The decrease in estrogen levels disrupts the body's thermoregulatory system, resulting in periodic reduction of core temperature. The body responds with peripheral vasodilation. Hot flashes can be triggered by caffeine, alcohol, stress, and hot weather. Some women wake up at night so drenched that they must change their sheets and nightclothes, sometimes more than once. This can lead to a serious disruption of sleep patterns.
Insomnia can result in irritability, fatigue, and problems with concentration.
Sleep can be disrupted by hot flashes and night sweats, or insomnia may be present without those symptoms. Some women report insomnia as their only perimenopausal symptom. Sleep disturbances may occur due to complex interactions between hormones and the neurotransmitter serotonin. Estrogen boosts serotonin in the brain and may delay its reabsorption. Declining estrogen means decreased levels of serotonin, which may lead to wakefulness and restless sleep.