Several factors can push sleep apnea from mild to severe, or make an already serious case harder to control. The most impactful are weight gain, sleeping on your back, alcohol use, and nasal congestion, but the full list runs deeper than most people realize. Understanding which ones apply to you is the fastest route to fewer breathing disruptions at night.
Sleep apnea severity is measured by the apnea-hypopnea index (AHI), which counts how many times per hour your breathing partially or fully stops during sleep. Mild is 5 to 14 events per hour, moderate is 15 to 30, and severe is above 30. Many of the factors below can shift you from one category to the next.
Weight Gain Has the Largest Effect
Excess body weight is the single most influential modifiable factor. Fat deposits around the neck and throat narrow the airway, and abdominal fat pushes up on the diaphragm, reducing lung volume. A landmark study of nearly 700 adults found that a 10% increase in body weight predicted roughly a 32% increase in AHI. The reverse was also true: a 10% weight loss predicted a 26% reduction in AHI.
Neck circumference is a useful proxy for this risk. A neck larger than 17 inches in men or 16 inches in women is a recognized risk factor for obstructive sleep apnea. Even modest weight gain that adds tissue around the throat can tip the balance toward more frequent breathing events, especially if your airway is already on the narrow side.
Sleeping on Your Back
Gravity works against you when you sleep face-up. In the supine position, the tongue and soft palate fall backward, narrowing or blocking the airway. Studies using position-specific monitoring show dramatic differences: the average AHI while sleeping on the back was about 60 events per hour, compared to roughly 24 on the right side and 30 on the left. That means back sleeping can more than double the number of breathing disruptions compared to side sleeping.
For people with position-dependent sleep apnea, simply staying off the back can be enough to bring the AHI into a manageable range. Positional therapy devices, or even a tennis ball sewn into the back of a sleep shirt, are low-cost interventions that can make a real difference.
Alcohol and Sedative Medications
Alcohol relaxes the muscles that keep your airway open, particularly the tongue. It does this by suppressing the nerve signals that normally maintain muscle tone during sleep. In both animal and human studies, alcohol has been shown to decrease activity in the genioglossus, the main muscle responsible for keeping the tongue from collapsing backward. Alcohol may also directly weaken the force-generating capacity of the tongue muscle by disrupting calcium signaling inside muscle cells.
The timing matters. Drinking within a few hours of bedtime has the strongest effect because blood alcohol levels peak while you’re in the early stages of sleep, when airway muscle tone is already naturally reduced.
Certain prescription medications produce similar effects. Opioid painkillers and benzodiazepines (a class of anti-anxiety and sleep medications) are both associated with the onset or worsening of sleep apnea. Muscle relaxants also carry this risk. Interestingly, newer non-benzodiazepine sleep aids (sometimes called Z-drugs) have not shown the same association in large pharmacovigilance analyses. If you use any of these medication classes and have sleep apnea, it’s worth discussing alternatives with your prescriber.
Nasal Congestion and Obstruction
When your nose is blocked, you switch to mouth breathing, which destabilizes the upper airway and makes collapse more likely. The cause of the blockage matters less than the blockage itself: allergies, sinus infections, a deviated septum, or swollen turbinates can all do it.
Allergic rhinitis is a particularly common culprit. One large study of about 5,000 adults found that people who reported nasal congestion from allergies on five or more nights per month were nearly twice as likely to have moderate-to-severe sleep-disordered breathing. Inflammatory conditions like allergic and non-allergic rhinitis cause mucosal swelling that increases nasal resistance, and nearly all patients with these conditions (over 95%) showed signs of nocturnal nasal obstruction. Treating the underlying nasal problem, whether with allergy management or surgical correction of structural issues, has been shown to reduce the number of apnea events.
Smoking
Tobacco smoke inflames and swells the tissues lining the upper airway, which narrows the space available for airflow. But the damage goes beyond inflammation. Nicotine also impairs the protective reflexes that normally keep the airway open. In animal studies, smoke exposure led to more apnea events and greater respiratory inhibition when the airway was stimulated. Nicotine applied directly to brainstem regions involved in breathing caused constriction of the upper airway.
Biopsy studies of the uvula (the tissue that hangs at the back of the throat) found that smokers with sleep apnea had increased markers of neuroinflammation compared to nonsmokers with the same severity of apnea. This suggests smoking adds a layer of nerve and tissue damage on top of whatever structural vulnerability already exists.
Aging and Muscle Decline
Sleep apnea tends to worsen with age, and this isn’t just because people gain weight over time. The pharynx itself becomes more collapsible. Several age-related changes contribute. The fat pads alongside the airway grow larger, the airway lengthens (particularly in women), and the muscles that hold the airway open lose their responsiveness.
In men specifically, the drop in airway muscle activity that occurs at the transition from wakefulness to sleep becomes more pronounced with age. There’s also a measurable decline in the genioglossus negative pressure reflex, the reflex that causes the tongue muscle to stiffen when airway pressure drops. When this reflex weakens, the airway is slower to defend itself against collapse.
Hormonal Changes After Menopause
Premenopausal women have significantly lower rates of sleep apnea than men of the same age, but that gap narrows sharply after menopause. The decline in estrogen and progesterone plays a direct role. Estrogen receptors are involved in the development and maintenance of upper airway muscles, and estrogen also influences where the body stores fat. Lower estrogen levels shift fat distribution toward the neck and abdomen, both of which increase airway vulnerability.
Progesterone acts as a respiratory stimulant, helping to maintain breathing drive during sleep. When progesterone levels fall after menopause, that protective effect is lost. Animal studies have shown that estrogen, and even plant-based estrogen compounds, can protect airway muscles from the kind of damage caused by the repeated oxygen drops that characterize sleep apnea. This helps explain why hormone replacement therapy has been associated with reduced sleep apnea symptoms in some postmenopausal women, though the decision to use hormone therapy involves weighing other health considerations.
Factors That Compound Each Other
These risk factors rarely exist in isolation. A person who gains 15 pounds, drinks wine before bed, and sleeps on their back is stacking three independent mechanisms that each increase airway collapsibility. Allergies that flare seasonally can turn a well-controlled case into a rough few months. Aging compounds nearly everything on this list by reducing the body’s ability to compensate.
The practical upside is that addressing even one or two of these factors can produce meaningful improvement. Weight loss and positional changes tend to deliver the most noticeable results, but eliminating alcohol before bed or managing chronic nasal congestion can bring your AHI down enough to change how you feel during the day.