FROM: J Manipulative Physiol Ther. 2016 (May); (39) 4: 267–278 ~ FULL TEXT
Kelly R. Holt, BSc (Chiro), Heidi Haavik, BSc (Chiro), PhD,
Arier Chi Lun Lee, PhD, Bernadette Murphy, DC, PhD, C. Raina Elley, MBChB, PhD
Research Fellow, Centre for Chiropractic Research,
New Zealand College of Chiropractic,
Mt. Wellington, Auckland, New Zealand
OBJECTIVE: This study assessed whether 12 weeks of chiropractic care was effective in improving sensorimotor function associated with fall risk, compared with no intervention, in community-dwelling older adults living in Auckland, New Zealand.
METHODS: Sixty community-dwelling adults older than 65 years were enrolled in the study. Outcome measures were assessed at baseline, 4 weeks, and 12 weeks and included proprioception (ankle joint position sense), postural stability (static posturography), sensorimotor function (choice stepping reaction time), multisensory integration (sound-induced flash illusion), and health-related quality of life (SF-36).
RESULTS: Over 12 weeks, the chiropractic group improved compared with the control group in choice stepping reaction time (119 milliseconds; 95% confidence interval [CI], 26-212 milliseconds; P = .01) and sound-induced flash illusion (13.5%; 95% CI, 2.9%-24.0%; P = .01). Ankle joint position sense improved across the 4- and 12-week assessments (0.20°; 95% CI, 0.01°-0.39°; P = .049). Improvements were also seen between weeks 4 and 12 in the SF-36 physical component of quality of life (2.4; 95% CI, 0.04-4.8; P = .04) compared with control.
CONCLUSION: Sensorimotor function and multisensory integration associated with fall risk and the physical component of quality of life improved in older adults receiving chiropractic care compared with control. Future research is needed to investigate the mechanisms of action that contributed to the observed changes in this study and whether chiropractic care has an impact on actual falls risk in older adults.
KEYWORDS: Accidental Falls; Aged; Chiropractic; Feedback, Sensory; Postural Balance; Proprioception; Quality of Life
From the FULL TEXT Article
Falls are a significant cause of death, injury, and loss of quality of life in older adults.  Falls account for more than 80% of injury-related hospital admissions in people older than 65 years, and they are the leading cause of injury-related death in older adults. [2, 3] Approximately 30%-40% of community-dwelling older adults suffer from at least 1 fall per year. [4, 5] This incidence rate rises dramatically with increasing age or when a variety of risk factors are present.  Compared with healthy community-dwelling older adults, the risk of falling increases in those experiencing lower limb muscle weakness (odds ratio [OR] = 4.4), gait deficits (OR = 2.9), or balance deficits (OR = 2.9); in those with a recent history of falling (OR = 3.0); and in individuals older than 80 years compared with those younger than 80 years (OR = 1.7).  Many of these risk factors are influenced by the general deterioration in the function of sensorimotor systems that regularly occur with normal aging.  Falls are often multifactorial in their origin, with no specific single cause being identified.  The most common causes of falls reported in the literature are accident and environment-related causes (31%), followed by gait and balance disorders (17%), and dizziness and vertigo (13%). 
The role that chiropractors and other manual therapists may play in preventing falls in their patients is currently unclear. To date, few controlled trials have investigated how chiropractors and other manual therapists may influence falls risk.  There is however a growing body of basic science evidence that suggests that chiropractic care may influence sensory and motor systems that potentially have an impact on some of the neuromuscular risk factors associated with falling.  The extent of this potential impact, if any, is currently unknown. This study aimed to investigate this potential relationship by assessing whether usual chiropractic care had an impact on measures of sensorimotor function associated with falls risk in older adults over a 12-week period.
Summary of Main Findings
The key findings in this study were that improvements were observed in the chiropractic group in joint position sense error, sound-induced flash illusion, and CSRT compared with the control group. Between-group differences were also observed in the physical component of health-related quality of life, with the chiropractic group improving compared with the control group between the 4- and 12-week assessments.
