Can perimenopausal hormone fluctuations contribute to sleep disturbance and cognitive symptoms?

Perimenopause involves a transition from relatively predictable ovulatory cycles to variable estrogen exposure and increasingly inconsistent ovulation. This physiology can be relevant to sleep and cognitive complaints, but the strength of evidence differs between these outcomes.

Hormonal changes

• Daily longitudinal SWAN hormone data show substantial cycle-to-cycle and person-to-person variability in estrogen markers and progesterone metabolites.
• Ovulatory cycles declined from 80.9% at the first assessment to 64.7% at the third, while prolonged anovulatory cycles increased from 8.4% to 24%. Thus, progesterone exposure—particularly luteal-phase progesterone—becomes intermittent rather than uniformly absent.
• Estradiol and FSH may fluctuate markedly; a single hormone test often does not represent usual ovarian function or transition stage.

Sleep evidence

• Changes in estradiol/FSH and lower estradiol have been associated with more nighttime awakenings, including after accounting for depressive and vasomotor symptoms.
• Vasomotor symptoms are an important pathway: hot flashes and night sweats are strongly associated with sleep complaints and can directly interrupt sleep.
• Treatment data provide indirect support: across 15 randomized trials, menopausal hormone therapy produced small subjective sleep improvements but no significant overall polysomnographic benefit. Estradiol plus intermittent micronized progesterone reduced reported sleep-onset latency and awakenings in one trial, without establishing a progesterone-specific effect.
• Sleep symptoms should also prompt assessment for chronic insomnia, sleep apnea, restless legs, mood symptoms, pain, and medications. CBT-I remains first-line for chronic insomnia.

Cognitive symptoms

• SWAN studies found small, temporary decrements in verbal episodic memory during early and late perimenopause and in processing speed during late perimenopause. These findings are not consistent across all tests or sites.
• Hormonal variability is therefore a credible contributor to “brain fog,” but direct causation—especially for progesterone—has not been established. Sleep disruption, anxiety, depression, and vasomotor symptoms may interact.

Bottom line

• Variable estrogen production and declining ovulatory progesterone exposure are established features of perimenopause; they can contribute to sleep disturbance, while their contribution to cognitive symptoms is plausible but less directly proven. Hormone therapy is not recommended solely to improve cognition.