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. 2021 Jan 22;11(2):81. doi: 10.3390/life11020081

Table 1.

Hair cortisol and sleep disorders in adults.

Reference Number of Adults and Mean Age Characteristics of Participants How the Analysis of Sleep was Performed Mean Concentration of Hair Cortisol (HCC) Main Findings of the Study Related to Hair Cortisol Concentration
Lanfear et al., 2020

  • N = 42

  • Age: 60–80 years

  • Mean age: 68.1 ± 5.3 years.

  • Male and female over the age of

    60 years; older adults in good general physical health.

  • Participants were divided into two categories based on whether they did or did not sleep during the day.

 An ad hoc questionnaire to capture physiological data: time and duration of daytime sleep.

  • HCC levels: 1.4–82.5 pg/mg

  • Median HCC: 5.65 pg/mg

  • Mean HCC: 10.5 pg/mg ± 13.6 pg/mg

  • Mean HCC in males (n = 20) was

    14.4 pg/mg

  • Mean HCC in females (n = 22) was

    6.8 pg/mg

  • HCC in older adults trends to be higher in comparison with toddlers and adolescents.

  • A significant difference in hair cortisol between males and females older adults.

  • No significant difference in hair cortisol between participants who did and did not sleep during the day.
Trikojat et al, 2017

  • Season Allergic Rhinitis (SAR) patients (n = 41)

  • Age mean:

    24.12 (±3.3) years

  • Healthy controls (n = 42)

  • Age mean:

    24.43 (±3.1) years.

  • SAR patients reported rhinitis symptoms exclusively during pollen season and had a positive skin prick test for at least one grass or tree pollen and/or elevated total IgE level (>100 IU/mL serum).

  • All patients were off allergy medication for at least seven days prior to testing.

 Pittsburgh Sleep
Quality Index (PSQI; Buysse et al., 1989).

  • Hair Cortisol, pg/mg

  • SAR patients:

    On-pollen season 5.4 (±4.3)

    Off-pollen season 4.2 (±2.5)

  • Healthy controls:

    On-pollen season 5.9 (±4.2)

    Off-pollen season 4.1 (±2.6)

  • No significant group differences in HCC could be found in both testing seasons.

  • On allergy season, Beck Depression Inventory II sum score correlates with PSQI but not with HCC in SAR patients.
Zhang et al, 2020

  • N = 435:

    men = 164

    women = 271

  • Age range

    (20–58) years,

  • Average age

    (38.32 ± 7.42) years.

 Participants are classified as:
  • Fixed day workers: 127 (29.20%)
  • Two-shift workers: 87 (20%)
  • Three-shift workers: 64 (14.71%)
  • Four-shift workers: 135 (31.03%)
  • Other workers: 22 (5.06%)
 The Pittsburgh Sleep Quality Index scale PSQI; Buysse et al., 1989)

  • HCC range: 1.07–9.67 ng/g hair

  • HCC median: 3.20 (2.15–4.71) ng/g hair

  • HCCs were dichotomized at Q3 (4.71 ng/g hair) threshold

  • HCC levels of workers with different shift patterns were significantly higher than that of fixed day shift workers.

  • Compared with workers with low and intermediate HCC, the prevalence of sleep disorders in workers with high HCC was significantly higher.
Wang et al., 2019

  • N = 68 females

  • Age range: 22–51 years

    (32.50 ± 6.13),

  • Participants were employees working in both clinical and management roles, who had worked continuously in the same position for at least 6 months, and

  • Participants had no history of mental illness and no history of psychotropic drug use for 1 week prior to the investigation, basing on the clinical records and self-report of each participant.

 Athens Insomnia Scale (AIS),

  • HCC median: 5.89 ng/g hair

  • Interquartile HCC range:

    2.20–10.74 ng/g hair

  • HCC was significantly associated with insomnia.

  • No significant mediating effect of HCC on the path from insomnia to burnout.

  • Both burnout and insomnia were associated with elevated HCC among female employees of hospital.
Colledge et al., 2017 Patients with aneurysmal subarachnoid hemorrhage (aSAH)
  • N = 32:
    22 women, 10 men;
  • Mean age: 57.4 ± 10.7 years;
Healthy controls
  • N= 17:
    11 women, 6 men;
  • Mean age = 59.8 ± 10.8 years
 Patients with aSAH following neurosurgical or endovascular intervention. The 7-item Insomnia Severity Index (Bastien CH, Vallieres A, Morin CM, 2001) HCC mean:
  • aSAH patients: 4.24 ± 2.91 nmol/L,
  • Healthy controls: 2.39 ± 1.26 nmol/L

  • HCCs were significantly higher in aSAH patients compared to healthy controls.

  • In aSAH patients, higher HCCs were significantly associated with increased sleep complaints.

  • aSAH patients exhibited more sleep complaints.
Feller et al., 2014

  • N = 680 participants

    (369 women)

  • Mean age: 65.8 years

  • Range age: 47–82 years.

 Participants in middle and old adulthood not using glucocorticoid-containing treatments. Average night and daytime sleep was collected using questionnaires

  • Mean ± SD HCC in the whole sample were 35.1 ± 32.8 pg/mg.

  • Mean ± SD SCC were 37.9 ± 34.0 pg/mg in men and 32.7 ± 31.6 pg/mg in women.

  • HCC outlying by 3 standard deviations (SD) from the mean were excluded (n = 18) after the initial elimination of extreme values >500 pg/mg (n = 8), resulting in a final sample of 654 participants for further analyses.

  • A linear increase in HCC with participant ages was found and this relationship was maintained regardless of the influence of other age-related variables (body mass, physical activity, alcohol consumption, smoking).

  • HCC was found to be positively related daytime sleeping.

  • In multiple regression analysis, daytime sleeping was not a predictor factor of HCC.