In general, women sleep better than men (Bixler et al 2009). They have more deep sleep, a slower age-related decline in delta activity (the marker of deep sleep), and twice as many sleep spindles (Gaillard and Blois 1981; Dijk et al 1989; Ehlers and Kupfer 1997). And yet, only 40% of women sleep well almost every night, and 46% of women complain of trouble sleeping almost every night (National Sleep Foundation 2007). Women go through phases in their life cycle that increase the risk of sleep disturbance. The menstrual cycle, pregnancy, and menopause are the principal modifying factors.
Menstruation. Menstrual-related hypersomnia is characterized by recurrent episodes of sleepiness in association with the menstrual cycle (American Academy of Sleep Medicine 2005). The condition generally occurs within the first months following menarche. Episodes of hypersomnia last 1 week and resolve with the occurrence of menses. Oral contraceptives eliminate sleepiness, suggesting a hormonal imbalance underlying this form of hypersomnia.
Pregnancy. Thirty percent of pregnant women rarely or never get a good night’s sleep whereas 84% experience a sleep problem a few nights per week compared to 67% of women overall. Forty percent report symptoms of sleep disorders, including snoring, sleep apnea, or restless legs syndrome (National Sleep Foundation 2007). More information about sleep disorders during pregnancy is covered in the “Pregnancy” section below.
Postpartum. Eighty-four percent of women experience insomnia a few nights per week following delivery. Forty-two percent rarely or never get a good night’s sleep whereas 19% experience postpartum blues or depression (Gay et al 2004). After parturition, sleep apnea improves significantly, both in REM (64 ± 11 to 22 ± 4 events per hour) and nonREM sleep (65 ± 18 to 18 ± 4 events per hour) (Edwards et al 2005).
Menopause. Postmenopausal sleep complaints increase to reach 35% to 60% of all women. In the absence of hormone replacement therapy, the risk of developing sleep apnea increases (Bixler et al 2001); in fact, in postmenopausal women, sleep apnea severity tends to equal that in men. Menopausal hot flashes display a circadian variation, with peak frequency in late evening, and are related to a change of unknown etiology in the central thermoregulatory response. Eighty percent of peri- and postmenopausal women with severe hot flashes have chronic insomnia (Ohayon 2006).
Sleep apnea. Outside pregnancy, sleep apnea syndrome of moderate to severe intensity (Apnea Hypopnea Index [AHI], more than 15 respiratory events/hour of sleep) is found in 2% of middle-aged women as opposed to 4% of middle-aged men (Young et al 1993). For mild cases (AHI, more than 5 events per hour), the ratio changes to 15% of men and 10% of women. Gender differences in sleep apnea are related to anatomical differences, with more upper body fat distribution in men and increased ventilation and upper airway muscle activity caused by the hormonal action of progesterone in women (Kapsimalis and Kryger 2002). In general, the risk of sleep apnea increases after menopause, presumably when the influence of progesterone declines and the anatomical differences with men become less marked; the risk in women tends to approach that in men until the age of 65 years, which is the age when the prevalence of sleep apnea peaks in women. Central sleep apnea occurs in women with congestive heart failure (odds ratio 3.5 for women) but with much lower frequency than in men (Sin et al 1999; Javaheri 2006). Women with sleep apnea complain of headaches in the morning more frequently than men, perhaps related to allodynia (lowering of pain threshold) in women with migraines (Young 2009), a condition that is well known to affect women more often than men at all ages. On the other hand, men with sleep apnea have a higher risk of suffering motor vehicle accidents, a feared complication of sleep apnea syndrome (Young et al 1997).
Restless legs syndrome. Restless legs syndrome is a frequently undiagnosed sensorimotor disorder that impairs sleep and reduces the quality of life. It is characterized by an urge to move the legs, usually with uncomfortable leg sensations, a worsening of symptoms at rest or inactivity, an aggravation of symptoms in the evening and at night, and relief with movement, walking, or stretching. Restless legs syndrome affects 5% to 10% of the general population, increases with age, and is more prevalent in women (Berger et al 2004; Allen et al 2005). Blood pressure and heart rate rise with periodic limb movements, increasing the risk of hypertension and cardiovascular disease (Pennestri et al 2007). Restless legs syndrome is more common in older women than in older men and appears with relative frequency during pregnancy. Restless legs syndrome affects one third of pregnant women during their third trimester and usually improves after delivery (Neau et al 2010). The transient pregnancy restless legs syndrome form is a significant risk factor for the development of a future chronic idiopathic restless legs syndrome form, and for a new transient symptomatology in a future pregnancy. In 1 study the authors found that mothers of children with ADHD had an increased risk of having restless legs syndrome (Gao et al 2011).
Insomnia. Insomnia is defined as the repeated difficulty initiating and maintaining sleep. The difficulty sets in despite adequate opportunity to sleep and results in daytime impairment (American Academy of Sleep Medicine 2005). Insomnia in women shows some variations mostly related to biological life cycles. The menstrual phase worsens sleep quality in 31% of menstruating women (Manber and Bootzin 1997). Pregnant women frequently describe difficulty sleeping.
Insomnia complaints increase in menopause, an epoch in the life cycle that is associated with sleep complaints in 35% to 60% of women (Zhang and Wing 2006). Commonly associated disorders are pain syndromes, fibromyalgia, depression, restless legs syndrome, and nocturnal sleep-related eating disorder. Insomnia in menopause should be considered a multifactorial alteration in which aging plays an important role.
Sleep-related eating disorder. Sleep-related eating disorder refers to recurrent episodes of involuntary eating and drinking during partial arousals from sleep with adverse consequences. Episodes occur without control by the individual. The episodes are generally not recalled, but a small number of patients have some awareness and retain fragmented memory of the episodes. The diagnostic criteria set forth by the International Classification of Sleep Disorders (ICSD-2) include consumption of peculiar foods in bizarre combinations and at times with inedible substances, like frozen pizza, buttered cigarettes, raw bacon, cat food, coffee grounds, and cleaning solutions (American Academy of Sleep Medicine 2005). In addition, there is sleep disruption with complaints of nonrestorative sleep, daytime fatigue, and somnolence. Sleep-related injuries may occur, and examples are burns, lacerations, poisoning, and injuries from inappropriate use of kitchen utensils or internal lesions from eating inedible substances. Patients may gain weight (mean weight gain 12.6 kg) (Schenck et al 1993) and become depressed. Sweets, pasta, peanut butter, milk, and dairy products are preferred items. Depending on the series reported, 60% to 83% of patients with sleep-related eating disorder are women (Winkelman 1998). Sleep-related eating disorder is more common between the ages of 22 and 40 years. Episodes may occur nightly, sometimes several times per night.