Low back pain-associated factors in female hospital-based personal care attendants

Abstract

BACKGROUND:

Low back pain (LBP) is common in personal care attendants because this profession requires much physical work. Information about the prevalence of LBP and LBP-associated risk factors in this group is limited.

OBJECTIVE

This study aimed to investigate the 1-year prevalence of LBP and identify LBP-associated factors in female hospital-based personal care attendants.

METHODS:

Forty-seven female hospital-based personal care attendants were recruited. The Nordic Musculoskeletal Questionnaire was used to investigate the prevalence of LBP during the recent 12 months. Participants completed a personal traits and associated factors questionnaire. Physical fitness and the knowledge test of body mechanics were assessed. Multivariable logistic regression analysis was used to explore LBP-associated factors.

RESULTS:

The 1-year prevalence of LBP was 46.8%. The strongest LBP-associated risk factor was poor abdominal muscle endurance, followed by insufficient knowledge on the test of body mechanics and higher psychological stress.

CONCLUSIONS:

The results demonstrate that the prevalence of LBP in female hospital-based personal care attendants appears to be high. Preventive programs should be initiated to reduce LBP-associated risk factors, such as improving abdominal muscle endurance, providing education in the proper use of body mechanics, and providing psychological intervention services for female hospital-based personal care attendants.

Keywords

Physical fitness knowledge of body mechanics psychological stress

1 Introduction

Low back pain (LBP) is a common and critical issue in personal care attendants. Studies show that 22.4%to 63%of personal care attendants have suffered from LBP during the most recent year of service [1 –4]. LBP is considered to be the most common cause of job-related disability and a key reason for absenteeism in the workplace [5]. Given the increase of people with disabilities as societies age, the need for personal care attendants is growing, which highlights the need for studies examining LBP in personal care attendants.

Hospital-based personal care attendants may be at a higher risk for LBP than personal care attendants in non-hospital workplaces because they face heavy, high-pressure workloads caring for patients who have more extensive injuries and require critical care. However, little is known about LBP problems among personal care attendants, especially hospital-based personal care attendants. In addition, approximately 90%of hospital-based personal care attendants in Taiwan are women [6]. They tend to work long hours—an average of 13.9 hours per day—and work an average of 5.77 days per week [6]. Furthermore, previous studies have shown that women are more prone to LBP than men [7 –11]. Therefore, this study aimed to investigate LBP in female hospital-based personal care attendants.

Information on LBP-associated factors among hospital-based personal care attendants is important for preventive intervention. LBP negatively affects the health of the personal care attendants and the patients who need them, which may further increase social and economic burdens [12]. The economic burdens of illness involve direct and indirect costs. While the medical expenses are direct costs, productivity losses and absenteeism are indirect costs, which are significant and cannot be ignored. The risk factors associated with LBP in health care workers and caregivers include (1) demographic background factors, such as age or being female [8 –11]; (2) lifestyle habit factors, such as smoking [8]; (3) work-related factors, such as lifting, patient handling and transferring, persistent awkward posturing, and insufficient knowledge of body mechanics during tasks [4 , 13–15]; and (4) psychosocial factors, such as perceived stress level and mood [8 , 16–18]. Physical fitness has been shown to be related to LBP in police employees and women [19, 20]. Exercise is currently recommended to prevent LBP in the general population [21]. However, whether physical fitness and exercise habits are related to the occurrence of LBP in hospital-based personal care attendants remains unclear.

For patients with LBP, x-ray imaging is the most common radiologic procedure used to check bone structures (bone disease, degeneration, fractures, dislocations, infections, and tumors) and support medical diagnoses. Obtaining an accurate diagnosis of causal mechanisms after LBP is critical because treatment approaches are specifically based on the causal mechanisms that sustain the pain. However, the connection between abnormalities found by x-ray imaging and the causes of specific cases of LBP is often unclear. Therefore, this study explored the relationship between abnormalities identified from x-rays by physicians and LBP among hospital-based personal care attendants.

Few studies have focused exclusively on LBP in hospital-based personal care attendants. Identifying factors related to LBP in this group is an important step in preventing LBP, if needed, and reducing personal, social, and economic burdens. Thus, the purpose of this study was to investigate the 1-year prevalence and risk factors of LBP in hospital-based personal care attendants. We believe early identification of LBP-related factors can help design preventive strategies to minimize the occurrence of LBP in this group.

