Estimates from the Global Burden of Disease (GBD) shows that about 15 % of the population has severe disability,1 and despite this, there is still little standardized information on the association of sociodemographic factors with disability, especially in low and middle-income countries.2,3 Low back pain (LBP) is one of the main causes of disability and need for rehabilitation services around the globe, and with population aging, this health condition becomes increasingly important in the context of health care.4,5 In 2015, LBP was responsible for 60.1 million disability-adjusted life years (DALYs), an increase of 54 % compared to 1990, with emphasis on a pronounced increase in low and middle-income countries.6

Most LBP cases have unspecific causes and a favorable prognosis, but recurrence of pain is common.7 Moreover, a proportion of these cases can lead to persistent disability.8 This requires deeper understanding of possible factors that can contribute to disabling LBP. Disability is an indicator that provides information about the impacts and needs inherent to the health of the population9 and complements mortality and morbidity data, helping to estimate the rehabilitation needs of the population.10

The World Health Organization (WHO), through the International Classification of Functioning, Disability and Health (ICF), defines disability as a generic term for impairments, activity limitations, and restrictions on participation. Disability represents the negative aspects of the interaction between an individual (with a health condition) and its contextual factors (environmental and personal factors). On the other hand, functioning indicates a positive interaction within this context.11

Other terms described by the ICF are: performance, which is defined as “performing tasks in the usual environment” and capacity, which is defined as “execution of tasks in a standard environment”.11 To perform a population-wide assessment of disability, the WHO prepared the Model Disability Survey (MDS), aligned with the ICF model, aiming to be an instrument for collecting information at a population level.9 The main objectives of MDS are to: provide estimates of the prevalence of disabilities comparable and standardized across countries; provide the necessary data and information to plan interventions, policies, and programs aimed to people with disability (PwD), and provide indicators to monitor the implementation of the recommendations of the Convention on the Rights of PwD.12

Despite the wide range of studies on LBP, there is a need for a better understanding of the association of sociodemographic factors with disability related to people affected by LBP. The study by Costa et al.13 discussed some sociodemographic factors, such as schooling and work, but on an occasional basis. Safiri et al14 in a study seeking to analyze the prevalence, death, and adjusted life years due to incapacity regarding musculoskeletal disorders, show that there is a shortage of data, mainly in developing countries, and this is a concern in GBD studies. Studies that focus on biological and cognitive aspects15 are more frequent, although the biopsychosocial nature and the relationship of the determinants of health and non-communicable chronic diseases are already discussed in the literature.16 The majority of existing research on this topic tends to focus on the individual and clinical perspective of the relationship between sociodemographic issues and pain, rather than analyzing it from a population-based standpoint. In addition, there are the limitations already described in the literature on the scarcity of data, underreporting, and the lack of a harmonized system to connect data sources.17 Furthermore, there is a notable lack of health surveys assessing the prevalence of LBP at the population level and, more importantly, its relationship with functioning, a need already recognized in the literature.18 Sharma and Mcauley18 defended in an editorial the need for research on LBP using reliable measures and valid and representative samples, with the incorporation of questions related to LBP in national health surveys as a possible solution. Thus, the aim of this study was to assess the prevalence of LBP and its association with capacity, performance, and sociodemographic variables in the Chilean population.

The study population was 12,265 people, of whom 2,737 (22.06 %) reported having LBP. The prevalence of LBP in the regions of Chile ranged from 0.1 % to 9.7 %, being higher in females (12.2 %), aged between 30 and 50 years old (7.7 %), with complete secondary level education (6.5 %), married/united (13.7 %), with the second lowest income quintiles (5.1 %), and who classified their health as regular (10.9 %) (Table 1).

Capacity and performance means are presented in Tables 2 and 3, respectively. The values are presented according to sociodemographic variables and all capacity and performance means are greater (i.e., greater impact) in the group with LBP. The exception is in health classification: participants who reported having very poor health and not having LBP showed worse levels of capacity and performance capacity and performance.

Among the sociodemographic variables, the profile of the population with the greatest impact on capacity and on performance was: being female, older, having the lowest educational level, widowed, unemployed, with the worst income quintiles, and classify their own health as poor. Regarding the type of housing, worse capacity and performance occurred for those who lived in precarious accommodations made with reused materials.

