Prevalence of Self-Reported Work-Related Lower Back Pain and Its Associated Factors in Ethiopia: A Systematic Review and Meta-Analysis

Introduction Low back pain is the commonest musculoskeletal disorder affecting every socioeconomic group of the world's population. The lifetime risk of developing low back pain is about 60%–80%. The pooled prevalence and associated factors of low back pain have not yet been determined in Ethiopia. Thus, this study was aimed at assessing the overall prevalence of low back pain and its associated factors in Ethiopia. Methods A systematic search of PubMed, Scopus, Science Direct, and Google Scholar for observational studies reporting data on the prevalence and associated factors of low back pain was conducted. Relevant data were extracted with a standardized data extraction excel form. Stata 14 was employed for the meta-analysis. Heterogeneity was assessed by Cochran's Q test and I2 values of a forest plot. Publication bias was checked using a funnel plot and Egger's test. A random-effects model was used in the analysis. Result A total of thirty-two studies were included for the systematic review. Twenty-four and sixteen studies were used to pool the overall low back pain prevalence and associated factors, respectively. The overall pooled annual prevalence of low back pain in Ethiopia was estimated to be 54.05% (95% CI: 48.14–59.96). Age, sex, body mass index, work experience, working hours, lack of safety training, awkward working posture, work shift, prolonged standing, lifting heavy objects, sleeping disturbance, history of back trauma, previous medical history of musculoskeletal disorder, and lack of adequate rest interval at work were significantly associated with low back pain. Conclusion The current systematic review and meta-analysis revealed a higher prevalence of lower back pain in Ethiopia. Most of the low back pain epidemiological studies conducted in Ethiopia focused on specific occupational settings, making pooling of data and comparison with other countries challenging. Thus, further general population studies are recommended.


