Undisturbed upright stance control in the elderly: Part 2. Postural-control impairments of elderly fallers

The Impact of Obstructive Sleep Apnea on Balance, Gait, and Falls Risk: A Narrative Review of the Literature

Falls-related hospitalization and injury rates are steadily increasing globally due to a growth in the aging population, and the associated health problems that increase risk of falls. One such associated health problem is sleep disturbances and disorders. Recent cohort studies have shown that subjectively reported poor quality sleep is associated with an increased risk of falls. Obstructive sleep apnea (OSA) is a common sleep disorder characterized by the repetitive reductions, or cessation, of airflow. Some studies have shown that OSA impairs posture/balance and gait with nocturnal hypoxemia the likely main cause. Emerging evidence suggests that treating OSA by continuous positive airway pressure (CPAP) can improve gait, but no studies to date have examined the effect of CPAP on posture/balance. The overall control of balance relies on a complex interaction between several physiological functions including vestibular, muscle, visual, and cognitive functions. We postulate that OSA impacts balance by affecting these different systems to various degrees, with the nocturnal hypoxic burden likely playing an important role. Importantly, these impairments in balance/posture and possible falls risk may be alleviated by OSA treatment. Larger mechanistic studies are needed to properly elucidate how OSA affects falls risk and future large-scale randomized control trials are needed to determine the effectiveness of OSA treatment in reducing the risk of falls.

Novel methodology for assessing total recovery time in response to unexpected perturbations while walking

Walking stability is achieved by adjusting the medio-lateral and anterior-posterior dimensions of the base of support (step length and step width, respectively) to contain an extrapolated center of mass. We aimed to calculate total recovery time after different types of perturbations during walking, and use it to compare young and older adults following different types of perturbations. Walking trials were performed in 12 young (age 26.92 ± 3.40 years) and 12 older (age 66.83 ± 1.60 years) adults. Perturbations were introduced at different phases of the gait cycle, on both legs and in anterior-posterior or medio-lateral directions, in random order. A novel algorithm was developed to determine total recovery time values for regaining stable step length and step width parameters following the different perturbations, and compared between the two participant groups under low and high cognitive load conditions, using principal component analysis (PCA). We analyzed 829 perturbations each for step length and step width. The algorithm successfully estimated total recovery time in 91.07% of the runs. PCA and statistical comparisons showed significant differences in step length and step width recovery times between anterior-posterior and medio-lateral perturbations, but no age-related differences. Initial analyses demonstrated the feasibility of comparisons based on total recovery time calculated using our algorithm.

Center of pressure characteristics from quiet standing measures to predict the risk of falling in older adults: a protocol for a systematic review and meta-analysis

BACKGROUND

Falling is the most common accident of daily living and the second most prevalent cause of accidental death in the world. The complex nature of risk factors associated with falling makes those at risk amongst the elderly population difficult to identify. Commonly used clinical tests have limitations when it comes to reliably detecting the risk of falling, but existing laboratory tests, such as force platform measurements, represent one method of overcoming this lack of a test. Despite their widespread use, however, Center of Pressure (COP) signal analysis techniques vary and there is currently no consensus on which features should be used diagnostically. Our objective is to identify, through a systematic review and meta-analysis, the COP characteristics of older adults (≥ 60 years old) during quiet bipedal stance which will allow fallers to be distinguished from non-fallers.

METHODS

The systematic review will include both prospective and retrospective articles. Five databases will be searched: PubMed, Cochrane CENTRAL, EMBASE, and ScienceDirect. In addition, a search of gray literature will be performed using Google Scholar and ClinicalTrials.gov. Searches will be circumscribed to include only older adults (aged over 60 years) who underwent a bipedal quiet standing measure of their balance and for whom the number of falls was reported. Two authors will independently assess the risk of bias for each included article using a 26-item checklist. Funnel plots will be drawn to attest of possible publication biases for each COP parameters. The results will be synthesized descriptively and a meta-analysis will be undertaken. When trial methodological heterogeneity is too great for pooling of the data into a meta-analysis, evidence strength will be evaluated using best evidence analysis.

DISCUSSION

Despite the numerous advantages of posturography, the diversity of studies exploring balance in older fallers has led to uncertainty regarding the method's ability to reliably identify fall-prone older adults. It is expected that the findings from this systematic review will help clinicians use bipedal quiet standing measures as a diagnostic test and allow researchers to explore COP characteristics to create better models for fall prevention care.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42018098671.

Effects of attentional focus and age on suprapostural task performance and postural control

PURPOSE

Suprapostural task performance (manual tracking) and postural control (sway and frequency) were examined as a function of attentional focus, age, and tracking difficulty. Given the performance benefits often found under external focus conditions, it was hypothesized that external focus instructions would promote superior tracking and reduced postural sway for both age groups, most notably as a function of tracking difficulty.