The respective adjusted ARMs and their 95 % CIs of variables associated with the worst capacity are as follows: LBP (1.77; 1.14, 1.21); female (1.12; 1.08, 1.16); age groups over 30 years old, being 30 to 50 years old (1.11; 1.05, 1.17), 50 to 65 years (1.34; 1.27, 1.41), 65 years and older (1.53; 1.45, 1.63); having worked for less than 1 hour in the last week (0.94; 0.90, 0.98)); having incomplete primary education (0.83; 0.77, 0.90), complete primary education (0.79; 0.73, 0.87), incomplete secondary education (0.83; 0.76, 0.91), complete secondary education (0.77;0.71, 0.84), incomplete higher education (0.82; 0.74, 0.91)), graduated (0.79; .72, 0.86); considered health as good (1.56; 1.45, 1.67), regular (2.24; 2.09, 2.40), bad (2.65; 2.46, 2.86), very bad (2.75; 2.51, 3.00).

For the performance variable, the following ARMs and 95 % CIs of the variables were associated: LBP (1.15; 1.12, 1.17); female (1.08; 1.05, 1.11), age groups older than 30 years, being +30 to 50 years (1.05; 1.01, 1.10), + 50 to 65 years (1.11; 1.06, 1.16), + 65 years old (1.25; 1.19, 1.30); having incomplete primary education (0.92; 0.87, 0.97), complete primary education (0.87; 0.81, 0.92), incomplete secondary education (0.91; 0.85, 0.97), complete secondary education (0.84; 0.7, 0.90), incomplete higher education (0.88; 0.82, 0.95), graduated (0.86; 0.80, 0.93); consider health as good (1.46; 1.37, 1.55), regular (1.95; 1.83, 2.08), bad (2.13; 1.99, 2.28), very bad (2.21; 2.06, 2.38).

The prevalence of LBP in the population of Chile is 22.06 %, with greater values in the Metropolitan region, women, those aged between 30 and 50 years, with complete secondary education, married or in a stable union, who had worked in the last week, income quintiles II, living in a house, and considering health as regular. People with LBP have worse capacity and performance levels, hence worse levels of functioning compared to people without LBP. Moreover, being female, widowed, the older the age, the worse the level of education and income, and worse the health rating, worse the capacity and performance levels. Furthermore, there were significant associations between LBP and sociodemographic factors such as being female, older age, worse level of education, and poorer health rating, which were correlated with better mean values of both capacity and performance in the LBP population. Additionally, having engaged in work during the previous week was associated with decreased capacity values in the LBP population.

The prevalence of LBP in Chile exceeds the global rate reported in 2017 (7.5 %), with a higher prevalence observed in females (8.0 %). However, in contrast to the global population where the highest frequency is observed in individuals over 65 years old, the age distribution in the present study yielded different findings.21 The prevalence data of the study, along with data from the National Health Survey in Brazil in 2018, showed that population with no education (25.6 %) with the highest prevalence of LBP and who reported having a poor or very poor health rating (43.9 %).22

The existing literature has already emphasized the importance of acknowledging the sociodemographic and economic context and the influence of personal beliefs and cultural factors on disability associated with LBP,23 which aligns with the findings of this study. LBP is widely recognized as a debilitating health condition and a leading musculoskeletal cause of years lived with disability.5 The results of the current study provide further evidence supporting this assertion, as individuals with LBP exhibited worse levels of capacity and performance.

Consistent with previous studies,24–26 our findings also support a higher prevalence of LBP in women. Fehrmann et al.27 observed a statistically significant difference between sexes in terms of domestic work, with women experiencing a greater impact. Additionally, limitations in social and recreational activities were more pronounced among younger men.27 These results further underscore the influence of sex and age on the functioning implications of LBP. As age increases, both capacity and performance show better means, indicating greater activity limitations and participation restrictions among older individuals. These findings align with the study by Fehrmann et al.27 which also demonstrated that the population with LBP experiences greater difficulties in mobility, self-care, and walking as age increases. Similarly, a German study demonstrated a significant positive association between age and subjective disability in patients with LBP.28 The aging process often involves neuromuscular and mechanical decline, which contributes to the loss or reduction of muscle strength and function. These factors can be intertwined with functional limitations and participation restrictions.29

Previous literature has already discussed the association between educational level and the prevalence of LBP, with lower education levels being linked to a higher prevalence of pain,16,30,31 and serving as a predictor of poorer outcomes and prolonged pain episodes.22 Most of the studies found present the correlation between a higher prevalence of LBP in individuals with lower education levels, however, they do not discuss the relationship between lower education and higher levels of disability. Our study revealed that those with lower education levels and LBP exhibited worse results in terms of capacity and performance. Lower levels of education can also be seen as an indicator of greater social vulnerability32 and, are also associated with poorer working conditions, lower income and worse access to health care.33,34

