Abstract

Physical inactivity is a major concern in public health globally. However, there is limited information on the impact of multi-site pain on active living. The aim of this study was to examine the associations between concurrent pain and leisure time physical activities. The study sample comprised 2628 adults from the 2003 to 2004 National Health and Nutrition Examination Survey (NHANES). Twelve-months prevalence of concurrent pain was 31.8%. Musculoskeletal comorbidity ranged between 77.8 % and 100%. The associations between pain sites were stronger in contralateral sides. Concurrent pain was positively associated with stretching (OR = 1.8, 95% CI 1.3-2.4, p = 0.000). Adults with concurrent pain were highly likely to engage in stretching exercises than other sport or exercise activities. We advocate a biopsychosocial approach in the management of adults with concurrent pain so as to achieve the recommended level of physical activity.

1. Introduction

Musculoskeletal pain is one of the most common conditions that occurs concurrently at more than one anatomical site (multi-site pain) ^{1, 2, 3, 4, 5}. Previous studies have shown that most people with musculoskeletal pain reported multifocal pain from a number of body sites simultaneously ^{1, 6, 7, 8}, and those local pains complement one another regardless of pain site ⁷. While the prevalence of pain is said to be high ³, scientific reports show that over 70% of adult population suffer from multi-site pain ^{4, 9, 10}. Available evidence suggests that the concurrence of pain is common, and it is becoming rare to find pain from only one specific anatomical body site. Additionally, the increase of the number of pain sites lowers functional abilities of individuals ¹¹. Pains at multiple sites, simultaneously, are associated with reduced physical performance ¹⁰, physical fitness, activities of daily living ^{1, 9, 12, 13} and overall quality of life ².

The World Health Organization (WHO) defines active living as a way of life that incorporate physical activity into daily routines. The goal of active living is to spend at least 30 minutes in physical activity daily. This goal can be achieved by means of transport, such as walking or cycling, daily exercise and fitness programs; participating in sport; playing in parks and recreational facilities; and taking stairs ¹⁴. Physical activity refers to as any bodily movement produced by skeletal muscles in the expense of energy ¹⁵. Physical inactivity and sedentary lifestyle are among the leading risk factor for premature death resulting from noncommunicable diseases. On the contrary, regular physical activity has health benefits associated with improved mental health and quality of life, and reduced risks of noncommunicable diseases such as cardiovascular diseases, stroke, diabetes and cancer ^{16, 17}. Worldwide, it is estimated that nearly 25% of adults and over 80% of adolescents do not meet the global recommendations for physical activity ¹⁶.

Physical inactivity is a major concern in public health globally ^{18, 19, 20}. Previous studies show that people’s participation in physical activity is influenced by a number of factors, such as, the built and natural environment in which they live, personal ²¹, psychological, socio-environmental ^{22, 23} and negative attitudes about physical activity and active transport ¹⁴. However, there is scarcity of published information on the impact of multi-site pain on active living. Therefore, in this study we investigated the effects of concurrent pain on physical activities integrated in everyday life in a population-based sample of adults with and without concurrence of pain by using the National Health and Nutrition Examination Survey (NHANES). The NHANES is the first of its kind to assess individual leisure time physical activities, including all common sports and exercises, and miscellaneous pains.

The aim of the present study was to examine the associations between pain co-occurrences in specified 11 major body regions, on the left and right side of the body, and leisure time physical activities. The specific objectives of this study were (i) to estimate the prevalence of multisite pain in adult population, (ii) to describe the networks of algesic body sites in relation to physical activities and (iii) to explore the association between daily human activities and concurrence of pain in adult population.

2. Materials and Methods

In this study, we used the 2003 to 2004 NHANES dataset. This dataset was considered because pain was not explored in the following cycles (to present). We included only adults with or without pain in one or more body sites and participated in either sport or exercise activity during leisure time thereby excluding children or adolescents under the age of 20 years. NHANES is a two-year cycle population-based survey designed by the U.S. National Center of Health Statistics (NCHS) to assess and monitor the health and nutrition of the U.S. household population. The survey uses a complex multistage sampling method where certain populations are oversampled to recruit a nationally representative sample and provide reliable estimates of health conditions of the U.S. inhabitants from different races and age groups. Both home interview and physical examination are conducted at home or in a specified mobile examination center by highly trained medical personnel. All methods are carried out in accordance with relevant ethical principles of the Declaration of Helsinki and all participants provide written informed consent. NCHS Research Ethics Review Board (ERB) approves the administration protocol. Data files are organized and circulated through the Centers for Disease Control and Prevention (CDC) website ²⁴.

