Sauna & cold

Heat induces hyperthermia that triggers heat shock protein production (up to 48% increase), vasodilation, and parasympathetic nervous system activation. The core temperature rise and subsequent cooling mimics the body's natural temperature-drop signal for sleep. Reduces inflammatory markers (CRP). The repeated stress-and-recovery pattern builds cardiovascular and nervous system resilience — hormesis.

Women get Alzheimer's at twice the rate of men, partly because estrogen protects neurons and brain blood vessels. When estrogen declines, brain blood flow drops and cognitive vulnerability rises. The KIHD Finnish study (Laukkanen et al. 2016) showed 4–7 sauna sessions per week reduced Alzheimer's risk by 65%. Cardiovascular risk also rises sharply during perimenopause — sauna provides cardiovascular conditioning equivalent to light-to-moderate exercise. Depression and anxiety spike during perimenopause; passive heat exposure independently improves mood.

●●●●● Strong — large prospective cohort data (KIHD), dose-response
Evidence is primarily for traditional dry sauna at 80–100°C. Infrared sauna (45–60°C) has cardiovascular and blood pressure data but lacks the specific dementia reduction evidence. If infrared is your only option, it still provides meaningful benefit through shared mechanisms. Traditional is preferred if accessible.

Start with 10 minutes, 3x/week. Build to 15–20 minutes, 4x/week over 4–6 weeks. Hydrate before and after. Best timing: evening, 1–2 hours before bed. If hot flashes are severe, start shorter and cooler — the paradox is that regular sauna actually improves thermoregulation over time.

Sleep improvement: 1–2 weeks of consistent use. Mood effects: 2–4 weeks. Cardiovascular markers: 8–12 weeks. Dementia protection: cumulative over years.

Cold shock activates the sympathetic nervous system, releasing norepinephrine (200–300% increase with just 20 seconds of immersion) and dopamine. These neurotransmitters improve mood, focus, and energy. Vasoconstriction followed by vasodilation improves vascular elasticity. Activates brown adipose tissue (BAT) for metabolic support.

●●●●● Moderate — strong mechanistic data, limited women-specific RCTs
The neurochemical response is well-documented. Women-specific perimenopause data is limited. Dr. Sims cautions that protocols designed for men (35–45°F) are too cold for most women and can cause excessive cortisol stress. Stick to the milder end and limit to 1–3 minutes.

Always heat first (sauna or hot shower), then cold. Start at 60°F for 30 seconds and build. End on cold if sleep is the goal (the body's subsequent rewarming triggers the sleep temperature cascade). End on rest/warmth if mood regulation is the priority. Cycle: sauna → cold → rest → repeat 2–3x.