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Sleep and gender
There are only minor differences in sleep requirements between males and females. The duration of sleep appears to be slightly longer in females and their circadian rhythm period length may be a few minutes shorter. The changes in sleep structure seen in the elderly are delayed in women compared to men and the dreams of women have a different content to those of men.
Nature of Sleep and its Disorders
Sleeping in women is considerably modified by the following.
In the follicular pre-ovulation phase oestrogen secretion is increased and this inhibits REM sleep. In the luteal (post-ovulation) phase increased progesterone production promotes sleep, particularly NREM sleep.
There is no clear-cut difference in the quality of sleep at night or daytime sleepiness between these two phases, but both premenstrual insomnia and excessive daytime sleepiness may occur. Premenstrual parasomnias, particularly sleep talking and sleep walking, are also recognized.
Little is known about the effects of the oral contraceptive pill on sleep, but progesterone containing preparations can cause excessive sleepiness.
In pregnancy there is an increase in both oestrogens, which inhibit REM sleep, and progesterones, which promote NREM sleep. Other hormonal changes, such as an increase in cortisol secretion, also modify the sleep patterns. Increase in prolactin during pregnancy increases the duration of REM sleep. Oxytocin is increased at night and may lead to excessive sleepiness.
The duration of sleep is often increased during the first trimester, falls to normal in the second and is reduced in the third . The complaint of excessive daytime sleepiness is most common in the first trimester and is associated with an increase in the total sleep time at night, but with reduced sleep efficiency. During the third trimester the duration of stages 3 and 4 NREM sleep is particularly reduced and daytime naps are frequently taken. Insomnia is commonly due to backache, nocturia, abdominal distension, fetal movements and heartburn.
Several specific sleep disorders arise in pregnancy .
Upper airway obstruction
The increase in oestrogen secretion causes hyperaemia, mucosal oedema and hypersecretion in the upper airway, particularly in the third trimester, with an increase in upper airway resistance. Snoring is more common and obstructive sleep apnoeas may develop.
Weight gain during pregnancy may also contribute.
There is an association between an increase in upper airway resistance during sleep and pregnancy hypertension and pre-eclampsia. Each arousal from upper airway obstruction increases the blood pressure temporarily and increases catecholamine secretion. The fetal outcome in pre-eclampsia is worse if obstructive sleep apnoeas are present, and the blood pressure can be reduced slightly by the application of nasal continuous positive airway pressure (CPAP) treatment.
Rapid eye movement (REM) sleep
Rapid eye movement sleep, or REM, is one of the five stages of sleep that most people experience nightly....
Changes in respiratory drive
Increased progesterone secretion increases the ventilatory drive. It acts on chemoreceptors on the ventrolateral surface of the medulla to reduce the arterial Pco2. This leads to central sleep apnoeas. There is a reduction in functional residual capacity and residual volume and an increase in ventilation-perfusion mismatching and elevation of the diaphragm due to the increased intra-abdominal pressure. The metabolic rate is also increased. These changes may lead to respiratory failure in neuromuscular and skeletal disorders, particularly during sleep .
Restless legs and periodic limb movements in sleep
Between 15 and 20% of women develop the restless legs syndrome during pregnancy. This is mainly related to iron deficiency, but folic acid deficiency may also be relevant. The restless legs syndrome occurs particularly in the third trimester especially if there are twins or triplets. Discomfort in the legs, insomnia and excessive daytime sleepiness may all develop, but usually resolve within 10 days of delivery of the fetus.
Reduction in caffeine intake during pregnancy and iron supplementation are often effective.
This may first appear during pregnancy or be worsened by pregnancy.
Sleep walking and sleep talking
These are less common in pregnancy, probably because of a decreased tendency to arouse from stages 3 and 4 NREM sleep as a result of increased progesterone secretion.
In the 24h before labour there is an increase in oestrogen secretion and a reduction in progesterone.
Immediately after delivery there is a rapid reduction in secretion of both these hormones and a reduction in NREM and REM sleep. Maternal factors related to caring for the new-born child and the need for feeding also contribute. This is followed by a period of hypervigilance for the child at night and a reduction in total sleep time and sleep efficiency for at least 1 month after delivery. Postnatal depression may also cause insomnia.
During lactation oestrogen and progesterone levels fall, but prolactin is secreted, particularly during stages 3 and 4 NREM sleep. Mothers who breast-feed have more prolonged stages 3 and 4 NREM sleep and less stages 1 and 2 NREM sleep than those who bottle-feed. REM sleep duration is increased in breastfeeding due to surges in prolactin secretion.
At the menopause the reduction of oestrogen and progesterone produced by the failing ovaries leads to increased gonadotrophin secretion. Insomnia is common and may be related to nocturnal hot flushes (flashes). The flushes begin with a sudden sensation of heat, particularly in the upper part of the body, associated with sweating. They usually last only a few minutes and vary considerably in intensity. They are most frequent after 6.00 pm, probably because of a circadian influence, and are due to abnormalities in temperature control in the preoptic hypothalamus, probably as a result of either oestrogen withdrawal or fluctuations in noradrenergic or 5HT activity within the brain. They can be relieved by oestrogen replacement treatment.
The blood pressure may rise and the risk of developing obstructive sleep apnoeas is increased fivefold after the menopause. This is partly due to a change in the distribution of body fat so that more is laid down in the upper part of the body, as in males. Hormone replacement treatment is slightly protective against obstructive sleep apnoeas after the menopause, but the risk of these occurring is still twice that of a premenopausal woman.
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