Computer-assisted personal interviewing (CAPI) approach was used to collect a wide range of demographics information, such as: age, gender, ethnicity (assigned as Mexican American, other Hispanic, non-Hispanic white, non-Hispanic black, or other race), citizenship status, education attainment (categorized as less than 9^th grade, 9 – 11^th grade, high school, some college or associates degrees and college graduates or above), marital status, height in standing position (in centimeters) and body weight (in kilograms).

Forty-eight categories of sport or exercise activities were incorporated in ‘Physical Activity – Individual Activities questionnaire,’ which aimed to inquire detailed information about specific leisure-time activities only. Participants were asked if they had undertaken any of those physical activities in the last month. Each reported activity was assigned a numeric code. The reported intensity level of each activity was coded and then classified into moderate or vigorous according to the metabolic equivalent (MET) for each activity. MET scores were then obtained from the reference manual and personal communication with the author. For each activity, the questionnaire recorded the following: the number of times the activity was done over the past 30 days; frequency of participation in different activities that was categorized as participation once a month, two to four times a month and five or more times a month; and the average duration the activity was done each time, in minutes. An exclusion was done for activities with reported duration of less than 10 minutes. If a respondent reported no leisure-time activities, there are no records in the file for that respondent. We dropped respondents who did not specify the actual activity because by recoding “other” leisure-time activities, it is possible for a respondent to have two records for the same activity with the same level of exertion.

To identify persons who had pain for the past one year, participants were asked, “During the past 12 months, have you had pain, aching, stiffness or swelling in or around a joint? [Do not include neck pain.]”. If the participant answered “yes”, this was followed with a question, “Were these symptoms present on most days for at least 1 month?” Finally, participants were asked to indicate body part(s) that had pain for the past twelve months on a self-assessment manikin portraying the front and back of a human figure. The pictorial identified a total of 48 body regions (such as, the head, neck, right shoulder, left shoulder) on both right and left sides of the body. In this study, we included major body sites as described by Kuorinka et al. ²⁵, i.e., the neck, and bilateral shoulders, elbows, wrists, hands, upper back, lower back, hips, knees, ankles, and feet. Depending on their responses, participants were classified into one of the three groups: no pain —if no pain was reported, single-site pain —if pain was reported in only one site, and multi-site pain —if pain was reported in more than one body site.

Descriptive analyses were performed to examine the sociodemographic characteristics of study participants. Means and standard deviations were calculated for continuous variables, and percentages for categorical variables. Concurrent pain was described, estimating its prevalence and describing its proportions for each of the 21 body sites. The associations between pain in different body sites were assessed, presenting odds ratio (OR) as measure of association and their 95% confidence interval. The regression analysis was fit for three different models separately, i.e., single-site pain versus no pain, multi-site pain versus no pain and multi-site pain versus single-site pain. Activities with participants less than 3% of the population were excluded from the analysis. The level of significance in each model was set at p < 0.05. All models were adjusted for age, gender, body mass index (BMI), activity level, number of times of participation in sport and exercise in a month and average duration of each activity in a month. We also constructed an undirected partial correlation network diagrams based on conditional proportion between pain co-occurrences in various parts of the body for activities that had significant associations. The networks were constructed according to Gausian graphical modeling with arctangent-penalized regulation method as recommended by Williams ²⁶. The initial correlation matrices for graph modeling were from the binary-data-specific tetrachoric correlation coefficients. The nodes are the body parts, and the connections are the partial correlations between pairwise painful body parts. Significance test of correlation was with p < 0.05, with > 95% of bootstrapped edge inclusion probabilities. The weak correlation was deleted, and only the connection with the partial correlation coefficient > 0.4 was retained ²⁷.

All analyses were conducted by using R software for Windows (version 4.1.0) and followed the analytic guidelines on the NHANES website. The sample weights were used to account for the complex sampling methods used during data collection so as to avoid biased estimates for the U.S. population.

3. Results

A total of 10,122 participants completed the 2003 to 2004 NHANES survey. The concurrence of pain was assessed only in adults thereby excluding children or adolescents under the age of 20 years, resulting in a sample size of 5,014 individuals. Out of 5,014 participants, 2729 individuals participated in sport and exercise activities. Moreover, 101 participants were excluded because of either participating in other activities not related to sport or exercise, or missing information, resulting in a final sample of 2628 participants that is representative of 128.3 million adults in the United States.