2 Methods

2.1 Study design and subjects

This cross-sectional study was conducted at the Kaohsiung Chang Gung Memorial Hospital in Taiwan by using the convenient sampling method. The Chang Gung Medical Foundation Institutional Review Board approved the protocol used in this study, and all participants signed a written informed consent form.

Forty-seven female personal care attendants working in the Department of Neurology were recruited. The Nordic Musculoskeletal Questionnaire (NMQ), using a figure depicting the anatomical area of pain, was administered and used to investigate the 1-year prevalence of LBP [22 –24].

2.2 Procedure

The participants were asked to complete a personal traits and associated risk factors questionnaire. Next, a lumbar x-ray examination was performed. Finally, participants undertook physical fitness tests, including hand grasp, hamstring flexibility, and abdominal and back muscle endurance.

2.3 Personal traits and associated risk factors questionnaire

To characterize the participant traits and associated risk factors, a questionnaire was developed for this study, with empirical support from previous studies reviewed on this topic. The questionnaire included several questions in 4 domains: (1) demographic background, (2) lifestyle habits, (3) work, and (4) psychosocial characteristics. The question details in each domain are listed as follows.

2.3.1 Demographic background

Items related to demographic and clinical background characteristics included age, height, weight, body mass index, marital status, and educational level.

2.3.2 Lifestyle habits

Items related to lifestyle habits included smoking, alcohol/coffee/tea consumption, and exercise.

2.3.3 Work

Items related to work included working experience, monthly working days, number of helpers, on-the-job and license training, knowledge tests, and work demand. In the current study, a knowledge test of body mechanics during rolling, transfer, and standing activities was developed, with 10 yes-and-no questions consisting of words and pictures. Participants received 1 point for each correct answer (score range: 0–10). For work demand items, participants answered how many times per day they helped clients with rolling, clapping, shower, feeding, toilet, dressing, transferring, making the bed, changing diapers, and physical activities.

2.3.4 Psychosocial characteristics

Items related to the psychosocial component included psychological stress and personal perceptions of salary and sleep. Psychological stress was assessed by Caregiver Strain Index (CSI), a 13-question self-administered questionnaire [25, 26]. Higher scores indicate a higher the level of psychological stress. A score of 7 or higher indicated a greater level of stress. Participants also reported their personal perceptions of their salary and sleep.

2.4 Clinical background

2.4.1 Lumbar x-ray examination

Each participant underwent a lumbar x-ray examination, and all images were interpreted by radiologists. The findings were viewed as normal or abnormal findings.

2.4.2 Physical fitness

Physical fitness, including hand grasp strength, hamstring flexibility, and abdominal and back muscular endurance, was assessed in accordance with testing methods developed by the Taiwan Institute for Occupational Safety and Health. Hand grasp strength was assessed with the JAMAR hydraulic hand dynamometer (Sammons Preston, Inc, Warrenville, IL). Hamstring flexibility was assessed by measuring finger-to-floor distance while the subject stood and bent her body forward. The best performance of hand grasp strength and hamstring flexibility during 3 trials was recorded. Abdominal muscular endurance was evaluated by the total number of repetitive abdominal curls in the supine position (curl-up) in a minute. Back muscular endurance was evaluated by the total numbers of trunk extension in the prone position performed in a minute. All results of muscle endurance were classified into poor or fair-good according to the norms for people of different ages and sexes.

2.5 Statistical analysis

Statistical analyses were performed using SAS 9.4 software (SAS Institute Inc., Cary, NC). Descriptive statistics, including independent t and Chi-square tests, were used to compare the general characteristics between participants with LBP (LBP) and without LBP (No-LBP). Potential factors of LBP were evaluated using univariable logistic regression. All factors with P≤0.15 in the univariable logistic regression analyses were entered into the multivariable logistic regression analysis with stepwise selection of the model. Odds ratios (ORs) of factors were generated from the logistic regression analyses. Statistical significance was set at α= 0.05.

3 Results

Of the 47 women recruited, 22 were in the LBP group and 25 were in the No-LBP group. The 1-year prevalence of LBP was 46.8%in these hospital-based personal care attendants. The characteristics in each group are provided in Table 1.