Introduction
Lower back pain (LBP) is the most common musculoskeletal disorder (MSD) affecting the adult population, with a lifetime prevalence of up to 84% [1,2]. e pain is felt by patients from the anatomical area of the back below the twelfth rib and above the inferior gluteal fold [3]. e symptoms can arise from many potential anatomic sources, such as nerve roots, muscles, fasciae, bones, joints, intervertebral discs (IVDs), and organs within the abdominal cavity [2,4,5]. e lumbar vertebrae are the main anatomical framework of the lower back. e lumbar vertebrae are interconnected by joint capsules, ligaments, tendons, and muscles. It has extensive innervation and vascular supply. e vertebral column is designed to be strong since it has to protect the spinal cord and spinal nerve roots. At the same time, it is highly flexible, providing for mobility in many different planes [2].
On average, 95% of low back disorders are nonspecific or strain/sprain. e pain may arise from any of the spinal structures: intervertebral disc, facets, ligaments, vertebrae, tendons, and muscles [6,7]. Conventionally, the origins of LBP are grouped under four categories: discogenic/neurological, muscular/ligamentous, structural, and other disorders [8].
Work-related LBP is any back pain considered clinically to have been probably caused, at least in part, or aggravated by job [9]. It causes considerable absence from work and loss in productivity, resulting in financial burdens to employers, employees, and healthcare system [10]. It was identified as one of the top three occupational health problems to be targeted by the World Health Organization (WHO) [11].
Previous investigations have explored that LBP is the cause for an estimate of 818,000 and 21.8 million disabilityadjusted life years (DALYs) in 2000 [10] and 2010 [12], respectively. Approximately, 60% to 80% of people will suffer from LBP at some point in their lifetime [12].
Globally, low back and neck pain were ranked as the 12th, 8th, and 4th leading cause of DALYs in 1990DALYs in , 2005, and 2015, respectively. From 1990 to 2015, low back and neck pain DALYs increased by 59.5%. In 2015, low back and neck pain were the leading cause of disability in most countries (the second leading cause of DALYs in high-income countries next to ischemic heart disease) [13,14]. e global 12-month prevalence of LBP was estimated to be 38% from a systematic review of the general population studies published between 1980 and 2009. e mean point prevalence was 18.3%. Its lifetime prevalence was also estimated to be 38.9% [15]. However, in two earlier global LBP prevalence systematic reviews, one using studies conducted from 1954 to 1993 [16] and the other using studies conducted from 1966 to 1998 [17], pooling of data was not possible as a result of methodological variability between studies. e annual, point, and lifetime LBP prevalence in the general population ranged from 22% to 65%, 12 to 33%, and 11% to 84%, respectively, according to the systematic review conducted using studies all over the world from 1966 to 1998 [17].
A systematic review of 27 studies conducted in Africa revealed that the mean LBP point prevalence among adolescents was 12%, while among adults, it was 32%. e average one-year prevalence of LBP among adolescents and adults was 33% and 50%, respectively. e average lifetime prevalence of LBP among adolescents was 36% and among adults was 62%. e most common population on which research had been conducted was "workers" (48%) [18].
LBP is the leading common MSD. It accounted for 81.3% [20] and 60.2% [21] in India and Nigeria, respectively, from total MSDs. Its prevalence varies across the job type. Particularly, the prevalence rate is increased among agricultural workers, carpenters, welders, drivers, truck and tractor operators, nurses, cleaners, and domestic assistants [9]. For instance, the 12-month prevalence of LBP was 76.6% among operating room nurses and 75.1% among X-ray technologists in Netherlands [22]. A recent meta-analysis showed that LBP is the most prevalent work-related MSD (62%) out of the nine musculoskeletal body regions among perioperative nurses [23].
Low back pain is a multifactorial problem having many possible etiologies. Determining risk factors for LBP is therefore a difficult task. A multitude of determinants of LBP and sciatica includes sociodemographic and individual factors, physical factors, and psychosocial factors [24].
Factors such as job dissatisfaction, low social support from colleagues or supervisors, job stress/high workload, feeling little pleasure, sleeping disturbance, and depression were also implicated to be associated with LBP in different studies [38,45,46]. e overall prevalence and risk factors of work-related LBP in Ethiopia have not yet been investigated. us, the main aim of this systematic review and meta-analysis was to estimate the pooled prevalence and identify the factors associated with work-related LBP in Ethiopia. Moreover, this study has also assessed the methodological quality of available studies. e results of this meta-analysis will help policy-makers and other concerned bodies to plan and implement strategies to prevent the impacts of LBP. It will also help researchers to improve future research quality on LBP in particular and musculoskeletal pain in general as the methodological quality of previous studies was critically appraised. e review question is as follows: what are the overall prevalence and associated risk factors of work-related LBP in Ethiopia?

Search Strategy.
Observational studies reporting the prevalence and associated factors of LBP in Ethiopia were gathered by using the following search approaches: (i) Search for published journal articles using international scientific databases including PubMed, Google Scholar, Science Direct, and Scopus (ii) Search for unpublished MSc/PhD thesis reports using Google, Google Scholar, and local university websites Study articles were retrieved by using search terms like ("prevalence" OR "magnitude" OR "epidemiology" OR "burden") AND ("associated factors" OR "risk factors" OR "factors") AND ("low * back pain" OR "back pain" OR "musculoskeletal disease" OR "musculoskeletal disorder OR musculoskeletal pain") AND "Ethiopia." All fields and MeSH terms were used to search PubMed. MeSH terms were not used to search the rest of the databases. e first search was done until the end of November 2019 and repeated on July 30, 2020. No date range restrictions were employed. Following the initial search, the articles that were included were also reference searched to exhaustively retrieve the articles. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline was strictly followed as shown in Figure 1. e full search strategy is available upon request from the corresponding author.

Criteria for Considering Studies for is Review
Observational studies (cross-sectional, cohort, and case-control) having relevant extractable data regarding the prevalence and associated factors conducted in Ethiopia at the community or facility level were included in the review. Both published and unpublished articles in the English language were included.

Exclusion Criteria.
Research articles that did not report the outcome of interest after reviewing were excluded. Studies conducted on specific age or sex categories were also excluded from the meta-analysis part because it creates more heterogeneity between studies.

