Effects of Low Back Pain on Motor Performance in Older People: A Systematic Review and Meta-analysis

Background: Research suggests that individuals with low back pain (LBP) may have poorer motor control compared to their healthy counterparts; however, the sample population of almost 90% of related articles are young and middle-aged people. There is still a lack of a systematic review about the motor performance of elderly people with low back pain. This study aimed to conduct a systematic review and meta-analysis to understand the effects of LBP on motor performance in eldly people. Methods: This systematic review and meta-analysis included a comprehensive search of PubMed, Embase, and Cochrane Library databases for full-text articles published before January 2020. Two independent reviewers screened the relevant articles, and disagreements were resolved by athird reviewer. Results: Thirteen case-control studies comparing motor performance parameters between LBP and healthy subjects and four randomised controlled studies on physical therapy to improve the motor performance of elderly people with LBP were included. The experimental group (LBP group) was associated with signicantly larger area of centre of pressure movement (P < 0.001),higher velocity of centre of pressure sway in the anteroposterior and mediolateral directions (P= 0.01 and P = 0.02, respectively), longer path length in the anteroposterior direction (P < 0.001), slower walking speed (P = 0.05), and longer timed up and go test time (P = 0.004) than the control group. Conclusion: The results show that motor performance is impaired in elderly people with LBP. We should pay more attention to the balance control of elderly people with LBP.

Balance dysfunction in the aging population is based on knowledge of the normal aging processes, loss of sensory elements, and loss of musculoskeletal function [15] . Motor performance declines with age due to biological changes (e.g. mobility, physical inactivity), which in turn can lead to falls [16,17] . LBP is a known independent risk factor for repeated falls in older women [18] .
What is the effect of aging combined with LBP? Here we aimed to conduct a systematic review and metaanalysis to understand the effects of low back pain in elderly people with the ultimate goal of providing better clinical research and treatment guidelines.

Literature search strategy
This review was conducted according to the guidelines outlined in the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) statement [19] . Two independent investigators screened the titles and abstracts of the retrieved studies to identify those appropriate for full-text review. Subsequently, they independently assessed the papers in full to identify thestudies to be included in the analysis. Any disagreements about inclusion were resolved by discussion and through arbitration by a third reviewer.

Selection criteria
The inclusion criteria were as follows: 1. Participants included elderly people with a mean age of ≥60 years who had chronic LBP 2. Randomised controlled trials (RCTs) or case-control studies 3. Intervention consisted of conservative treatment (e.g. exercise and manual therapy such as massage) 4. Outcome measures included a measure of motor performance (e.g. balance and gait) that uses highly valid and reliable methods (such as static and dynamic petrographic analyses, centre of pressure [COP] analysis, centre of gravity analysis, and timed up and go test) to re ect their dynamic or static balance or motor performance 5. All articles had to have been available in the English language and published in full within a peerreviewed journal The following exclusion criteria were used: The search strategy is displayed in Figure 1. Two reviewers independently screened all abstracts of articles potentially meeting the inclusion criteria; the full texts of those articles were subsequently reviewed. The reviewers then met with the entire review team and resolved any disagreements via consensus. The initial search yielded 2291 publications. Following the title andabstract screening, 35 full-text articles were retrieved. The full-text review was completed to determine nal inclusion; 17 articles (13 case-control studies [20][21][22][23][24][25][26][27][28][29][30][31][32] , four RCTs [33][34][35][36] ) met the inclusion criteria. Only the 13 case-control studies were included in the meta-analysis.
Quality assessment RCT study quality was assessed using the PEDro methodological quality scale [37] , an evaluation tool with 11 tests and a total score of 11 points. The higher the score, the higher the research design quality. Quality was also assessed using the Cross-sectional/Prevalence Study Quality (AHRQ) [38] , which also has 11tests and a total score of 11 points [38] . The two researchers independently evaluated all studies that met the inclusion criteria; there were no signi cant intergroup differences.

Data Extraction
For each study that met the full inclusion and exclusion criteria, information regarding study design and outcome measures (e.g. COP, one-leg stance time) were extracted. The major results of each study were brie y summarised; all focused on balance function. The meta-analysis data were collected from the results sections and tables of the manuscripts. The graphs were also used to extrapolate the data. If it was impossible to collect the data from the manuscript, the corresponding author of the manuscript was contacted twice before the study was excluded.

Results
Search Findings Figure 1 illustrates the search ndings. Using the search terms, 1059 articles were detected in PubMed, 112 in EMBASE, and 1120 in the Cochrane Library. Of these 2291 articles, the rst reviewer retained 107 articles after the rst screening round and the second reviewer retained 79. Altogether, the remaining articles were screened a second time using the ve criteria; articles were assessed and retained based on their quality. Table 1 details the characteristics of the 13 included case-control studies of the effects of LBP on motor performance in elderly people. We used the AHRQ to assess study quality (Table 2). Table 3 details the characteristics of the included studies of the effects of physical therapy on motor performance in elderly people; four articles met the criteria requirement, but the main outcome was not about the motor performance or balance function. Four RCTs studies were assessed using the PEDro methodological quality scale.
After a detailed screening, we ultimately used the data of case-control studies to conduct the metaanalysis.  [20] Case-contro l 60. 5 [29] Case-cont rol  ) [20] Y Brum agne (2004 ) [22]   therefore, we extracted data from three articles. No significant difference was noted between the two groups ( Figure 2). A total of four studies used COP parameters to measure motor performance, which was recognised as a valid and reliable method. The larger the COP area, the worse the balance. Older adults with LBP had a longer path length and larger area of COP movements than older adults without LBP (Figure 3).
COP anteroposterior velocity, mediolateral velocity, and anteroposterior range A total of four studies used COP sway velocity parameters to measure motor control (Figures 4 and 5), while two studies used COP sway range parameters to measure motor control( Figure 6). The higher the COP sway velocity, the longer path length in the anteroposterior direction and the more unstable the patient. The three parameters also demonstrated that older adults with LBP would have higher velocity and larger COP movements than older adults without LBP.

