Perimenopause doesn't just disrupt sleep — it restructures it. Declining progesterone removes a natural brain sedative called allopregnanolone. Erratic estrogen fragments deep sleep and triggers night sweats that cause micro-arousals you may not remember. A 2023 meta-analysis found insomnia is the most prevalent menopausal symptom globally. Cathy covers the science of what's happening to your sleep architecture, CBT-I evidence, magnesium, and what actually helps.