Effects of lifestyle factors on concentrations of salivary cortisol in healthy individuals.

OBJECTIVE

Salivary cortisol is widely used in occupational health research. However, many ordinary daily activities can influence the concentrations of cortisol and the interpretation of field studies. The aim of the present study was to evaluate the effect of lifestyle factors on salivary cortisol in everyday settings.

MATERIAL AND METHODS

Healthy employees participated in one or more sub-studies on the effect of eating a vegetable salad versus protein-rich mid-day meal (n = 40), drinking coffee and smoking (n = 12), drinking alcohol (n = 32), awakening at different times (n = 29) and exercising (n = 21). Cortisol in saliva was measured by radioimmunoassay (RIA).

RESULTS

When eating a mid-day meal, salivary cortisol was increased by 10 % (CI -1 % to 24 %) 1 h after eating compared to before eating in the case of both types of meal. Salivary cortisol increased by 80 % (CI 9 % to 199 %) after exercising compared to before exercise. The relative awakening response was approximately 100 % when using an alarm clock on both work-days and days off. However, the awakening response was 39 % (CI 10 % to 75 %) on a day off with spontaneous awakening. No effects of alcohol, coffee or smoking were observed.

DISCUSSION

In field studies, the biological variation in salivary cortisol may be reduced by restricting physical exercise and in collecting pre-meal samples. However, the protein content of food and moderate consumption of alcohol had no effect on concentrations of cortisol. Differences in relative awakening responses on work-days and days off are related to time and mode of awakening.