Neck pain can have an adverse impact on balance control. The Balance Error Scoring System (BESS) is a widely used for assessing static balance across various populations. However, its application in evaluating balance in patients with chronic subclinical neck pain (SNP) has been limited by the absence of normative data.
ObjectiveThis study aimed to develop normative values for the BESS in participants with chronic SNP, stratified by age and gender.
Methods310 participants aged 20–69 years with chronic neck pain and no balance-affecting disorders were included. Each age group had 31 participants who underwent balance assessment using the Thai BESS version (BESS-TH), involving three test positions (double leg, single leg, tandem stance) performed on two surfaces (rigid and foam).
ResultsThe average BESS-TH score in 10 groups were 14.90 ± 4.55 and 17.55 ± 4.44 in 20–29 years, 19.29 ± 5.66 and 20.61 ± 4.40 in 30–39, 22.32 ± 5.04 and 22.23 ± 5.19 in 40–49 years, 25.00 ± 7.25 and 27.94 ± 6.40 in 50–59 years, and 30.32 ± 7.36 and 30.65 ± 8.38 scores in 60–69 years for men and women respectively. The BESS scores demonstrated an upward trend with increasing age categories.
ConclusionsThis study established a comprehensive normative database for the BESS across various age groups of adults with chronic SNP, emphasizing the age-related deterioration in balance. Precise normative data tailored to specific populations are crucial for accurate balance assessment and targeted interventions.
The Balance Error Scoring System (BESS) is a widely utilized measurement tool for assessing static balance performance.1 Scholars from the University of North Carolina created the BESS instrument in 1999 with the intention of assisting clinicians in the assessment of postural stability.1 This balance measurement comprises multiple subtests, with increasing difficulty levels achieved by reducing support and altering standing surfaces, thereby challenging the participant's balance abilities. The BESS has been used to determine balance deficit and has been extensively employed in numerous research studies investigating balance across various participant groups.1–8 The researchers endorsed their selection of the static balance tool by emphasizing the BESS test's clinical usefulness of the BESS test, its’ simplicity, inexpensive cost, and practicality for assessing postural stability.1,9
Neck pain (NP) refers to the experience of discomfort and pain in the neck area. It can occur with or without pain in the head, torso, or upper extremities.10 NP is one of the most common musculoskeletal disorders worldwide, according to the 1990–2019 Global Burden of Disease research.11,12 NP has a significant prevalence in Thailand, reaching up to 81.9 %, and was listed as one of the top three musculoskeletal (MS) diseases in numerous occupations.13–17 When individuals experience NP, they may encounter conditions such as: sensory input disturbances;18–20 aberrant muscle activity;21–23 reduced muscle endurance in the deep cervical muscles;23,24 changes in the anatomy of their cervical spine;19,25,26 difficulties in regulating head and eye movements;18 restricted range of motion,23 and impaired awareness of the position and movement of their neck.18,19,27 These conditions can decrease balance performance28–33 and eventually lead to altered walking patterns.18,34–36 Subsequently, these factors may increase the likelihood of falls and fall-related injuries in patients with NP,37–39 a concern corroborated by physiotherapists with 30 years of experience who have observed balance problems and increased falling rates among NP patients. Falling in NP patients has been reported at 18.7 % in male elderly patients during the previous 12 months.40 Falling or losing balance can lead to fractures in the hip or lower limbs,40 brain injury,41 and a fear of falling,38,42 all of which can impede regular everyday activities.42,43
Some researchers targeting patients with NP have focused on the initial stage of NP known as "subclinical neck pain" (SNP). Individuals with SNP experience mild to moderate persistent neck pain and have not sought any therapy for their condition; as a result, they are more likely to experience less neck pain and disability compared to those who have actively sought treatment.24,27
