© Borgis - New Medicine 1/2004, s. 12-16
Anna Skalska1, Tomasz Ocetkiewicz1, Marek Żak2, Tomasz Grodzicki1
Influence of Age on Postural Control Parameters Measured with a Balance Platform
1Department of Internal Medicine and Gerontology, Jagiellonian University School of Medicine, Kraków, Poland
Head of Department: Prof. Tomasz Grodzicki MD, PhD
2Chair of Clinical Rehabilitation, Academy of Physical Education, Kraków, Poland
Head: Prof. Krzysztof Spodaryk MD, PhD
Summary
Aim. Increased body sway in an upright position, represented by the displacement of the centre of feet pressure, is a result of impairment of the postural control system.
The aim of the study was to evaluate the influence of age on postural control measurements, measured with a balance platform.
Method. 97 persons were divided into 3 groups: I – 34 volunteers, mean age 23.18±1.99 years, II: 17 persons, mean age 51.06±4.76 yrs., III: 46 persons, mean age 73.26±8.36 yrs. During quiet standing on the balance platform, the length of path of the centre of pressure, its mean velocity, and mean displacement in the lateral and antero-posterior directions were measured.
Results. All parameters of body sway were significantly lower in the youngest group, when compared with the middle-aged (p<0.005) and elderly groups (p<0.0001). The results in groups II and III did not differ, except that the average lateral deflection during an eyes-closed test was significantly higher in the oldest group, p<0.02. All measurements correlated significantly with age, p<0.0001.
Conclusion:
1. Postural sway increases with age, which is represented by an extension of the length of path of the centre of feet pressure, and by an increase in its lateral and antero-posterior displacements.
2. Impairment of the postural control mechanism appeared at about 40 years of age, which can be due to both ageing and comorbidity.
3. The average lateral displacement of the centre of feet pressure seems to be the best indicator of the influence of age on the postural control system.
INTRODUCTION
Balance is the ability to maintain the body´s centre of gravity over its base of support (1). It depends on the efficiency of the balance control system, based on central processing of visual, vestibular and somatosensory inputs, and proper neuromuscular response (2, 3, 4, 5, 6, 7). The function of this complex feedback system deteriorates with age and increased comorbidity (3, 5, 8, 9, 10) This results in increased body sway during stable standing (3, 5, 11, 12, 13, 14), and is a significant independent predictor of the risk of falling (5, 15, 16).
To estimate the sway, measurement of the movement of the centre of foot pressure (CFP) a computerized balance platform is used (3, 5, 6, 10, 11, 12).
The aim of this study was to evaluate the influence of age on postural control, measured using the parameters of the centre of foot pressure, using a computerized balance platform.
MATERIAL AND METHOD
Subjects
Ninety-seven participants were divided into 3 age groups. The first group consisted of 34 healthy volunteers (24 women and 10 men) aged between 17 and 28 years, mean age – 23.18±1.99. The second group included 17 persons, 8 women and 9 men, aged 41 to 60 yrs., mean age 51.06±4.76. In the third group were 46 people, 30 women and 16 men, aged 61-95, mean age 73.26±8.36. Groups II and III included hospital patients. The main causes of their admission to hospital were pneumonia or exacerbation of coronary heart disease. Most of them also suffered from arterial hypertension, congestive heart failure, diabetes mellitus, chronic obstructive pulmonary disease, or arthritis, but the examination was performed during a stable period in their illness. All the study participants were able to walk on their own and were able to maintain an upright position.
Procedure
The balance test was performed with an Italian Cosmogamma balance platform. This comprises: a dynamometric balance platform, and an IBM AT PC computer with an appropriate program for diagnostic tests. After a 5-minute rest in a sitting position, the examined patient was placed on the platform in the upright position, with the upper extremities parallel to the body. Bare feet were aligned with the centre line of the platform, with a distance of 7 cm between the right and left first metatarsal bones, and the lateral ankles on a line 14 cm from the rear edge of the platform.
