Upper Airway Dilator Muscle Activity During Sleep Onset.

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Disorders of breathing during sleep are recognised as a major health problem. Of these, Obstructive Sleep Apnoea is the most prevalent, occurring in approximately 4% of the male and 2% of the female population. In this disorder the upper airway collapses during sleep causing cessation of airflow and subsequent oxygen desaturation. The airway is thought to occlude because dilator muscles are unable to sustain patency in the face of the negative pressures generated by inspiratory effort. In order for patency of the airway to be re-established some form of arousal from sleep must occur . As the UA is likely to collapse on the resumption of sleep, the cycle becomes repetitive, causing significant sleep disruption. OSA is a significant health risk, being associated with increased risk of cardiovascular disorders, increased mortality, excessive daytime sleepiness, reduced daytime performance and increased risk of accidents. In previous work we have demonstrated that normal sleep related changes in the activity of upper airway dilator muscles result in a reduction in the calibre of the airway at sleep onset. This exposes some individuals, such as those with narrow airways, to airway obstruction during sleep. We have also reported that elderly men have larger reductions in upper airway muscle activity at sleep onset than younger men, suggesting one reason why they may have a higher prevalence for Obstructive Sleep Apnea. The aim of the present project is to determine what causes the larger reductions in upper airway muscle activity in older males. The answer to this question will contribute to understanding why this group is so susceptible to Obstructive Sleep Apnea and will elucidate the mechanisms leading to the disorder.