Work related low back pain and associated factors among hairdressers in Mekelle, Tigray, Ethiopia; cross-sectional study. CURRENT STATUS: POSTED

Background Low back pain is one of the most prevalent musculoskeletal conditions and the most common cause of disability. Hairdressers are one of the high-risk professionals for work-related musculoskeletal disorders like low back pain. However, studies on the prevalence and associated factors of low back pain among hairdressers are scarce. The objective of the current study is to assess the magnitude and associated factors of work related low back pain among hairdressers working in female beauty salons. Method An institutional-based cross-sectional study was employed from January 05 up to February 28, 2018. The sample (n=344) hairdressers were selected randomly from all-female beauty salons of Mekelle city. A structured questionnaire adapted from a standardized Nordic questionnaire and other similar studies was used. Binary logistic regression analysis was performed to identify factors associated with low back pain. The Adjusted Odds Ratio (AOR) with a 95% Confidence Interval (CI) was estimated to show the strength of association. A p-value of < 0.05 was used to declare statistical significance.

Low back pain (LBP) is a common health problem, which most people experience at some point in their lifetime (1). Back pain can be categorized into specific or non-specific back pain. Non-specific back pain is diagnosed when the cause of the back pain is unknown and specific back pain refers to a specific cause for the pain, for example, an infection or a fracture (2). LBP can be acute, sub-acute or chronic, affecting all ages from children to elderly and is a very common reason for medical consultations (3).
The 2010 global burden of disease study estimated that low back pain ranked highest in terms of years lived with disability (YLDs), and sixth in terms of overall burden disability-adjusted living years (DALYs) (4). It has a numerous economic burden on individuals, families, communities, and country in general with the estimated point prevalence range from 1.0% to 58.1%, and 1-year prevalence from 0.8% to 82.5% globally(1). [7]Although it was largely thought of as a problem confined to western countries; LBP is also a major problem in low and middle-income countries (5). In Ethiopia, researches are available in the literature on low back pain, especially among professionals like nurses, teachers and taxi drivers with 12-month prevalence ranging (45 -71%) (6)(7)(8). LBP may be associated with different biomechanical factors (heavy physical work, awkward static and dynamic working postures, and lifting), psychosocial factors (low level of job control, high psychological demands, and high work dissatisfaction) and individual factors (younger age, female gender, black or African American race, smoking, high BMI, and co-morbidity) (9).
Hairdressing is one of the high-risk occupations to sustain low back pain. According to a study in the USA, hairdressers were one of the top 15 high-risk occupations for back pain attributed to activities at work in females among 45 major occupations (10). In the African continent, a study from Nigeria and Egypt shows that low back pain was one of the highly prevalent work-related musculoskeletal disorders among hairdressers with annual prevalence (76.3%) and (12.5 %) respectively (11,12). In Ethiopia, one study found that the prevalence of work-related musculoskeletal disorder was 76.6% and the low back was one of the most commonly affected body parts that account 71.5% among the hairdressers of Addis Ababa (13).
Despite the hairdressing salon, businesses are growing in number and the professionals are prone to low back pain, epidemiological studies that assess the magnitude of LBP among these workers are limited and little is known about the associated factors of LBP among the hairdressers in Mekelle and other parts of Ethiopia. Implementing a rehabilitation course brought a good outcome on the musculoskeletal pain value and prevention after 1.5 years of follow-up among Finland hairdressers who had visited a physician and a physiotherapist (14). Therefore, identifying the associated factors is essential for prevention, providing rehabilitation courses and professional recommendation on the ergonomic and biomechanical posture for hairdressers. The main aim of this study is to determine the magnitude and associated factors that contribute to the development of LBP among workers engaged in hairdressing activity.

Study design and setting
An institutional-based cross-sectional study was conducted in Mekelle city, Tigray, northern Ethiopia from January 05 up to February 28, 2018. Mekelle city is located in the northern part of Ethiopia in Tigray national regional state, at a distance of 783 km from Addis Ababa. Its location is 13º32'' North latitude and 39 º 28' East longitude. Mekelle has a city administration, municipality, 7 sub-cities (15).
According to the Tigray Bureau of trade, industry and urban development office 451 licensed and registered female beauty salons were found in the city.

Study and source population
The source populations of the study were all hairdressers working in all-female beauty salons of Mekelle city. All hairdressers who had one year and above work experience on the job and working in the sampled female beauty salons of Mekelle city were the study participants.

