Salivary cortisol as a marker of self-perceived stress while commuting on Atlanta roadways during peak hours

Abstract

Previous research has assessed individual exposures experienced during daily commuting, in occupational settings, and residences. In most metropolitan areas, the psychosocial stress factors also contribute to total daily environmental exposure. The aim of this work was to characterize differences in cortisol concentrations, a biomarker of psychosocial stress, collected in saliva before and following a scripted rush hour commute for 102 study participants. In addition, we compared salivary cortisol with other metrics of self-perceived stress, via questionnaire data. Results presented here were generated using data from two phases of the Atlanta Commuters Exposures studies (ACE-1 and ACE-2), which examined the impact of traffic air pollution on cardiorespiratory health while commuting on Atlanta roadways. Salivary cortisol was assessed by collecting saliva from study subjects immediately before and after the commute. The commutes each lasted for approximately 2 hours. In ACE-1 study, all the participants did two highway commutes separated by a one week period. Post-commute cortisol levels (1413.6±813.3 pg/ml) were higher than pre-commute cortisol levels (730.6±602.3 pg/ml). In ACE-2 study, each participant did a highway commute. Half of these study participants, the following week, also did a side street commute and the other half served as control i.e. did not do any commute and stayed indoors for the 2 hour period. Results indicated that the median cortisol concentrations post-commute was higher than pre commute for almost 95 percent of the study subjects. For highway commutes in ACE-2, the mean post-commute cortisol levels were 1520.5±713.5 pg/ml and pre-commute levels were713.5±725.2 pg/ml. For side-street commutes the levels were: post-commute, 1475±949.5 pg/ml; pre-commute = 652.7±532.7 pg/ml. Cortisol levels for controls were 1180.3±940.2 pg/ml for post-control versus 763.9±801.3 pg/ml for pre-control period. These results indicate that salivary cortisol may be used an effective means of assessing self-perceived psychosocial stress during commuting.