UARS is a condition described in the 1990s by Dr Christian Guilleminault. He was studying young, fit men and women who were chronically tired. Sleep tests were providing limited insight into apnoeas and airway obstructions so initially, he had no explanation for the patients’ symptoms.
However, with more detailed analysis he noticed a pattern. All subjects of the study were experiencing multiple arousals during the deeper stages of their sleep.
With further investigations, Dr Guilleminault noticed that the narrowing of the airway was resulting in an increased resistance to airflow. This required stronger inspiratory efforts (in order to survive) that ended in an arousal.
Multiple micro-arousals during the deep delta-wave sleep results in a heightened stress response all day long which is one of the three drivers behind all the negative effects of sleep apnoea syndrome. These recurrent microarousals are called Respiratory Effort-related Arousals (RERAs).
Commonly known “Young, fit female syndrome”, UARS is much more difficult to diagnose than sleep apnoea because the patient does not necessarily have the characteristic 10-second long “apnoeas” that are the hallmark of an obstructive sleep apnoea diagnosis.
More often than not, the traditional indices or parameters used to measured sleep quality, such as Apnoea/Hypopnoea Index (AHI) and Oxygen Desaturation Index (ODI) are not as bad in UARS patients compared to sleep apnoea patients. This is because in patients with UARS the pressure receptors in the throat quickly pick up an oncoming obstruction and send the signal to the brain to effect an arousal. The muscles in the upper airway tighten up and prevent the collapse so minimal apnoeas and hypopnoeas which affects the AHI, RDI and ODI.
The ‘hypervigilance’, whether is be conscious or subconscious, means an increased baseline level of sympathetic activity. This increase sympathetic drive while one sleeps can lead to impaired bowel functions as well as increased anxiety and panic attacks.
UARS patients also tend to have:
- cold hands
- low blood pressure
- orthostatic intolerance
Dr Steven Park has written a great blog post about this silent epidemic.