JMIR Publications

ABSTRACT

Background:

Chronic stress is increasing in prevalence and it is associated with several physical and mental disorders. Assessment of chronic stress is mostly performed by administrating questionnaires. Despite being convenient and valid tools, questionnaires do not inform on the detrimental effects of chronic stress on physiological functioning, which could be relevant for better characterization of stress and for tailoring stress management. Continuous measurement of vital signs in daily life and chronic stress detection algorithms could serve to this purpose. To this aim, it is paramount to model the effects of chronic stress on human physiology and include other cofounders, such as demographics, enabling to enrich population wide approach with individual variations.

Objective:

The main objectives of this study are to investigate the effect of chronic stress on the heart rate (HR) over time and test a possible modulation effect by gender and age in a healthy cohort.

Methods:

Chronic stress was assessed with the Perceived Stress Scale (PSS) inquiring on the degree to which situations in one’s life are appraised as stressful during the last month. Hourly heart rate (HR) was measured as the average HR derived from an electrocardiogram (ECG) signal, continuously measured over five days using a wearable health patch device. Models are compared including a trigonometric fit over time with four harmonics, gender, age, the PSS score and whether it was a workday or weekend-day as predictors.

Results:

As main effects, gender, the hour of the day and the four harmonics over time had a significant effect on the HR. Two three-way interaction effects were found. The interaction of age, whether it is a work- or weekend day and the circadian harmonic over time was significantly correlated to the HR (χ22 = 7.13, P = .028) as well as the interaction of gender, PSS score and the circadian harmonic over time (χ22 = 7.59, P = .023).

Conclusions:

The results of this study indicate that both baseline HR and daily fluctuations of HR are individual and time-dependent, and that although chronic stress does not relate to the average HR of an individual, it does influence the HR circadian pattern. This correlation of chronic stress with the HR over time is gender specific and possibly related to the evolution-based energy utilization strategies, as suggested in related literature studies. More research , including daily cortisol, longer recordings and wider population, should be done to confirm this interpretation. This would enable the development of more complete and personalized models of chronic stress.