Gender Differences in Postural Instability by Posturography among Patients with Prehypertension

ABSTRACT IMAGE

INTRODUCTION

Independence in daily activities relies heavily on maintaining controlled body posture, which requires continuous adjustments to balance, with sensory inputs coordinated with neuromuscular performance.^[1] Postural instability can significantly affect daily functions and is often associated with psychological issues such as depression.^[2] It is also a major cause of falls, especially among older adults and individuals with vestibular, visual, musculoskeletal, or neurological disorders. Proper posture involves the coordination of multiple systems, including baroreceptors, the cerebellum, and the vestibular and cochlear systems, which help stabilize blood pressure during positional changes, contributing to overall balance.^[3]

Postural instability can be influenced by both modifiable factors–such as stress, lifestyle, and environmental exposures–and non-modifiable factors, like age.^[4] While much research on postural stability has focused on elderly populations and those with vestibular disorders, the effects of prehypertension on balance are less understood.^[5] Prehypertension, a growing concern, is an early stage of hypertension, which is known to impair physical function and disrupt autonomic balance.^[6] However, the relationship between prehypertension and postural instability remains underexplored. This knowledge gap is critical, as early intervention could help prevent the progression to hypertension and its related complications.

The center of pressure (CoP) is a key indicator of postural stability, reflecting motor system activity during standing. Impaired sensory and motor function can lead to body sway and CoP displacement (dCoP), signaling instability.^[7] Computerized posturography, a validated and reliable tool, is commonly used to assess postural stability with high test–retest reliability.^[8] Gender differences also affect postural stability, with women experiencing a higher incidence of falls than men. This is mostly because women lose bone density and muscle mass earlier than men do, which raises their risk of instability.^[9]

This study aimed to address the gap in knowledge by assessing postural stability in prehypertensive individuals compared to normotensive controls. It also seeks to determine whether prehypertension exacerbates postural instability, particularly in women, thereby providing insights into the physiological impact of this condition and informing potential preventive strategies.

MATERIALS AND METHODS

This cross-sectional study was conducted in the outpatient departments of General Medicine and Physiology at a tertiary care hospital in Hyderabad, Telangana. The study was approved by the Institutional Ethics Committee (AIIMS/BBN/IEC/MAY 2024/410-R). With the assumed prevalence of postural instability among patients with prehypertensive of approximately 50%, and the population of 70 subjects with prehypertension in 3-month duration, the sample size came out to be 60. Systolic blood pressure (SBP) between 120 and 139 mmHg and diastolic blood pressure (DBP) of 80–89 mmHg was considered as prehypertension.^[6] The consecutive sampling method was used to achieve the sample size. After obtaining informed consent, 60 prehypertensive and 60 normotensive individuals were recruited into the study based on inclusion and exclusion criteria. Participants aged 18–50 years, of both genders, with prehypertension and normotension were eligible for inclusion. Exclusion criteria encompassed obesity; known cardiac or renal disease; a history of back pain, fractures, arthritis, or lower limb surgery; vestibular disorders; hypothyroidism; diabetes mellitus; central nervous system disorders such as stroke, migraines, Parkinsonism, or cerebellar conditions; neuropsychiatric disorders; and alcohol addiction; on treatment with drugs affecting the postural instability.

Baseline assessments were conducted, including sociodemographic data (e.g., age and gender), and physical examinations (e.g., body mass index [BMI], pulse rate, and blood pressure). Before the test, participants were advised to have a small breakfast and avoid coffee and intense activity for 10 h. Posturography was performed using a Nintendo Wii Fit Plus balance board, USA, which measured CoP displacement in the mediolateral (ML) direction and sway distance. The balancing board was wirelessly attached to LabChart software and PowerLab 8/35 (Analog Digital [AD] Instruments) for gathering data.

Participants underwent a balance assessment using a Wii Balance Board wirelessly connected to a PowerLab 8/35 system (AD Instruments) and Lab Chart software to measure the ML displacement of the CoP and sway distance. The trial began with participants standing on the board with eyes open (baseline) for 1 min, followed by 1 min with eyes closed, and then 1 min with eyes open again. Subsequently, participants performed a right sway movement for 30 s with eyes open, maintaining a straight body posture using the ankle strategy. This was followed by a 1-min rest while standing on the board with eyes open. Next, participants performed a left sway movement for 30 s under similar conditions. The trial concluded with another 1-min rest standing on the board with eyes open. CoP displacement and sway distance were recorded in all positions to evaluate balance and postural control.