Sample size and sampling technique
The sample size for the study was determined using the formula of the single population proportion.
There were 451 female beauty salons registered by license registration of the Tigray Bureau of trade, industry and urban development office. The registration list contains the name and address of the beauty salons. The sample, 344 beauty salons were selected using simple random sampling by a lottery method using the name of beauty salons from the list. Then the sample 344 hairdressers were collected randomly from the selected female beauty salon.
Data collection and quality control An interviewer-administered questionnaire was used. The questionnaire was first prepared in English then translated into the local language "Tigrigna" and then back to English to ensure consistency. The data collection tool was pretested in 10% of the sampled population. Some modification on the questioners was done and the same understanding in all the data collectors was created. The questions to detect the self-reported low back pain were adapted from the standardized Nordic questionnaire (16). Questions adapted from other studies with some modification was used to assess the socio-demographic, working environment and psychosocial status of the participants. The psychosocial factors job satisfaction and job stress were measured using the 9 items of job satisfaction scale as yes (32 -50) and no (10 -31) (17) and the workplace stress by 8 item scale as yes with a total score of (16 -40) and no (≤ 15) (18).
Eight data collectors (physiotherapists and nurses) and two supervisors (physiotherapists) were involved in this data collection. Both the data collectors and supervisors had taken two days of training before the actual data collection time about all aspects of data collection tools, questioning techniques, and ethical issues. The collected data were checked out for completeness and clarity by the principal investigator and supervisors. Data cleanup and cross-checking were done before analysis.

Data analysis
Data were entered, coded, cleaned and analyzed using the IBM Statistical Package for Social Sciences (SPSS) version 23 for windows. Mean with its standard deviation and median with its range were determined to summarize and present numeric variables. Summarized frequencies and proportions of categorical variables were presented using text and tables. The logistic regression model was used to identify factors associated with low back pain. Independent variables with a p-value less than < 0.25 in the bivariate logistic regression were fitted into the multivariate logistic regression for controlling the possible main effect of confounders and are reported using CORs. Model fitting was checked using log-likelihood, Hosmer and Lemeshow goodness of fit test. Finally, variables with P < 0.05 in the multivariate analysis were considered statically significant and presented by AOR with 95% C.I.

Operational definition
Work related low back pain: is self-reported pain, ache or discomfort for at least 2 working days during the last 12 months in the lower back. These symptoms often appear and aggravated at work that disappears during rest and after work ends (19).

Socio-demographic/Individual characteristics of hairdressers
There were 344 sampled hairdressers participated in this study giving a response rate of 314 (91.3%) of the total study participants. The majority of the hairdressers 289 (92%) were females with the     (Table 4).

