Cortisol Awakening Response in Elite Military Men: Summary Parameters, Stability Measurement, and Effect of Compliance

Abstract

The cortisol awakening response (CAR) holds promise as a clinically important marker of health status. However, CAR research is routinely challenged by its innate complexity, sensitivity to confounds, and methodological inconsistencies. In this unprecedented characterization of CAR in elite military men (N = 58), we established summary parameters, evaluated sampling stability across two consecutive days, and explored the effect of subject compliance. Average salivary cortisol concentrations increased nearly 60% within 30 minutes of waking, followed by a swift recovery to waking values at 60 minutes. Approximately one in six were classified as negative responders (i.e., <0% change from waking to 30-minute postawakening). Three summary parameters of magnitude, as well as three summary parameters of pattern, were computed. Consistent with our hypothesis, summary parameters of magnitude displayed superior stability compared with summary parameters of pattern in the total sample. As expected, compliance with target sampling times was relatively good; average deviations of self-reported morning sampling times in relation to actigraph-derived wake times across both days were within ±5 minutes, and nearly two-thirds of the sample was classified as CAR compliant across both days. Although compliance had equivocal effects on some measures of magnitude, it substantially improved the stability of summary parameters of pattern. The first of its kind, this study established the foundation for a program of CAR research in a profoundly resilient yet chronically stressed population. Building from this, our forthcoming research will evaluate demographic, biobehavioral, and clinical determinants of CAR in this unique population.

Anabolic hormone profiles in elite military men

“…This is consistent with our prior comparison of magnitude and pattern estimates of cortisol in these same men. 1,2 The stable parameters of magnitude in DHEA and testosterone are also very consistent with the broader literature. 4,7,11,34 Additionally, removal of noncompliant subjects did not appreciably affect measurement of either hormone.…”

“…Limitations of this study are recognized in prior reports. 1,2 Most notably, we were unable to include an internal control group. With this in mind, comparison to hormone concentrations observed in other studies is muddled by differing conditions and methodologies.…”

“…Each parameter is described in Table I. Compliance with target sample times was also empirically assessed; this procedure is detailed in Taylor et al 1 Data were analyzed using SPSS statistical software, version 19.0 (IBM Corp., Armonk, NY). Distribution characteristics for all continuous variables were examined to determine if assumptions of normality were met, following conservative predefined limits (e.g., skewness between −1 and 1, 37 kurtosis between −3 and 3 38 ).…”

“…The present study was designed to (1) establish summary parameters of anabolic hormone (DHEA and testosterone) function in 58 elite military men, (2) evaluate the stability of summary parameters across 2 consecutive days of sampling, and (3) explore the effect of subject compliance with sampling times. As was shown with respect to cortisol in these men, 1 we hypothesized that summary parameters of magnitude across the morning samples would reveal superior stability compared with summary parameters of pattern. In addition, we expected that summary parameters of daily hormone function (e.g., morning to evening slope) would demonstrate high stability.…”

“…We recently characterized awakening responses 1 and daily patterns 2 of the catabolic stress hormone cortisol in elite military men. Anabolic hormones (e.g., dehydroepiandrosterone [DHEA 3,4 ] and testosterone [5][6][7] ) roughly follow the same daily pattern, loosely correlate to cortisol across the day, 4 and appear to counteract cortisol's catabolic and neurodegenerative effects.…”