The impact of pharyngeal fat tissue on the pathogenesis of obstructive sleep apnea
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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.
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.
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).
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.
KeywordsObstructive sleep apnea Obesity Pharyngeal fat Computed tomography Weight loss
We express our special thanks to Taina Poutiainen, a specially trained nurse, and Riitta Myllykangas, a dental hygienist, for their contributions to this study. In addition, warm thanks go to Veli-Matti Vartiainen, oral radiologist, and Anna Sutela, neuroradiologist, of the Department of Clinical Radiology, Kuopio University Hospital and University of Eastern Finland, for the demonstrative MRI figure. The members of Kuopio Sleep Apnea Group Matti Pukkila, Tatu Kemppainen, Tomi Laitinen, Tiina Lyyra-Laitinen, Ritva Vanninen, Heimo Viinamäki, Keijo Peuhkurinen, Kari Punnonen, Kati Venäläinen, Erkki Soini and Janne Martikainen are also cordially acknowledged. This study was supported by grants from the Hospital District of Northern Savo, Kuopio University Hospital, the Finnish Cultural Foundation and the Pulmonary Association Heli.
Conflict of interest
We declare that we have no conflicts of interest.
Role of funding sources
The funding sources had no role in the study design or in the collection, analysis or interpretation of the data.
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