Compared With the Literature
It is difficult to make comparisons between the results of different intervention trials that investigate joint position sense because of the heterogeneity of outcome measures that are used in its assessment. Improvements in joint position sense error of up to 6° have been reported following a variety of interventions in clinical populations. [10, 19, 20] However, the baseline joint position sense error observed in this study was only 1.83° (SD = 0.57°), meaning that a 6° improvement would be impossible to achieve. The previous study that is most relevant to the present study reported a significant 0.28° (SD = 0.12°) overall improvement in the absolute constant elbow joint position sense error in a subclinical neck pain population immediately after cervical chiropractic adjustments.  Together, these results suggest that chiropractic care may have a beneficial effect on proprioception, but it is yet to be determined whether this effect is clinically meaningful.
The interesting finding in the CSRT assessment was that the 4-week assessment showed little change between groups, with the chiropractic group experiencing a very small, nonsignificant improvement compared with control (9 milliseconds; P = .8; 95%, CI ?56 to 74). This lack of improvement at 4 weeks may be important, as it suggests that longer-term chiropractic care may be required to have a significant effect on some physiologically important aspects of sensorimotor function.
The baseline CSRT values observed in this study (combined mean = 1171 milliseconds, SD = 200 milliseconds) were consistent with those reported in similar populations elsewhere in the literature (993 milliseconds, SD = 197 milliseconds to 1264 milliseconds, SD = 268 milliseconds). [11, 15, 21, 22] The between-group CSRT improvement that resulted following 12 weeks of chiropractic care (119 milliseconds) is consistent with, or exceeds, the reported results in other intervention trials involving CSRT. [23-25]
No significant differences were observed between groups in postural stability, suggesting that chiropractic care did not lead to a significant improvement in postural stability in older adults in this study. However, with such a large percentage of older adults failing the test, it is possible that the test is simply too challenging for this population. It may also be insensitive to small but significant improvements in postural stability that occur following an intervention, if they exist. A systematic review concluded that a limited amount of research has been published that supports a role for manual therapy in improving postural stability and balance.  The findings of this study do not add any further support to this potential role.
The chiropractic group became less susceptible to the sound-induced flash illusion compared with the control group in the present study. The sound-induced flash illusion is considered to be resistant to change, with only 1 study published that has reported an improvement in illusion performance following an intervention.  This study reported a similar magnitude of change in susceptibility to the illusion as the present study, following feedback training with the added motivation of a monetary reward based on the participants’ performance accuracy. However, the authors concluded that the perception of the illusion did not change following feedback training. Instead, participants described subtle phenomenological differences between percepts induced by the illusory and nonillusory conditions that helped them to discriminate between the 2 conditions. The findings reported by Sturnieks et al  indicate that feedback training did not change the perception of the illusion, which suggests that the current study is the first to report an improvement in the perception of the sound-induced flash illusion following an intervention. This is also the first study to report improvements in multisensory integration in a group receiving chiropractic care.
The present study is one of the few randomized controlled trials to report the effect of chiropractic care on health-related quality of life in an older adult population. A small number of controlled trials have reported similar findings to those reported here in different study populations. [26-28] The small sample size and relatively short duration of the study, combined with uncertainty surrounding the results, suggest that caution should be used when interpreting the SF-36 results. The results do however suggest that chiropractic care had a positive influence on the SF-36 PCS scores, which warrants further investigation.
A number of possible mechanisms of action may have contributed to the changes observed in this study. Firstly, chiropractic care may influence neuroplastic processes within the central nervous system through altered afferent input due to improved/altered spinal function. Secondly, chiropractic care may have an influence on pain that, in turn, affects cognition, particularly with respect to attentional focus, and physical function. Thirdly, chiropractic care may have resulted in changes in muscle strength or muscle activation patterns. Lastly, placebo effects may have been involved.
As a pragmatic effectiveness trial, with a “black-box” intervention, no firm conclusions can be made regarding which, if any, of these potential mechanisms made a significant contribution to the results that were observed. Future research is required to help gain a greater understanding of the mechanisms of action that may have been associated with the results of this study.
