2020 Volume 2 Issue 4 Pages 113-120
BACKGROUND
Low back pain (LBP) is an important problem in occupational health, but little is known about LBP in nursery school teachers.
METHODS
To determine the prevalence of LBP that needed medical treatment, LBP in their lifetime, factors associated with LBP, and work environment in nursery school teachers, we performed a cross-sectional study at Sakyo-ku in Kyoto City. We used multivariable logistic regression models to assess factors associated with LBP that needed medical treatment during the year.
RESULTS
Of 410 teachers in 21 nursery schools, 154 (37.6%) participated in the study. Sixty-four teachers (41.8%) had LBP that needed medical treatment during the year, and 128 (83.7%) had LBP in their lifetime. As factors associated with LBP, age (adjusted odds ratio [AOR] [per 10-year increase], 1.48; 95% confidence interval [95%CI], 1.06–2.07), unnatural posture (AOR, 5.14; 95%CI, 1.51–17.45), mental health (AOR, 1.89; 95%CI, 1.07–3.33), and psychological demand from job (AOR, 1.92; 95%CI, 1.24–2.97) were suggested. Three of 15 nursery schools employed industrial physicians, and precautions of LBP were taken in two schools.
CONCLUSIONS
Further investigations if intervention of these factors associated with LBP as work management to prevent LBP in nursery schools reduced their LBP are required.
Low back pain (LBP) is an important problem in occupational health [1, 2]. Generally, previous studies suggested that risk factors of LBP, including those in the general population and other occupational employees, were age, bending forward, kneeling, monotonous work, and depressive symptoms [3, 4]. In nursery school teachers, previous cross-sectional studies suggested that 40% of childcare workers have LBP during the year, and in Japan, many nursery school teachers leave jobs in a few years due to their health problems [5–7]. As factors associated with LBP in nursery school teachers, overcommitment, age, physical workload, and mental burden in dealing with children and parents have been suggested [5, 8].
However, in nursery school teachers, LBP that needed medical treatment during the year was not examined for associated occupational factors. LBP that needed medical treatment is one of the most serious conditions because LBP impairs the quality of life and requires enormous cost of care [9, 10].
Here, we investigated the prevalence of LBP that needed medical treatment during the year, factors associated with LBP that needed medical treatment during the year, and work environment in nursery school teachers.
This is a cross-sectional study that used a self-administered questionnaire. We explained our survey to the representatives of 27 nursery schools in Sakyo-ku Hoikushikai whose nursery schools belonged to Sakyo-ku in Kyoto City, and 21 schools agreed to participate in this survey. Sakyo-ku Hoikushikai is a branch of Zenkoku Hoikushikai, which is the largest association of nursery school teachers in Japan to promote children and their parents’ welfare. We performed the survey in 21 nursery schools. The participants were nursery school teachers in 21 nursery schools who agreed to complete the survey. The total number of nursery school teachers in the setting was calculated using the open data on nursery schools reported by Kyoto City [11].
DATA COLLECTIONWe collected the questionnaires from October 2017 to March 2018. We sent two types of questionnaires to each nursery school with reply envelopes and asked participants to return them individually. We made phone calls three times and sent a mail to every nursery school as a reminder to increase the response rate.
QUESTIONNAIREA self-administered questionnaire on the participant’s health was prepared and answered by nursery school teachers, except principals. This questionnaire was anonymous and had an explanation on the top page that we regarded the return of this questionnaire as provision of informed consent. We also asked about the work management to prevent LBP in nursery schools to the manager of each facility using another questionnaire.
OUTCOMESThe main outcome was LBP that needed medical treatment and had been treated at a medical institution during the year. We included all types of medical institution, such as hospital, clinic of licensed masseur, acupuncture clinic, and chiropractic clinic. We also collected data on LBP in their lifetime.
EXPOSURESAs exposures, we selected six possible factors associated with LBP from the panel discussion, which consisted of nursery school teachers, epidemiologists, and an orthopedist based on previous studies. Possible factors associated with LBP included age; frequency of taking unnatural posture within one month, such as bending forward and kneeling; monotonous work; mental health within one month; smoking; and psychological demand from the job [4, 8]. The frequency of taking unnatural posture within one month was classified as not presenting unnatural posture if they answered “none” or “seldom” and presenting unnatural posture if they answered “sometimes,” “often,” or “always.” As for monotonous work, we recategorized the groups of “strongly disagree” and “disagree” into “not engaging monotonous work” and the groups of “agree” and “strongly agree” into “engaging monotonous work.” Smoking status was categorized into the following two groups: “have never smoked” and “had ever smoked.” Mental health within one month was measured using the five-question Mental Health Inventory (MHI-5) from the mental health domain of the SF-36, and psychological demand from the job was measured using the 22-item short version of the Job Content Questionnaire (JCQ) [12–15]. The MHI-5 score ranged from 0 to 100, and a lower score suggested more depression. The psychological demand score ranged from 12 to 48, and a higher score suggested more psychological demand from the job. We collected these data using a questionnaire for each participant’s health.