In a population-based survey conducted in Canada, it was observed that individuals with lower education levels utilized fewer healthcare services for the treatment of back pain.35 Corroborating with this finding, Romero et al.36 examined data from the Brazilian National Health Survey and found that individuals with higher education levels were 2.39 times more likely to receive physical therapy treatment for back problems. These studies raise important considerations regarding whether reduced healthcare seeking barriers to access, and utilization that the population with lower education levels may encounter could lead to difficulties in performing activities and subsequent negative impacts on capacity and performance. On the other hand, it is important to emphasize that enhancing the educational level can help overcome barriers to accessing health services for the general population. Therefore, in the present study, individuals with lower levels of education may encounter more obstacles when trying to access health services.37

The relationship between work and health is intricate and multifaceted, and while evidence suggests that individuals in better job positions tend to have better overall health outcomes, there is a higher prevalence of LBP among unemployed individuals.38 This complex association may be attributed to various factors, including difficulties faced by individuals with worse functional abilities in accessing employment opportunities or being exposed to unfavorable working conditions. Furthermore, theories propose that unemployment can lead to reduced income, potentially impacting healthcare access and quality of care.39 Consistent with existing literature, our study findings indicate that unemployed individuals exhibited worse levels of capacity, thus supporting the notion that employment status is linked to functioning.

One notable limitation of our study is its reliance on secondary data, which may have inherent biases and limitations. The nature of the information regarding the presence of pain is self-reported, which could lead to distortion regarding the location of pain, as the survey does not provide a body map to illustrate the location. Additionally, participants could underestimate or overestimate pain due to inadequate understanding of the questions. It should also be noted that the study is aimed at the general population, not just those experiencing LBP. Another factor to consider is reverse causality; thus, it is not possible to establish a causal relationship between exposure and outcomes. Therefore, causal inferences were not made; rather, correlations were inferred. Another limitation is the use of 2015 data; however, the study provides important and novel information for the field. There are gaps in the literature regarding the association between functioning and sociodemographic factors in individuals with LBP. Furthermore, the survey uses an instrument that evaluates functioning based on the ICF, which is recommended and endorsed by the WHO, effectively capturing its complexity and the individuality of the population. It also includes a representative sample from a middle-income country, which is another gap identified in the literature. Therefore, several noteworthy strengths of the study should be emphasized. First, our research employed a rigorous sampling methodology, ensuring a representative sample of the population of a middle-income country. This population-level perspective provides valuable insights into the prevalence and impact of LBP within a broader context. Furthermore, the utilization of participant-reported data allowed for a subjective assessment of individuals1 own health conditions, capturing their personal experiences, restrictions, limitations, and potentialities. This approach contributes to a more comprehensive understanding of the lived experiences of individuals with LBP. Additionally, our study is one of the pioneering efforts to employ the MDS as recommended by the WHO to gather information. This standardized approach enhances the comparability and generalizability of our findings.

Moreover, the results of our research hold implications for health policy development, as they shed light on the health needs and functioning of the population. By moving beyond traditional morbidity and mortality indicators, our study provides valuable insights for policymakers to design targeted interventions and allocate resources effectively, particularly in countries that prioritize health equity as a fundamental principle of their healthcare systems.35 The perspective of physical therapy in primary care helps promote functioning and prevent disability, incorporating a biopsychosocial approach.

Identifying the profile of patients most affected and with the greatest impact on functioning can help guide actions by the government, universities, healthcare professionals, and civil society to assist in the management and prevention of LBP. These actions can include, for example, adapting effective interventions from other countries to minimize costs and demand for healthcare services, non-work-related absenteeism, and disability.40 In the context of clinical assessment, studies indicate that social factors are not adequately evaluated in this setting, and the data from the present study demonstrate the need for these factors to be an important component of medical history.41 By integrating this knowledge into clinical practice, physical therapists can better identify at-risk populations, tailor interventions to address the specific needs and barriers faced by different demographic groups, and implement more effective strategies for pain management and functioning recovery.

There is a higher prevalence of LBP among specific sociodemographic groups, including females, aged 30-50, with complete secondary education, residing in metropolitan region, married or in stable unions, employed part-time, living in houses, and reporting regular health. The population with LBP exhibited significantly poorer levels of capacity and performance compared to those without LBP. Sex, age, education, and health status were associated with both capacity and performance, while health status alone influenced capacity values. These findings underscore the need for a comprehensive biopsychosocial analysis of LBP, considering sociodemographic factors, to inform targeted health policies and optimize healthcare planning.