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    Causes of Obstructive Sleep Apnea

    Obstructive Sleep Apnea and Overweight

    More than half of people with obstructive sleep apnea are either overweight or obese, which is defined as a body mass index (BMI) of 25-29.9 or 30.0 or above, respectively. In adults, excess weight is the strongest risk factor associated with obstructive sleep apnea.

    Each unit increase in BMI is associated with a 14% increased risk of developing sleep apnea, and a 10% weight gain increases the odds of developing moderate or severe obstructive sleep apnea by six times. Compared to normal-weight adults, those who are obese have a sevenfold increased risk of developing obstructive sleep apnea. But the impact of BMI on obstructive sleep apnea becomes less significant after age 60.

    BMI isn't the sole marker of obesity that's important. Men with a neck circumference above 17 inches (43 centimeters) and women with a neck circumference above 15 inches (38 centimeters) also have a significantly increased risk of developing obstructive sleep apnea.

    In addition, extreme obesity (defined as a BMI above 40) is associated with obesity-hypoventilation syndrome (Pickwickian syndrome), which can occur alone or in combination with obstructive sleep apnea. In this syndrome, which affects up to 25% of the extremely obese, excess body fat not only interferes with chest movement but also compresses the lungs to cause shallow, inefficient breathing throughout the day and night.

    Although modest weight loss improves obstructive sleep apnea, it can be difficult for fatigued and sleepy patients to lose weight. In extremely obese patients, bariatric surgery is associated with an 85% success rate in improving the symptoms of obstructive sleep apnea.

    Demographics and Obstructive Sleep Apnea

    In middle-aged adults, the prevalence of obstructive sleep apnea is estimated to be 4%-9%, although the condition is often undiagnosed and untreated. Among people over age 65, it's estimated that at least 10% have the condition. Aging affects the brain's ability to keep upper airway throat muscles stiff during sleep, increasing the likelihood that the airway will narrow or collapse.

    Obstructive sleep apnea is up to four times as common in men as in women, but women are more likely to develop sleep apnea during pregnancy and after menopause. In older adults, the gender gap narrows after women reach menopause.

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