Contribution of male sex, age, and obesity to mechanical instability of the upper airway during sleep

1 Division of Pulmonary and Critical Care Medicine and 2 Department of Surgery, Johns Hopkins School of Medicine, Baltimore, Maryland; and 3 Western Australia Sleep Disorders Research Institute, Sir Charles Gairdner Hospital, and School of Anatomy and Human Biology, University of Western Australia, Perth, Western Australia, Australia Submitted 16 January 2008 ; accepted in final form 10 April 2008 Male sex, obesity, and age are risk factors for obstructive sleep apnea, although the mechanisms by which these factors increase sleep apnea susceptibility are not entirely understood. This study examined the interrelationships between sleep apnea risk factors, upper airway mechanics, and sleep apnea susceptibility. In 164 (86 men, 78 women) participants with and without sleep apnea, upper airway pressure-flow relationships were characterized to determine their mechanical properties [pharyngeal critical pressure under hypotonic conditions (passive Pcrit)] during non-rapid eye movement sleep. In multiple linear regression analyses, the effects of body mass index and age on passive Pcrit were determined in each sex. A subset of men and women matched by body mass index, age, and disease severity was used to determine the sex effect on passive Pcrit. The passive Pcrit was 1.9 cmH 2 O [95% confidence interval (CI): 0.1–3.6 cmH 2 O] lower in women than men after matching for body mass index, age, and disease severity. The relationship between passive Pcrit and sleep apnea status and severity was examined. Sleep apnea was largely absent in those individuals with a passive Pcrit less than –5 cmH 2 O and increased markedly in severity when passive Pcrit rose above –5 cmH 2 O. Passive Pcrit had a predictive power of 0.73 (95% CI: 0.65–0.82) in predicting sleep apnea status. Upper airway mechanics are differentially controlled by sex, obesity, and age, and partly mediate the relationship between these sleep apnea risk factors and obstructive sleep apnea. physiopathology; pharynx; obstructive sleep apnea Address for reprint requests and other correspondence: S. P. Patil, Johns Hopkins Sleep Disorders Center, Div. of Pulmonary and Critical Care Medicine, The Johns Hopkins Asthma and Allergy Center, 5501 Hopkins Bayview Circle, Baltimore, MD (e-mail: spatil{at}jhmi.edu )