Back pain prevalence and associated factors in Brazilian Unified Health System users

ABSTRACT

BACKGROUND AND OBJECTIVES:

Back pain is one of the main causes of disability worldwide, resulting in higher rates of work absenteeism and years lived with disability. This study aimed to evaluate back pain prevalence and its associated factors in Primary Health Units (PHU) users.

METHODS:

A community-based cross-sectional study was conducted at PHU located in Pelotas, Brazil. Fifteen individuals of each PHU, aged 18 years or more, were interviewed (n=540). Back pain was defined as pain in one to three back areas (neck, dorsal and lumbar). Demographic, economic, behavioral, nutritional status (body mass index) and health characteristics were assessed as covariates. Poisson regression was used to estimate the prevalence ratio and 95% confidence intervals.

RESULTS:

Prevalence of back pain in PHU users was 20% (95%CI 16.8 - 23.6). Fair (PR 2.66 95%CI 1.00 - 7.09) and poor (PR 3.65 95%CI 1.31 - 10.16) self-perceived health, musculoskeletal disease (RP 2.71 95%CI 1.84 - 3.98) and current smoking (PR 1.71 95%CI 1.18 - 2.47) were associated with back pain.

CONCLUSION:

Back pain is a common problem in PHU users in Brazil. Patients with musculoskeletal disease, who are current smokers and have a poor self-perceived health, are more likely to experience back pain.

Keywords:
Back pain; Chronic pain; Unified Health System

RESUMO

JUSTIFICATIVA E OBJETIVOS:

A dor nas costas é uma das principais causas de incapacidade em todo o mundo, resultando em maiores taxas de absenteísmo no trabalho e anos vividos com incapacidade. Este estudo teve como objetivo avaliar a prevalência de dor nas costas e seus fatores associados em usuários de Unidades Básicas de Saúde (UBS).

MÉTODOS:

Foi realizado um estudo transversal de base comunitária em UBS localizadas em Pelotas, Brasil. Foram entrevistados 15 indivíduos de cada UBS, com idade igual ou superior a 18 anos (n=540). A dor nas costas foi definida como dor em uma a três áreas das costas (pescoço, dorsal e lombar). Características demográficas, econômicas, comportamentais, nutricionais (índice de massa corporal) e de saúde foram avaliadas como covariáveis. A regressão de Poisson foi utilizada para estimar a razão de prevalência e os intervalos de confiança de 95%.

RESULTADOS:

A prevalência de dor nas costas em usuários de UBS foi de 20% (IC95% 16,8 - 23,6). Autopercepção de saúde regular (RP 2,66 IC95% 1,00 - 7,09) e ruim (RP 3,65 IC95% 1,31 - 10,16), doença musculoesquelética (RP 2,71 IC95% 1,84 - 3,98) e tabagismo atual (RP 1,71 IC95% 1,18 - 2,47) foram associados à dor nas costas.

CONCLUSÃO:

A dor nas costas é um problema comum em usuários de UBS. Pacientes com doença musculoesquelética, fumantes atuais e com autopercepção de saúde ruim são mais propensos a sentir dor nas costas.

Descritores:
Dor crônica; Dor nas costas; Sistema Único de Saúde

INTRODUCTION

Back pain is one of the main causes of disability worldwide, resulting in higher rates of work absenteeism and years lived with disability¹. In Southern Latin America, low back pain (LBP) and neck pain have a prevalence of 8.0% and 5.6%, respectively². Furthermore, chronic back pain prevalence, defined as pain in cervical, thoracic or lumbar area, is 17.7%³. LBP etiology includes myofascial pain, facet joint pain, discogenic pain, spinal stenosis, and might be worsened by psychological and disease related factors⁴. Approximately 80% of patients who experience LBP seek a healthcare professional to manage their pain. The general practitioner is the healthcare professional most sought by LBP patients⁵,⁶.

The Brazilian Unified Health System (SUS – Sistema Único de Saúde) was founded based on a new political and organizational formulation, aiming to reorganize health actions and services established in Brazil’s 1988 Constitution⁷. This system emerges as a decentralized strategy for attention and healthcare, using primary care as users main gateway⁸,⁹. Additionally, communication with SUS’ entire healthcare network takes place through Primary Health Units (PHU)¹⁰.

PHU are strategically located close to people’s home, school, and work. They are composed of multidisciplinary teams which play an important role to provide quality primary care to Brazilian public health system users¹⁰. Simple and cheap procedures are performed at PHU, where staff members are capable of solving most of the community’s common health problems.