Data Extraction.
Important data including author, publication year, number of study participants, study design, study area, sampling procedure, prevalence of LBP, and risk factors with their odds ratio were extracted using a consistent Microsoft Excel format.
Variables mentioned in two or more included studies were selected to be included in this systematic review and meta-analysis. Moreover, the variables should be significantly associated with LBP in at least one included study.

Methodological Quality Assessment of Studies.
e methodological quality of the included studies was assessed using the "Newcastle-Ottawa Quality Assessment tool adapted for cross-sectional studies" [47], which was previously used by Leboeuf-Yde and Lauritzen, 1995 [16], Walker, 2000 [17], Louw, 2007 [18], and Morris, 2018 [19] for a similar purpose (see Additional file 1). e tool contains three parts: representation of the target population, data quality, and case definition of the LBP. e tool has ten items, each having equal weight, and the total score was 100. " e Joanna Briggs Institute (JBI) Critical Appraisal Checklist for Case Control Studies, 2017" [48] was used to appraise one case-control study (see Additional file 1). Two of the authors (MJ and MA) independently evaluated the methodological quality of the studies. Differences in opinion between the reviewers were discussed until consensus was reached.

Statistical Analysis.
Review data were extracted using Microsoft Excel format and exported to Stata/SE 14 for analysis. Forest plot was done to check heterogeneity between the studies. In the forest plot, χ 2 test, I 2 test, and P values were checked for heterogeneity. A value of zero indicates true homogeneity, while values of 25%, 50%, and 75% indicate low, moderate, and high heterogeneity, respectively [49]. Due to an anticipated heterogeneity, a random-effect Der Simonian and Laird's model [50] was applied to estimate the pooled prevalence of LBP.
Possible publication bias was also evaluated objectively by using Egger's correlation and Begg's regression intercept tests at a 5% significant level [51]. Furthermore, to reduce the random discrepancies between the point estimates of the primary study, subgroup analysis was carried out based on occupation of the study participants and the region where the studies were conducted. A univariate metaregression model was also carried out to identify the possible sources of heterogeneity by considering study characteristics, such as publication year and sample size. A metaregression analysis was performed to assess the different factors associated with LBP.
2.6. Definition of Terms 2.6.1. LBP. LBP is the experience of pain, ache, or discomfort, felt below the costal margin and above the inferior gluteal folds, with or without leg pain for at least one-day duration [3].

Lifetime Prevalence.
Lifetime prevalence is the experience of LBP at any point in the individual's lifetime.

Annual Prevalence.
Annual prevalence is the experience of LBP at any point in the past 12 months.

Study Identification.
A search of the important databases yielded a total of 394 articles. One unpublished MSc thesis was also found. After removal of 42 duplicate and 301 unrelated articles, 52 studies were selected for in-depth screening. After title and abstract screening, 42 full-text articles were assessed for eligibility. 10 articles were again excluded by the exclusion criteria after full-text reading. 32 articles were finally included for the review and metaanalysis ( Figure 1). e search strategy and results obtained using PubMed are shown in Additional file 2. A list of the excluded studies and the reasons for their exclusion is available from the corresponding author.

Characteristics of Included Studies.
A total of 32 observational studies with a sample size of 13,859 respondents were included in this review. e characteristics of the included studies are shown in Tables 1 and 2. e articles range in date from 2009 to 2020 with the mean year of publication being 2017. 75% of the included studies were published or conducted during and after the year 2017. e majority of the included studies [31] were cross-sectional by design. Most of the studies were conducted in Addis Ababa (11 studies) and Oromia (10 studies). e other eight studies were conducted in two regions: 6 in Amhara and 2 in Tigray.
In those studies that reported data about gender distribution, 49.64% of the respondents were females. However, data on gender distribution were missing in three of the included studies, namely, Lette et al. [75], Lamina   Sample size varied from 100 [73] to 814 [68] (mean � 433.09 ± 162.93); response rate varied from 82.3% [67] to 100% [57, 66, 69-71, 74, 76] (mean � 95 ± 5.23). ree studies (Jeon and Jeon [87], Yitayeh et al. [72], and Abir et al. [86]) did not report the response rates. In the case-control study, Deksisa et al. [82], the response rate is not applicable. In 22 of the studies, an interviewer-administered standardized questionnaire was used as a data collection tool, while in the rest 9 studies, self-administered questionnaire was employed. In one study, Abir et al. [86], a combination of questionnaire, interview, and document review was employed. e questionnaire employed by most of the included studies was adapted from the Standardized Nordic Questionnaire for the Analysis of Musculoskeletal Symptoms (SNQAMS) [3]. 30 of the studies reported data about the prevalence of LBP, whereas 18 studies recorded data about the factors associated with the development of LBP.