Table 1
Comparison of groups without LPB (No-LBP) and with LBP on characteristics

No-LBP N = 25 LBP N = 22 P value

Demographic background

Age 50±6.43 51.45±5.71 0.42

Height 156.7±5.56 156.05±4.76 0.68

Weight 59.82±7.75 60.09±8.79 0.91

Body mass index 24.46±3.64 24.65±3.25 0.85

Marital status 0.27

Unmarried 1(4) 4(18.18)

Married 16(64) 13(59.09)

Others 8(32) 5(22.73)

Education level 0.56

Elementary school and below 6(24) 3(13.64)

Junior and senior high school 17(68) 18(81.82)

College and above 2(8) 2(4.55)

Lifestyle habits

Smoking 0 0 1

Alcohol consumption 0 0 1

Coffee consumption 8(32) 11(50) 0.21

Tea consumption 7(28) 9(40.91) 0.35

Exercise (hour/week) 2.23±3.64 2.11±4.36 0.92

Work-related description

Working experience (year) 10.76±6.37 12.41±6.02 0.37

Monthly working days 22.74±2.66 21.39±2.49 0.08

Number of helpers 0.08±0.27 0.14±0.35 0.54

Receiving on-the-job training 25(100) 21(95.45) 0.28

Receiving license training 23(92) 20(90.91) 0.89

Knowledge test (points) 8.72±1.06 7.82±1.53 0.02^*

Knowledge total points≥8 22(88) 13(59.09) 0.02^*

Work demand (count/day)

Rolling 5.94±4.18 7±5.59 0.46

Clapping 5.46±5.17 5.89±5 0.78

Shower 1.06±0.46 1.18±0.36 0.33

Feeding 3.48±2.99 3.5±2.66 0.98

Toilet 4.04±4.17 3.89±4.81 0.91

Dressing 1.48±0.68 1.32±0.70 0.43

Transferring 0.88±1.51 1.05±2.19 0.77

Making the bed 0.84±0.79 0.78±0.67 0.77

Changing diapers 2.38±3.03 1.93±2.97 0.61

Physical activities 2.08±2.3 2.68±3.03 0.44

Psychosocial component

Caregiver Strain Index (CSI) 3.52±2.62 4.91±2.22 0.06

Sufficient salary (self-perceived) 22(88) 17(77.27) 0.33

Sufficient sleep (self-perceived) 12(48) 11(50) 0.89

	No-LBP N = 25	LBP N = 22	P value
Demographic background
Age	50±6.43	51.45±5.71	0.42
Height	156.7±5.56	156.05±4.76	0.68
Weight	59.82±7.75	60.09±8.79	0.91
Body mass index	24.46±3.64	24.65±3.25	0.85
Marital status			0.27
Unmarried	1(4)	4(18.18)
Married	16(64)	13(59.09)
Others	8(32)	5(22.73)
Education level			0.56
Elementary school and below	6(24)	3(13.64)
Junior and senior high school	17(68)	18(81.82)
College and above	2(8)	2(4.55)
Lifestyle habits
Smoking	0	0	1
Alcohol consumption	0	0	1
Coffee consumption	8(32)	11(50)	0.21
Tea consumption	7(28)	9(40.91)	0.35
Exercise (hour/week)	2.23±3.64	2.11±4.36	0.92
Work-related description
Working experience (year)	10.76±6.37	12.41±6.02	0.37
Monthly working days	22.74±2.66	21.39±2.49	0.08
Number of helpers	0.08±0.27	0.14±0.35	0.54
Receiving on-the-job training	25(100)	21(95.45)	0.28
Receiving license training	23(92)	20(90.91)	0.89
Knowledge test (points)	8.72±1.06	7.82±1.53	0.02^*
Knowledge total points≥8	22(88)	13(59.09)	0.02^*
Work demand (count/day)
Rolling	5.94±4.18	7±5.59	0.46
Clapping	5.46±5.17	5.89±5	0.78
Shower	1.06±0.46	1.18±0.36	0.33
Feeding	3.48±2.99	3.5±2.66	0.98
Toilet	4.04±4.17	3.89±4.81	0.91
Dressing	1.48±0.68	1.32±0.70	0.43
Transferring	0.88±1.51	1.05±2.19	0.77
Making the bed	0.84±0.79	0.78±0.67	0.77
Changing diapers	2.38±3.03	1.93±2.97	0.61
Physical activities	2.08±2.3	2.68±3.03	0.44
Psychosocial component
Caregiver Strain Index (CSI)	3.52±2.62	4.91±2.22	0.06
Sufficient salary (self-perceived)	22(88)	17(77.27)	0.33
Sufficient sleep (self-perceived)	12(48)	11(50)	0.89

Data are presented as the mean±standard deviation or number (%).^*Statistically significant (P < 0.05).

