Circadian rhythms are intrinsic 24-hour cycles that regulate various physiological processes, including hormone secretion, core body temperature, and cardiovascular function (1). Blood pressure (BP) follows a well-established circadian pattern, typically characterized by higher readings during the day and a physiological dip at night during sleep. This nocturnal "dipping" is essential for cardiovascular recovery and health. A disruption in this pattern has been linked to an increased risk of hypertension, left ventricular hypertrophy, and other cardiovascular morbidities (2,3).

Medical students often experience significant academic stress, irregular sleep schedules, and reduced sleep quality due to their demanding training programs. These factors are known to interfere with the body's natural circadian rhythms and may alter BP regulation (4,5). Moreover, studies have shown that sleep deprivation and poor sleep quality can lead to elevated sympathetic activity and impaired autonomic balance, both of which are known contributors to altered BP profiles (6,7). The phenomenon of "non-dipping"—defined as less than a 10% drop in nocturnal BP—has been increasingly observed among young adults with disrupted sleep, which may represent an early marker for future cardiovascular risk (8).

Despite the growing evidence on the interplay between sleep and cardiovascular health, limited data are available regarding the circadian patterns of BP and their correlation with sleep habits in young adults, particularly medical students. Assessing this relationship could help identify early signs of cardiovascular dysregulation and promote timely lifestyle interventions.

Hence, this study aims to assess the circadian variations in blood pressure and examine their correlation with sleep quality and patterns in medical students.

The study population consisted of 100 undergraduate medical students aged between 18 and 25 years, selected through simple random sampling. Inclusion criteria were healthy students without any known history of cardiovascular, renal, or endocrine disorders. Individuals on any medications affecting blood pressure or sleep were excluded.

Sleep Assessment:

Sleep quality was evaluated using the validated Pittsburgh Sleep Quality Index (PSQI) questionnaire. Based on the PSQI global score, participants were categorized as good sleepers (score ≤5) and poor sleepers (score >5). Data on sleep duration, latency, and disturbances were also recorded.

Blood Pressure Monitoring:

All participants underwent 24-hour ambulatory blood pressure monitoring (ABPM) using a calibrated digital ABPM device. The monitor was programmed to record BP every 30 minutes during daytime (6:00 AM to 10:00 PM) and every 60 minutes during nighttime (10:00 PM to 6:00 AM). Participants were instructed to follow their routine daily activities while avoiding intense physical exertion during the monitoring period.

Daytime and nighttime systolic and diastolic BP averages were calculated. The nocturnal dipping pattern was assessed by comparing the average nighttime BP to daytime BP. A drop of less than 10% was defined as a non-dipping pattern.

Data Analysis:

Data were entered into Microsoft Excel and analyzed using SPSS version 25.0. Continuous variables were expressed as mean ± standard deviation (SD). Independent t-tests were used to compare BP values between good and poor sleepers. Pearson correlation coefficients were calculated to assess the relationship between sleep duration and blood pressure parameters. A p-value <0.05 was considered statistically significant.

The study included 100 medical students (mean age: 21.2 ± 1.8 years), comprising 60 males and 40 females. Based on PSQI scores, 55 students were categorized as good sleepers, and 45 as poor sleepers. The average sleep duration was 7.2 ± 0.6 hours for good sleepers and 5.6 ± 0.8 hours for poor sleepers (p<0.01).

Blood Pressure Profile:

Daytime and nighttime systolic and diastolic blood pressure readings were compared between the two groups. Poor sleepers exhibited significantly higher average daytime systolic BP (126.3 ± 9.5 mmHg) compared to good sleepers (118.7 ± 7.3 mmHg; p=0.004). Similarly, the mean nighttime diastolic BP was elevated in poor sleepers (74.2 ± 6.8 mmHg) versus good sleepers (69.5 ± 5.9 mmHg; p=0.02). The percentage of students exhibiting a non-dipping BP pattern was greater in the poor sleep group (31.1%) than in the good sleep group (10.9%) (Table 1).

Table 1: Comparison of Blood Pressure Parameters Between Good and Poor Sleepers

Correlation Analysis:

Pearson correlation showed a significant negative correlation between sleep duration and nighttime systolic BP (r = -0.38, p<0.01), as well as with the prevalence of non-dipping patterns (r = -0.41, p<0.01) (Table 2).

Table 2: Correlation Between Sleep Duration and Blood Pressure Parameters

As seen in Table 1 and Table 2, reduced sleep quality and shorter sleep duration were associated with elevated blood pressure and disrupted circadian BP rhythm.

This study highlights a significant association between altered sleep patterns and disrupted circadian variations in blood pressure among medical students. The findings indicate that students with poor sleep quality exhibit elevated daytime and nighttime blood pressure levels and a higher prevalence of non-dipping blood pressure patterns compared to their well-rested peers.

The physiological dipping of nocturnal blood pressure is a critical aspect of cardiovascular regulation, and its absence (non-dipping pattern) has been associated with increased cardiovascular morbidity and mortality (1,2). Our findings align with previous research demonstrating that individuals with impaired sleep exhibit sympathetic overactivity and altered autonomic balance, contributing to sustained elevations in blood pressure throughout the night (3,4). This dysregulation is particularly concerning in young adults, as it may serve as a precursor to future hypertensive disorders and endothelial dysfunction (5).

Sleep deprivation and poor sleep quality have been shown to activate the hypothalamic-pituitary-adrenal (HPA) axis, increase cortisol secretion, and reduce baroreceptor sensitivity, all of which contribute to elevated blood pressure (6,7). In the current study, poor sleepers had significantly higher mean systolic and diastolic pressures during both day and night, consistent with similar studies conducted among university students and young professionals (8,9).

The increased prevalence of the non-dipping pattern in poor sleepers (31.1%) compared to good sleepers (10.9%) supports existing literature that links disrupted sleep with impaired nocturnal blood pressure regulation (10). Studies have shown that the absence of the normal nocturnal decline in BP is associated with target organ damage, including left ventricular hypertrophy and microalbuminuria, even in normotensive individuals (11,12).

Moreover, the negative correlation observed between sleep duration and nighttime BP in this study reinforces the hypothesis that shorter sleep is detrimental to cardiovascular health (13). This is in agreement with findings by Spiegel et al. and Sauvet et al., who demonstrated that short sleep duration compromises vascular endothelial function and elevates nighttime BP (14,15).

The use of ambulatory blood pressure monitoring (ABPM) in our study provides a reliable method to detect circadian fluctuations in BP, offering advantages over isolated clinic measurements (6). ABPM also allows detection of white-coat hypertension and masked hypertension, which may go unnoticed in conventional assessments (7).

Despite the strengths, this study has certain limitations. The sample was limited to one medical institution, and self-reported sleep quality could be influenced by recall bias. Additionally, we did not account for dietary factors, caffeine intake, or physical activity levels, which might also affect BP readings.

Future longitudinal studies with larger samples and objective sleep monitoring techniques such as actigraphy or polysomnography are recommended to further validate these findings. Interventions to promote better sleep hygiene among medical students may be crucial in reducing early cardiovascular risk.

This study demonstrates that poor sleep quality and reduced sleep duration are significantly associated with elevated blood pressure and a higher prevalence of non-dipping patterns among medical students. These findings underscore the importance of maintaining proper sleep hygiene to preserve circadian blood pressure regulation and reduce early cardiovascular risk in young adults.

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