Quality Assessment Results of Included Studies.
e mean methodological quality score of the 32 included studies was 84.51%. 12.5% of the studies scored 100%. Criteria item 2 is not applicable to 7 of the studies because their response rate is 100%. Considering the mean methodological score, the authors determined arbitrarily the threshold for acceptable study quality to be 70%. Two studies, Abir et al., [86] and Jeon and Jeon, [87], were excluded from further analysis as they scored below 70% (Table 3).

Definition of Low Back Pain.
Out of the thirty-two studies included, only eleven specified the minimum duration of the episode to be counted as a case of LBP. Seven of them specified the minimum duration as "2-3 days," while four of them specified the minimum duration as "at least one day." Twenty-five studies stated the anatomic location of the pain in their case definition. Fourteen mentioned the area as "the lower back, lumbar, or buttock area" and the rest eleven identified it as "the area of the back below the 12th rib (costal margin) and above the inferior gluteal fold." Six studies did not provide the case definitions of LBP.

Prevalence of Low Back Pain.
e 12-month prevalence of LBP ranges from 3.21% in office workers to 82.93% in nurses. ere were about 6,753 cases of self-reported LBP out of the 13,265 study participants of the 30 studies that Table 1: Characteristics of the included studies, part one: publication year, setting, population, region, and design of the study.
Journal of Environmental and Public Health reported magnitude. e mean annual prevalence of LBP was 50.69% ± 17.75. All primary studies retrieved focused on a specific occupation. e magnitude and related factors associated with LBP were well studied in the nursing profession (9 studies) and industry workers (6 studies). ere was no LBP prevalence study found conducted on the general population in Ethiopia. All were done using a certain specific occupation. e mean prevalence of LBP in the studies that defined the anatomical area as the "posterior aspect of the body from the lower margins of the twelfth ribs to the lower gluteal folds" (50.39%) was comparable with that in studies that did not specify the anatomic location (50.06%).

Pooled Prevalence of Low Back Pain.
Not all studies included in the systematic review were pooled in the metaanalysis to keep homogeneity. Pooling of studies was evaluated not only by methodological quality but also by their similarity in the study population (general or working), age, sex, and definition of LBP. Considering this evaluation criterion, in addition to the studies excluded by poor methodological quality, four more studies were excluded objectively from the main meta-analysis. ese were Delele [88] (because it used only children and youngsters less than the age of 18 years); Tefera et al. [68] (because it used only young adolescents in the age of 14-17 years); Yosef et al. [62] (because it used only female respondents); and Henok [74] (because it used only male respondents).
Twenty-four studies were therefore finally pooled to estimate the prevalence of LBP in Ethiopia. e studies selected for the pooling of LBP prevalence were those studies that reported similar recall periods of LBP prevalence; studies that used both genders; studies that did not use a specific age population; studies that mentioned a similar anatomic location of pain. All included studies in the systematic review were done on a certain working population. Although the difference in the type of work the study subjects were engaged in was noted, the pooling of the data was decided by the authors as work-related LBP. erefore, the data pooled in this meta-analysis included the adult working population of both genders. e overall pooled 12-month prevalence of self-reported work-related LBP from 24 Ethiopian studies yielded 54.05% (95% CI: 48.14-59.96) (Figure 2). Only five studies provided data about seven-day LBP prevalence and the pooled prevalence was estimated to be 37.48% (95% CI: 22.63, 52.33). e pooled point LBP prevalence (40.82%) was estimated from only two studies.
ere was no sufficient number of studies to pool the lifetime prevalence of LBP. e I 2 statistic revealed considerable heterogeneity between the studies (I 2 � 97.6, P ≤ 0.001). Hence, a random-effects model was used to estimate the pooled prevalence of LBP in Ethiopia.