Strengths and Limitations
This pragmatic randomized controlled trial limited the number of exclusion criteria that were used and provided participating chiropractors with flexibility when it came to making case management decisions. A “usual care” control group was also used, and blinding of chiropractors or participants was not attempted because of the challenges associated with blinding in a trial investigating a manual therapeutic intervention.  Convenience sampling was used to recruit chiropractic practices to assist with the study and volunteers to participate in the study, which may have resulted in selection bias. Together, these aspects of the study design mean that few conclusions can be made about mechanisms of action that may have been involved. It is also possible that placebo effects or performance bias associated with the attention received by the chiropractic group had an impact on the study results. Multiple outcome measures were analyzed without making adjustments to P values. Adjustments were not made to avoid errors of interpretation. This approach has been recommended as appropriate, particularly when exploring new areas of research.  Even so, using multiple comparisons means that the amplitude of effect size should be regarded as tentative until the results are corroborated by further study. 
Another potential limitation of the study is that the outcome measures used in this trial may have lacked sensitivity to change or clinical significance. Issues with sensitivity to change, responsiveness, and floor and ceiling effects have been identified in relation to the postural stability measures used in the present study. A number of alternative methods of examining postural stability were reviewed, but there is currently little agreement between authors concerning the most appropriate method for documenting improvements in postural stability in relatively healthy community-dwelling older adults following an intervention. [23, 31]
The 12-week follow-up period used in this study means that this is one of the few trials that has investigated the effect of chiropractic care on sensorimotor function that involved more than a single intervention session.  This is a strength of the study. However, a number of the outcomes assessed improved significantly between the 4- and 12-week assessments. It is unclear if improvements would have continued beyond 12 weeks of care.
Implications of the Findings
This study found that joint position sense error, CSRT, and the sound-induced flash illusion improved in the older adults receiving 12 weeks of chiropractic care. These outcome measures are associated with an individual’s risk of falling, [12, 11, 32] which opens up the possibility that chiropractic care may play a role in preventing falls in older adults. However, the clinical significance of the changes observed is somewhat debatable and should be considered when interpreting these findings. [7, 11, 12, 32] It should also be acknowledged that, until the results of the study are corroborated and further research is conducted that investigates the effect of chiropractic care on the rate of falls in older adults, the implications of the study from a policy or public health perspective remain limited.
Further research is required to investigate which mechanisms were involved in the improvements observed in this trial. Further research should also attempt to investigate whether the improvements in sensorimotor function and multisensory integration observed in the chiropractic group also reflect a reduction in overall fall risk.
The results of this trial indicated that aspects of sensorimotor integration and multisensory integration associated with fall risk improved in a group of community-dwelling older adults receiving chiropractic care. The chiropractic group also displayed small, statistically significant improvements in health-related quality of life related to physical health when compared with a “usual care” control. These results support previous research which suggests that chiropractic care may alter somatosensory processing and sensorimotor integration.  However, limitations of the trial design mean that no firm conclusions can be made about potential mechanisms of action associated with the improvements that were observed.
This study builds on previous research and makes a significant contribution to the literature, as the bulk of this previous research comes from single–intervention session basic science trials in relatively healthy younger people and, often, the changes reported do not indicate whether they reflect clinically relevant improvements or not.  This is the first trial to report improvements in multisensory integration in a group receiving chiropractic care. The chiropractic intervention was well tolerated by the older adults in this trial with no serious adverse events being reported that were due to the chiropractic intervention.
Sensorimotor function and multisensory integration associated with falls risk improved in older adults receiving chiropractic care compared with control participants over 12 weeks.
The physical component of quality of life improved in older adults receiving chiropractic care compared with control participants over 12 weeks.
Funding Sources and Potential Conflicts of Interest
This study was funded by Australian Spinal Research Foundation LG2008-4/LG2010-3 and the Hamblin Chiropractic Research Fund Trust. No conflicts of interest were reported for this study.
Concept development (provided idea for the research): K.H., H.H., C.R.E., B.M.
Design (planned the methods to generate the results): K.H., H.H., C.R.E., B.M., A.C.L.L.
Supervision (provided oversight, responsible for organization and implementation, writing of the manuscript): C.R.E., H.H., B.M.
Data collection/processing (responsible for experiments, patient management, organization, or reporting data): K.H.
Analysis/interpretation (responsible for statistical analysis, evaluation, and presentation of the results): K.H., A.C.L.L.
Literature search (performed the literature search): K.H.
Writing (responsible for writing a substantive part of the manuscript): K.H.
Critical review (revised manuscript for intellectual content; this does not relate to spelling and grammar checking): H.H., C.R.E., B.M., A.C.L.L.
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