3.1 Personal traits and associated risk factors questionnaire

3.1.1 Demographic and clinical background characteristics

The characteristics of demographic and clinical background did not differ between No-LBP and LBP groups (P > 0.27 for all) (Table 1). Both groups were middle aged (No-LBP group: 50±6.43 years; LBP group: 51.45±5.71 years). Height, weight, body mass index, marital status, and education level were similar in the 2 groups.

3.1.2 Lifestyle habits

The No-LBP and LBP groups did not differ in personal habits (P > 0.21 for all) (Table 1). None of the participants were smokers or alcohol drinkers. About 30%of the participants in the No-LBP and about 40%to 50%participants in the LBP were coffee and/or tea drinkers. The No-LBP and LBP groups spent 2.23 and 2.11 hours/week exercising, respectively. The weekly exercise duration did not significantly differ between the two groups.

3.1.3 Work-related description

The No-LBP and LBP groups demonstrated similar work characteristics, except for the monthly working days and the performance in the knowledge test. The No-LBP participants tended to have more monthly working days (P = 0.08), but the difference in the average working days between the two groups was less than 2 days (Table 1). The mean score on the knowledge test (maximum score: 10) was higher in the No-LBP group (8.72) than in the LBP group (7.82) (P = 0.02) (Table 1). A greater proportion of participants demonstrated a score greater than 8 points in the No-LBP group (88%) than in the LBP group (59.09%)(P = 0.02) (Table 1). In addition, the No-LBP and LBP groups had similar required work tasks (P > 0.33 for all).

3.1.4 Psychosocial component

The No-LBP group tended to have higher psychological stress than the LBP group (P = 0.06) (Table 1). The groups had similar perceptions of salary and sleep (P = 0.33 for both).

3.2 Clinical background

3.2.1 Lumbar X-ray examination

The rate of abnormalities on the lumbar X-ray examinations did not significantly differ between the No-LBP (80%) and LBP (86.36%) groups.

3.2.2 Physical fitness

Hand grasp, hamstring flexibility, and back muscle endurance were similar between the two groups (P > 0.33 for all) (Table 2). However, a greater percentage of No-LBP participants (68%) demonstrated fair to good abdominal muscle endurance than LBP participants (40.91%) (P = 0.06) (Table 2).

Table 2
Comparison of clinical background, including lumbar x-ray examination and physical fitness, between groups without (No-LBP) and with LBP (LBP)

No-LBP N = 25 LBP N = 22 P value

Lumbar X-ray examination 0.56

Abnormal 20(80) 19(86.36)

Normal 2(20) 3(13.64)

Hand grasp 0.33

Poor 3(12) 5(22.73)

Fair-Good 22(88) 17(77.27)

Hamstring flexibility 0.56

Poor 5(20) 6(27.27)

Fair-Good 20(80) 16(72.73)

Abdominal muscle endurance 0.06

Poor 8(32) 13(59.09)

Fair-Good 17(68) 9(40.91)

Back muscle endurance 0.78

Poor 7(28) 7(31.82)

Fair-Good 18(72) 15(68.18)

	No-LBP N = 25	LBP N = 22	P value
Lumbar X-ray examination			0.56
Abnormal	20(80)	19(86.36)
Normal	2(20)	3(13.64)
Hand grasp			0.33
Poor	3(12)	5(22.73)
Fair-Good	22(88)	17(77.27)
Hamstring flexibility			0.56
Poor	5(20)	6(27.27)
Fair-Good	20(80)	16(72.73)
Abdominal muscle endurance			0.06
Poor	8(32)	13(59.09)
Fair-Good	17(68)	9(40.91)
Back muscle endurance			0.78
Poor	7(28)	7(31.82)
Fair-Good	18(72)	15(68.18)

LBP indicates low back pain Data are presented as the number (%).

3.3 Determinants of LBP

Determinants of LBP are presented in Table 3. In model 1, the univariable logistic regression analyses revealed that a low score on the knowledge test of body mechanics was negatively related to LBP (OR, 0.58; 95%confidence interval [CI], 0.35–0.59). Further, potential factors of LBP included monthly working days, abdominal muscle endurance, and psychological stress (CSI score) (P = 0.06–0.08) (Table 3, model 1).