Subgroup Analysis.
To identify the possible sources of heterogeneity among the included studies, subgroup analysis was performed using occupation, region, sample size, and publication year to estimate the overall prevalence of LBP. Administrative regions of Ethiopia and occupations mentioned by the primary studies were used for grouping. e minimum adequate sample size for a cross-sectional study (422) was used as a cut-off value to group by sample size. In order to group by publication year, three consecutive years were grouped together by judgment. Accordingly, the highest LBP burden was observed among the studies conducted in Tigray region (74.8%) and the lowest was observed to be in Harari and Dire Dawa (38.12%) (Figure 3). Subgroup analysis by occupation revealed that the lowest LBP was observed among industry workers with a prevalence of 48.39% (95% CI: 35.61, 61.17) (Figure 4). e highest prevalence was observed among hair dressers (71%). e subgroup analysis by sample size also showed a significant difference between studies conducted with a sample size >422 (60.51%) and ≤422 (51.36%) ( Figure 5). e prevalence of LBP was found to be 60%, 48

Sensitivity Analysis.
ere were six studies excluded from the main meta-analysis with reason. e annual LBP prevalence in these six studies ranged between 3.21% and 65%. Had these six studies been included to estimate the pooled LBP prevalence in the meta-analysis, it would have been 50.68%. e pooled annual prevalence of LBP in all the 30 studies identified reporting magnitude (including the six studies already excluded) was found to be 50.68% (95% CI: (41.12, 60.24)). e pooled annual prevalence of LBP using the 24 methodologically sound studies was 54.05% (95% CI: 48.14-59.96). us, limiting the analysis of studies based on methodological quality score therefore significantly increased the annual LBP prevalence from 50.68% to 54.05%.

Journal of Environmental and Public Health
Respondents who were 30 and above years of age were 1.74 times more likely to develop LBP than those who were below 30 (POR: 1.74, 95% CI (1.25, 2.41)) ( Figure 8). e odds of developing LBP were 1.47 times more likely among females than males ( Figure 9). Respondents whose BMI was greater than or equal to 25 kg/m 2 had 1.62 times odds of developing LBP compared to those whose BMI was below 25.
Study participants who had five or more years of work experience were 2.26 times more likely to have LBP than those of workers with work experience of less than five years. ose who work for 8 or more hours per day had 2.69 times odds of developing LBP compared to those who work for less than 8 hours. e likely hood of developing LBP among respondents who lacked health and safety training increased by 2.16 times compared to those who took the training. Respondents whose job requires assuming awkward working postures such as repetitive bending, twisting, and overstretching had increased odds of having LBP by 197% (POR: 2.97) compared to those whose task does not require. e other work-related factor significantly associated with LBP was heavy weight lifting. Respondents who were involved in heavy weight lifting activities were 1.49 times more likely to have LBP than those who were not involved.
Workers who had both shifts (day and night) were 1.61 times more likely to develop LBP than those who worked only in the day shift (POR � 1.61; 95% CI: 1.11, 2.32). Workers who had a history of back trauma were 3.46 times more likely to develop LBP than those who did not have trauma. ose who had a previous medical history of MSD were 5.06 times more likely to have LBP than those who did not have.

