Abstract
Objective
This study aimed to evaluate sleep behaviors among college students, to assess salivary alpha-amylase (sAA) and heart rate variability (HRV) in association with stress, and to investigate sleep-related factors including sAA, HRV, and stress among them.
Methods
Saliva samples for sAA assessment and HRV measurements in the supine position were taken between 3 PM and 6 PM. The level of prolonged psychological stress for the previous week was evaluated using the Korean version of the Global Assessment of Recent Stress (GARS-K), and sleep behaviors were assessed using an actigraphy device.
Results
A total of 86 healthy college students participated in this study. Sleep behaviors of the college students were not good, with 84% sleep efficiency (SE) and 62.7 min wake after sleep onset (WASO). The average sAA level was 65.8 U/mL in the participants. Although neither the sAA level nor HRV indices were significantly correlated with prolonged psychological stress, decreased normalized high frequency (nHF) on HRV was independently associated with a higher level of stress when adjusted for age and sex. Higher stress (r = −0.276, P = 0.011) and lower sAA (r = 0.266, P = 0.030) had significant correlations with shorter time in bed; however, it was sAA that was independently associated with time in bed (β = 0.244, p = 0.044). Decreased nHF (β = 0.245, P = 0.027) and higher body mass index (BMI) (β = −0.224, P = 0.043) were independently related to and poorer SE.
Conclusions
Poor sleep behaviors were associated with decreased parasympathetic activity, a physiological change to psychological stress, rather than with psychological stress itself among college students. Thus, sAA and HRV should be considered as significant factors for impaired sleep behaviors in relation to psychological stress.