Cortisol (4-Point Salivary)

•Observational— Cohort-validated diurnal slope predicts mortality

What the 4-point test captures

• Cortisol awakening response (CAR): the surge 30–45 min after waking; absent or blunted CAR associates with chronic stress, burnout, depression, and post-trauma states.
• Diurnal slope: how steeply cortisol falls from morning peak to evening trough; flat slope predicts mortality in multiple cohorts.
• Bedtime cortisol: elevation suggests stress, sleep disturbance, or Cushing’s.

Why salivary vs. serum

Saliva measures free (unbound) cortisol — the biologically active fraction. It avoids needle-stick stress affecting the measurement. Useful for at-home collection across the day.

When to consider

• Suspected adrenal insufficiency (with morning serum cortisol).
• Cushing’s evaluation (bedtime salivary is screening test).
• Burnout, chronic fatigue, persistent insomnia evaluation.
• Functional medicine / longevity practice context.

Cautions

• Cortisol is highly modifiable — recent stress, illness, exercise, meals, caffeine, alcohol all affect it.
• "Adrenal fatigue" is not a clinically validated diagnosis; flat slopes reflect dysregulation but the term itself lacks endocrine standing.
• Single tests have high variability; repeat over multiple days for baseline.

Related entries

Sleep optimization, HRV, Frailty.