Association of musculoskeletal pain with poor sleep quality in public school teachers

Abstract

BACKGROUND:

Teachers perform repetitive movements all day, which can cause pain in body regions. This article analyzes the association of pain with sleep quality in this population.

OBJECTIVE:

The objective of the study was to analyze the relationship of musculoskeletal pain and sleep quality in teachers from public schools.

METHODS:

The sample consisted of 242 teachers, selected in a random process. Musculoskeletal pain and sleep quality were evaluated by using a questionnaire. The association between sleep quality and musculoskeletal pain was evaluated using the chi-square test. The magnitude of the associations was verified by Binary Logistic Regression, adjusted by sex, age, BMI, and socioeconomic status.

RESULTS:

Teachers with poor sleep quality presented higher body mass index (BMI) values when compared to teachers with good sleep quality (27.9 vs 26.0, p = 0.012). Teachers with poor sleep quality were approximately twice as likely to report thoracic pain (OR = 2.16[95% CI = 1.12–4.16]), wrist pain (OR = 3.28[95% CI = 1.18–9.07]), low back pain (OR = 3.09[95% CI = 1.29–7.41]), and ankle/foot pain (OR = 2.83[95% CI = 1.32–6.08]).

CONCLUSIONS:

Teachers with poor sleep quality were approximately twice as likely to present pain in several body parts. Our findings revealed that poor sleep quality was significantly associated with musculoskeletal pain in Brazilian teachers of public schools, regardless of confounding factors.

Keywords

Adults body pain sleep disorders epidemiology

1 Introduction

Teachers correspond to a large group of workers who frequently suffer from musculoskeletal injuries as well as mental and psychological conditions, impacting their job and those students who depend on them [1]. Besides that, teachers play an essential role in the educational system, and the knowledge about the aspects of their health should be addressed and considered for professional actions and quality of life, mainly about frequent work-related outcomes in this population, as sleep quality [2] and musculoskeletal pain [3].

Previous studies show the prevalence of musculoskeletal pain in teachers is above 50% and linked to job demands [4], which can be a determinant factor for these professionals, as the musculoskeletal pain directly affects health and quality of life [3]. Musculoskeletal disorders also affects the well-being in the working environment [5], and was associated with depression in workers [6]. In a study with Slovenian teachers, Kovač et al. (2013) observed approximately 30% of teachers presented injuries in the feet and ankles [7]. Goossens et al. (2016), in a study with Belgian teachers, reported a high number of major injuries in the back (low back and cervical region) and knees [8].

The work-related musculoskeletal disorders were considered as alterations in body structures in the musculoskeletal system, nerves, and localized system of blood circulation, caused or aggravated by the work activities or work environment [9]. In case of teachers, the high prevalence of musculoskeletal disorders can be due to excessive execution of blackboard activities which compromises the upper limbs and trunk, and causes pain in corporeal regions such as the neck, shoulder, and lower back [10]. Teachers reported that musculoskeletal disorders limit their work in 15% of cases, and the prevalence of feeling pain is even higher when considering the last 12 months [11]. Maintaining the standing posture for long periods during professional activities may negatively influence the quality of life of school teachers [10]. Workers that regularly perform hand-based activities present a propensity to report body pain mainly in lower back and shoulders [12]. In this sense, the lower limbs consistently support the discharge of the body structure, which may also lead to musculoskeletal problems [13]. Interventions on musculoskeletal disorders in workers could recommend the adoption of exercises beyond only ergonomic modification in their occupational activities [14].

