How can a weight-loss drug fight sleep apnea?

Teachable moment in classrooms:

1. respiratory system chapter – anatomy of the upper airways
2. muscular system chapter – anatomy of the muscles of the tongue and pharynx
3. nervous system chapter – location of satiety center in the hypothalamus

The news item:  Recently the following report appeared online:

FDA approves weight loss drug Zepbound for sleep apnea

Zepbound, Eli Lilly’s weight loss drug, can now be used to treat obstructive sleep apnea in adults with obesity, the FDA said.

The report states that 39 million adults with obesity in the USA might benefit from this drug treatment. Studies showed that Zepbound significantly reduced the obstruction events in patients. The article also provides a brief description of apnea events, and alternative treatment methods of sleep apnea.

So, Why Do I Care??  Sleep apnea, or more precisely, obstructive sleep apnea, is a sleep disorder that affects millions of adults in the US who suffer from obesity.  Those people are not just losing sleep, but are at higher risk for several cardiovascular diseases, and for daytime sleepiness.  While there are limitations (such as side effects) to the wide use of this drug treatment, it adds to the list of possible treatment options physicians can subscribe.

Plain English, Please!!!   First, let’s talk about sleep apnea.  Apnea is a brief closure of the airways where the closure stops air from getting into the lungs.  The lower portion of our airways have solid cartilage framework (trachea, bronchi), so narrowing rarely occurs; it is always open, like a steel pipe.  However, in the upper airways (mouth, soft palate) we have muscles that surround those airways, and the inappropriate relaxation of the muscles can lead to closure of the upper airway; imagine putting on a sock: it’s easy when we open it up with our fingers, but it’s harder to put our toes through it when the sock is collapsed on the floor. The loss of oxygen flow awakens the person, and repeated instances of apnea leads to poor quality sleep.

Second, let’s talk about throat muscles.  Skeletal muscles in the throat (anatomically called pharynx) and in the soft palate (by specific names: the tensor palatini, levator palatini muscles), and in the tongue (namely the genioglossus muscle) are the airway dilator muscles. During sleep, when most skeletal muscles are relaxed, these muscles are restarted through a reflex, so our airways remain open. When these muscles are made to contract the sock is pulled wide open.

Third, let’s talk about the link between obesity and sleep apnea. Obesity (BMI larger than 30) often leads to fat accumulation in the neck area, and the physical mass of the fat prevents the contraction of the airway dilating muscles. Not surprisingly, weight loss can lessen the severity of sleep apnea. Zepbound causes weight loss, and the improvement of sleep apnea comes about by reducing the amount of fat in the neck area, and allowing the airway dilator muscles to do their job.  The more weight the patients lose the lower their obesity level will be, and, therefore, the lower the frequency of obstructive sleep apnea will be. Zepbound acts on the hypothalamus in the brain and reduces the appetite of the patient, who will experience weight loss as the result.