OTHER CHARACTERISTICS OF PARTICIPANTSWe determined sex, years of service, work status, comorbidities, and history of depression and bone fracture as participants’ characteristics. We also asked the type of medical institutions, medical treatments, and JCQ’s other domains (skill discretion, decision authority, decision latitude, supervisor support, coworker support, and social support) using the questionnaire for each participant’s health. The ranges of the scores for JCQ’s other domains were 12–48, 12–48, 24–96, 4–16, 4–16, and 8–32, respectively. A higher score suggested a better condition.
WORK MANAGEMENTWith regard to the questionnaire for managers, we determined the employment of industrial physicians, regular assessment of work environment, regularly scheduled meetings for solving problems of work environment, and precautions of LBP.
STATISTICAL ANALYSISIn the descriptive analysis, median and interquartile range (IQR) were used to summarize continuous variables. Number and percentage (%) were used to summarize categorical variables.
In the univariate analysis, we used the Wilcoxon rank-sum test for continuous variables and Fisher’s exact test for categorical variables. In the multivariable analysis, a logistic regression model was employed to examine factors associated with LBP that needed medical treatment during the year. We used six possible factors associated with LBP as independent variables in the model. Taking unnatural posture and monotonous work were treated as dichotomous variables in the model. Age (per 10-year increase) and scores of mental health and psychological demand from the job (both were converted to z scores) were treated as continuous variables in the model. We used a complete set for the analysis, excluding those with missing values of LBP and possible factors associated with LBP mentioned above. We used Stata® 14.2 (StataCorp, College Station, TX, USA) in all analyses.
The study was performed according to the Declaration of Helsinki and approved by the Kyoto University Graduate School and Faculty of Medicine Kyoto University Hospital Ethics Committee (approval number R1210).
Of the 410 teachers recruited from 21 nursery schools, 154 (37.6%) participated in the present study. One was excluded from the analysis because of missing data. Of the 153 teachers, 64 (41.8%) received medical treatment for LBP during the year, and 128 (83.7%) had LBP in their lifetime. Nursery school teachers’ characteristics are shown in Table 1. The median age was 41 years. Ten male teachers (6.5%) participated in the study, and most participants were female. Forty-four (69%) of 64 teachers who received medical treatment during the year visited chiropractic clinics. Regarding medical treatment, of 64 teachers who received medical treatment during the year, 49 (77%) received massage, and 43 (67%) used an anti-inflammatory analgesic plaster.
| Total (n = 153) | LBP (−) (n = 89) | LBP (+) (n = 64) | Missing | P-value | |
|---|---|---|---|---|---|
| Age (years), median, [IQR] | 41 [31–52] | 36 [28–50] | 44 [33.5–52.5] | 0 | 0.043† |
| Male, n (%) | 10 (6.5) | 3 (3.4) | 7 (10.9) | 1 (0.7) | 0.096‡ |
| Years of service (years), median, [IQR] | 12.8 [4.8–19.8] | 11.8 [4.8–18.0] | 14.0 [4.4–24.8] | 46 (30.0) | 0.50† |
| Full-time employee, n (%) | 117 (76.5) | 69 (77.5) | 48 (75.0) | 0 | 0.85‡ |
| Smoking, n (%) | 22 (14.4) | 9 (10.1) | 13 (20.3) | 1 (0.7) | 0.010‡ |
| Comorbidities | 9 (5.9) | ||||
| Diabetes mellitus, n (%) | 0 (0) | 0 (0) | 0 (0) | ||
| Hypertension, n (%) | 5 (3.3) | 3 (3.4) | 2 (3.1) | 1.00‡ | |
| Dyslipidemia, n (%) | 7 (4.6) | 1 (1.1) | 6 (9.4) | 0.021‡ | |
| History | 9 (5.9) | ||||
| Depression, n (%) | 6 (3.9) | 4 (4.5) | 2 (3.1) | 1.00‡ | |
| Bone fracture, n (%) | 29 (19.0) | 12 (13.5) | 17 (26.6) | 0.057‡ | |
| Other possible factors associated with LBP | |||||
| Unnatural posture, n (%) | 126 (82.4) | 68 (76.4) | 58 (90.6) | 1 (0.7) | 0.048‡ |
| Monotonous work, n (%) | 138 (90.2) | 80 (92.0) | 58 (90.6) | 2 (1.3) | 0.78‡ |
| Mental health (0–100), median, [IQR] | 55 [45–65] | 55 [45–60] | 55 [45–65] | 6 (3.9) | 0.14† |
| Psychological demand (12–48), median, [IQR] | 35 [32–39] | 34.5 [32–38] | 36.5 [32–41] | 5 (3.3) | 0.032† |
IQR, interquartile range. LBP, low back pain that needed medical treatment during the year. †Wilcoxon rank-sum test, ‡Fisher’s exact test.