Likewise, it was observed that poor sleep quality highly impacts the daytime activities and have been prevalent in population with chronic pain [15]. Sleep quality corresponds to an extremely important factor for health: when sleep quality is poor it may contribute to episodes of musculoskeletal pain [16]. It was previously observed that insufficient sleep increases fatigue and pain [17]. These symptoms could be related to a hyperalgesic effect [18], since poor sleep was related to lower electroencephalogram activity in the insular and cingulate regions, which could be related to increase of nociceptive pathways, impairment of the perception of somatosensory stimuli, and dysregulation of dopaminergic pathways [19]. These mechanisms can reduce the pain threshold, increasing pain sensitivity. In general, the relationship between sleep and pain has been considered bidirectional, in which high levels of pain could also interfere in sleep quality [20]. Given that pain is an injury caused by an aggressive agent to the body structure, an adequate period and quality of sleep are beneficial due to the release of neuromediators directly related to pain [20]. Relevant evidence of this relationship suggests that the development of chronic pain might negatively influence sleep quality [21]. Teachers tend to stand for prolonged periods [22] and may face daily stressful situations in their jobs [23]. The body mass index (BMI) presents a relationship with musculoskeletal pain [24] and sleep disturbance [25]. When the BMI deviates from the normal range, it can be associated with body problems. Besides that, it was observed a relationship with back pain and sociodemographic factors [26].

However, it is important to highlight that some studies investigated the relationship between sleep and pain in teachers did not consider a range of possible confounding factors, such as weight status, sociodemographic and economic conditions [27]. Therefore, this study aimed to verify the association between poor sleep quality and musculoskeletal disorders in public school teachers, regardless of potential confounding factors, such as sex, age, BMI, and socioeconomic status.

2 Methods

2.1 Sample

This study was conducted in Presidente Prudente, a city in the Southeast region of Brazil, from 2016 to 2017. The city has approximately 210 thousand inhabitants and a human development index of 0.84. In addition, 650 teachers work in public schools, distributed in 23 schools. Considering the objective of recruiting teachers from the different regions of the city (north, south, east, west, and central), two schools from each region were randomly selected for the evaluation. For the sample calculation, a total of 650 teachers from the Education Department of the city were considered, an outcome prevalence of 50% used in epidemiological studies [28], with a 95% confidence interval and a standard error of 5%, which generated a required sample of 242 teachers, corresponding to 37.3% of the total sample of teachers from the city. This study was approved by the Ethics and Research Committee of the Sao Paulo State University, process number CAAE:45486415.4.0000.5402.

2.2 Data collection

Data collection was performed in the school environment while teachers developed the planning of student activities in a restricted classroom, with application of the questionnaires and collection of anthropometric data of the participants. Any questions raised by the participants were clarified by the evaluators. All teachers enrolled in this study agreed to participate by signing the Term of Free and Informed Consent, which made it clear that the data would be used for this research.

2.3 Anthropometry

The teachers were evaluated by previously trained professionals. Participants were required to wear light clothes and be barefoot. Body weight was measured using a digital scale of the brand Plenna^® with an accuracy of 0.1 kg and capacity of 180 kg. Height was evaluated by a portable stadiometer with a precision of 0.1 cm and total height of 2.20 meters. These measures were used to calculate body mass index (BMI), through division of the body weight by the square of height (BMI = kg/m²).

2.4 Musculoskeletal pain

The Nordic Osteomuscular Symptoms Questionnaire was used to measure musculoskeletal symptoms. This instrument is used to verify the occurrence of symptoms in the context of ergonomic or occupational health, and has previously been used in epidemiological studies among similar population in Brazil [29] and Latin-America [11], which presented a good reliability in Brazilian population (Kappa varying from 0.88 to 1.00) [30]. The instrument is self-administered, with easy to understand questions and multiple choices. The questionnaire contains a figure of the human body for the participant identify the location of possible musculoskeletal pain, divided into nine body regions (cervical, shoulders, thoracic, elbows, wrist/hands, low back, hips/thighs, knees, and ankles/feet).

2.5 Sleep quality

The quality of sleep was evaluated by the Mini Sleep Questionnaire validated for the Brazilian population and has good values of reliability of the Brazilian Portuguese Version of the Mini-Sleep Questionnaire (Cronbach’s alpha≥0.700) [31]. This questionnaire contains aspects such as restless sleep, sleeping medication, nighttime snoring, headache on waking up in the morning, and morning tiredness. The sum of these factors generates a score where higher values correspond to worse sleep quality. Teachers with a score greater than or equal to 25 in this instrument were considered as presenting poor sleep quality, as according to the instrument, this is the cut-off point for poor sleep quality.