However, their organization, applicability and development demand complex studies and deep knowledge regarding population reality¹¹. Users who seek care in PHU are, in general, individuals from a less privileged social level and can also be in vulnerability, who need equity in healthcare¹². As PHU are the community closest option of health care, this study aimed to 1) evaluate the prevalence of back pain (cervical, thoracic and lumbar) in PHU users and 2) to evaluate what factors were associated with back pain prevalence in this population.

METHODS

A community-based cross-sectional study was conducted at PHU located in the city of Pelotas, RS, Brazil. The structure of the manuscript agreed with STROBE requirements¹³. According to 2010 Demographic Census (IBGE), Pelotas is a city with approximately 327,778 inhabitants. Overall, there are 38 PHU located in the city urban area. Two PHU for specific populations (prisoners and children) were excluded. Following the worldwide prevalence of chronic pain (i.e., 35.5%)¹⁴, a sample size of 540 participants was calculated, with 80% power and 95% confidence level. In each PHU (i.e., 36 in urban Pelotas), 15 individuals, aged 18 or more, were interviewed (n=540). Participants were asked to take part in the study regardless of the reason they sought care in the PHU.

After the Municipal Health Department authorized the study, the PHU were contacted. Interviews were scheduled with the PHU head chief aiming not to disturb the unit’s normal operation. Data collection took place between March and June 2018, and interviews were conducted individually.

The first subject located on the right side of the room, starting from the entrance door was the first person asked to participate in the study. Then, the next subject located on the left side of the first participant was the next and so on, until the predetermined number of 15 participants was reached¹⁵,¹⁶. Individuals who were accompanying patients, who were not PHU users, as well as people unable to express themselves due to a health disability, did not participate in the study.

Back pain was defined as pain in one to three back areas (neck, dorsal and lumbar). Participants were asked about pain experience by the question: “Did you feel any pain this week”? If participants answered positively, a human body image in supine position was showed, and participants were then asked to point the pain location on the image. Participants who pointed one or more back areas on the image were considered as experiencing back pain.

Covariates

Demographic (age and gender), economic (wage), behavioral (smoking, alcohol intake, physical activity level and TV watching), nutritional status (body mass index) and health (self-perceived health, depression, musculoskeletal disease and drug treatments) characteristics were assessed. Age was divided into three categories: 18-39, 40-59, 60 or more years. Economic level was determined by the number of self-reported wages and classified in less than one wage, one to two wages and more than three (one minimal wage was R$ 954,00). Medical diagnostic of depression and musculoskeletal disorders were assessed by the questions of a Brazilian national survey¹⁷. Self-perceived health was classified in excellent/very good, good, fair and poor. Participants were asked about alcohol intake and had three response options: “no”; “yes, sometimes”; and “yes, every day’’. For analysis purposes, participants who reported alcohol intake sometimes or every day were classified by “yes”. The number of continuously used drugs was classified in none, one or two and three or more. Body mass index was calculated from self-reported height and weight, following the World Health Organization recommendation (normal <25 kg/m², overweight 25-29.9 kg/m² and obese ≥30 kg/m²). Smoking was categorized into never smoked, former-smoker and current smoker (one or more cigarettes per day for more than one month). Leisure-time physical activity was assessed through the International Physical Activity Questionnaire long version (IPAQ). A cut-off point of 150 minutes per week was used to classify subjects as active (150 min/week or more) or insufficiently active (below 150 min/week)¹⁸. Television time was calculated considering three or more hours per day.

The study was approved by the Research Ethics Committee from the Physical Education Faculty, Federal University of Pelotas (protocol number: 2.496.718).

Statistical analysis

EpiData 3.1 was used to structure the dataset. Descriptive analyzes of the sample, according to back pain report, are presented as relative and absolute frequencies. Prevalence ratio and 95% confidence interval between back pain and independent variables were estimated with crude and adjusted analyzes, using Poisson regression. A p<0.2 was considered aiming to control for potential confounders. Analyzes were conducted using Stata statistical software (StataCorp. 2012, Stata Statistical Software: Release 12, Version 12.1, StataCorp L P, College Station, TX, USA) with the significance level set at 0.05.

RESULTS

Overall, data of 540 users in 36 PHU from Pelotas were analyzed. Back pain prevalence was 20.0% (95%CI 16.8; 23.6). Higher frequencies of back pain were observed in those participants who were female, aged 40-59, smokers, with fair and poor self-perceived health, reported musculoskeletal disorders, depression, and continued use of drugs (Table 1).