In the univariate analysis, results showed that age in participants with LBP (median [IQR], 44 [33.5–52.5] years) was older than those without LBP (median [IQR], 36 [28–50] years). Dyslipidemia was more common in teachers with LBP (9.4%) than in those without LBP (1.1%). Taking unnatural posture was more frequent in teachers with LBP (90.6%) than in those without LBP (76.4%). The domain score of the psychological demand from the job (median [IQR], 36.5 [32–41]) was higher in teachers with LBP than in teachers without LBP (median [IQR], 34.5 [32–38]). Regarding monotonous work, history of bone fracture, and MHI scores for mental health, there was no difference between teachers with LBP and those without LBP. As shown in Supplemental Table 1, the domain scores of supervisor support (median [IQR], 12 [10–12]) were lower in teachers with LBP than in teachers without LBP (median [IQR], 12 [12–15]).
The results of the multivariable analysis are shown in Table 2. A total of 143 nursery school teachers without missing data were included in this analysis, and 60 (42.0%) of them had received medical treatment for LBP during the year. Age (adjusted odds ratio [AOR], [per 10-year increase], 1.48; 95% confidence interval (95%CI), 1.06–2.07), frequency of unnatural posture (AOR, 5.14; 95%CI, 1.51–17.45), mental health (AOR, 1.89; 95%CI, 1.07–3.33), and psychological demand from the job (AOR, 1.92; 95%CI, 1.24–2.97) were associated with LBP that needed medical treatment during the year.
| Factors associated with LBP | Adjusted odds ratio | 95%CI |
|---|---|---|
| Age (per 10-year increase ) | 1.48 | 1.06–2.07 |
| Smoking | 2.66 | 0.93–7.59 |
| Unnatural posture | 5.14 | 1.51–17.45 |
| Monotonous work | 1.32 | 0.29–5.95 |
| MHI-5 score (per point) | 1.89 | 1.07–3.33 |
| Psychological demand (per point) | 1.92 | 1.24–2.97 |
LBP, low back pain that needed medical treatment during the year. CI, confidence interval. MHI-5, five-question Mental Health Inventory
Table 3 shows the results of the questionnaire for work management completed by 15 school managers. Regularly scheduled meetings for solving problems in the work environment were held at 10 nursery schools (66.7%). However, only three nursery schools employed industrial physicians, and precautions of LBP were taken in two schools. Eleven nursery schools did not regularly assess work management.
| No | Yes | Missing | |
|---|---|---|---|
| Employment of industrial physicians, n (%) | 12 (80.0) | 3 (20.0) | 6 |
| Regular assessment of work environment, n (%) | 11 (73.3) | 4 (26.7) | 6 |
| Regularly scheduled meeting for solving problems of work environment, n (%) | 5 (33.3) | 10 (66.7) | 6 |
| Precautions of LBP, n (%) | 13 (86.7) | 2 (13.3) | 6 |
LBP, low back pain.
We performed a survey on LBP in nursery school teachers. We found that 128 teachers (83.7%) had LBP in their lifetime, and >40% of nursery school teachers received medical treatment for LBP during the year. LBP was associated with unnatural posture, mental health, and psychological demand from the job. In most nursery schools, work management might be insufficient.
An occupational guideline suggests that, generally, 60–80% of adults have a history of LBP [16]. Compared with the guidelines, the prevalence of LBP is relatively high in nursery school teachers.
There are limited studies on the prevalence of LBP during the year and LBP that needed medical treatment during the year in nursery school teachers [5, 6]. Considering that the one-year prevalence of LBP in previous studies was approximately 40%, most patients with LBP may need medical treatment since our study revealed that 41.8% of nursery school teachers received medical treatment for LBP [5, 6]. A previous study suggested that the prevalence of LBP that needed medical treatment during the year was 40.5% in healthcare workers. The severity of LBP in nursery school teachers may be similar to that in healthcare workers [17].
With regard to the risk factors of LBP, a previous study on the general population and a systematic review on the general population and other occupational employees suggested that as age increased to 65 years and frequency of bending forward increased, kneeling was longer, monotonous work and depression existed, and the incidence of LBP increased [3, 4]. Our study focused on LBP in nursery school teachers, suggesting that, in nursery school teachers and general population and other occupational employees, some factors associated with LBP were similar.
Another study analyzed videos of nursery school teachers, which revealed that they frequently took unnatural posture and spent >30% of work time taking unnatural posture to care for small children on the floor [18]. Reducing the frequency of unnatural posture may contribute to improving LBP in nursery school teachers.