2.6 Socioeconomic condition

Socioeconomic condition was verified by the questionnaire of the Brazilian Association of Research Companies (ABEP), based on a system of scoring determinants such as quantity of household rooms and appliances, degree of education of the head of the family, and access to public services. The distribution of classes was based on probabilistic studies, where the class profile is domicile, and the total score obtained represents class cut-offs from A to D-E. The estimate for the Average Household Income is also present in the questionnaire, and aims to characterize the population included in the study [32].

2.7 Statistical analysis

The descriptive analyses of the data with normal distribution are presented as mean, standard deviation, and frequency. The association between sleep quality and musculoskeletal pain in teachers was performed using the chi-square test. In addition, binary logistic regression was used to verify the magnitude of association between variables in an unadjusted model and adjusted for covariates, such as gender, age, socioeconomic status, and BMI. The confidence interval considered was 95% and the statistical significance was fixed at 5%. The statistical package used was SPSS version 15.0.

3 Results

A total of 242 teachers from the public school system were recruited, with a mean of 45.0 (±10.97) years of age. Teachers with poor sleep quality presented higher BMI values when compared to teachers with good sleep quality (27.93 vs 26.00, p = 0.012). No significant differences in age, weight, and height were found according to sleep quality. This information is presented in Table 1.

Table 1
Characteristics of the sample

High sleep quality Mean (SD) Poor sleep quality Mean (SD) p

Age 45.10 (10.97) 44.86 (9.96) 0.875

Weight 71.00 (16.68) 75.33 (16.47) 0.071

Height 164.76 (8.97) 164.08 (8.14) 0.569

BMI 26.00 (4.92) 27.93 (5.47) 0.012

Sleep score 19.17 (3.94) 33.77 (7.08) ≤0.001

	High sleep quality Mean (SD)	Poor sleep quality Mean (SD)	p
Age	45.10 (10.97)	44.86 (9.96)	0.875
Weight	71.00 (16.68)	75.33 (16.47)	0.071
Height	164.76 (8.97)	164.08 (8.14)	0.569
BMI	26.00 (4.92)	27.93 (5.47)	0.012
Sleep score	19.17 (3.94)	33.77 (7.08)	≤0.001

SD: Standard Deviation; BMI: Body mass index. Sleep score: The quality of sleep was evaluated by the Mini Sleep Questionnaire; Teachers with a score greater than or equal to 25 in this instrument were considered as having poor sleep quality.

Table 2 presents information on poor sleep quality and musculoskeletal pain in teachers. A significant association was found between poor sleep quality and chest pain (p = 0.02), low back pain (p = 0.02), and pain in the feet and ankles (p = 0.01). It should be noted that the prevalence of pain in the thoracic, wrist, low back, knee, and foot regions was elevated, above 75% in teachers with poor sleep quality.

Table 2

Association between poor sleep quality and musculoskeletal pain in public school teachers

	n total (n = 224)	Poor sleep quality (n = 149)	Chi-square test
Variables	N	n (%)	p-value
Neck
No Pain	179	120 (67.0)	1.000
Pain	44	29 (68.9)
Thoracic
No Pain	147	90 (61.2)	0.021
Pain	76	59 (77.6)
Shoulder
No Pain	181	116 (64.1)	0.107
Pain	42	33 (78.6)
Elbow
No Pain	198	130 (65.7)	0.418
Pain	25	19 (76.0)
Wrist
No Pain	189	121 (64.0)	0.058
Pain	34	28 (82.4)
Low Back
No Pain	177	111 (62.7)	0.021
Pain	45	37 (82.2)
Hip/Thigh
No Pain	201	131 (65.2)	0.224
Pain	21	17 (81.0)
Knee
No Pain	191	127 (66.5)	1.000
Pain	31	21 (67.7)
Ankle/foot
No Pain	163	100 (61.3)	0.007
Pain	60	49 (81.7)

