Detecting physiological stress responses in daily life using additional heart rate: Association with individual characteristics and affective states.

Repeated physiological stress responding in daily life is a main mediator of the association between chronic stress and somatic disease. Scalable methods to detect physiological stress responses in daily life are lacking. A potential solution is "additional heart rate" (aHR), which estimates cardiac autonomic responses to psychological stress by subtracting the expected heart rate based on physical activity and posture from the observed heart rate. Here, we identified prolonged periods (>6 min) of substantial increases (>10 BPM) in aHR (aHR periods) in 24-hour recordings of electrocardiogram and accelerometer signals in a healthy sample (n = 827). We examined the heritability and test-retest reliability of the total duration and mean intensity of aHR periods in an exploratory analysis, and then their association with individual characteristics and affective states. Results revealed moderate temporal test-retest reliability (r = .42 and .40) and modest heritability (h² = .15 and .11) of the duration and intensity of aHR periods. Duration and intensity of aHR periods decreased significantly with age (R2 = .02) and BMI (R2 = .01), and males exhibited longer aHR periods than females (3.93 vs 3.20 min/hour, t = 3.16). Neuroticism and exercise behavior were not associated with duration or intensity of aHR periods. Within-person analyses revealed a marginal positive association of aHR periods with momentary negative affect (β = 0.095, p = .033), but not with positive affect. Correcting heart rate for physical activity and posture can thus enable detection of physiological stress responses in daily life, but monitoring over longer periods of weeks to months is necessary to characterize individual risk for stress-related disease outcomes.