Characteristics unique to females with obstructive sleep apnoea (OSA) or OSA/hypopnoea syndrome (OSAHS) in their clinical presentation, pathophysiology, comorbidities and treatment response compared to males with OSA/OSAHS

Pathophysiology of OSA/OSAHSUpper airway less collapsible
Shorter airway length, which increases with age
Lower critical closing pressure
Subcutaneous and peripheral fat distribution
Prolonged partial upper airway obstruction leading to increased respiratory resistance, increased end-tidal CO2
Lower chemoresponsiveness
Lower metabolic rate
Less respiratory drive instability
Progesterone stimulates ventilation
Higher CO2 sensitivity and lower upper airway resistance during the luteal phase of menstrual cycle (high progesterone levels)
Premenopausal females have lower apnoeic thresholds
 In pregnancyReduction in airway size, fluid retention, weight gain, nasal obstruction
Reduced functional respiratory capacity and residual volume
Increased minute ventilation
High progesterone leading to increased upper airway dilator muscle activity
Enhanced chemoreceptor responsiveness
Right-shifted oxygen dissociation curve
Increased maternal heart rate and stroke volume
Less time in the supine position
Clinical presentation
 OverallMore likely to present with insomnia, mood disturbances, nightmares, fatigue, lack of energy
Greater impairment of quality of life
Higher healthcare expenditure
Higher rate of sick leave, impaired work performance, divorce
Hypothyroidism more common
Less intense snoring
 PregnancyIncreased snoring as pregnancy progresses
Snoring/OSA associated with pregnancy-induced hypertension, intra-uterine growth retardation, hypertension and diabetes mellitus
 MenopauseClinical presentation attributed to menopause
Doubling of OSA/OSAHS prevalence in menopause
Findings on sleep studies (polysomnography/polygraphy)Lower AHI overall
Shorter apnoeic episodes
More frequent subcriterion events
Lower proportion of supine OSA
Higher frequency of REM-related OSA
Longest apnoeas associated with more severe arterial oxygen desaturation
Increased sleep fragmentation in pregnancy
ComorbiditiesMore systemic inflammation for given AHI
More peripheral and subcutaneous fat distribution premenopausally
Pharyngeal collapsibility in females awaiting bariatric surgery correlates with degree of insulin resistance
Responses to treatmentCPAP trial should be symptom-driven (AHI lower for given clinical symptoms)
Lower CPAP pressures more common
MRS use may be higher in mild OSA/OSAHS
Greater voluntary weight loss sustained, but smaller relative drop in AHI

CO2: carbon dioxide; AHI: apnoea–hypopnoea index; REM: rapid eye movement; MRS: mandibular repositioning splints.