The mean age of study participants was 47 years with standard deviation (SD) of ±18 years. Prevalence of multi-site pain was over 2 folds higher compared with single-site pain. The proportion of females who reported multisite pain was higher compared with males. Participants aged between 40 and 59 years reported pain at more than one site at a higher percentage compared with other age groups. Individuals with high school education or higher, non-Hispanic whites, and those who were obese reported higher prevalence of multi-site pain than comparable groups in their respective categories. Detailed participant characteristics are presented in Table 1.

The prevalence of musculoskeletal pain in each body site was less than 20%, and only the right foot had no co-occurrence of pain in other body sites (Table 2). The regional concurrence of pain in one side of the body was higher in contralateral side and proximal body sites in the ipsilateral side (Table 3). Nearly one-third of study participants had concurrent pain. The proportion of subjects with single-site pain was lower compared to those with pain in more than one site (Table 4). Majority of participants with musculoskeletal comorbidity reported pain in more than four sites. For all body sites, musculoskeletal comorbidity was high for right knee and right foot (Table 5).

Having pain in one body site was associated with pain in other sites, and pain in one side of the body was also associated with having pain in the counter part of the same region in the other side. For example, having right hand pain increased nearly 400 odds of developing pain in the left hand. Also, the associations between proximal sites were stronger than between more distal sites. For instance, neck pain had stronger associations with upper back compared with ankles (Table 6).

In model 2 and 3, stretching was positively associated with multi-site pain ([OR = 1.8, p = 0.000] and [OR = 1.9, p = 0.006], respectively). Significant associations of other exercises observed across all models were negative. The comparison of the second and third model showed that stretching was positively associated with concurrent pain (Table 7).

Figure 1 shows a partial correlation network of concurrent pain and physical activity. The four panels show the pain concurrence networks among selected four activities that showed significant association with pain co-occurrence; i.e., walking, running, golf and stretching. The size of a node is according to the weighted degree, that is, the sum of edge weights belonging to a node. Results showed that pain concurrence had its own spectrum on each activity. Multi-site pain composite spectrum suggested that all sports/exercises had a common risk of pain, and the distribution of risk correlations was distinctive (Figure 1).

4. Discussion

To the author’s knowledge, this is the first large-scale population-based study in adults to evaluate the association between concurrence of pain in different body regions and different sport and exercise activities by using NHANES database. The associations were estimated by using multivariate regression analysis with adjustments for demographic characteristics and other potential confounders. The main findings of the current study showed that 31.8% of study participants reported having concurrent pain for the past 12 months. Having pain in one body site was highly associated with pain in another site and that having pain in one side of the body was associated with having pain in the counter part of the same region in the other side. Participants who reported having concurrent pain had higher odds of engaging in stretching exercises than other sport/exercise-related physical activities.

The prevalence of individuals with pain during the past twelve months in the present study was 46.7%. This finding was consistent with finding from a population-based study done in the United Kingdom (U.K.), which reported a prevalence of 45%. ². The similarity observed in the current and previous studies shows that despite the variation in social and topographical characteristics across the subjects, nearly half of the adult population are suffering from musculoskeletal pain at one or more body parts. Findings from this study show that musculoskeletal pain occurring in more than one body site concurrently was higher than single-site pain for all body sites. For every pain site assessed there was at least one other site of pain in a proportion ranging between 77.8% and 100%. This finding is compatible to that from a previous study that showed for every pain site there was at least one other site of pain in a proportion of 72% up to 90% ⁶. Similarly, another analogous study reported over 85% occurrence of pain from at least one other region for every pain site ⁸. Correspondingly, a previous study ²⁸ also found that over 88% of study sample had concurrent pain. The results showed a considerably higher proportion of the co-occurrence of pain in multiple body site than single site-pain, thus suggesting that single-site pain is uncommon in adult population.

In our study, musculoskeletal co-morbidity was high for all body sites, that is to say, the proportion of concurrent pain was high (31.8%). This corresponds to previous study, which reported a proportion of 30.1% ⁶. This similarity follows a statement from previous study describing that in the general population, those reporting single-site pain often report pain at other sites, and that single-site pain increases the risk for pain at other sites ¹. Likewise, frequent multi-site pain in population-based studies was observed in several European countries ^{12, 29}. The probable reason for this observation could be that regional muscles and bones responsible for executing a particular function are interconnected with each other, hence a fault to one structure may alter function of the other. For example, trigger points of the neck muscles are manifested as headache ³⁰, and the shortening of the gastrocnemius and soleus muscles causes pain in the hips and knees ³¹. Another possible reason may point to the effects of mechanical stress imposed to multiple locations by some physical activities including sport and exercise activities.