Balance, or postural control, involves the visual, vestibular, and somatosensory systems. These three systems are seen as subsystems responsible for providing sensory information to the central nervous system (CNS).44 Balance dysfunction or decreased balance capability has been observed in individuals experiencing chronic neck pain (CNP).28–33 The underlying reason giving rise to balance impairment is altered sensory input or sensory mismatch from the receptors located in the neck area, particularly reduced sensitivity of the somatosensory receptors in the neck muscles.45,46 This produces a mismatch between abnormal information from the cervical spine and normal information from the vestibular and visual system resulting in misinterpretation by the CNS and consequent balance disturbance.18 To measure balance performance in patients with NP, there are many clinical tools, these include: force plates,29–31 Single Leg Balance Test (SLBT),29,30,47 Romberg test,29,30 Tandem stance test, and the BESS test.3,48
The BESS is one of these tools with demonstrated acceptable validity and moderate to high reliability.3,48 The BESS exhibited fewer ceiling and floor effects compared with other balance tests.8,48,49 However, to apply or evaluate balance impairment among patients with NP in research or clinical settings, one needs normative database to interpret the balance status.6 In the clinical setting, normative data or norms refer to data that describe typical characteristics within a specific group at a given time. These data are highly valuable to primary care physicians.50 The BESS normative data serve as a reliable source for interpreting balance status. However, the applicability of previously developed normative databases to different populations is limited due to diversity and variation in sociocultural backgrounds, health conditions, and the characteristics of each population which may influence balance control.6,51 Some studies of BESS test norms have demonstrated the effect of gender where some points in life demonstrate similarities and differences between male and female.6–8,52 Currently, BESS normative data is primarily available for amateur high school and college athletes,8 as well as healthy adults,6–8,52 but lacks applicability for individuals with CNP, a population known to experience static balance impairment.29,31–33
Evaluating balance ability in patients with neck pain using the BESS has proven clinically challenging due to a lack of normative data. This limitation significantly impedes the clinical utility and effectiveness of the test in assessing balance deficits associated with neck pain. The current study aims to address this gap by establishing a comprehensive normative data set for the general adult population with chronic SNP, stratified by age and gender in order to compare the balance status among these sub-populations.
MethodsA cross-sectional study was conducted from April 2023 to December 2023, approved by the Local Centre for Ethics in Human Research (HE662005) of Khon Kaen University, Thailand. The trial was also registered in the Thai Clinical Trial registry (TCTR20230411003). Our procedures were conducted following the STROBE criteria.53
ParticipantsA cohort of 310 participants, aged 20–69 years, equally distributed across 5 age ranges, with 31 participants per gender in each age range, were recruited through promotional channels (posters and social media) targeting individuals with chronic SNP. The participants were eligible provided they met the particular inclusion requirements; 1) have experienced SNP for a minimum of three months;23,24,27 2) age range between 20 and 69 years;6,7 3) body mass index (BMI) lower than 30 score;3 and 4) report mild to moderate pain on the visual analog scale (VAS; 5–74 mm).3 Participants were excluded from the study if they had: any history of visual, auditory, vestibular, or neurological deficits;3 whiplash associated disorder and/or head/neck injuries;54 previous cervical or thoracic spinal surgery due to traumatic injuries or surgical interventions of the spine or lower limbs within the prior year;3,6 had neurological or psychiatric disease;54 medical conditions that could affect balance negatively;3,6 chronic musculoskeletal diseases; fractures and injury of the lower extremities;3,7,55 a Beck Depression Inventory (BDI) score > 30/63;3 a Dizziness Handicap Inventory (DHI) score > 30/100;3 positive vertebro-basilar artery insufficiency test (VBI test);54 or taking any sedative drug or alcohol within the past 48 h.3
The total sample size of 31 participants in each age range was calculated using the formula (n=Z2∝/2σ2/e2)56 and setting variables according to data from an earlier study.6 Considering 10 groups of participants (age groups: 20–29, 30–39, 40–49, 50–59, 60–69 years; and gender: male and female), the total sample size was 310.
ProcedurePrior to commencing the study, all 310 participants provided informed consent. Subsequently, they underwent interviews to collect demographic information and screening for exclusion criteria. Thereafter, the participants performed the six positions of the BESS assessment.
