A study published in Psychoneuroendocrinology found that blunted cortisol responses may be a biomarker for insomnia.
Individuals with no history of insomnia were recruited by the Henry Ford Health System in the United States to participate in this study. Participants completed the Trier Social Stress Test (TSST; n=35) or the Cold Pressor Task (CPT; n=34). Insomnia risk was evaluated using the Ford Insomnia Response to Stress Test (FIRST) instrument and related with the hypothalamic-pituitary-adrenal axis and autonomic nervous system measures.
The TSST and CPT study populations were 51% and 50% women respectively, and aged mean 46.5 (range, 23-64) and 28.29 (range, 19-48) years, respectively.
Cortisol levels during the TSST were associated with time (b, -0.21; P <.001) and the time-by-FIRST group interaction (b, -0.19; P <.01), in which individuals with high FIRST scores had a blunted curvature in cortisol levels (b, -0.30; P <.001). Individuals with high FIRST scores had lower cortisol levels overall (mean, 260.34 vs 465.13; P <.0001).
Heart rate was associated with the TSST risk group with a significant time effect (b, 2.6; P <.001) and heart rate was observed to decrease significantly during the recovery period (b, -4.2; P <.001).
For the CPT cohort, there were also significant time effect for cortisol levels (b, -0.22; P <.001) and time-by-FIRST group interaction (b, 0.13; P <.05). High FIRST scores were associated with blunted curvature in cortisol levels (b, -0.16; P <.001) and lower total cortisol production (mean, 17.33 vs 26.90; P <.01).
Heart rate was not a significant moderator for CPT but was associated with the FIRST group (b, -0.74; P <.05).
The major limitation of this study was that it was not designed to assess potential mechanisms between blunted cortisol response and insomnia risk.
The study authors concluded, “Though further research is required to better characterize the role of blunted cortisol in the etiology of insomnia, our results replicate prior work and demonstrate a blunted cortisol response to stress is a reproducible biomarker for premorbid insomnia, regardless of the risk factors measured (familial risk or sleep reactivity) or laboratory stressors used (TSST or CPT). Moreover, this study identifies the FIRST as an instrument that differentiates between those with and without blunted hypothalamic-pituitary-adrenal axis functioning in individuals at risk for insomnia.”
Reffi AN, Cheng P, Kalmbach DA, et al. Is a blunted cortisol response to stress a premorbid risk for insomnia?Psychoneuroendocrinology. 2022;144:105873. doi:10.1016/j.psyneuen.2022.105873