RESULTS

A total of 120 participants were included in the study, comprising 60 males (50%) and 60 females (50%). Each gender group consisted of 30 individuals with prehypertension and 30 normotensive controls. Among male participants, the mean age of the prehypertensive group was 38.23 ± 7.42 years, while that of the normotensive group was 36.9 ± 9.1 years (P = 0.537). The mean BMI was also comparable between the two groups (24.72 ± 2.78 kg/m² in prehypertensive males vs. 25.31 ± 3.18 kg/m² in normotensive males; P = 0.443). However, both SBP and DBP were elevated in prehypertensive males compared to normotensives (SBP: 131.87 ± 3.5 mmHg vs. 110.07 ± 4.37 mmHg, P < 0.001; DBP: 84.93 ± 4.15 mmHg vs. 73.93 ± 2.8 mmHg, P < 0.001). The mean pulse rate was also significantly higher in the prehypertensive group (82.67 ± 10.26 bpm) compared to normotensive males (77.83 ± 5.79 bpm; P = 0.03). In terms of posturography parameters, prehypertensive males demonstrated significantly greater baseline displacement of the desired center of pressure (dCoP) (145.17 ± 88.58 cm) compared to normotensive males (105.6 ± 22.65 cm; P = 0.024). A similar significant difference was observed in right sway dCoP values (98.27 ± 88.31 cm vs. 45.1 ± 17.92 cm; P = 0.003). In addition, the baseline sway distance was markedly increased in prehypertensive males (1.5 ± 1.97 cm) compared to their normotensive counterparts (0.33 ± 0.47 cm; P = 0.004). These findings are summarized in Table 1 and illustrated in Figure 1.

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Figure 1:

Posturography parameters among males with prehypertension and normotension. (^*signifies P < 0.05, ^**signifies P < 0.01, dCoP: Center of pressure displacement).

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The mean age of prehypertensive females was 43.27 ± 7.36 years, compared to 41.87 ± 6.35 years in normotensive females (P = 0.434). Similarly, the BMI was comparable between the groups (24.97 ± 2.78 kg/m² in prehypertensive females vs. 23.82 ± 2.96 kg/m² in normotensive females; P = 0.145). However, both SBP and DBP were significantly higher in the prehypertensive group. The mean SBP was 129.53 ± 7.13 mmHg in prehypertensive females compared to 98.9 ± 6.2 mmHg in normotensives (P < 0.001), while the mean DBP was 85.5 ± 3.06 mmHg versus 67.7 ± 4.86 mmHg, respectively (P < 0.001). In addition, the mean pulse rate was significantly elevated in prehypertensive females (86.97 ± 6.64 bpm) compared to normotensive females (77 ± 6.7 bpm; P < 0.001).

With regard to posturography parameters, baseline displacement of the desired center of pressure (dCoP) was significantly higher in prehypertensive females (125.12 ± 63.15 cm) than in normotensive females (87.48 ± 22.91 cm; P = 0.004). A similar significant increase was observed in the eyes-closed dCoP values (115.7 ± 62.7 cm vs. 90.27 ± 20.17 cm; P = 0.042). Conversely, sway distance during the eyes-open condition was significantly reduced in the prehypertensive group (0.72 ± 0.48 cm) compared to normotensives (1.63 ± 0.68 cm; P < 0.001). These findings are summarized in Table 2 and illustrated in Figure 2.

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Figure 2:

Posturography parameters among females with prehypertension and normotension. (^*signifies P < 0.05, ^**signifies P < 0.01, ^***signifies P < 0.001, dCoP: Center of pressure displacement).

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Prehypertensive males were significantly younger than females (38.23 ± 7.42 years vs. 43.27 ± 7.36 years, P = 0.011). No significant differences were observed in BMI (P = 0.738), SBP (P = 0.116), DBP (P = 0.550), or pulse rate (P = 0.060) between male and female prehypertensives. Displacement of CoP across all positions was comparable between the sexes (all P > 0.05). A notable finding was the significantly lower sway distance in the eyes open position among prehypertensive females compared to males (0.72 ± 0.48 cm vs. 1.5 ± 1.94 cm, P = 0.021). These results are presented in Table 3 and illustrated in Figure 3.

