OSA stands for obstructive sleep apnoea, or obstructive sleep apnea, depending on which part of the world you come from.
OSA is one of a constellation of disorders referred to generally as 'sleep disordered breathing'.
As the names suggest, OSA and sleep disordered breathing relate to conditions where the sufferer's airway is compromised during sleep. Milder (but still serious) forms of sleep disordered breathing, such as snoring, allow the sufferer to breathe while asleep. That said, the noise of snoring is a loud signal that the airway is constricted and consequently the airflow is not natural and effortless.
Think of it this way: If you saw someone who was wide awake, but they were breathing like a snorer, you'd be worried about them and concerned for their health. Yet when we see a person snoring and thus exhibiting the same laboured breathing while asleep, we tend to think of it as normal. The truth is, snoring and other forms of sleep disordered breathing are very common, but they are certainly not normal or healthy.
OSA is a more severe form of sleep disordered breathing. In patients suffering from OSA, the tissue of the soft palate (i.e., the soft part of the roof of the mouth), the uvula (the droopy flap of tissue at the back of the soft palate), the tongue and the pharyngeal walls (i.e., the airway above the windpipe or trachea, where there is no rigid structure to hold the airway open) tend to collapse into the upper airway, preventing inhalation.
Patients with OSA are frequently unaware of the existence of their condition, because they are asleep while it is happening. Often the first notice they get of the condition is when their sleeping partner nudges them awake to get them breathing again. Diagnostic sleep studies (polysomnograms) are used to monitor and record exactly what happens while the patient is asleep and to determine the degree of severity of any OSA.
OSA does not typically self-resolve, meanining some form of treatment or intervention will be required. Treatment of mild OSA is commonly done via oral appliance therapy, which involves the custom fitting of dental devices which typically hold the lower jaw and connected tissue clear of the airway. In more severe cases of OSA, the best treatment is continous positive airway pressurisation (CPAP). CPAP works by feeding gently pressurised air into the patient's airway, to create an 'air splint' which holds the walls of the upper airway apart.
Common consequences and co-morbidities associated with OSA include hypertension, gastro oesophageal reflux disease (GERD, or acid reflux), ischemic heart disease, depression, obesity, type 2 diabetes, loss of libido and impotence ... plus much more.
OSA should be treated, not tolerated. The numerous negative consequences can be avoided or more successfully treated once the OSA has been resolved.