Discussion
e 12-month prevalence of LBP in the current systematic review ranges from 3.21% in office workers to 82.93% in nurses. However, limiting the reports only to methodologically sound studies changed the range from 25.61% to 82.93%. As stated in other similar systematic reviews [15][16][17][18][19]89], it is very challenging to compare and pool the prevalence of LBP between populations as there are considerable methodological variabilities across studies. All previous attempts to pool the prevalence of LBP were not successful because of methodologic heterogeneity and poor qualities of studies. Some of the various methodological differences include variability in sample size; differences in LBP case definition, particularly prevalence period, minimum duration of pain, and anatomic location of the pain;    Journal of Environmental and Public Health using nonstandard tools for measurement of outcomes; and heterogeneity in the study population such as age and sex. However, the improvement in methodologic homogeneity, especially the relative similarity in data collection tools and LBP case definitions seen in the studies included in our review, justified the pooling of LBP prevalence. On the other hand, comparison of the current systematic review and meta-analysis with other previous systematic reviews is difficult and should be interpreted cautiously. is is because the current review involved the working population while previous reviews involved the general population [15,17], the elderly [90,91], adolescents [92], and children [93]. e current one-year pooled prevalence of LBP in Ethiopia (54.05% (95% CI: 48.14-59.96)) was comparable with a mean estimate of Nigeria (55.39%) [89]. e 12month prevalence of LBP in Nigeria ranged from 32.5% to 73.53% [89], which is different from the current finding (25.61% to 82.93%). All reviewed studies were occupationbased and did not depict a true general population prevalence of LBP in both the present review and the case of Nigeria. Another systematic review conducted in Africa reported a 12-month prevalence of LBP ranging from 14% to 72% [18]. e current meta-analysis overall estimate lies in this range. e pooled annual prevalence of LBP in Ethiopia (54.05%) was more or less comparable with a study in Botswana (55.7%) [39] and the recent systematic review conducted using African studies published after 2006 (57%) [19]. e lowest prevalence observed in the African studies systematic review (51%) was higher than the current lowest prevalence (25.6%).
A systematic review of LBP using studies conducted between 1966 and 1998 by Walker [17] revealed a point prevalence ranging from 12% to 33%; one-year prevalence ranging from 22% to 65%; and lifetime prevalence ranging from 11% to 84%. A higher annual LBP prevalence range (25.61% to 82.93%) was observed in the current systematic review and meta-analysis since the studies included were done on the vulnerable population (working population), whereas Walker [17] included only studies conducted on the general population, excluding the working population.
In a systematic review of general population studies conducted from 1980 to 2009, the global 12-month prevalence was estimated to be 38%, which is much lower than the current meta-analysis (54.05%). is discrepancy is likely to be due to the variation in the study population (general versus working population). e mean point prevalence from the same systematic review was 18.3%, which is again lower than our current point prevalence estimate (40.86%).