Table 1
Descriptive characteristics, and crude analysis of back pain of Brazil Primary Health Unit users, 2018 (n=540)

Variables	Total sample n	Back pain %	PR	CI 95%	p-value
Gender					0.131
Male	147	15.7	1.0	–
Female	393	21.6	1.38	(0.91 – 2.10)
Age (years)					0.051
18-39	179	14.0	1.0	–
40-59	213	23.9	1.71	(1.11 – 2.65)
60-90	147	21.8	1.56	(0.97 – 2.51)
Income					0.401
< 1 wage	205	21.0	1.0	–
1-2 wages	274	20.4	0.97	(0.68 – 1.39)
> 3 wages	60	15.0	0.72	(0.37 – 1.38)
Health self-perception					<0.001
Excellent/very good	63	6.4	1.0	–
Good	199	12.1	1.90	(0.68 – 5.27)
Fair	215	24.7	3.88	(1.46 – 10.32)
Poor	63	42.9	6.75	(2.51 – 18.19)
Depression					<0.001
No	388	16.2	1.0	–
Yes	151	29.8	1.84	(1.31 – 2.56)
Musculoskeletal disease					<0.001
No	374	11.5	1.0	–
Yes	166	39.2	3.41	(2.43 – 4.78)
Smoking					0.007
Never smoker	276	15.9	1.0	–
Former smoker	155	21.9	1.38	(0.92 – 2.06)
Smoker	109	27.5	1.73	(1.15 – 2.60)
Alcohol intake					0.785
No	359	20.3	1.0	–
Yes	181	19.3	0.95	(0.66 – 1.37)
Leisure-time physical activity					0.172
0-149 minutes	432	21.2	1.0	–
≥ 150 minutes	106	15.1	0.71	(0.44 – 1.16)
TV watching					0.306
< 3 hours	339	18.9	1.0	–
≥ 3 hours	195	22.6	1.20	(0.85 – 1.68)
Body mass index					0.577
Normal	174	20.1	1.0	–
Overweight	186	22.6	1.12	(0.75 – 1.67)
Obesity	154	17.5	0.87	(0.55 – 1.37)
Use of drugs					0.002
None	197	12.7	1.0	–
1-2	172	23.3	1.83	(1.16 – 2.89)
≥ 3	171	25.2	1.98	(1.27 – 3.10)

• PR = Prevalence ratio; CI = Confidence interval of 95%.

The crude analyzes between back pain and covariates is displayed in Table 1. Mid-age adults were 71% (95%CI 1.11; 2.65) more likely to report back pain. Regarding health characteristics, those who perceived their health as fair or poor (PR 3.88 95%CI 1.46; 10.32; PR 6.75 95%CI 2.51; 18.19, respectively), who reported depression (PR 1.85 95%CI 1.31; 2.56) and musculoskeletal disease (PR 3.41 95%CI 2.43; 4.78) were more likely to experience back pain. Smoking (PR 1.73 95%CI 1.15; 2.60) and using one or more drugs (PR 1.83 95%CI 1.16; 2.89; PR 1.98 95%CI 1.27 - 3.10, for 1-2 and ≥ 3, respectively) were also associated with back pain.

Table 2 shows the adjusted analyzes between back pain and covariates. No association was observed with gender, age, income, depression, alcohol intake, BMI, TV watching and leisure-time physical activity. Fair (PR 2.66 95%CI 1.00 - 7.09) and poor (PR 3.65 95%CI 1.31 - 10.16) self-perceived health and musculoskeletal disease diagnosis (PR 2.71 95%CI 1.84 - 3.98) as well as current smoking (PR 1.71 95%CI 1.18 -2.47) remained associated with back pain. (Table 2).

Table 2
Adjusted analysis of back pain according to exposure variables of Brazil Primary Health Unit users, 2018 (n=540)

Variables	PR	CI 95%
Gender
Male	1.0	–
Female	0.95	(0.63 – 1.42)
Age (years)
18-39	1.0	–
40-59	0.92	(0.58 – 1.46)
60-90	0.78	(0.47 – 1.29)
Income
< 1 wage	1.0	–
1-2 wages	0.95	(0.67 – 1.35)
> 3 wages	0.91	(0.47 – 1.78)
Health self-perception
Excellent/Very good	1.0	–
Good	1.76	(0.65 – 4.73)
Fair	2.66	(1.00 – 7.09)
Poor	3.65	(1.31 – 10.16)
Depression
No	1.0	–
Yes	1.18	(0.84 – 1.66)
Musculoskeletal disease
No	1.0	–
Yes	2.71	(1.84 – 3.98)
Smoking
Never smoker	1.0	–
Former smoker	1.23	(0.84 – 1.82)
Smoker	1.71	(1.18 – 2.47)
Alcohol intake
No	1.0	–
Yes	1.03	(0.72 – 1.48)
Leisure physical activity per week
0-149 minutes	1.0	–
≥ 150 minutes	0.85	(0.53 – 1.36)
TV watching
< 3 hours	1.0	–
≥ 3 hours	1.22	(0.89 – 1.68)
Body mass index
Normal	1.0	–
Overweight	1.21	(0.83 – 1.75)
Obesity	0.83	(0.54 – 1.27)
Use of drugs
None	1.0	–
1-2	1.30	(0.80 – 2.12)
≥ 3	0.96	(0.53 – 1.72)

• PR = Prevalence ratio. CI = Confidence interval of 95%.