Discussion
The study was designed to evaluate the prevalence and associated factors of the WRLBP among hairdressers in Mekelle city, Tigray Ethiopia. This study found that the prevalence rate of WRLBP within the past 12 months was (47.5%) which is comparable with studies done in, South Africa, Brazil, Greece and United Kingdom (39%-53%) (20)(21)(22)(23). The prevalence was higher compared to the studies conducted in Ibadan Southwest Nigeria, France, and Egypt which were (12.5% -31%) (12,24,25).
However, it is lower relative to studies done in Taiwan, Nigeria and Addis Ababa, Ethiopia (71.5% -83%) (11,13,26). The difference might be due to differences in sample size, the definition of low back pain, study area, workload and the difference in assessment tools of the studies. Example, The study conducted in Egypt, that reported a low prevalence of LBP (12.5%) was a comparative study with a small sample size among 80 hairdressers and 50 office workers (12). On the other way hairdressers in Addis Ababa, Ethiopia showed more prevalence of LBP(71.5%) than this study (13). It could be due to more sample size or as the participants were from the capital city of the country they might be open enough to report their pain. In general, the high prevalence of LBP among hairdressers might be due to the stress imposed on the lower vertebral structures by working in prolonged bending and twisting in awkward way working posture. This was supported by the study in the USA, on which hairdressers were one of the top 15 high-risk occupations for back pain among 45 major occupations (10).
In this study, the majority of the hairdressers, 72.5% and 45.6% of those with WRLBP reported that LBP affected their working and leisure time activities respectively. The United States Bureau of labor statistics found that 53% reported taking sick leave and 10% of them got a permanent work disability pension as a result of back pain (27). Similarly, studies conducted in Greece cosmologist, UK, and Egypt hairdressers indicate LBP affected carrying out normal activities and absence from work was indicated because of LBP (12,20,21). This may show that LBP has a negative impact on the economic, social and productivity of hairdressers.
This study found that hairdressers working on bending and twisting in awkward back posture were more likely to develop WRLBP. This is supported by the study conducted among Egypt and Brazil hairdressers (12,22). Incorrect body mechanics during tasks such as bending, turning and focusing on the task places stress on the highly mobile lumbosacral part of the spine (23). Bending incorrectly places a mechanical strain on the posterior longitudinal ligament, which results in stress on the facet joints thereby resulting in LBP (23,28). On the contrary, awkward posture was not significantly associated with the musculoskeletal study conducted in Addis Ababa, Ethiopia (13). This might be due to the difference in hairdressing style in different settings and variation in hairdressers' awareness towards comfortable body posture when performing tasks and availability of modernized ergonomic tools.
In this study hairdressers who spent more working days in a week (more than 4 days) in hairdressing, activity was more likely to develop WRLBP which is consistent with two studies conducted in Nigeria (11,25). But not among the Taiwanese hairdressers (26). The possible explanation could be as the number of working days increased, the number of customers or workload exceeds this may expose the hairdressers to the risk factors of LBP repeatedly. The study on which the majority of participants worked more days per week indicated that hours spent working per week correlated significantly (p=0,002) with how participants bent during their tasks, using their backs rather than their hips and knees (29). This may result in muscle fatigue, decrease fitness and increase pain or discomfort in the musculoskeletal system.
Hairdressers who work in the hair washing job category were more likely to develop WRLBP in this study. It might be due to the washing job category more involves the bending and twisting movements of the spine that can lead to mechanical LBP. This is supported by the study from the USA which reported the prevalence of back pain increased as the time spent on repeated strenuous physical activities and the time spent on repeated bending, twisting, or reaching on a typical job is increased (10). On the other way, hairdressing tasks do not significantly affect discomfort in body regions of Taiwanese hairdressers (26). The difference might be the economical difference between the countries which may affect to get the latest and adjustable hairdressing tools.
This study found that hairdressers who used a washing basin with adjustable height were less likely to develop WRLBP or had a preventing role compared to those who were not used. Similarly, the incidence of back pain was significantly lower in those hairdressers who used ergonomically adjusted types of equipment (13,23). An ergonomically correct washing basin is easily adjustable and maneuverable and allows for easy and regular changes in posture, thereby breaking the chain of a sustained position (23). The possible explanation maybe when the height is adjustable to the height of hairdressers the spine will be in an upright or erect position that could decrease the awkward or uncomfortable posture of the hairdressers. A study on ergonomic analysis of a hair salon revealed that fixed-height chairs and tables could put hairdressers in uncomfortable positions like twisting and bending to reach the different hairdressing materials (28,29).
Hairdressers who had job stress in this study were more likely to develop WRLBP this is supported by the study conducted among France hairdressers and WHO report, psychosocial factors appear to play a substantial role in the frequency of low back pain (2,24). Similarly, job stress was one of the psychosocial demands associated with increased risk of LBP(31). It might be those who were stressed in their job had different physical influences and workloads that may affect the occurrence of LBP.
This research addressed one of the major occupational health problems among the neglected group of hairdressing workers. However, as it is a 12-month self-reported pain or discomfort there might be recalled bias, hence there might be over and underestimation of the magnitude of LBP. These could lead to a possible variation in the estimation of association among WRLBP and other variables. It is also a cross-sectional study design, in which the temporal occurrence of LBP outcomes cannot be proved and the study also lacks a comparison group. It is advised in future research projects to analyze in-depth by considering postural assessment and objective measurement of the ergonomic tools.

Conclusions
This study has shown that low back pain is a common work-related health problem among

Acknowledgments
The authors would like to acknowledge the Mekelle University College of health sciences for funding the research. We also like to express special thanks to the national, regional state of Tigray Bureau of trade, industry and urban development as they provide us the necessary data about the number of salons in each sub-city. The authors would also like to acknowledge, the study participants, data collectors and supervisors of the study.

Ethics approval and consent to participate
Ethical clearance was obtained from the ethical review committee of the College of Health Sciences of Mekelle University. Written informed consent was obtained from each of the study participants after being informed in detail about the objective, purpose, benefit, risk, and the confidentiality of the information and the voluntary nature of participation. Besides, participants who had severe low back pain during the data collection time were advised and referred, for further care to the department of physiotherapy, Ayder Comprehensive Specialized Hospital.

Consent for Publication
Not applicable.

Availability of data and materials
Data will be available upon request from the corresponding author.