The magnitude of the associations between poor sleep quality and musculoskeletal pain are presented in Table 3. Teachers presenting poor sleep quality were approximately twice as likely to have thoracic pain (OR = 2.19 [95% CI = 1.16–4.14]) and this association remained significant after adjusting for confounders such as sex, age, and socioeconomic status in model 1 (OR = 2.28 [95% CI = 1.19–4.37]) and after insertion of BMI in model 2 (OR = 2.16 [95% CI = 1.12–4.16]). This relationship was also observed in relation to pain in the wrist, in which teachers with poor sleep quality were 3.28 times more likely to present pain in the wrist. Poor sleep quality in teachers was also associated with increased chances of low back pain and ankle/foot pain.

Table 3

Association between poor sleep quality and musculoskeletal pain in public school teachers

	Crude OR (CI95%)	P	Model 1 OR (CI95%)	P	Model 2 OR (CI95%)	P
Neck
No Pain	1.00		1.00		1.00
Pain	0.95 (0.47–1.90)	0.851	0.95 (0.46–1.95)	0.887	0.96 (0.46–2.00)	0.910
Thoracic
No Pain	1.00		1.00		1.00
Pain	2.19 (1.16–4.14)	0.015	2.28 (1.19–4.37)	0.012	2.16 (1.12–4.16)	0.021
Shoulder
No Pain	1.00		1.00		1.00
Pain	1.51 (0.85–2.51)	0.160	1.58 (0.87–2.89)	0.131	1.62 (0.89–3.00)	0.118
Elbow
No Pain	1.00		1.00		1.00
Pain	4.17 (0.51–33.99)	0.182	4.13 (0.50–33.78)	0.185	3.57 (0.43–29.58)	0.237
Wrist
No Pain	1.00		1.00		1.00
Pain	2.62 (1.04–6.65)	0.042	3.32 (1.21–9.11)	0.020	3.28 (1.18–9.07)	0.022
Low Back
No Pain	1.00		1.00		1.00
Pain	2.75 (1.20–6.26)	0.016	3.27 (1.37–7.79)	0.007	3.09 (1.29–7.41)	0.011
Hip/Thigh
No Pain	1.00		1.00		1.00
Pain	2.27 (0.73–7.01)	0.154	3.10 (0.88–11.02)	0.079	3.00 (0.84–10.77)	0.091
Knee
No Pain	1.00		1.00		1.00
Pain	1.05 (0.47–2.38)	0.891	1.04 (0.46–2.36)	0.913	0.94 (0.41–2.16)	0.888
Ankle/foot
No Pain	1.00		1.00		1.00
Pain	2.80 (1.35–5.80)	0.005	3.07 (1.44–6.52)	0.004	2.83 (1.32–6.08)	0.007

Model 1: Adjusted by sex, age, and socioeconomic level; Model 2: Model 1 adjusted by BMI; Bold letters: statistically significant.

4 Discussion

The main findings of this present study were that poor sleep quality was associated with musculoskeletal pain in Brazilian public school teachers. The major regions of the body where the study participants mentioned pain and which were associated with sleep quality were the thoracic, wrist, low back, ankle, and foot regions, regardless of sex, age, socioeconomic level, and BMI.

The relationship between poor sleep quality and musculoskeletal pain may occur due to some determinant factors such as constant stress exposure and high workload [33, 34]. The worse sleep quality in teachers was associated with psychological distress, aggravated by discrimination about weight status and physical disability [35]. In the sense of weight-related psychological and health problems, the teachers with poor sleep quality showed higher BMI values in the present study, and body fatness has been linked to a series of health problems in different populations [24]. Overweight / obesity is a factor that should be controlled when analyzing the relationship between musculoskeletal pain and sleep quality, as it presents strong associations with both these factors [36, 37]. However, the relationship between poor sleep quality and musculoskeletal pain among teachers remained significant even after insertion of BMI as a potential confounder variable in statistical analysis.

