Age and the metabolic syndrome affect salivary cortisol rhythm: data from a community sample

Measurement of cortisol levels in saliva is a marker of free hormone. How salivary cortisol rhythm is affected by age, gender, the metabolic syndrome and estrogen-progestin therapy was evaluated in a community sample of adults.

One hundred twenty volunteers recruited from the Hospital staff and family members of the Endocrinology Unit were instructed to collect 7 salivary samples: the first on awakening (F(0)) and 6 more (F(1.5), F(5), F(6), F(10), F(11.5) and F(14)) over the next 14 hours. Each volunteer also underwent a complete physical evaluation and a comprehensive medical history was taken. Salivary cortisol was measured using a radioimmunometric assay. Daily cortisol secretion was evaluated computing the Area Under the Curve (AUC(F0)(→)(F14)); the F(14)/F(0) ratio was calculated as a marker of cortisol rhythm.

Median F(14) levels were higher in the subjects in the third tertile of age than in those falling in the second or in the first age tertile (respectively, 2.09 vs 1.33 vs 1.25 ng/mL, p=0.023 and p=0.006), in the hypertensive volunteers (2.44 vs 1.44 ng/mL, p=0.030) and in those with the metabolic syndrome (2.95 vs 1.4 ng/mL, p=0.002), with an elevated median F(14)/F(0) ratio (0.48 vs 0.19, p=0.006). According to the Kruskal-Wallis analysis of variance, the most important factor affecting F(14) value was age (p=0.001). AUC(F0)(→)(F14) was not influenced by gender, age, metabolic syndrome or estrogen-progestin therapy.

While it did not affect the daily cortisol rate, late-night salivary cortisol levels were found to be increased in the subjects in the higher age tertile and in those with the metabolic syndrome.