Journal of Environmental and Public Health
Another possible cause for the high pooled prevalence demonstrated in our current meta-analysis could be the age range of the respondents in the included studies apart from the inclusion of only studies conducted on a working population. As noted above in the Results section, in the majority of the studies, the respondents' mean age ranges from 25 to 35 years. erefore, the inclusion of the middleaged adult population in the review might have contributed to the higher prevalence of LBP as also reported in previous studies [15,25,94,95].
Our subgroup analysis showed the annual prevalence of LBP among nurses to be 53.4%, which is in agreement with a study done in India (53.4%) [96], but lower than the studies in Iran (74.3%) [97], Nepal (75.7%) [98], and Uganda (58.7%) [99]. It was also lower than the systematic review done in Africa among nurses (64.07%) [100]. Such differences can be attributed to the general work environment variation between health service settings across countries, particularly related to the variation in the number of nursing staff and workload. e other possible reason for the higher prevalence among nurses in other countries could be the higher proportion of female-to-male ratio in the nursing profession compared to Ethiopia. e annual pooled prevalence of LBP among industry workers in our subgroup analysis was 48.39% (95% CI: 35.61, 65.19). It was lower than the studies conducted using a similar industrial population in Iran (57.1%) [101], Kosovo (61.6%) [102], and Nigeria (59.5%) [103]. A comparison with previous studies is shown in Table 7.   e results of the present systematic review and metaanalysis found out that several physical, sociodemographic, and individual factors are associated with LBP. e current meta-analysis of risk factors showed age to significantly affect the chance of developing LBP, which is in line with previous systematic reviews such as Louw [18], Hoy [25], Hoy [15], Manchikanti [24], and Jordaan [26]. According to a study done in India [32] among textile industry workers, age ≥35 years was found to have 9 times more risk than age <35 years (AOR � 9.45; 95% Cl: 5.24,17.01). e increased occurrence of LBP as age advances can be explained by increased disc degeneration and decreased elasticity of ligaments. e prevalence of disc degeneration was 34% in 20-39, 59% in 40-59, and 93% in 60-80 years old persons in MRI study [104]. Lumbar spine stability diminishes following lumbar disc degeneration. An unstable lumbar spine then imposes a higher biomechanical demand on the ligaments, capsules, muscles, and facets [9].
Our current analysis of risk factors revealed that LBP was more prevalent in the female gender, which is consistent with other systematic reviews such as Louw [18], Jordaan [26], and Wang [27]. Osteoporosis, menstruation, pregnancy, and giving birth could contribute to the increased prevalence of LBP in females compared to males [15]. e other individual factor found to be associated with LBP was BMI. is finding was consistent with other studies in the United States [36], Israel [34], Norway [35], and India [32]. Among textile industry workers in India [32], obese subjects were highly affected by LBP (AOR � 9.14; 95% CI: 4.95, 16.87). In a meta-analysis of 33 studies by Shiri [33], obesity was associated with increased prevalence of LBP (POR: 1.33; 95% CI: 1.14, 1.54) in cross-sectional studies and (POR � 1.53; 95% CI: 1.22, 1.92) in cohort studies. Although several literature studies mentioned the association of BMI with LBP, the exact mechanism of how increased BMI or body height causes LBP remains unclear [34].
Work experience of more than five years, working more than eight hours per day, and working in both shifts (day and night) were associated with an increased risk of LBP compared to their counterparts. Similar reports from the United States [105] supported our finding of increased working hours spent on repeated activities and back pain. e association of work shift and LBP was also demonstrated in other reviews and studies [40,41]. e increased occurrence of LBP in those who work in both shifts might be due to disturbance of the normal circadian rhythm and increased workload during the nighttime. e other significantly associated factor identified was health and safety training. Workers who took ergonomics training (occupational health and safety training) were less likely to report LBP than those who did not. A similar finding was observed in Hong Kong [106]. It is obvious that  workers who are aware of ergonomic precautions are likely to implement preventive measures and will reduce their exposure to MSDs including LBP.
Similar to the reports of Bongers et al. [38] and Malikraj [20], our study demonstrated that awkward working posture (frequent bending, twisting, and overstitching) is a major risk factor for LBP. A similar finding was also reported from a study in Nigeria [42], Saudi Arabia [43], and Malaysia [44]. Frequent bending and twisting were reported to be the most frequent causes of back injuries in England [107]. Lateral bending and twisting while lifting heavy objects were found to be harmful [108,109]. Bad body postures during work such as twisting, leaning, bending, kneeling, overstretching, and squatting are believed to increase spinal stress and accelerate degenerative changes in the disc and other structures [110,111].    Previous findings indicated that types of jobs that require static work postures, such as prolonged standing and sitting, increase the risk of developing LBP [24,112], which is consistent with our current findings. Prolonged standing causes excessive strain on the lumbar spine and other anatomical structures responsible for the development of MSDs, including LBP.
Workers involved in heavy weight lifting had an eight times higher incidence of low back injuries than sedentary work [113]. Another prospective cohort study also identified heavy weight lifting as an important physical risk factor [38]. Heavy physical strain, frequent lifting, vibration, and postural stress are likely to result in disc degeneration and LBP [24].
Although the relationship can be two-sided, sleeping disturbance was significantly associated with LBP in the current meta-analysis. Another recent meta-analysis [114] revealed a similar association but with relatively lower odds (1.52) than the present study (2.07).
Having a history of back trauma as well as a previous medical history of MSD was associated with increased risk of LBP in the present work with higher odds than all other risk factors. A history of work-related low back injury was positively associated with LBP in a study done in Canada [115] (AOR � 3.66; 95% CI: 2.48, 5.42). A history of musculoskeletal disease was also associated with an increased risk of LBP (OR � 7.1) in a study conducted in Vietnam [116]. e current systematic review and meta-analysis did not show a statistically significant association between physical exercise and LBP, which is consistent with other previous systematic reviews [117,118]. However, in other systematic reviews, conflicting evidence has been reported between leisure-time physical activity and LBP. For instance, Hosam et al. in their systematic review and meta-analysis of crosssectional studies found a significant reduction in LBP among individuals who perform physical exercise [119]. Similarly, Shiri and Falah Hassani [28] reported a decreased risk of chronic LBP among individuals who engaged in medium  and high-level leisure-time physical activities in a metaanalysis of cohort studies. On the other hand, a systematic review of observational studies reported an increased risk of LBP among individuals who perform strenuous physical activity [120].
None of the psychosocial factors in the analysis of risk factors in this meta-analysis showed a significant association with LBP, although some of the included studies have reported associations. As opposed to our findings, studies elsewhere showed low job satisfaction, high workload, and decreased social support from colleagues or supervisors to be associated with LBP [38,45,46]. is difference could be attributed to the variation in the social work environment and workload between Ethiopia and other countries. Cigarette smoking, alcohol drinking, night shift, and employment status did not show a significant association with LBP in this meta-analysis of risk factors.

