Sleep apnea develops when something repeatedly blocks or disrupts your breathing during sleep. It’s not a condition you catch like an infection. It results from a combination of physical traits, lifestyle habits, and sometimes underlying medical conditions that make your airway more likely to collapse or your brain less reliable at signaling you to breathe. Understanding what causes it can help you recognize your own risk and, in some cases, reduce it.
Roughly 15 to 30 percent of middle-aged men and 10 to 15 percent of middle-aged women have obstructive sleep apnea, the most common form. Many don’t know it. The condition is diagnosed based on the number of times your breathing pauses per hour of sleep, measured by a score called the Apnea-Hypopnea Index (AHI). An AHI of 5 to 14 is mild, 15 to 30 is moderate, and above 30 is severe.
Excess Weight and Neck Size
Carrying extra weight is the single biggest modifiable risk factor for obstructive sleep apnea. Fat deposits around the neck, tongue, and throat narrow the airway, and the added tissue mass makes it easier for the airway walls to collapse when muscles relax during sleep. A neck circumference greater than 17 inches in men or 16 inches in women is a well-established warning sign, typically reflecting excess fat in the neck area that crowds the breathing passage.
Weight doesn’t have to be extreme to matter. Even moderate weight gain can shift someone from occasional snoring into measurable apnea, and weight loss often reduces severity significantly. That said, plenty of people at a normal weight develop sleep apnea too, especially as they age or if they have certain facial or throat anatomy.
Anatomy That Narrows the Airway
Some people are simply built with a smaller or more collapsible airway. A naturally narrow throat, a recessed jaw, a thick tongue base, or a low-hanging soft palate all reduce the space air has to flow through. When the muscles in the back of the throat relax during sleep, that already-tight space can close off entirely.
In children, the most common structural cause is enlarged tonsils and adenoids. The tonsils sit at the back of the mouth and the adenoids at the back of the nose, and when they’re oversized, they physically block airflow during sleep. This is why tonsil removal often resolves sleep apnea in kids. Adults can have similar issues with bulky throat tissue, though the causes are more varied.
Age and Gender
Sleep apnea becomes dramatically more common with age. A large study tracking over 38,000 people found that among those with normal body weight, only about 11 percent of men under 50 had sleep apnea, compared to nearly 38 percent of men 50 and older. For women, the jump was even steeper: from under 3 percent before age 50 to about 16 percent after. The muscles that hold the airway open lose tone over time, and tissue naturally becomes floppier.
Men develop sleep apnea at roughly two to three times the rate women do, at least until menopause. After menopause, women’s rates climb substantially, suggesting that hormonal changes play a protective role earlier in life. Fat distribution also differs: men tend to accumulate more fat around the neck and upper airway than premenopausal women do.
Alcohol, Sedatives, and Sleeping Position
Alcohol relaxes the muscles that keep your airway open, making it more collapsible during sleep. It also dulls your brain’s arousal response, meaning you’re slower to wake up and resume breathing when an obstruction occurs. Sedative medications work through a similar mechanism. Even one or two drinks in the evening can measurably increase the number of breathing pauses in someone already prone to apnea.
Sleeping on your back makes things worse for most people. In the supine position, gravity pulls the tongue and soft tissue backward into the airway. Research consistently shows that the number of breathing disruptions roughly doubles when sleeping on your back compared to your side. In one systematic review, the average AHI in the supine position was 34.2, compared to 15.1 on the side. Some people have sleep apnea only when they sleep face-up and breathe normally on their side.
Genetics and Family History
Sleep apnea runs in families, and it’s not just because families share eating habits. About 40 percent of the variation in sleep apnea severity can be explained by genetic factors. First-degree relatives of someone with sleep apnea are significantly more likely to snore or have observed breathing pauses during sleep, even after accounting for differences in weight, age, and gender.
What gets inherited isn’t sleep apnea itself but the traits that lead to it: the shape of your face and jaw, how your body distributes fat, how your brain’s breathing control center responds to drops in oxygen, and how strongly your airway muscles activate during sleep. Researchers have identified specific gene variations linked to airway inflammation, oxygen levels during sleep, and the brain’s control of tongue muscles. These don’t guarantee you’ll develop sleep apnea, but they tilt the odds. If sleep apnea is common in your family, your threshold for developing it is likely lower.
Medical Conditions That Increase Risk
Several health conditions make sleep apnea more likely. Hypothyroidism (an underactive thyroid) can cause tissue swelling and weight gain that narrow the airway. Polycystic ovary syndrome, which involves hormonal imbalances and often weight gain, is also linked to higher rates. Acromegaly, a condition involving excess growth hormone, can enlarge the tongue and other soft tissues in the throat.
Neurological events like stroke or traumatic brain injury can depress muscle tone and blunt the brain’s ability to respond to airway obstruction, pushing someone toward sleep apnea even without the typical physical risk factors.
Central Sleep Apnea: A Different Mechanism
Not all sleep apnea comes from a blocked airway. Central sleep apnea happens when the brain intermittently stops sending the signal to breathe. The airway stays open, but the effort to inhale simply doesn’t happen for several seconds at a time.
Heart failure is the most common driver. Roughly 40 percent of people with congestive heart failure develop central sleep apnea. The mechanism involves fluid shifts and changes in blood carbon dioxide levels that confuse the brain’s breathing control system. When the heart isn’t pumping efficiently, fluid can back up into the lungs, and the brain overcompensates by cycling between breathing too much and not breathing at all. Opioid medications can also cause central sleep apnea by suppressing the brainstem’s respiratory drive.
How Sleep Apnea Gets Diagnosed
If you recognize several risk factors in yourself, the next step is a sleep study. The gold standard is polysomnography, an overnight test in a sleep lab that monitors brain waves, eye movements, muscle activity, heart rhythm, and breathing patterns all at once. For many people, though, a home sleep test is sufficient. You wear a simplified device to bed that tracks breathing effort, airflow, and blood oxygen levels. It’s less comprehensive but far more convenient, and it’s accurate enough to confirm or rule out obstructive sleep apnea in most straightforward cases.
The distinction matters because treatment depends on both the type and severity. Mild positional sleep apnea in a side sleeper who occasionally rolls onto their back is a very different situation from severe apnea driven by obesity and a narrow airway. Knowing which risk factors apply to you helps guide what comes next.