Longitudinal Analysis of Cardiovascular Parameters across Multiple Measurement Sessions: A Repeated Measures Study
A.Y. Solomon*, J.S. Kumbet
Department of Anatomy, College of Health Sciences, Nile University, Abuja, Nigeria
*Corresponding Author
DOI: https://doi.org/10.51244/IJRSI.2025.120700195
Received: 13 July 2025; Accepted: 19 July 2025; Published: 19 August 2025
Background: Cardiovascular parameters exhibit temporal variability that may influence clinical assessment and treatment decisions. Understanding the patterns of blood pressure and heart rate changes across multiple measurement sessions is crucial for accurate cardiovascular risk stratification.
Objective: To investigate the longitudinal changes in systolic blood pressure (SBP), diastolic blood pressure (DBP), and pulse rate across four measurement sessions and examine their relationships with anthropometric parameters.
Methods: A prospective repeated measures study was conducted with 53 healthy participants (aged 18-65 years) over multiple measurement sessions. Cardiovascular parameters including SBP, DBP, and pulse rate were measured using standardized protocols. Anthropometric measurements including height, weight, and BMI were recorded. Statistical analysis employed repeated measures ANOVA and Friedman tests to assess temporal variations.
Results: Significant temporal variations were observed in SBP (χ² = 79.829, p < 0.001) and pulse rate (χ² = 74.371, p < 0.001), while DBP remained stable across sessions (χ² = 3.700, p = 0.296). The most pronounced SBP increase occurred between sessions 1 and 2. Mean SBP ranged from 118.5 ± 12.3 mmHg to 125.2 ± 14.1 mmHg across sessions. Pulse rate showed considerable variation with coefficients of variation ranging from 8.2% to 12.7%. Weak to moderate correlations were found between anthropometric parameters and cardiovascular variability.
Conclusions: Systolic blood pressure and pulse rate demonstrate significant session-to-session variability in healthy adults, while diastolic blood pressure remains more stable. These findings have important implications for clinical practice and research protocols, suggesting the need for multiple measurements to obtain accurate cardiovascular assessments.
Keywords: blood pressure variability, cardiovascular parameters, repeated measures, longitudinal analysis, pulse rate
Cardiovascular disease remains the leading cause of morbidity and mortality worldwide, necessitating accurate and reliable methods for assessment and monitoring (1, 2). Blood pressure measurement, a cornerstone of cardiovascular evaluation, is subject to considerable temporal variability that can significantly impact clinical decision-making (3, 4). The phenomenon of blood pressure variability has gained increasing recognition as an independent predictor of cardiovascular outcomes, beyond traditional mean blood pressure values (5, 6).
Short-term blood pressure variability, occurring within hours or days, reflects the dynamic nature of cardiovascular regulation and is influenced by multiple factors including autonomic nervous system activity, environmental conditions, psychological stress, and physical activity (7, 8). Studies have demonstrated that elevated blood pressure variability is associated with increased risk of stroke, myocardial infarction, and overall cardiovascular mortality (9, 10). The clinical significance of this variability extends beyond pathological conditions, as it also affects the accuracy of blood pressure classification in apparently healthy individuals (11, 12).
The measurement of blood pressure in clinical and research settings typically involves single or limited repeated assessments, which may not adequately capture the true cardiovascular status of an individual (13, 14). Current guidelines recommend multiple measurements to improve accuracy, yet the optimal number and timing of measurements remain subjects of ongoing investigation (15, 16). The white-coat effect, characterized by elevated blood pressure readings in clinical settings compared to home or ambulatory measurements, further complicates the interpretation of single-session measurements (17, 18).
Pulse rate variability, often studied in conjunction with blood pressure, provides additional insights into cardiovascular autonomic function (19, 20). Heart rate variability has been extensively studied as a marker of autonomic nervous system balance and cardiovascular health (21, 22). The relationship between blood pressure and heart rate responses during repeated measurements may reveal important physiological patterns relevant to cardiovascular risk assessment (23, 24).