Table 3
Determinants of low back pain (LBP) by logistic regression

Model 1^† Model 2^‡

LBP/No-LBP LBP /No-LBP

OR (95%CI) P value OR (95%CI) P value

Work-related description

Monthly working day 0.8 (0.64–1.03) 0.08

Knowledge test per unit increase 0.58 (0.35–0.95) 0.03^* 0.51(0.30–0.88) 0.015^*

Psychosocial component

CSI per unit change 1.27 (0.99–1.63) 0.06 1.34 (1.001–1.8) 0.0489^*

Poor abdominal muscle endurance 3.07 (0.93–10.14) 0.07 4.57 (1.1–18.99) 0.04^*

	Model 1^†		Model 2^‡
	OR (95%CI)	P value	OR (95%CI)	P value
Work-related description
Monthly working day	0.8 (0.64–1.03)	0.08
Knowledge test per unit increase	0.58 (0.35–0.95)	0.03^*	0.51(0.30–0.88)	0.015^*
Psychosocial component
CSI per unit change	1.27 (0.99–1.63)	0.06	1.34 (1.001–1.8)	0.0489^*
Poor abdominal muscle endurance	3.07 (0.93–10.14)	0.07	4.57 (1.1–18.99)	0.04^*

LBP, low back pain; OR, odds ratio; and CI, confidence interval. ^†Univariable logistic regression. ^‡Multivariable logistic regression. ^*Statistically significant (P < 0.05).

In model 2, the multivariable logistic regression analysis revealed that poor abdominal muscle endurance, high psychological stress, and low scores on the knowledge test of body mechanics were factors related to LBP. Participants with poor abdominal muscle endurance were 4.57 times more likely to have LBP than those with fair-to-good abdominal muscle endurance (OR, 4.57; 95%CI, 1.1–18.99). A 1-point increase on the knowledge test decreased LBP by 51%(OR, 0.51; 95%CI, 0.33–0.88). A 1-point increase in the CSI score increased LBP by 134%(OR, 1.34; 95%CI, 1.001–1.8) (Table 3, model 2).

4 Discussion

This study showed a high prevalence of LBP in female hospital-based personal care attendants, with almost half reporting LBP in the previous year. This is not surprising, given that this profession requires much physical effort. In addition, poor abdominal muscle endurance, insufficient knowledge of body mechanics, and high psychological stress were the three most common factors in the occurrence of LBP. Specifically, participants with poor abdominal muscle endurance appeared to have a 457%higher risk of developing LBP compared with their counterparts (fair-to-good). A 1-point increase on the knowledge test decreased LBP by 51%. A 1-point increase in the CSI score increased LBP by 134%. Abnormalities identified from x-ray images were not related to LBP, thus highlighting the importance of abdominal muscle endurance, knowledge test of body mechanics, and psychological stress in female hospital-based personal care attendants.

The most dominant risk factor in the current study was poor abdominal muscle endurance. Participants with poor abdominal muscle endurance appeared to have a non-negligible risk of developing LBP (457%). Although patients with LBP demonstrate muscle weakness in both the abdominal and back muscles [19], the participants in this study with LBP reported poor muscle endurance in their abdominal muscles but not in their back muscles. We speculate that the reason for the apparent lack of back muscle endurance problems may be that the participants’ work as personal care attendants generally requires them to maintain a standing posture, which relies on the persistent activation of back muscles; therefore, the deterioration of back muscle endurance may not be significant. Sufficient muscle endurance is critical for preventing injuries. Repetitive curl-up exercises have been shown to improve abdominal muscle endurance, increasing electromyography activity in the rectus abdominis and in the cross-sectional area of the abdominal muscles [27]. We suggest that abdominal muscle strengthening exercises, such as repetitive curl-up exercises, should be emphasized in female hospital-based personal care attendants.

The second dominant risk factor found in this study was the performance on the knowledge test. Despite the similar work tasks required of each group, the two groups may perform the tasks in different ways. The No-LBP group participants had higher scores on the knowledge test, implying that participants in the LBP group have poorer knowledge of body mechanics and are more likely to perform work tasks in an inefficient way.

