This study aimed to investigate the cardiovascular impact during daytime
naps among students at the Federal University of Rio Grande do Norte
(UFRN). The data collection instrument consisted of six online
questionnaires, clinical examinations, actigraphy for at least 5 consecutive
days, and daytime polysomnography (PSG), where information on the
cardiovascular autonomic profile was collected in the different wake-sleep
stages from PSG data. Sleep windows were identified and calculated for
the N1, N2, N3, and REM sleep stages. Fifteen individuals (7 female and
8 male) participated in the study, all university students, mostly medical
(60%, n=9) and biomedical (13.3%, n=2) students, with an average age of
approximately 23 years (mean 22.6±3.2), predominantly with a Body Mass
Index (BMI) less than 24 kg/m² (mean 23.7±4.6). As a result, 93.3% (n=14)
of the volunteers presented poor sleep quality, 33.3% (n=5) presented
excessive sleepiness, in addition, 86.6% (n=13) presented moderate or
high stress and approximately 80% (n=12) had some degree of insomnia
(subthreshold or moderate insomnia). Actigraphic data revealed a typical
profile of young university students, with relatively short sleep duration
(mean TTS of 6.5±1 h), moderate sleep efficiency (83.7±9), and highly
variable sleep onset latencies (4.6±5), demonstrating the frequent sleep
deprivation in these individuals. Through the assessment of heart rate
variability (HRV) (frequency and time domains) during wakefulness
(before the nap), it was possible to identify a positive correlation between
Social Jet Lag (SJL) and LF (r: 0.54, p-value: 0.034), indicating greater
sympathetic activation and a state of physiological alertness. Furthermore,
when comparing HRV during wakefulness and during sleep, it was
observed that during sleep there was a reduction in SDNN (p-value: 0.00),
an increase in pNN50 (p-value: 0.02), a significant reduction in LF values
(p-value: 0.03), and an increase in HF values (p-value: 0.03). Therefore,
the combination of the three markers (SDNN, pNN50, and LF) presents a
typical physiological pattern in healthy young adults under laboratory
conditions: sleep with higher vagal tone, less overall variation, and a
decrease in slow LF oscillations, while wakefulness maintains greater
multimodal variability resulting from internal and external stimuli. In
general, studies show that LF values tend to be higher during wakefulness
and lower during NREM sleep, due to the more stable vagal predominance
during sleep. The finding of higher heart rate during sleep reinforces the
relevance of napping as an autonomic regulation strategy, capable of
mitigating the effects of stress and promoting sympathovagal balance in
young populations subjected to intense academic demands. Thus, the
data indicate that daytime napping may represent a strategy to mitigate
the negative impacts of psychosocial stress and sleep deprivation in
young university students.