Anthropometric parameters, particularly body mass index (BMI), are well-established determinants of cardiovascular risk and are closely associated with blood pressure levels (25, 26). The relationship between BMI and blood pressure variability, however, has received less attention in the literature (27, 28). Understanding how anthropometric factors influence cardiovascular parameter stability across multiple measurements could inform both clinical practice and research methodology (29, 30).
The present study was designed to address these knowledge gaps by conducting a comprehensive longitudinal analysis of cardiovascular parameters across multiple measurement sessions. The primary objectives were to quantify the degree of variability in systolic blood pressure, diastolic blood pressure, and pulse rate across four measurement sessions, and to examine the relationships between these parameters and anthropometric characteristics. We hypothesized that significant variability would be observed in cardiovascular parameters across sessions, with potential differential patterns between systolic and diastolic blood pressure measurements.
Study Design and Participants
This prospective repeated measures study was conducted at the Department of Anatomy, College of Health Sciences, Nile University, Abuja, Nigeria. The study protocol was approved by the institutional review board (31) and conducted in accordance with the Declaration of Helsinki. Written informed consent was obtained from all participants.
A total of 53 participants were recruited through convenience sampling from the local community. Inclusion criteria comprised adults aged 18-65 years with no history of cardiovascular disease, diabetes, or current use of antihypertensive medications. Exclusion criteria included pregnancy, acute illness, or inability to provide informed consent.
All participants provided written informed consent prior to enrollment. The study protocol was designed to minimize potential confounding factors while maintaining ecological validity for real-world cardiovascular assessment scenarios. Participants were instructed to maintain their usual lifestyle patterns throughout the study period to ensure that measurements reflected typical physiological variations rather than intervention-induced changes.
Measurement Protocol
Cardiovascular and anthropometric measurements were obtained during four separate sessions conducted over a period of 12 hours. Each session was scheduled at consistent times of day to minimize circadian influences on cardiovascular parameters (32, 33). Participants were instructed to avoid caffeine, alcohol, and vigorous physical activity for at least 2 hours prior to each measurement session (34, 35).
Blood pressure measurements were obtained using standardized protocols recommended by the American Heart Association (36). Participants were seated in a quiet room for at least 5 minutes before measurement, with feet flat on the floor and back supported. An appropriately sized cuff was placed on the non-dominant arm at heart level (37). Systolic and diastolic blood pressures were recorded using a validated automated oscillometric device, with measurements repeated three times at 1-minute intervals and the average calculated for analysis (38).
Pulse rate measurements were obtained simultaneously with blood pressure using the same automated device. Additional pulse rate measurements were obtained manually by palpation of the radial artery to ensure accuracy (39). Heart rate variability parameters were not assessed in this study, focusing instead on mean pulse rate values across sessions.
Anthropometric Measurements
Height was measured using a calibrated stadiometer with participants standing barefoot in the Frankfurt horizontal plane (40). Weight was obtained using a calibrated electronic scale with participants wearing light clothing and no shoes. Body mass index was calculated as weight in kilograms divided by height in meters squared (41). All anthropometric measurements were performed by trained personnel following standardized protocols to ensure consistency and accuracy (42).
Statistical Analysis
Statistical analyses were performed using SPSS software package with significance set at p < 0.05 (43). Descriptive statistics were calculated for all variables, including means, standard deviations, and ranges. Normality of data distribution was assessed using the Shapiro-Wilk test (44).
The primary analysis employed Friedman tests to assess differences in cardiovascular parameters across the four measurement sessions, as this non-parametric approach is appropriate for repeated measures data that may not meet parametric assumptions (45, 46). Post-hoc pairwise comparisons were conducted when significant main effects were identified, with appropriate corrections for multiple comparisons (47).
Correlation analyses were performed using Pearson product-moment correlation coefficients to examine relationships between cardiovascular parameters and anthropometric measurements (48). Correlations were classified as weak (|r| < 0.3), moderate (0.3 ≤ |r| < 0.7), or strong (|r| ≥ 0.7) based on established conventions (49).