Every person participated in two tests, one with the eyes open, and the second with eyes closed. To perform the analysis, we used 4 parameters:
1.The length of the CFP path, meaning the distance of movement of the centre of feet pressure – DCFP (mm) (Figure 1),
Fig. 1. Examples of the path length for the CFP: a/ short but displaced in left and posterior direction; b/ long.
2.The mean velocity of the CFP – VCFP (mm/s),
3.The mean displacement of the CFP in the lateral plane – MLCFP(mm); (Figure 2),
Fig. 2. The examples of normal (a) and increased (b) CFP measurements in lateral and antero-posterior direction represented by higher sticks.
4.The mean displacement of the CFP in the antero-posterior plane – APCFP (mm).
Statistical analysis
The statistical analysis was performed with the STATISTICA 6.0 PL program. Descriptive statistics were used to identify mean values and standard deviations. Because the data were not normally distributed, we used the Mann – Whitney test for unconnected pairs to compare the data. To establish the relationship between age and postural stability parameters, the Spearman correlation coefficient was used.
RESULTS
Because a comparison of the results obtained in men and women did not show any differences, in further analysis both genders were considered together in each group. The mean values and standard deviations of parameters of CFP movement, obtained in each group in the eyes-open test are shown in Table 1, and in the eyes-closed test in Table 2.
Table 1. Mean values and standard deviations of the CFP movement parameters obtained in the eyes-open condition for each group:
| Parameter | Group I N = 34 | Group II N = 17 | Group III N = 46 | P gr. II vs. III |
| Age (years) | 23.18 ? 1.99 | 51.06 ? 4.76 | 73.26 ? 8.36 | |
| DCFP (mm) | 176.4 ? 77.6 | 296.9 ? 166.8* | 281.4 ? 93.7¨ | 0.79 |
| VCFP (mm/s) | 5.9 ? 2.5 | 9.9 ? 5.6* | 9.4 ? 3.3¨ | 0.85 |
| MLCFP (mm) | 1.8 ? 0.99 | 3.2 ? 1.1* | 3.6 ? 1.4¨ | 0.38 |
| APCFP (mm) | 2.2 ? 0.89 | 3.2 ? 1.3* | 3.3 ? 1.2¨ | 0.5 |
*p<0.0001 for comparison group I vs. II
?p<0.0001 for comparison group I vs. III
Table 2. Mean values and standard deviations of the CFP movement parameters obtained in the eyes-closed condition for each group:
| Parameter | Group I N = 34 | Group II N = 17 | Group III N = 46 |
| Age (years) | 23.18 ? 1.99 | 51.06 ? 4.76 | 73.26 ? 8.36 |
| DCFP (mm) | 180.5 ? 64.4 | 332.5 ? 233.1* | 355.0 ? 133.7¨ |
| VCFP (mm/s) | 6.0 ? 2.2 | 11.1 ? 7.7* | 11.7 ? 4.5¨ |
| MLCFP (mm) | 1.7 ? 0.6 | 3.4 ? 1.5** | 4.2 ?1.4¨# |
| APCFP (mm) | 2.3 ? 0,9 | 4.1 ? 3.0** | 3.4 ? 1.2¨ |
*p<0.005 for comparison group I vs. II
**p<0.0001 group I vs. II
?p<0.0001 group I vs. III
#p<0.002 group II vs. III
All the sway parameters were significantly lower in the younger group I, in comparison with group II (middle-age) and group III (elderly). Comparison of the results in groups II and III did not show differences, with the exception of MLCFP under the eyes-closed condition, which differs significantly (p <0.002).
All the CFP parameters were significantly dependent on age (Table 3).