BESS Thai version (BESS-TH) is a static balance test that is concise and straightforward to administer. BESS-TH comprises three stances executed on both solid and foam surfaces with eyes closed: double-leg stance (hands on hips, feet together), single-leg stance (standing on non-dominant leg, hands on hips), and tandem stance (non-dominant foot positioned behind the dominant foot in a heel-to-toe pattern).48 The participants each followed the same sequence (as shown in Fig. 1). The score reflects the errors counted by the evaluator during each 20 s trial. An error is defined as any deviation from the correct test posture, such as opening the eyes, taking the hands off the hips, stepping, stumbling, or falling out of position, lifting the forefoot or heel, abducting the hip by more than 30°, or failing to return to the test position within 5 s. The total summation score might be 0 (no error) to 60 (poor static balance).1,57 A highly experienced evaluator (Research AL) with high inter-rater reliability with another physiotherapist with 30 years clinical experience of orthopedic physiotherapy (0.922, 95 % CI = 0.864–0.956)48 assessed all 310 participants with chronic SNP.
Data analysis
The Statistical Package for Social Sciences (SPSS) version 28 (IBM Corp., Armonk, NY) was utilized for data analysis. Descriptive statistics were used to report demographic characteristics and mean BESS measurement values for each age range and gender. In comparing subgroup analysis by gender, the Shapiro-Wilk test was used to determine normal distribution of both genders. The non-parametric analysis, in this study used the Kruskal-Wallis test with Bonferroni method to determine the differences of BESS scores between each age range in both males and females.
ResultsDemographic characteristicsDemographic information of the 310 patients with chronic subclinical neck pain is presented in Table 1. The average age of the participants was 44.46 ± 14.36 years, with the average neck pain duration and intensity of pain of 44.81 ± 49.28 months, and 4.15 ± 1.80 score, respectively.
Descriptive statistics of demographic data for 310 patients with chronic subclinical neck pain.
The average values of age, BMI, pain duration, and VAS stratified by age range and gender are present in Table 2.
Descriptive statistics of demographic data according to age group and gender.
BMI: Body Mass Index.
VAS: Visual Analogue Scale.
The normative data of BESS-TH for participants, categorized by age range and gender, are presented in Table 3.The average BESS-TH scores of the total participants of 20–29, 30–39, 40–49, 50–59, and 60–69 years were 16.23 ± 4.65, 19.95 ± 5.07, 22.27 ± 5.07, 26.47 ± 6.94, and 30.48 ± 7.82 scores, respectively. The BESS scores demonstrate an upward trend as age increases. The mean BESS-TH scores for males were lower than females in the 20–29, 30–39, 50–59, and 60–69 years age ranges, with a statistically significant difference observed in the 20–29 years group (p-value=0.024). For both genders, the BESS-TH score is likely to increase in concordance as the age of the individual increased.
Normative reference values for the BESS-TH stratified by age and gender.
SD: standard deviation.
Following the overall Kruskal-Wallis tests, post-hoc pairwise comparisons revealed specific age group differences within each gender (Fig. 2).
For males, participants aged 20–29 years demonstrated significantly different BESS scores compared to those aged 40–49, 50–59, and 60–69 years (all p < 0.001). Significant differences were also found between the 30–39 years group and both the 50–59 (p = 0.001) and 60–69 (p < 0.001) year groups. Further, the 40–49 age group differed significantly from the 60–69 age group (p = 0.008).
Similarly, for females, the 20–29 years age group showed significantly different scores compared to the 40–49 (p = 0.046), 50–59 (p < 0.001), and 60–69 (p < 0.001) year groups. The 30–39 years group also differed significantly from the 50–59 (p = 0.001) and 60–69 (p < 0.001) year groups. Lastly, comparisons involving the 40–49 years group showed significant differences relative to the 50–59 (p = 0.025) and 60–69 (p = 0.008) year groups.