METHOD

Postural sway, frequency of postural adjustments, and tracking accuracy under two levels of task difficulty were assessed for younger (M(age) = 20.98 years) and older (M(age) = 70.80 years) participants while they manually tracked a pursuit-rotor target. Participants received instructions to focus on either their actions (internal focus) or the effect of their actions (external focus).

RESULTS

Analyses revealed a beneficial effect of an external focus on suprapostural performance on the less-difficult (0.5 Hz) tracking task, and this performance was associated with a modest improvement in medial-lateral postural sway.

CONCLUSION

The findings offer limited support for external focus-of-attention benefits under a mildly challenging tracking task. While older adults tend to adopt a conservative postural control strategy regardless of tracking task difficulty, external focus instructions on a suprapostural task promoted a modest, beneficial shift in postural control.

Episodes of falling among elderly people: a systematic review and meta-analysis of social and demographic pre-disposing characteristics

CONTEXT

The multifactorial nature of falls among elderly people is well-known. Identifying the social-demographic characteristics of elderly people who fall would enable us to define the typical profile of the elderly who are at risk of falling.

OBJECTIVE

We aimed to isolate studies in which the social-demographic risk factors for falls among the elderly have been evaluated and to carry out a meta-analysis by combining the results of all of these selected studies.

METHOD

We did a systematic literature review using the key words "accidental fall / numerical data" and "risk factors." Inclusion criteria entailed the selection of articles with the following characteristics: population of subjects aged 60 years or over, falls that took place in everyday life, and social-demographic risk factors for falls.

RESULTS

3,747 indexed articles published between 1981 and 2007 were identified, and 177 studies with available data were included, of which 129 had data on social-demographic risk factors for falls. Difficulties in activities of daily living (ADL) or in instrumental activities of daily living (IADL) double the risk of falling: The OR and 95% Cl were 2.26 (2.09, 2.45) for disturbance ADL and 2.10 (1.68, 2.64) for IADL. The OR and 95% Cl for Caucasians were 1.68 (0.98 - 2.88) and 0.64 (0.51 - 0.80) for Hispanics. In the subgroup of patients older than eighty, being married protected people from falling with an OR and 95% Cl =0.68 (0.53 - 0.87).

CONCLUSION

Defining factors that create a risk of falling and protect elderly people from falls using social-demographic characteristics lets us focus on an "at risk" population for which a specific program could be developed.

Can tactile plantar stimulation improve postural control of persons with superficial plantar sensory deficit?

BACKGROUND AND AIMS

Complex interactions between visual, vestibular and somatosensory information and the cerebellar system are involved in the maintenance of upright posture. Previous studies have shown that normal aging and pathologies may lead to deterioration of the control of upright standing posture.

METHODS

In order to investigate postural control during quiet standing in the elderly, the center of pressure (CoP) was analysed on two force platforms in three different groups. The first group was composed of 13 healthy older adults (O), the second consisted of 9 older adults with plantar sole deficit (OD), and the third (control) group was composed of 8 young healthy subjects (Y). All subjects were tested with eyes closed, before and after tactile plantar stimulation lasting ten minutes. Center of pressure displacements were analyzed in terms of sway area, mean velocity, and mean root mean square (RMS) along both mediolateral and antero-posterior axes.

RESULTS

Results showed that, before tactile plantar stimulation, the sway area and mean RMS were greater in O and OD subjects compared with Y ones. After tactile plantar stimulation, a decrease in the mean RMS was observed in OD subjects, this effect being significant only for the medio-lateral axis.

CONCLUSIONS

These results suggest that application of tactile plantar stimulation may compensate a loss of superficial plantar sensitivity.

Effets immédiats de séances de rééducation des membres inférieurs par balneotherapie sur le contrôle de l'équilibre

OBJECTIVE

The aim of this study was to compare the immediate effects of standard physiotherapy (S) and balneotherapy (B) on the postural capacity of subjects with lower-limb injuries.

METHODS

The postural sway of 12 voluntary subjects was evaluated before (REF1 and REF2) and after two different physiotherapy sessions performed in the swimming pool (B) or under (S). The centre of pressure (CP) trajectory was recorded by use of a force platform. CP displacements in the mediolateral and anteroposterior axes were then separated into two elementary superimposed components: the horizontal motion of the centre of gravity (CG) and the difference between the CP and the vertical projection of the CG (CP-CG). The amplitude of the latter component (CP-CG) is thought to express neuromuscular activity. All trajectories were then analysed in terms of classical and frequency parameters.

RESULTS

Postural sway did not differ before and after the physiotherapy sessions. Following both sessions, the mean CG velocity decreased significantly (P<0.5). The area of CP-CG trajectory was diminished solely by the aquatic exercise (P<0.5) and was associated with decreased amplitude of motion along the anteroposterior axis (P<0.05), which suggests decreased neuromuscular activity to maintain posture.

CONCLUSION

Interestingly, decreased motion was observed along the anteroposterior axis, which corresponds to ankle movements. Exercising lower-limb muscles under water could reinforce proprioceptive input, resulting in a better postural control.