The occurrence of musculoskeletal pain in teaching professionals was observed in different body regions in the present study. Goossens et al. reported the most affected body regions in teachers were the cervical, low back, and knee regions, corroborating in parts with the present study in which episodes of pain were observed in two of these regions [8]. Chaiklieng & Suggaravetsiri argue that these injuries can be caused by the prolonged efforts and behaviors of these professionals, like stretch to write on board and the use of high heel shoes [38], which may be related to the higher prevalence of females in the present study and its possible association of inadequate shoes with prolonged standing. In this sense, the different body regions and limbs affected by musculoskeletal disorders can also be related with gender and disciplines taught, where some of them may demand more time in standing, use of board and transporting work materials.

In addition, the amount of teaching activities may also be related to poor sleep quality in teachers. Bannai et al., when analyzing the time working in hours/week in Japanese teachers, observed that male teachers with a workload per week greater than 60 hours were twice as likely to present sleep disorders [39]. One of the possible reasons is that overwork could be related to less time for rest and relaxation and also excessive fatigue, which would impair sleep [40]. Another factor could be derived from stress situations in which teachers have to deal with students and their parents, like managers and co-workers, in addition to the stress derived from the charges of the administration of the school. Association of emotional exhaustion with high quantity of weekly lessons, environmental noise, personal satisfaction, and depersonalization in Brazilian teachers has been documented [41], which can be aggravated by the workplace psychological harassment suffered by this population [42]. This exposure may cause alterations in the hypothalamus, increasing the activity in the nervous system which could impair wakefulness [43].

In this sense, the hypothesis that sleep disorders and musculoskeletal pain could be related seems plausible, mainly in teachers. In a longitudinal study developed by Rasmussen-Barr et al. with adults in Sweden it was observed that moderate or severe sleep disorders were associated with low back pain [44]. Tekeoglu et al. observed relationships between poor sleep quality and pain in industry workers with shoulder impingement syndrome in Finland [45]. Sleep latency time and quality are prime factors for recovery of physical capacities [46]. However, when sleep time is short or the sleep quality is poor it can trigger a series of psychological and physical alterations [47, 48], mainly increasing muscle tension and contributing to pain episodes in different regions of the body [49].

In an attempt to explain this association between musculoskeletal pain and poor sleep quality, the effort demands of these professionals should also be considered. For example, teachers may use the board for an extended period of time while standing. This could be one of the reasons for the observed findings between poor sleep quality and pain in the feet and ankles, as these regions support the entire structure of the individual. In addition, other studies have observed an association of back pain with sleep quality [50], and according to the International Classification of Diseases (ICD-10), the prevalence of referrals to physiotherapy for musculoskeletal diseases is high [51]. Regarding the wrists, the repetitive movement performed by teachers in the classroom, linked to poor sleep quality, may be one of the reasons for the observed findings in this body region.

4.2 Limitations

There are important limitations in this study, the cross-sectional design prevents the analysis of cause and effect relationships between sleep disorders and skeletal muscle pain, in addition to the direction of this causality. The measurement of sleep by self-report questionnaire may also be considered a limitation, such as other instruments which have been used to assess Musculoskeletal disorders with high reliability in workers [52] and its methodological approaches can limit comparisons with Nordic questionnaire, even though a reliable and valid instrument. For future studies we suggest objective evaluation of sleep, as well as a longitudinal design to verify the incidence and direction of causality in these teaching professionals, once the musculoskeletal pain can be affected to the age and bad ergonomic posture of working years.

However, as an innovative aspect of the present study, the population evaluated stands out, as this study appears to be the first to investigate the association between musculoskeletal pain and sleep quality in school teachers. Another positive point to mention is the control for confounding variables, including body adiposity by BMI, sex, age, and socioeconomic status, avoiding possible bias inherent to these factors in the analyzes. Finally, the large number of teachers evaluated in the public network (approximately 40% of the total number of teachers) and the randomized sample process should be highlighted.

5 Conclusion

Results from this study suggest that sleep disorders were associated with musculoskeletal pain in various regions of the body in teachers. Health promotion actions contributing to improvements in sleep quality and prevention of musculoskeletal pain should be considered in order to increment the quality of life of these professionals.

Conflict of interest

None to report.

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