DISCUSSION

One out of five PHU users reported pain in their back. Having a poor health self-perception, a musculoskeletal disease and smoking were associated with higher prevalence of back pain in PHU users. Other sociodemographic, health and behavior characteristics were not associated with back pain in this population.

Back pain prevalence in PHU users is in the range of general population prevalence studies worldwide. Specifically, studies on back pain report prevalence of 13.9% in México¹⁹, 22.6% in Poland, 28.8% in Germany²⁰ and 31.5% in Australia²¹. A population-based study conducted in Pelotas, southern Brazil, found a one-year prevalence of 63.1% of back pain, being LBP the most prevalent, followed by thoracic and neck pain, respectively²².

Sampling variation process, as well as different characterization and the establishment of pain site, could make it difficult to compare data with other studies and could also explain the high range of prevalence among them. Also, one should note that PHU users are a specific population, which includes low economic status people and who exclusively use the public health system in Brazil. This population particularity could explain the difference among back pain prevalence in a population-based study and in a PHU-based study conducted in the same city.

LBP is the reason for 2.3% of general practitioner visits²³. Patients seek care in PHU for many reasons (e.g., take control drugs, routine practitioner visit, dental care, specialist referral, group activities diagnosis and treatment of chronic conditions such as diabetes, tuberculosis, and hypertension). Additionally, Brazil has a self-medication prevalence of 35%, which could lead individuals to take analgesics and non-steroidal anti-inflammatory drugs without consulting a general practitioner first. These factors could also have an influence on back pain prevalence found in this study.

The worse the subject’s perception of his/her health, the higher the frequency of comorbidities, being chronic spinal pain the most reported chronic condition²⁴. LBP had a negative effect in functionality, presenting negative implications on life quality, and a higher impact on this parameter than knee pain²⁵,²⁶. Also, health-related quality of life in LBP patients could be as low as in other chronic condition patients, such as kidney failure²⁷. Even though, health perception was measured by a general question, this study indicates an association among fair/poor self-perceived health and back pain.

Back pain could be related to specific spine conditions such as inflammatory or mechanical disturbances, as well as other conditions (e.g., inflammatory or infectious disease, tumor, or metabolic disease). Also, could be considered non-specific, that is, without a specific diagnosis²⁸,²⁹. Patients with musculoskeletal disorders generally look for general practitioner treatment, as well as for drugs to relieve pain intensity, which might explain the present findings on the association of back pain and musculoskeletal disease. Furthermore, it is important to highlight that PHU are the easiest and nearest health facility to seek care.

Association between smoking and back pain has been well established in literature. Data from a meta-analysis study indicate higher odds of back pain in former smokers (OR 1.27) and ever smokers (OR 1.26), in comparison with never smokers³⁰. Additionally, a study with US adults observed that back pain prevalence in current smokers is higher when compared to former and never smokers. Also, back pain prevalence of former smokers is higher than never smokers³¹. However, only ever smoker category was associated with back pain in the present study.

Even tough there is evidence on the protective effect of leisure-time physical activity on back pain³², the present study did not show an association between these variables. However, people who experience pain might be less likely to engage in physical activity to avoid worsening their pain¹⁶. This might explain the lack of association found in this study. However, future studies in PHU users should focus on physical activity and back pain.

Limitations of this study should be listed. First, different types of PHU (standard, Family Health, or mixed) offer different health care treatments. Actions and resources are more adequate in Family Health Program, because they are directed to programmatic actions, home activities and greater involvement with the community. On the other hand, in standard PHU, treatment depends on the patient’s initiative to seek care, which could interfere in their pain condition³³. Second, pain was assessed only in the last week, which doesn’t allow to make inferences about pain chronicity. However, to the authors knowledge this is the first study to evaluate back pain prevalence in PHU user’s population. In addition, the study assessed a representative sample of PHU users, providing information on a well-represented sample of such population.

CONCLUSION

In summary, the conclusion is that back pain is a common problem among PHU users, and is associated with musculoskeletal disease, smoking behavior and a poor health perception. Further studies are necessary to elucidate pain outcomes in this population, such as pain intensity, duration and disability.

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Publication Dates

• Publication in this collection
  06 June 2022
• Date of issue
  Apr-Jun 2022

History

• Received
  02 Feb 2021
• Accepted
  12 Apr 2022