Gait (speed) and TUG
A total of three studies use the gait test ( Figure 7) and two studies use the TUG (Figure 8) to compare the dynamic balance between individuals with LBP and those without LBP. The result showed that, compared to healthy individuals, patients with LBP walked more slowly and needed more time to complete the TUG test.

Relative Proprioceptive Weighting
Two studies compared the RPW between the two groups but found no significant intergroup difference (Figure 9).

Risk bias of the studies included in the meta-analysis and sensitivity analysis
Using STATA software to assess the study biases and sensitivity analysis (Table 4), the sensitivity results suggested that our meta-analysis results are relatively stable.

Discussion
To our knowledge, this is the rst systematic review and meta-analysis to focus on LBP and motor performance in elderly people. This systematic review aimed to estimate the effect ofLBP and physical therapy on motor performance in elderly people. Our results demonstrated that elderly people with LBP have poorer motor performance than those without LBP. In our rapidly aging society, the proportion of elderly patients with chronic LBP is increasing annually, and the occurrence of pain, bad moods, functional inactivity, reduced quality of life, and increase in fall risk also increase [39] . We must provide effective intervention measures to improve elderly peoples' quality of life and reduce the economic losses and physical and emotional traumacaused by chronic LBP.
The aging process results in changes in the central nervous system, peripheral nervous system, and the musculoskeletal system [40,41] . Pain itself has a wide range of effects on motor function [42]. People who experience chronic pain display changes in motor patterns, exercise coordination, and the ability to maintain stability in response to external disturbances. Pain induces spinal motility restrictions, lumbar proprioceptive losses, weakening of lower-extremity sensory feedback, and trunk muscle weakness and atrophy [26,28,29,32] . Thus, when aging is combined with LBP, impaired motor performance and balance dysfunction worsen. However, almost 90% of articles to date focused on young and middle-aged people. It is conceivable that conditions associated with younger and middle-aged people are more optimistic no matter the motor performance or responsive to treatment. It is also possible that older adults with LBP should be subjected to different assessments and interventions than younger adults to account for the differences in therapeutic approaches and treatment outcomes. Given the age disparities in LBP people, in addition to solving the pain issue, it is important to focus on the motor performance and balance function of older individuals. As we all know, balance control with age is among the majorrisk factors for falls, which is a di cult problem what the world faces, especially as the population continues to age [43] .
Poor motor performance in elderly people with LBP means they cannot perform accurate movements and ambulation [44,45] , which in turn affect their physical activities. In our result, TUG, one-leg stance, postural sway, and gait are valid fall-risk assessment tools [46][47][48][49] ; poor outcomes on the TUG and postural sway tests may indicate an increased risk of falling that could lead to disastrous consequences. Problems with motor performance or balance are also reportedly associated with fall risk. Physical therapists in the clinical setting should be aware of an increased risk of falling among their patients.
There is some evidence that LBP impacts the equilibrium of older individuals. However, only one study in this review assessed reactive motor performance function, and none assessed the effect of dual tasks on motor performance in older individuals with LBP. The two conditions are very important in the occurrence of falls among elderly people. Our results demonstrated that the group of elderly patients with LBP has not received su cient attention, as there were only four articles about the effect of physical therapy on motor performance in this population. Future studies must focus more on this issue, especially on motor performance or balance function in these patients. The results of this review depended on the outcome measures examined, and the small sample sizes may have limited the power of our ndings. Therefore, futureresearch should include adequate sample sizes and must be combined with myoelectric and neural electrical activity and gait analyses to evaluate dynamic-static equilibrium and reactive balance, which could better re ect the effect of the central nervous system on peripheral control.

Study limitations
This review included only case-control and RCTs. Furthermore, the present review did notincorporate non-English studies. This may limit the validity of our ndings and must be taken into consideration when interpreting its overall generalizability. The limited number of case-control studies did not allow a subgroup meta-analysis, and we did not include RCTs in the meta-analysis. However, we achieved the main aim of our review, which was to estimate the effectof LBP on motor performance in elderly people and provide comprehensive information for thedesign of future studies.

Conclusion
In summary, the study results indicate evidence in favour of a negative effect of LBP on motor performance.However, further studies are required before a broad conclusive statement onthis subject can be made.  Centre of pressure, anteroposterior velocity Centre of pressure, mediolateral velocity Centre of pressure, anteroposterior range Timed up and go test