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Figure 3:

Posturography parameters among both genders with prehypertension. (^*signifies P < 0.05, dCoP: Center of pressure displacement).

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DISCUSSION

This study assessed postural instability using posturography in individuals with prehypertension, focusing on gender differences and identifying potential risk factors. We studied the Displacement of CoP and sway distance in standing with eyes open, standing with eyes closed, right sway with eyes open, and left sway with eyes open positions. The results revealed notable associations between prehypertension and impaired postural control, with distinct gender-based variations.

Prehypertensive males exhibited significantly higher systolic and DBP and pulse rate compared to normotensive males. Posturography metrics showed significantly increased baseline displacement of CoP (dCoP) and sway distance in prehypertensive males, particularly during baseline and right sway conditions compared to normotensive males. In contrast, prehypertensive females demonstrated significantly higher dCoP in baseline and eyes-closed conditions compared to normotensive females. However, sway distance was notably reduced in prehypertensive females during eyes-open conditions. Gender comparisons within the prehypertensive group revealed that females had lower sway distance in eyes-open conditions compared to males, while other postural metrics showed no significant differences.

To the best of our knowledge, no previous studies have specifically investigated postural balance in individuals with prehypertension. Prior research has established a link between hypertension and impaired postural control, attributed to baroreceptor dysfunction, vascular stiffness, and reduced cerebral perfusion.^[10-12] This study extends these findings to prehypertensive populations, demonstrating that balance impairments can manifest even at this earlier stage.

The present study demonstrated significant gender-related differences in postural stability, with women exhibiting poorer balance compared to men, especially in eyes-closed conditions. This observation aligns with the findings of Riva et al., who reported sex-related differences in the stability index measured with and without visual control.^[13] Their study indicated that women had significantly poorer balance than men, supporting the notion that gender plays a crucial role in postural stability. Similarly, Skalska et al. and Stemplewski et al. also observed gender-related differences in stability indicators, further corroborating our results.^[14,15]

Kim et al. identified marked gender-related differences in seniors, with a notable deterioration in stability indices, such as increased CoP displacement velocity and overall reaction force, particularly in the ML direction.^[16] Although Kim et al.‘s^[16] study focused on an elderly population, the observed trend of poorer postural stability in women is consistent with our findings in a younger demographic, suggesting that gender disparities in balance may persist across different age groups. In contrast, Røgind et al. found no significant differences in postural stability between men and women aged 20–70 years.^[17] Older men showed less postural control than women in a study done by EspinozaAraneda et al.^[18] and Becker et al. Noted a significant difference among genders in static posturography with eyes-closed position.^[19]

This discrepancy may be attributed to differences in study populations, methodologies, or the parameters measured. Unlike Røgind et al.,^[17] our study employed computerized posturography to assess CoP displacement and sway distance, which might offer greater sensitivity in detecting subtle differences in postural stability between genders.

The findings suggest that prehypertension is associated with impaired postural stability, likely driven by underlying vascular and autonomic dysregulation. The increased sway distance and CoP displacement in prehypertensive males in comparison to controls, especially during baseline and right sway positions, may indicate reduced neuromuscular efficiency or altered proprioceptive control, which can be improved by neuromuscular training.^[20] On the other hand, prehypertensive females showed better control during eyes-open conditions compared to controls, suggesting a greater reliance on visual feedback as a compensatory mechanism, similar to the study done by Sung and Lee^[21] The observed gender differences in sway characteristics may reflect hormonal influences, structural variations in musculoskeletal systems, or differences in neuromuscular control strategies.

To the best of our knowledge, this is the first study to investigate postural instability in prehypertensive individuals using posturography. The study highlights the importance of early assessment of postural instability in prehypertensive individuals to prevent falls and associated complications. Posturography may serve as a valuable tool for detecting subclinical balance impairments in this population. The gender-specific differences underscore the need for tailored interventions, such as balance training programs emphasizing proprioceptive feedback for males and visual-motor integration exercises for females.

CONCLUSION

This study highlights the presence of postural instability in prehypertensive individuals, with notable gender-specific differences in balance control strategies. These findings emphasize the need for early detection and targeted interventions to mitigate balance impairments in prehypertensive populations.