Sex and Multiple Factors Influencing Respiratory Event Duration in Sleep Apnea

The most common factors affecting the duration of abnormal respiratory events in adult obstructive sleep apnea (OSA) include sex, age, weight, sleep stage, and sleeping position, according to study findings published in Sleep Medicine Reviews.

The duration of respiratory events causes variation in physiologic responses including blood pressure, duration of arousals, severity of desaturations, and heart rate. This means estimating the risk for OSA-related comorbidities should take into account the duration of respiratory events. Understanding the mechanisms and causes for different OSA expressions is significant. Investigators aimed to portray the effect of the most typical factors that affect the duration of abnormal respiratory events in adult OSA.

Investigators noted the more reactive upper airway in women vs men contributes to women having shorter respiratory events. Women have lower apnea-hypopnea index (AHI) and more frequent insomnia vs men. Women face a greater proportion of their respiratory events in rapid eye movement (REM) sleep, and REM-related OSA is common in women (62%) vs men (24%).

Increased circulatory delay associated with aging is the most likely cause of longer respiratory events among older adults (women and men) vs younger adults. The increase in body weight associated with increasing age seems a prominent factor increasing the prevalence of OSA among older adults.

Weight loss is associated with OSA improvement, and women with OSA are more obese than men with OSA. The median duration of apneas, hypopneas, and desaturations in all OSA severity levels is decreased by an increase in body mass index. Increased adipose tissue in the upper airways leads to longer respiratory events.

Apnea events tend to be longer in REM sleep vs nonrapid eye movement sleep. There are conflicting results in some studies speculating longer apnea events are related to age and obesity instead of sleep stage. Investigators noted duration of respiratory events in REM sleep may be modulated by the magnitude of sleep deprivation, number of arousals, sleeping position, and body weight.

Supine position vs lateral position leads to longer apneas and hypopneas. When sleep position is changed from supine to lateral, collapsibility is decreased possibly leading to upper airway collapse. They noted specifically the head/neck position vs general sleeping position may more strongly modulate upper airway function in patients with OSA.

Investigators believe these factors interact in a complex way with each other to affect duration of sleep-related respiratory events. They suspect multiple variables not included in this review (alcohol consumption, sleep deprivation, various medications, degree of sleep fragmentation, comorbidities, and ethnic and genetic aspects) are also significant in determining respiratory event duration.

They suspect physiologic aspects of pharyngeal collapsibility, arousal threshold, and circulatory delay may have a significant effect on respiratory event duration.

They concluded, “It is clear that the AHI alone is insufficient to explain the multifactorial nature of OSA, determine the severity of OSA, or estimate the risk for OSA-related health consequences.” They wrote “At least the characteristics of apnea and hypopnea events (duration and type) and the number, duration, and depth of desaturation events should be considered while diagnosing and estimating the severity of OSA.” They added consideration of the known factors — sex, age, body weight, sleep stage, and sleeping position — affecting the duration of respiratory events is significant in the patient/clinician relationship.