Salivary cortisol level, salivary flow rate, and masticatory muscle activity in response to acute mental stress: a comparison between aged and young women.
BACKGROUND
Age-related effects on physiological stress reactions regarding changes in salivary cortisol concentration, saliva flow rate, and masticatory muscle activity, as well as the corresponding perceived mental stress and performance in response to acute stressors, have not yet been fully described.


OBJECTIVE
Thus, the aim of this study was to assess the age-related variations in these variables in response to minor acute and naturalistic stressors in terms of computer tasks.


METHODS
13 aged (60-70 years old) and 13 young (20-30 years old) women with frequent practice and long experience with computer use were recruited by personal contact and flyers. The subjects were healthy and had full dental arches and no orofacial pain. The computer tasks were randomized and comprised a mentally demanding, modified Stroop colour-word test (CWT) and a less demanding reference test, both with a duration of 20 min and with equal physical demand. Visual analogue scales for global assessment of mental stress and perceived task difficulty and performance, measurements of saliva flow rate and cortisol concentration (unstimulated whole saliva), as well as surface electromyography of the temporalis and masseter muscles were used for assessment, and Spearman correlation analysis and Anova with repeated measures were used for statistical evaluation.


RESULTS
The perceived task-related stress and task difficulty were significantly higher and the personal satisfaction with the task performance significantly poorer in the aged women. The cortisol concentration, indicating the stress level, showed a small, but significant increase in response to the tasks. Also the saliva flow rate increased. This response was most pronounced in the aged and during the CWT. The average electromyogram varied significantly between age groups and tasks, with higher levels and shorter relative periods with gaps in the aged women and in the CWT. In addition, the peak activity of the jaw elevator muscles at mouse clicking was significantly elevated as a form of co-activation or attention-related activity.


CONCLUSIONS
The study showed marked differences in the response to mental demands in aged as compared with young women. The mental stress, reflected by increases of salivary cortisol concentration, saliva flow rate, visual analogue scale ratings, and activity level of the jaw elevator muscles, was more pronounced in the aged women in response to the computer tasks.
Department of Oral Medicine, Clinical Oral Physiology, Oral Pathology and Anatomy, School of Dentistry, Faculty of Health Sciences, University of Copenhagen, 20 Nørre Allé, DK-2200, Copenhagen, Denmark. merete.bakke@odont.ku.dk
Merete
M
Bakke
Anette
A
Tuxen
Carsten Eckhart
CE
Thomsen
Allan
A
Bardow
Tine
T
Alkjaer
Bente Rona
BR
Jensen
D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D004576:Electromyography; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000032:analysis*; D008410:Masticatory Muscles / Q000502:physiology*; D008606:Mental Processes / Q000502:physiology; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology; D012463:Saliva / Q000737:chemistry* / Q000378:metabolism; D012469:Salivary Glands / Q000378:metabolism*; D012636:Secretory Rate / Q000502:physiology; D013315:Stress, Psychological / Q000503:physiopathology* / Q000523:psychology*; D013564:Sympathetic Nervous System / Q000503:physiopathology
D006854:Hydrocortisone