We suggest that information on correct body mechanics while caring for patients should be emphasized in on-the-job training and/or license training. Studies have confirmed that education intervention programs in LBP prevention are effective in improving nurses’ knowledge of body mechanics [28, 29]. However, another study found on-the-job training (30-minute lecture and 6 minutes of stretch exercises) had little effect on pain reduction in female caregivers with LBP in nursing homes [30]. The difference in the findings between these two studies may result from the application of the knowledge delivered. Although lectures were offered to the female caregivers with LBP, this knowledge may not have been applied to their routine care work because they did not have the educational background of medicine like the nurses. Thus, incorporating incentives to use the knowledge gained from education in body mechanics in their daily routine may help reduce LBP among female hospital-based personal care attendants. In addition, strengthening exercises instead of stretching exercises before the occurrence of LBP may significantly lower or even prevent LBP in these attendants.

The third dominant factor identified in this study was the CSI score. Although participants with and without LBP showed similar psychological stress as assessed by CSI (P = 0.06; Table 1), high psychological stress was related to the occurrence of LBP. This finding is supported by the relationship between the mood of caregivers and LBP [16]. LBP in health care workers is correlated to perceived stress level and job satisfaction [8, 17]. Our cross-sectional study does not provide evidence of the casual relationship between LBP and high psychological stress; however, this study showed that LBP in female hospital-based personal care attendants was multifactorial and included physical and psychological factors. Preventive programs and interventions should be multidimensional for this specific group.

Because the proportion of abnormalities on x-ray images did not differ between the two groups, abnormalities identified via x-ray images were not an LBP-related factor in hospital-based personal care attendants. This indicates that the significant difference between the two groups may be soft tissue related. This speculation was supported by the finding that poor abdominal muscle endurance was the most important risk factor for LBP. This study thus supports provision of strengthening exercises for abdominal muscles in hospital-based personal care attendants.

Neither monthly working days nor regular exercise were related to LBP in this study. The number of monthly working days tended to higher in the No-LBP group (Table 1) but was not significantly associated with LBP, implying that the number of monthly working days does not contribute to LBP in this group and that the current workload may be appropriate. In addition, although regular exercise is related to the reduction of LBP in the general population [7], low and high levels of total physical activity are both associated with an increase in LBP in the working population [20]. The current study does not support the contention that physical inactivity is a risk factor for LBP. On the contrary, we suggest that the level of activity of hospital-based personal care attendants during work may already be adequate and that their increasing physical activity level may have no significant effect on the occurrence of LBP.

A few limitations to the current study should be mentioned. First, our sample was relatively small and homogeneous. The participants in this study were recruited from only one hospital. This study used a convenient sampling method, and thus, the sample recruited may not be representative of the whole population. A large number of personal care attendants at various hospitals representing different areas of Taiwan should be included in future studies. Second, LBP was self-reported, and a diagnosis by orthopedists to specify a cause was not performed. Further studies are necessary to identify the risk factors for LBP with different diagnoses of causal mechanisms. Third, a limited number of LBP-related factors were investigated in this study. Other risk factors, such as the physical fitness of other muscle groups, should be investigated in further studies.

Last, this cross-sectional study does not support a cause-effect relationship between factors and LBP. The study did, however, identify several LBP-related factors, and future studies should evaluate these relationships. Long-term intervention studies are needed to verify the effect of abdominal strengthening exercises, knowledge education, and psychological intervention services in female hospital-based personal care attendants.

5 Conclusion

This study confirms a high prevalence of LBP in female hospital-based personal care attendants. The three most important risk factors for female hospital-based personal care attendants were poor abdominal muscle endurance, insufficient knowledge of body mechanics, and high psychological stress.

Footnotes

Acknowledgements

This study was funded by the Chang Gung Memorial Hospital (CMRPG890391, BMRP553), Healthy Aging Research Center at the Chang Gung University (EMRPD1G0241), and the Ministry of Science and Technology (NSC101-2314-B-010-067, MOST105-2314-B-010-056) in Taiwan.

Conflict of interest

None to report.

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	Model 1^†		Model 2^‡
	LBP/No-LBP	LBP /No-LBP
	OR (95%CI)	P value	OR (95%CI)	P value
Work-related description
Monthly working day	0.8 (0.64–1.03)	0.08
Knowledge test per unit increase	0.58 (0.35–0.95)	0.03^*	0.51(0.30–0.88)	0.015^*
Psychosocial component
CSI per unit change	1.27 (0.99–1.63)	0.06	1.34 (1.001–1.8)	0.0489^*
Poor abdominal muscle endurance	3.07 (0.93–10.14)	0.07	4.57 (1.1–18.99)	0.04^*