Stress can harm different areas of sleep health in young adults who are good sleepers.
Stress can damage sleep in good sleepers, especially those who have high sleep reactivity (H-SR). Of the sleep stages, non-REM stages 1 (N1) and 2 (N2) and REM sleep are more easily affected, whereas N3 sleep is fairly stable, according to Nature and Science of Sleep.
This study was conducted to analyze changes and links of stress and high sleep reactivity on the macro-structure and orderliness of sleep and cortisol levels in good sleepers.
Adequate sleep is important for maintaining normal physiological and psychological functions, and patients with long-term insomnia usually present with serious impairments in physical and mental functions, including lowered immunity, underpowered academic performance, memory loss, and more.
A total of 62 good sleepers aged 18 to 40 years were recruited, with 32 in the stress group and 30 in the control group. Each group was divided further into high sleep reactivity (H-SR) and low sleep reactivity (L-SR) subgroups based on the Ford Insomnia Response to Stress Test, which measured how susceptible they were to sleep difficulties after common stressful situations. Every participant completed 2 nights of polysomnography in a sleep laboratory. Prior to conducting polysomnography on the second night, the stress group finished the Trier Social Stress Test, which acted as a stressor, in addition to saliva collection.
First, durations of N1, N2, and REM sleep decreased when exposed to stress, and the values of approximate entropy, sample entropy, fuzzy entropy, and multiscale entropy grew under stress and sleep reactivity (SR) side effects. Stress also increased REM density and H-SR amplified cortisol reactivity.
Of interest, the authors said that the shortening of REM has multiple unfavorable effects. Poor REM causes subjectively poor sleep, and REM can regulate negative emotions and transform and integrate daytime memories, and more. REM changes can also cause mood swings, weaken the stability of memory, and affect learning efficiency. In the present sample, those with H-SR were more likely to have shortened REM sleep duration and were more susceptible to these effects following stress.
It was also found that N3 may be more stable than other sleep stages and may be the last to be affected by stress.
Prior studies have shown that in healthy people with H-SR, stress is more likely to lead to prolongation of sleep latency, an increase in wakefulness after sleep onset, and a decrease in sleep efficiency; they also had an increased risk of acute insomnia. Studies have also found that stress can significantly shorten REM in good sleepers with H-SR and usually shortened N1 and N2.
In this study, the shortening of total sleep time in good sleepers with H-SR after stress was chiefly caused by a decrease in N1, N2, and REM, but it was not related to N3. Nevertheless, N1% had grown with no change in N2%. The authors ventured that the reason for this association might be related to the lack of sleep stability in the H-SR participants.
The results suggest that shallow sleep and REM are more likely to be affected, while deep sleep is fairly stable.
In terms of cortisol, the stress hormone, good sleepers with H-SR presented stronger salivary cortisol responses than those with L-SR after experiencing the same stress. Also, even following recovery time, salivary cortisol levels in those with H-SR did not come back to baseline levels as quickly as those in those with L-SR.
The high cortisol response curve of H-SR good sleepers might be due to the young age of the participants and their limited experience withsleep disorders and stress. Additionally, personality might play a role, with more “neurotic” types feeling more stressed.
Mediation and exercise, along with other interventions, might prevent the onset of stress-induced insomnia and help those at high risk for insomnia improve their stress resilience.
The authors said that the primary limitation of this study was its small sample size and lack of follow-up of the participants to determine if their sleep returned to normal after undergoing stress, due to the COVID-19 pandemic.
“Under mild-to-moderate stress, cortisol responses were stronger in participants with H-SR compared to those with L-SR. Stress and H-SR play driving roles in the development of insomnia,” the study authors concluded.
Feng YZ, Chen JT, Hu ZY, et al. Effects of sleep reactivity on sleep macro-structure, orderliness, and cortisol after stress: a preliminary study in healthy young adults. Nat Sci Sleep. 2023;15:533-546. doi:10.2147/NSS.S415464