In the present study, we found an unexpected association that individuals with lower mental health were less likely to have LBP that needed medical treatment. A previous meta-analysis suggested that depression was a risk factor for noncompliance in medical treatments [19]. One possible explanation for the unexpected results is that those with lower mental health might have difficulties visiting medical institutions even if they have LBP [4].
Previous studies have suggested that psychological demand from the job is associated with LBP [20–22]. In our study, after adjusting for other potential factors associated with LBP, there was an association between psychological demand from the job and LBP that needed medical treatment. Participants in this study were nursery school teachers, and psychological demand from the job was relatively higher compared with those in other occupations in companies and factories [23]. Concurrently, the domain scores of supervisor support were higher in teachers without LBP. Compared with the previous study, the score of supervisor support was relatively high [23]. With supervisor support, psychological demand and risk of LBP might be reduced. Reducing psychological demand from the job might be useful in improving LBP in nursery school, although future interventional studies are required.
With regard to the management of the work environment, we found no previous studies on nursery schools. In Japan, facilities that do not meet the criteria of the law are not obliged to assign industrial physicians for the management of the work environment in facilities. For example, if the number of employees in a facility is <50, industrial physicians do not have to manage the work environment [24, 25]. In this survey, few nursery schools asked industrial physicians to manage the work environment, assessed their work environment regularly, or took precautions of LBP. There is a possibility that the work environment in nursery schools is not sufficiently managed. Some previous studies suggested the importance of precautions in the workplace, such as ergonomic or psychological intervention [26, 27]. When they conduct regular assessments and precautions and reduce psychological demand from the job and frequency of taking unnatural posture with the help of experts such as industrial physicians, the prevalence of LBP may be improved.
The strength of this study is that it is the first report to identify factors associated with LBP that needed medical treatment during the year specific to nursery school teachers and work management in nursery schools.
This study has several limitations. First, there are several potential sources for selection bias. The response rate was only 38%. Although we reminded nursery school teachers in this survey several times, nursery school teachers who were not interested in LBP would not answer the questionnaire. Therefore, the true prevalence could be lower than observed. In contrast, nursery school teachers who were absent from work would have difficulty answering the questionnaire. Moreover, many nursery school teachers leave jobs in a few years due to health problems, including LBP [7]. Such teachers tend not to be included in the study. If such teachers were included, the prevalence would be higher. Second, the survey was performed in a small district in Japan, and our findings may not be applicable to other regions. Third, the time when we measured factors associated with LBP may be after treatment for LBP. However, LBP reoccurs easily [28]. Particularly, LBP that needed medical treatment during the year reoccurred in more than half of cases in a previous study [29]. It suggests that, in most nursery school teachers who had LBP, we measured factors associated with LBP before the next recurrence of LBP. Lastly, this was a cross-sectional study. The possibility of reverse causation cannot be denied although some factors associated with LBP were suggested as risk factors in previous cohort studies in the general population and other occupational employees [4]. Prospective studies with larger sample sizes are needed to clarify the causal relationship and incidence of LBP in nursery school teachers. As for work management, randomized controlled trials are needed to clarify if work management can reduce the incidence of LBP.
From the results of the survey on LBP in nursery school teachers, we found that >40% of nursery school teachers received medical treatment for LBP during the year. LBP was associated with unnatural posture, mental health, and psychological demand from the job. LBP might improve with the help of an expert who could manage these factors associated with LBP.
We have no conflicts of interest to declare.
We would like to thank Yuki Suzuki and Fumiyo Hiranuma in Kazenoko Hoikuen and nursery school teachers in Akaimi Hoikuen for designing the survey and collecting data and Sakyo-ku Hoikushikai for collecting data. We would like to thank Editage (www.editage.com) for English language editing.
| Total (n = 153) | LBP (−) (n = 89) | LBP (+) (n = 64) | Missing (n = 1) | P-value | |
|---|---|---|---|---|---|
| Skill discretion (12–48), median, [IQR] | 36 [34–38] | 36 [32–38] | 38 [34–40] | 4 | 0.18† |
| Decision authority (12–48), median, [IQR] | 36 [28–40] | 36 [32–36] | 32 [28–40] | 3 | 0.59† |
| Decision latitude (24–96), median, [IQR] | 70 [64–76] | 70 [66–76] | 68 [62–78] | 5 | 0.91† |
| Supervisor support (4–16), median, [IQR] | 12 [11–14] | 12 [12–15] | 12 [10–12] | 3 | 0.027† |
| Coworker support (4–16), median, [IQR] | 12 [12–14] | 12 [12–15] | 12 [12–13] | 4 | 0.13† |
| Social support (8–32), median, [IQR] | 24 [22–28] | 24 [23–29] | 24 [22–26] | 4 | 0.054† |
IQR, interquartile range. LBP, low back pain that needed medical treatment during the year. †Wilcoxon rank-sum test.