Participant Characteristics
The study included 53 participants with complete data available for pulse rate analysis and 52 participants for blood pressure analysis (one participant excluded due to technical measurement issues). The participant characteristics and baseline measurements are presented in Table 1. The sample demonstrated typical anthropometric characteristics for the studied population, with a mean age of 28.4 ± 8.7 years, 32 males (60.4%) and 21 females (39.6%). Mean BMI was 24.2 ± 3.8 kg/m², with the majority of participants (75.5%) having normal BMI values.
Table 1: Participant Characteristics and Baseline Measurements
Parameter | Mean ± SD | Range |
Age (years) | 28.4 ± 8.7 | 18-65 |
Height (cm) | 168.2 ± 9.1 | 152-186 |
Weight (kg) | 68.5 ± 12.3 | 45-95 |
BMI (kg/m²) | 24.2 ± 3.8 | 18.2-32.1 |
Baseline SBP (mmHg) | 121.3 ± 13.2 | 95-148 |
Baseline DBP (mmHg) | 78.6 ± 9.4 | 62-95 |
Baseline Pulse Rate (bpm) | 72.8 ± 11.5 | 55-98 |
Blood Pressure Variability Across Sessions
Friedman test analysis revealed significant differences in systolic blood pressure across the four measurement sessions (χ² = 79.829, p < 0.001, n = 52). This finding indicates substantial temporal variability in systolic blood pressure, with effect sizes suggesting clinically meaningful differences between sessions. The pattern of change showed the most pronounced increase occurring between sessions 1 and 2, suggesting potential acclimatization or stress-response effects.
Figure 1: Systolic & Diastolic Blood Pressure Trends, Pulse Rate Trends and BMI distribution
Figure 2: Statistical comparisons between measurement sessions. Systolic BP – Friedman test: χ² = 79.829, p = 0.0000 (n=52) Diastolic BP – Friedman test: χ² = 3.700, p = 0.2958 (n=52) Pulse Rate – Friedman test: χ² = 74.371, p = 0.0000 (n=53)
Figure 3: Systolic BP showed significant variation across sessions (p < 0.001), Diastolic BP remained relatively stable (p = 0.296), and pulse rate varied significantly between sessions (p < 0.001). largest systolic BP increase occurred between sessions 1 and 2. Strong correlations (|r| > 0.7): WEIGHT (kg) BMI (kg/m2): r = 0.955
Systolic Blood Pressure Analysis:
Friedman χ² = 79.829, df = 3, p < 0.001 (n = 52)
Effect size: Large (Kendall’s W > 0.3)
In contrast, diastolic blood pressure demonstrated remarkable stability across measurement sessions, with Friedman test results showing no significant differences (χ² = 3.700, p = 0.296, n = 52). This finding suggests that diastolic blood pressure may be less susceptible to short-term variability factors compared to systolic blood pressure, consistent with physiological principles of cardiovascular regulation.
Diastolic Blood Pressure Analysis:
Friedman χ² = 3.700, df = 3, p = 0.296 (n = 52)
Effect size: Small (Kendall’s W < 0.1)
The differential patterns observed between systolic and diastolic blood pressure variability align with previous research indicating that systolic pressure is more sensitive to environmental and physiological influences. This finding has important implications for clinical measurement protocols and the interpretation of blood pressure readings in both clinical and research settings.
Pulse Rate Variations
Pulse rate demonstrated significant variability across measurement sessions, with Friedman test results showing χ² = 74.371, p < 0.001 (n = 53). The magnitude of this effect was comparable to that observed for systolic blood pressure, suggesting similar underlying mechanisms may influence both parameters during repeated measurements.
Pulse Rate Analysis:
Friedman χ² = 74.371, df = 3, p < 0.001 (n = 53)
Effect size: Large (Kendall’s W > 0.3)
The temporal pattern of pulse rate changes paralleled that of systolic blood pressure, with similar increases between early and later sessions. This concordance suggests shared physiological or psychological factors influencing both cardiovascular parameters during the measurement process.
Anthropometric Correlations
Correlation analysis revealed a strong positive relationship between weight and BMI (r = 0.955, p < 0.001), which was expected given the mathematical relationship between these variables. This correlation served as a validation of data quality and measurement consistency across the study protocol.
