Elsevier

Gait & Posture

Volume 60, February 2018, Pages 93-98
Gait & Posture

Full length article
An exploratory study examining factors underpinning postural instability in older adults with idiopathic neck pain

https://doi.org/10.1016/j.gaitpost.2017.11.016Get rights and content

Highlights

  • Older adults with idiopathic neck-pain demonstrate postural control deficits.

  • Deficits were not associated with physical-activity or other functional measures.

  • Results suggest a cervical spine cause of postural instability.

  • Future research in older adults with neck-pain is needed to identify mechanisms.

Abstract

There is limited understanding of potential mechanisms underpinning postural control deficits in people with neck pain. This study examined several characteristics that might explain impaired postural stability in a group of older adults with neck pain, and compared the results in this cohort with that of asymptomatic controls. In this cross-sectional study we compared physical activity, lower limb motor and sensory function, vestibular and visual function, falls efficacy and dizziness handicap in 84 older adults with (n = 35, age 69.6 ± 6.3) and without (n = 49, age 69.4 ± 4.7) idiopathic neck-pain. Additionally, dynamic balance was assessed using the dynamic gait index (DGI) and standard and wavelet analysis of static balance was computed after data capture. Physical activity levels, lower limb motor and sensory function, vestibular function and visual contrast sensitivity were not different between groups (p > 0.05). The neck-pain group demonstrated higher falls efficacy (p = 0.01), greater levels of dizziness handicap (p < 0.01), and higher CoP velocity measures in the moderate (1.56–6.25 Hz) and low (0.39–1.56Hz) frequency bandwidths. Our results suggest that neck-pain induced postural control deficits in older adults may not be associated with the physical activity levels, lower limb motor and sensory function, or vestibular and visual function. Inferring from wavelet analysis results, we speculated that sensory re-weighting may have occurred to compensate for the deficits in neck proprioception. Further research is warranted to determine neck specific mechanisms underpinning postural control dysfunction in neck pain.

Introduction

The cervical spine plays a critical role in sensorimotor function. Abundant cervical mechanoreceptors are important in integrating multisensory afferent input from the vestibular, visual, proprioceptive and central nervous systems (CNS). Individuals with NP have demonstrated sensorimotor disturbances, amongst which is the negative impact of NP on postural stability [1]. Of greater relevance is that older adults with NP have demonstrated poor dynamic postural stability placing them at a higher risk of falls [2]. The potential serious consequences of falls and the burden it imposes on public health [3] highlights the need for a comprehensive assessment to inform intervention for this population. Unfortunately, there is limited understanding of the fundamental mechanisms underlying NP related postural control deficits.

Because of the multi-sensory complex nature of postural control, it is important to explore whether other factors that might negatively impact on postural stability such as physical activity levels, lower limb sensory and motor function, and vestibular and visual function are different in older adults with and without NP. First, level of physical-activity has been negatively associated with onset of NP [4]. Lower levels of physical activity may be associated with poorer lower limb function such as reduced strength and flexibility [5] and consequently contribute to a decrease in postural stability in older adults with NP. In particular, big toe flexor strength [6], range-of-motion [7], light touch sensation [8] and ankle vibration sense [9] have been closely associated with postural stability in older adults. Second, a disruption in the dynamics between the intimately blended systems involved in sensorimotor control could be expected in older adults with neck pain (NP) [1]. This is not only due to diminished cervical proprioception but also a progressive decline in vestibular, visual and CNS function with ageing. Moreover, vestibular dysfunction and specific to vision, deficits in visual contrast sensitivity, have been associated with increased falls risk [10], [11], hence supporting the need to explore vestibular and visual function in older adults with NP.

As a preliminary step towards understanding mechanisms contributing to the development of postural control deficits in older adults with NP, in addition to clinically relevant balance measures and standard centre-of-pressure (CoP) measures, we will use analytical techniques of wavelet analysis. This technique decomposes the postural sway data into multiple independent frequency distinct bandwidths each hypothesised to identify with physiological significance of postural movements associated with muscular proprioception (1.56–6.25 Hz) [12], cerebellar (0.39–1.56 Hz) [12], vestibular (0.10–0.39 Hz) [13] and visual (<0.10 Hz) [14] systems.

Given the aforementioned background, this cross-sectional, exploratory study sought to understand the mechanisms underlying postural control deficits in older adults with and without NP by (i) comparing several features that might relate to impaired postural stability but not directly related to the cervical spine to determine their influence, including level of physical-activity, lower limb, vestibular and visual function, as well as (ii) employing the use of wavelet analysis of standing balance. We hypothesized differences between groups in the level of physical-activity, lower limb, vestibular and visual function and that wavelet analysis will demonstrate changes in frequency measures in the NP group.

Section snippets

Participants

This cross-sectional study involved 84 older adults with (n = 35, mean age 69.63 ± 6.3 years) and without (n = 49, mean age 69.5 ± 4.9) idiopathic NP. Participants aged 60 years and older were recruited using convenience sampling. Participants were given an option of location of testing; either at the research laboratory or at their residence. Participants were included in the NP group if they reported chronic NP for ≥3 months, neck disability index (NDI) of ≥10% (worst) and neck-related pain intensity

Statistical analysis

Descriptive analyses compared demographic and clinical characteristics between groups. Wilcoxon-Mann-Whitney or Welch-t tests compared continuous data and Fisher’s Exact, Chi square or linear by linear tests was used to test for differences in proportions. Regression analysis was performed to adjust for potential confounding variables (number of co-morbidities, BMI and fall history). All statistical calculations were performed using the STATA version 11.0 statistical software. Statistical

Results

Table 1 compares the demographic and clinical characteristics between groups. Physical-activity level, lower limb motor and sensory function, vestibular function and visual contrast sensitivity were similar in both groups (p > 0.05). Older adults with NP obtained poorer ABC (p = 0.01), lower DGI (p = 0.02) and higher DHI scores (p < 0.01). By design, older adults in the NP group showed significantly higher NDI compared to healthy controls (p < 0.001). Number of co-morbidities and BMI showed trends

Discussion

In this exploratory cross-sectional study, we compared various physical function tests and characteristics in older adults with and without NP. Contrary to our hypothesis, there were no significant differences in physical activity level, big toe strength, ankle range-of-motion, lower limb light touch and vibration sense, vestibular function and visual contrast sensitivity. In addition, the NP group had lower balance confidence (p = 0.01) and greater dizziness handicap (p < 0.01). As expected, older

Limitations

The results of this study must be interpreted in the light of our study limitations. Firstly, whilst the vestibular tests selected were clinically relevant, they may lack precision to detect subtle deficits in eye movement, and may increase the likelihood of under reporting vestibular impairments. Nevertheless, subjects with obvious vestibular pathology were excluded from the study. Secondly, given the way the DHI was structured, misinterpretation of questions to represent the neck problem and

Conclusion

In conclusion, the results of our study indicate that NP related postural control deficits in older adults may not be associated with the level of physical-activity, lower limb motor and sensory function, vestibular function and visual contrast sensitivity. The changes in postural activity are most likely due to NP and associated musculoskeletal impairments altering cervical proprioceptive input to the sensorimotor control system. Wavelet analysis suggests, sensory reweighting was in place to

Conflict of interest

The authors declare that they have no conflict of interest.

Acknowledgements

We are grateful to all participants who volunteered for this study.

June Quek received a PhD scholarship funded by Singapore General Hospital. Author RAC is supported by a National Health and Medical Research Council R.D. Wright Biomedical Fellowship (#1090415). This played no role in any aspect of the study. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

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