Table 3. The correlation between the parameters of CFP movement and the age of the subjects, in the whole group of examined persons:
| Investigated correlation | R coefficient |
| Eyes-open test | Age - DCFP | 0.49* |
| Age - VCFP | 0.46* |
| Age - MLCFP | 0.59* |
| Age - APCFP | 0.5* |
| Eyes-closed test | Age - DCFP | 0.57* |
| Age - VCFP | 0.55* |
| Age - MLCFP | 0.75* |
| Age - APCFP | 0.38* |
*p<0.0005
The dependence on age of the mean lateral displacement in the eyes-closed test was also significant in all subjects aged more than 40 (r = 0.38, p = 0.002) (Figure 3).
Fig. 3. The correlation between age and average lateral displacement of the centre of foot pressure during standing with eyes closed, in subjects over 40.
Our results confirm that there is better balance control in young healthy people. All CFP movement parameters were significantly lower in the group of young healthy volunteers compared with the older people, both in the eyes-open and eyes-closed tests. Also, all the parameters independent on visual control were significantly correlated with age. All systems involved in balance control deteriorate with age. Among the reasons for deterioration, ageing and concomitant diseases are of great importance (3, 5). The complicated balance system has many ways to compensate for failure of one component (5, 17), but when more components fail, maintenance of a stable posture becomes more difficult, and the body sway increases.
Age changes in the peripheral and central nervous system result in slower nerve conduction velocities and a delayed reaction time. In addition, the ability to integrate numerous stimuli worsens. Age changes in the eye can also contribute to postural instability (3). It is estimated that visual control reduces swaying by to 50% (6), and also improves a subjective feeling of stability (18). Ageing is also connected with dysfunction of the vestibular system, diminished perceptual responses, muscle atrophy, and loss of muscle strength (3, 19). Although our results are consistent with reviews done by other researchers (20), not all authors found differences in sway parameters, comparing younger and older groups using a static platform. Similar values in younger and older groups in balance tests performed under the eyes-open condition were obtained by Schiepatti et al., but he found significantly different sway parameters between old and young groups in the eyes-closed test. He also found that swaying increased in a group of patients suffering from neuropathies and Parkinson´s disease (18). Further Condron et al. measured the amplitude of lateral sway on a static platform, and did not find any difference between young and elderly healthy groups. But, they found a significant difference in this parameter when comparing healthy young with elderly people at risk from falls (11). Although elderly group was classified as healthy, their physical functioning was limited, and some of the subjects had to use a walking stick. A possible explanation for the apparent discrepancies between our and other researchers´ results is the fact that our groups of middle-aged and elderly people were recruited from hospitalized persons, although all of them were examined during a stable period of their illness. Chronic diseases may result in decreased cerebral perfusion, fatigue, confusion, or dyspnoea, which in turn may result in instability or dizziness. Also, drugs which are used in these diseases may contribute to instability for various reasons, including postural hypotension, fatigue, dehydration, electrolyte disturbance, and disruption of functioning in the central nervous system (19). In both Schiepatti et al. and in Condron et al. studies, persons who were ill or had limited physical function had significantly worse values of postural control parameters in comparison with young healthy subjects, which makes these results closer to ours (11, 18).
The lack of differences in most of the parameters of sway between the middle-aged and the elderly group suggests that coexistence of ageing and chronic diseases can reduce the efficiency of the balance control system earlier. It seems that critical impairment occurs at about 40 years of age. Observation of significantly increased sways after 40 years of age has already been reported (13, 21).
The presence of a relationship between mean lateral displacement of the CFP and age over 40 (despite an absence of differences between middle-aged and elderly groups) suggests that the influence of age on the postural control mechanism is mostly expressed in the frontal plane. Maki et al., and Bergland et al demonstrated that the amplitude of lateral movement of the CFP is an independent predictor of falls. This suggests that improvement of balance control in that particular plane can help to prevent falls.
CONCLUSION
1.Postural sway increases with age, which is represented by an extension of the length of the CFP path, and by increase of its lateral and antero-posterior displacement.
2.Impairment of the postural control mechanism occurred at about 40 years of age, which can be due to both ageing and comorbidity.
3.The average lateral displacement of the centre of feet pressure seems to be the best indicator of the influence of age on the postural control system.
Piśmiennictwo
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