Additional correlation analyses between cardiovascular parameters and anthropometric measurements revealed patterns consistent with established literature on obesity and cardiovascular risk. The strength of these relationships varied across measurement sessions, suggesting that the association between body composition and cardiovascular parameters may be influenced by temporal factors.
Principal Findings
This study provides compelling evidence for significant temporal variability in cardiovascular parameters across multiple measurement sessions. The most striking finding was the substantial variability observed in systolic blood pressure and pulse rate, contrasted with the remarkable stability of diastolic blood pressure. These differential patterns highlight the complex nature of cardiovascular regulation and have important implications for clinical practice and research methodology (50, 51).
The magnitude of systolic blood pressure variability observed in this study (χ² = 79.829, p < 0.001) represents a large effect size, indicating clinically meaningful differences between measurement sessions. This level of variability exceeds what might be expected from measurement error alone and suggests genuine physiological or psychological factors influencing blood pressure across repeated assessments (52, 53). The clinical significance of such variability has been increasingly recognized, with studies demonstrating that blood pressure variability independently predicts cardiovascular outcomes beyond mean blood pressure levels (54, 55).
Mechanisms of Blood Pressure Variability
The differential patterns observed between systolic and diastolic blood pressure likely reflect distinct physiological mechanisms underlying their regulation (56, 57). Systolic blood pressure is primarily determined by cardiac output and arterial stiffness, parameters that can be rapidly influenced by sympathetic nervous system activity, stress hormones, and environmental factors (58, 59). The significant increase observed between sessions 1 and 2 may represent an acclimatization response, where participants become more comfortable with the measurement procedure, or conversely, a sensitization effect where repeated exposure increases physiological reactivity (60, 61).
Diastolic blood pressure, reflecting peripheral vascular resistance during cardiac relaxation, appears to be more stable and less susceptible to acute influences (62, 63). This stability may be attributed to the more tonic nature of peripheral vascular regulation compared to the dynamic changes in cardiac output that influence systolic pressure (64, 65). The clinical implications of this differential stability are significant, as they suggest that diastolic blood pressure measurements may provide more consistent readings across multiple sessions, while systolic measurements may require careful consideration of measurement context (66, 67).
Clinical Implications
The findings of this study have direct implications for clinical practice and cardiovascular risk assessment (68, 69). The substantial variability in systolic blood pressure and pulse rate across sessions challenges the reliability of single-measurement approaches commonly used in clinical settings. Current hypertension guidelines recognize the importance of multiple measurements but may not adequately account for the degree of session-to-session variability demonstrated in this study (70, 71).
The clinical decision-making process for hypertension diagnosis and treatment often relies on blood pressure measurements obtained during a limited number of clinical encounters (72, 73). Our findings suggest that this approach may lead to misclassification of cardiovascular risk, particularly for systolic hypertension, where the observed variability could result in patients being incorrectly categorized as normotensive or hypertensive depending on the session of measurement (74, 75).
Limitations and Future Directions
Several limitations of this study were acknowledged. The sample size, while adequate for detecting the observed effects, may limit generalizability to broader populations. The participants were primarily healthy adults, and the patterns of variability might differ in populations with established cardiovascular disease or other comorbidities. Future studies should examine cardiovascular parameter variability in diverse clinical populations to determine whether similar patterns persist across different health states.
Systolic blood pressure and pulse rate demonstrate significant session-to-session variability in healthy adults, whereas diastolic blood pressure remains more stable. These findings emphasize the importance of multiple measurements for accurate cardiovascular assessment and have implications for both clinical practice and research. Healthcare providers should consider this natural variability when making clinical decisions based on cardiovascular parameter measurement.
Ethical Considerations
This study was conducted in accordance with the Declaration of Helsinki and approved by the institutional review board of Nile University, Abuja, Nigeria. All participants provided written informed consent prior to enrollment. No conflicts of interest were reported by the authors.
Conflicts Of Interest
The authors declare no conflicts of interest related to this study.