Assessing the Cortisol Curve

The adrenal hormone cortisol impacts nearly all the body’s systems. Cortisol levels fluctuate throughout the day, normally peaking in the morning hours and bottoming out at night. In studies, deviations from this pattern are associated with signs and symptoms of adrenal dysfunction. One such dysfunctional pattern is a flat cortisol curve in which the amount of cortisol secreted (high or low) shifts very little throughout the day. In both healthy and clinical populations, a flattened cortisol curve has been robustly associated with a shorter lifespan and negative health indicators.

Results of one such study indicated that a flattened cortisol curve statistically predicted poor survival time in patients with metastatic breast cancer.¹ Natural killer cell numbers and activity were also decreased. In the patients studied, 70% had flattened cortisol curves, presumably due to the physical and emotional stress of their diagnosis and treatment.¹ Flattening of the cortisol curve has also been shown to predict early death from lung cancer and has been associated with low T-cell lymphocyte counts.²

In another study of healthy individuals, diurnal cortisol patterns were measured for two years and participants were then followed for six to eight more years.³ Participants were mostly middle-aged (average of 61 years). Flattened cortisol curves correlated with mortality from all causes, including cardiovascular deaths.³

Measuring cortisol over the course of a day may predict health outcomes both for patients with diseases and for seemingly healthy individuals. Understanding the factors that affect cortisol secretion can inform appropriate treatment interventions. One remarkable finding is that neighborhoods with more stressors are correlated with flattened cortisol curves for the populations who live there, suggesting that social status may be a factor in cortisol patterns.⁴ Indeed, a study of First Nations people—a population that has a higher incidence of mental disorders and non-communicable diseases, as well as a long history of racial discrimination—found blunted cortisol awakening responses, too.⁵

REFERENCES

1. Sephton SE, Sapolsky RM, Kraemer HC, Spiegel D. Diurnal cortisol rhythm as a predictor of breast cancer survival. J Natl Cancer Inst. 2000;92(12):994-1000. doi: 10.1093/jnci/92.12.994.
2. Sephton SE, Lush E, Dedert EA, et al. Diurnal cortisol rhythm as a predictor of lung cancer survival. Brain Behav Immun. 2013;30(Suppl):S163-70. doi: 10.1016/j.bbi.2012.07.019.
3. Kumari M, Shipley M, Stafford M, Kivimaki M. Association of diurnal patterns in salivary cortisol with all-cause and cardiovascular mortality: findings from the Whitehall II study. J Clin Endocrinol Metab. 2011;96(5):1478-85. doi: 1210/jc.2010-2137.
4. Karb RA, Elliott MR, Dowd JB, Morenoff JD. Neighborhood-level stressors, social support, and diurnal patterns of cortisol: the Chicago Community Adult Health Study. Soc Sci Med. 2012;75(6):1038-47. doi: 10.1016/j.socscimed.2012.03.031.
5. Berger M, Leicht A, Slatcher A, et al. Cortisol awakening response and acute stress reactivity in First Nations people. Sci Rep. 2017;7(41760):1-10. doi: 10.1038/srep41760.