Sleep apnoea not just a problem for obese people

A new study has found that just over half of people with obstructive sleep apnoea (OSA) aren’t obese, even though obesity is a strong risk factor for sleep apnoeaThe research from Neuroscience Research Australia (NeuRA) and the Prince of Wales Hospital (POWH) also confirms that the cause of sleep apnoea, for those that fall into the normal and overweight BMI category, is different and thus requires a different treatment, which presents a challenge for clinicians.

Obstructive sleep apnoea, a common condition that affects more than one million Australians, occurs when the throat closes off many times throughout the night – up to 100 times per hour of sleep – which limits breathing.

Obesity can cause an anatomical obstruction of the upper airway and is a well-established risk factor for sleep apnoea. However, more than half the population referred to the POWH Sleep Clinic for suspected OSA was not obese.

This is the first study to highlight that respiratory arousal, a key contributor to OSA that is not related to anatomy, differs in non-obese versus obese patients. The latter population responds well to continuous positive airway pressure (CPAP) treatment, but this is not the case with normal-to-overweight patients.

The study found that the majority of non-obese patients suffer from a low respiratory arousal threshold, which means they have a greater tendency to wake easily. This may be a factor that limits their tolerance for CPAP therapy.

“Non-obese OSA patients are a challenging group to treat with existing therapies as they are less adherent and compliant with CPAP therapy compared to obese patients with sleep apnoea,” says study author Assoc Prof Danny Eckert.

Accordingly, clinicians need to keep BMI in mind when prescribing therapies for patients. “Specifically, they may need therapies that target causes other than upper airway anatomy such as sleep promotion aids to allow for deeper more stable sleep and breathing,” says Assoc Prof Eckert. “Or they could use these approaches in combination with the CPAP for greater therapeutic advantage. This also means that doctors and clinicians need to look for other symptoms associated with OSA when patients present with sleeping issues beyond obesity and anatomical issues”.

Assoc Prof Eckert reiterated that CPAP remains the first-line treatment recommendation, regardless of BMI, but that more research was required to better understand the treatment needs for non-obese patients.

This study will be published in the Journal of Clinical Sleep Medicine.