Limitations
Hotel housekeepers, hair dressers, drivers, barbers, bank workers, and cobble stone workers were each represented in the systematic review and meta-analysis by only one study. Most of the significant work-related factors of LBP in these studies were not included in the analysis because the factors should be found in at least two studies.
Extracting data on risk factors from the original studies was a challenging task as there is no homogeneity in constructing and measuring the factors. As a result, some studies were omitted from the analysis of risk factors, and this could introduce bias.
It should be noted that causal relationships cannot be established from the results of the factor analysis since most of the studies included in the meta-analysis were crosssectional by design.

Conclusion
is systematic review and meta-analysis revealed a high burden of LBP in the working segment of the Ethiopian population. A high burden of LBP among teachers, nurses, industry workers, drivers, hair dressers, hotel housekeepers, cobble stone workers, and bank workers was noted. Ergonomic, individual, and sociodemographic factors associated with LBP have been identified and their strength of association has also been measured in the present work. e current systematic review and meta-analysis indicated that implementing appropriate interventional ergonomics programs in the workplace and providing training to the workers could help reduce LBP incidence. e authors recommend conducting a more comprehensive study involving the general population at the community level. Moreover, future studies shall have uniformity in their methodology, especially in terms of data collection tools and case definition so that further pooling and comparison will be possible. Only one study has been found conducted among agricultural field workers. Further research may be needed to investigate the situation of LBP in this significant segment of the Ethiopian population. Further large-scale prospective studies are needed to determine if the associations of LBP with the factors identified in this metaanalysis are causal.

AOR:
Adjusted odds ratio BMI: Body mass index IVD: Intervertebral discs CI: Confidence interval LBP: Low back pain MRI: Magnetic resonance imaging MSD: Musculoskeletal disorder OR: Odds ratio POR: Pooled odds ratio SNQAMS: Standardized Nordic questionnaire for the analysis of musculoskeletal symptoms WHO: World Health Organization.
Data Availability e datasets used and/or analyzed during the current study are available from the corresponding author upon reasonable request.

Conflicts of Interest
e authors declare that they have no conflicts of interest.

Authors' Contributions
Mihretu Jegnie developed the protocol and design of the study. Mihretu Jegnie and Mekbeb Afework performed the article searching, data extraction, and analysis. Mihretu Jegnie was a major contributor in writing the manuscript. Mekbeb Afework reviewed and assessed the quality of the manuscript. Both authors read and approved the final draft.