeal fat pad seems to play an important role in the development of disease in overweight patients. Furthermore, weight reduction by lifestyle intervention-based programme reduces both central obesity and pharyngeal fat pads, resulting in an improvement of OSA.