Seasonal differences in rhythmicity of salivary cortisol in healthy adults

Abstract

The existence of seasonal changes in secretion of stress hormones and inflammatory mediators by humans is not certain. Here, we aimed to determine whether concentrations of cortisol and IL-6 displayed seasonal rhythmicity. The study was performed in Poznań, Poland (52°N, 16°E) in 7 healthy female volunteers (age 22.6 ± 0.8 yr). Samples of whole mixed unstimulated saliva were collected in winter (February) and summer (June) at 2-h intervals over a 24-h period and analyzed for cortisol and IL-6 by immunoassays. During each season, the subjects answered questionnaires related to their sleeping habits, food intake, physical activity, and perceived seasonality. It turned out that salivary concentrations of cortisol followed a daily rhythm both in winter and summer, as determined by a cosine analysis. However, compared with the winter season, a midline-estimating statistic of rhythm in the summer was significantly higher. Moreover, the rhythm acrophase occurred ~4 h later in the summer than in the winter, whereas the amplitudes did not differ. These fluctuations did not correspond to sleeping habits, food and fluid intake, physical exercise, and the self-assessed chronotype. However, the individuals with higher scores on the seasonal affective disorder scale showed a tendency toward lower relative cortisol amplitude in the summer. In contrast to cortisol, salivary IL-6 concentration did not display daily rhythmicity, and its concentrations did not differ significantly between the seasons. In conclusion, in the summer, cortisol level in saliva is elevated, and its circadian pattern of secretion is shifted. The causes for these alterations do not seem to be related to lifestyle and thus remain to be established.

Associations of testosterone and cortisol concentrations with sleep quality in Japanese male workers

“…Third, blood samples were collected during daytime at approximately lunch time (between 11:30 a.m. and 1:00 p.m.) at the workplace because the study was conducted at the annual health check. Testosterone and cortisol concentrations change with circadian rhythms and seasonal variations [ 42 , 43 ]; therefore, time of blood sampling should be controlled. Finally, confounding factors, such as aging, chronic illness, and health behavior, may affect testosterone and cortisol concentrations [ [44] , [45] , [46] , [47] , [48] ].…”

An exploratory study of short-term camping in Antarctica: Hormonal and mood states changes

“…In this sense, the volunteers reported increased fatigue (worn out, exhausted, sleepy and tired) and reduced vigor (lively, energetic, active, and alert), indicating worsening in subjective indexes of physiological strain at the end of the camp. It is also possible that the increase in cortisol reflects environmental stress, including an augmented exposure to light (Kanikowska et al 2019, Leproult et al 2001, Scheer and Buijs 1999, the days with almost 24 h of light during summer camps in Antarctica. The higher morning cortisol concentration led to an increased cortisol amplitude in the second week of camping.…”

The Value of HPA Axis Hormones as Biomarkers for Screening and Early Diagnosis of Postpartum Depression: Updated Information About Methodology

“…The collection of samples for measuring CRH levels, which fluctuate in a pulsatile manner, may not be restricted to a particular time of the day, but sampling for ACTH and cortisol (in blood or saliva), which have ultradian rhythms, should be carefully timed ( 64 , 83 , 84 ). Cortisol concentration may fluctuate with time and age ( 85 ) and with seasons and external stimulation ( 86 , 87 ), which results in different reference ranges and inconsistent conclusions. CRH and ACTH circulate at very low concentrations, and the measurement of ACTH requires careful handling and highly sensitive detection methods such as radioimmunoassay ( 66 ).…”