DiscussionGenerally, normative data of the BESS test prove beneficial to use as the comparative values help analyze balance status. Prior studies which have provided normative data have exclusively focused on examining healthy people and amateur high school and college athletes6–8,52 meaning there is currently a lack of BESS normative data for neck pain patients.
This study demonstrated that the BESS-TH score was inclined to increase in concordance with the increased age. The BESS scores of patients with chronic SNP were notably higher compared to those of healthy participants and athletes reported in previous studies.6,7,52 This study of chronic SNP demonstrated significant differences in all age ranges and genders (p-value = 0.001–0.037) except for ages 20–29 years (Supplementary material: Table 1) compared with the study of Shamshiri (2020) which demonstrated p-value of 0.620 in healthy adults. Balance performance can be affected by problems in any one of the sensorimotor or musculoskeletal systems.44 The mechanism to support the finding of balance deficit in patients with neck pain can be explained in many ways. People with NP can have sensory input alteration and sensory discrepancy18 due to the receptors of somatosensory, visual, and vestibular systems and the connections between these systems.58–61 Balance interruption could be caused by decreased sensitivity of proprioceptors in the neck muscles.45,46 This is corroborated by animal research demonstrating that the output of muscle spindles in the neck muscles is considerably altered after stimulation of nociceptors in the neck muscles and cervical facet joints.61,62 Another reason, is that altered cervical muscle activation patterns and motor control are found in patients with CNP.63 Painful cervical muscle has been reported to have morphological differences from non-painful neck muscle,25,46,64–66 and identified abnormalities in muscle strength, muscle endurance,67–69 muscle activity,21,70–72 muscle fatigue,73,74 and found significant decreased type-I slow twist muscle fiber and increased type-II fast twist muscle fibers.75 Poor neck muscle performance resulting from a combination of altered neural muscle control and muscle fiber properties, may trigger or sustain neck pain which the feed forward response to initiate the specific muscle group may be delayed to reactive the outer force,70 indicating a change in the method utilized by the central nervous system to control the cervical spine.
Patients with CNP have been reported as having cervical muscle impairment which may be associated with abnormalities in cervical motor behavior (timing and activation),21,76,77 a reduction in the cross-sectional area of cervical muscles,25,66,78 as well as muscular functional impairments in strength, endurance, precision and acuity, and range of motion.67–69,79 The cervical muscles especially the deep cervical muscles consist of a high number of muscle spindles, considered the most important component of the proprioceptive system located in the cervical region.18 They play an essential role in the control of cervical postural alignment, intersegmental stability, and the fine-tuning of intervertebral movement.80 The anatomical and functional changes in the deep muscles of the cervical spine can alter the discharge of muscle spindles, hence altering the afferent input.81,82 The finding suggests that individuals with CNP have complicated and multidimensional neck muscle dysfunction. The effect of pain on multiple levels of the neurological system might influence muscle spindle’ sensitivity and the cortex’s representation and control in response to cervical afferent input.61,83,84
This study demonstrated gender differences in BESS scores for the 20- to 29-year-old age group, with males exhibiting significantly lower (better) scores than females by a difference of 2.65. While previous studies have also reported gender differences in BESS values across various age ranges,6,8 the specific age range differed from the current study. Additionally, when comparing with another static balance test (SLBT), lower balance performance has been observed in females aged 18–39 years85 and Nakhostin-Ansari et al. (2022) also reported gender can effect balance performance at 18–29 years and over 60 years while performing the functional reach test, SLBT, and timed UP and GO tests.51 With regard to proactive balance, males may have an advantage over than females since they can compensate for their poorer balance with stronger muscle strength.86