The association between two pain sites demonstrate that having pain in one body site is associated with pain in another site, and that having pain in one side of the body is also associated with having pain in the counter part of the same region in the other side and vice versa. Additionally, the associations between proximal sites were stronger than between distal sites. Moreover, the associations of ipsilateral body sites proximal to the affected sites were higher than contralateral body sites of the same region. Similar findings were reported in previous studies showing significant associations for pain at anatomically adjacent sites ^{32, 33}. Our findings are analogous to the concept described in former study ³⁴ showing that having one regional pain increases the chances of developing another, and that the risk increases with the number of pain initially taken as references. For example, in Fig. 1, the nodes with high weighted degree are more susceptible to the influence of other parts to concurrent pain. Therefore, the results suggest that bilateral shoulders, knees, and lower back are more prone to clinical symptoms. In clinical practice, more attention to the areas with highly weighted degree, such as hands, feet and upper back, may achieve better results when the treatment of symptomatic local areas fails to achieve expected outcomes. The overlooks of the pain concurrence networks offer new insights for clinical pain management and rehabilitation.

Our study showed that there was a strong association between physical activity and pain concurrence. Regardless of the reference group, multi-site pain was positively associated with stretching exercise (p < 0.05); that is, participants with pain at multiple sites were highly likely to participate in stretching exercises than other sport/exercise activities. This finding coincides with findings reported by Naugle et. al., who found that each physical activity behavior had varying impact on the inhibitory and facilitatory processes of pain in older adults ³⁵. Similarly, it has been reported that high levels of disability resulting from chronic pain affect levels of physical activity ³⁶. There are two main possibilities to explain this finding. One, exercising while having pain at multiple body sites may lead to temporal summation of pain. Eventually, sensitivity to physical activity may develop because of pain-related fear of movement ³⁷. Two, reduced physical activity because of pain at multiple body sites, age and gender ³⁸. Therefore, older adults with pain at multiple body sites are likely to avoid most activities involving movements provoking the pain and rather prefer exercises with less pain provocation movements —stretching in this case. Yet, stretching is easier to perform thus an option for most adults with concurrent pain.

Further findings from the current study suggested that pain concurrence had its own spectrum on each sport or exercise activity (Figure 1). This finding is supported by previous research reporting that exercise intensity and duration have significant relationship with pain development depending on sex/gender of an individual ³⁹. Similarly, it has been reported that engaging in sports at a highly competitive level increases the likelihood to have current pain symptoms ⁴⁰. Perhaps, these findings from previous studies may explain the variation of pain concurrence in selected activities in our study. Nodes with strong connections are more important or critical than those with weak connections. Treating them first, in patients with concurrent pain, maybe a better option for effective relief.

This study has not only demonstrated the magnitude of co-occurrence of pain in multiple body sites over the period of one year but has also illustrated the impact of multi-site pain on reduced levels of physical activity. Also, this study has highlighted that pain concurrence had its own spectrum on each sport or exercise activity, and the correlation network suggested potential pain targets during clinical examination and intervention of pain. Despite large sample size, our findings had several limitations: NHANES being cross-sectional, the associations that we observed in this study might not be causal and might have resulted from other potential confounders that we did not adjust for. Additionally, the 12 months period prevalence used in self-reported questionnaires might have been too long thus subjecting participants to recall bias. Nevertheless, participants were asked to take time and fill the questionnaire with every detail they could possibly remember. Also, NHANES data are based on self-reported questionnaires, which could easily subject respondents to misclassification of responses.

5. Conclusion

Findings from our study demonstrated that pain concurrence had its own spectrum on each sport or exercise activity. Participants who reported having concurrent pain were highly likely to engage in stretching exercises than other sport- or exercise-related physical activities. We advocate a biopsychosocial approach in the management of adults with concurrent pain so as to achieve the recommended level of physical activity.

Acknowledgements

We extend our gratitude to all individuals at the U.S. National Center for Health Statistics of the Centers for Disease Control and Prevention who were responsible for planning, conducting and managing NHANES and circulating the datasets of NHANES on their website.

Statement of Competing Interests

The authors have no competing interests.

Funding

This research was funded by National Key R&D Program of China Project No. 2020YFC2008500.

List of Abbreviations

CAPI: Computer-assisted personal interviewing

ERB: Research Ethics Review Board

MET: metabolic equivalent

NCHS: United States National Center of Health Statistics

NHANES: National Health and Nutrition Examination Survey

References