Clearly increasing age affects balance performance. Thus, future research should compare and each age range group in both genders. Nevertheless, the increased score in both genders of NP patients was consistent with their increased age, as was the case with the BESS of healthy adults from previously conducted studies.6,7,52 The highest aged patients with SNP in the current study reported the highest BESS scores compared with the other group ages. This current study demonstrated the BESS score for both gender, male, and female at 30.48 ± 7.82, 30.32 ± 7.36, and 30.65 ± 8.38, respectively. The BESS score of patients with NP differed from the healthy participants by a score of 8–10. Aging healthy people have been shown to have decreased balance status due to changes in their sensory and motor function with reported mean of BESS score at age 60- to 69-year-old group of 20.38 ± 7.87,52 19.9 ± 7.17 and 22.30 ± 6.22 for males and 27.39 ± 7.69 for females.6 All three studies reported lower BESS scores compared with the patients with neck pain in this study. The data from the current study confirms and supports prior research demonstrating that patients with neck pain have the potential for balance impairment.32–34 The impairments in sensory, motor control, or central processing function that may result from a particular pathology that affects a specific component of these systems, or the general progressive decline of function due to ageing, are some of the potential causes of balance impairment in the elderly population.87,88 Additionally, older persons have a decreased capacity to adjust to incoming sensory input while sustaining balance88 and they also have reduced capability to adapt to inaccurate sensory visual or proprioceptive input to maintain balance.89
In 2021 Wah and coworkers investigated the effect of neck exercise on patients with NP and used balance status (with BESS) as their outcome measurement.3 They set their inclusion criteria as BESS scores of at least 15, and measured it in participants aged 18 to 25 years. They reported mean BESS score at baseline as 25.21 to 26.21 for both genders. So, for this age range they reported having higher BESS scores compared with those in the current study (BESS=16.23±4.65). The reasons to explain the different scores may arise from the target populations (academic students with SNP), the age range of participants, socioeconomic background, and inclusion criteria.
Research results (Table 2) indicate that the severity of neck pain demonstrates a nonlinear correlation with age, however on consideration of mean in each age range, pain was a slightly lower in young adults (20–29 years) and older adults (60–69 years), whereas middle-aged persons frequently reported slightly elevated pain intensity levels. This finding may arise because young adults benefit from better tissue resilience, healing capacity, less degenerative changes,90,91 and better coping mechanisms,92 leading to lower pain intensity. Despite having more signs of cervical degeneration, older adults often report lower pain, possibly due to adapted pain thresholds,93 more effective coping strategies,92 and changes in central pain processing.94 In contrast, middle-aged adults experience the highest pain levels, likely due to accumulated mechanical stress,95,96 early degenerative changes,97 and psychosocial factors.98
Our normative data aimed to enhance the usefulness of the BESS by categorizing participants based on age and gender. However, there are some limitations regarding the use of our results to generalize for all NP patients because this study was conducted on participants with SNP which is a subset of NP. Additionally, the current study used a smaller sample size compared to the previous studies conducted on healthy adults being 589,52 1236,7 1051,6 and young athletes at 6762.8 Moreover, the selection of participants was limited to collecting only one region in Thailand. Future studies should consider expanding the scope of inclusion criteria to include other neck pain groups, increasing the sample size, and potentially using cluster sampling.
ConclusionThis study provides a normative data set for different age groups of adults with subclinical neck pain, assessed using the Balance Error Scoring System (BESS). Our results demonstrate the BESS scores exhibit an increase with age and have a greater score in patients with neck pain compared with healthy adults reported in previous studies indicating greater balance problems for patients with neck pain. Males had lower BESS scores than females in 20–29, 30–39, 50–59, and 60–69 years, and this difference was significant in the 20–29-year-old cohort.
CreditTaxonomy statementAll authors have made substantial contributions to the conception or design of the work. AL performed acquisition of data with assistance from TC; AL, TC, and RP analysis, interpretation of data and wrote manuscript; AL, RP, TC and RB drafted the work or substantively revised it and approved the submitted version.
The authors declare no compiting interest.
This work was supported by Research Fund for Supporting Lecturer to Admit High Potential Student to Study and Research on His Expert Program Year 2021 of Khon Kaen University, Thailand, however, the sponsor did not have any role in the study design, data collection, data analysis, interpretation, or writing of the report. The authors express gratitude to the participants who willingly took part in this study, as well as to the research assistant who provided the data collection.
