Abstract
Background
To date, no studies have investigated the relationship between one’s dominant hand and neck/shoulder pain. The aim of this prospective cohort study was to explore the relationship between one’s dominant hand and the severity of neck/shoulder pain. We also examined the relationship between the dominant hand and the onset of neck/shoulder pain at follow-up among workers without neck/shoulder pain at baseline.
Methods
We conducted a prospective cohort study of 9451 workers. The dominant hand was measured by 10 items from the Japanese version of the Flanders Questionnaire at the baseline survey. We assessed neck/shoulder pain using a numeric rating scale. We calculated the unstandardized coefficient (B) using multiple regression analysis and the incidence rate ratio (IRR) for neck/shoulder pain using modified Poisson regression among workers who were free of neck/shoulder pain at baseline.
Results
Among the 9451 respondents for the baseline survey, 6156 responded to the follow-up survey (response rate: 65.1%). Mixed-handed workers reported a higher degree of neck/shoulder pain than right-handed workers (B, 0.33; 95% CI, 0.09-0.58). Among 2481 participants, mixed-handed workers also had a higher IRR for neck/shoulder pain (IRR, 1.27; 95% CI, 1.01-1.61). There was no difference in any of the left-handers compared with the right-handers.
Conclusions
The study found that mixed-handed workers had higher levels of neck/shoulder pain than right-handed workers, and the incidence rate was also higher among mixed-handed workers. Employers should consider these findings when designing work environments, managing tasks, and providing occupational health training to optimize worker comfort and safety.
Keywords: dominant hand, mixed-handed, neck/shoulder pain, prospective cohort study, work-related illness
Key points:
Neck/shoulder pain is increasing among workers, and musculoskeletal prevention is an important issue in the occupational health sector.
Although continuous work and maintaining the same posture are known risk factors, the relationship between the dominant hand and neck/shoulder pain remains unclear.
This study found that mixed-handed workers had a higher severity and incidence of neck/shoulder pain compared with right-handed workers.
A work environment suitable for workers with dominant hands may help prevent neck/shoulder pain.
1. Introduction
The dominant hand varies from person to person and is typically categorized as right-handed, left-handed, or mixed-handed, with proportions differing by country. Among Japanese individuals, the prevalence of left-handedness is 6.2% in men and 4.2% in women. Left- and mixed-handed individuals, referred to as non–right-handed individuals, constitute approximately 10% of the Japanese population.1 The proportion of left-handedness tends to be higher among children than among adults, as it often decreases with age because of corrective measures in childhood. Thus, left-handedness tends to decline gradually with age. Additionally, individuals who are neither strictly right- nor left-handed are classified as mixed-handed. Many of these individuals were originally left-handed but learned to use both hands after being influenced by sociocultural factors and corrective measures in childhood. Notably, women are less likely to be left-handed than men, likely because of the higher rate of corrective measures.2,3 Consequently, the proportion of left-handed individuals varies by age and sex.
Previous research has shown that the dominant hand influences the effects of motion on the body.4 Work tasks performed with the dominant hand often involve techniques honed through training and experience, whereas tasks done with the nondominant hand involve less proficient movements, potentially resulting in differences in force application and body load. Most people naturally prefer to use their dominant hand for work tasks; however, because most equipment is designed for right-handed individuals, left-handed individuals often either work with their nondominant right hand or adapt right-handed equipment to their left hand. In the first scenario, even if the right hand is used, the applied force and physical load of left-handed individuals may differ from right-handed ones. In the second scenario, right-handed equipment is handled by the left hand, resulting in different muscle usage and postures, leading to variations in the physical load. 4,5 These differences may affect the incidence of musculoskeletal symptoms such as neck/shoulder pain in right-handed and left-handed workers.
To date, no studies have examined the relationship between one’s dominant hand and the prevalence of neck/shoulder pain. The prevalence rates of musculoskeletal pain are notably high, with low back pain being the most common, followed by neck/shoulder pain.6 The level of neck/shoulder pain likely varies with dominant hand usage due to differences in upper limb load; however, this has not been thoroughly investigated.
This prospective cohort study aimed to explore the relationship between the dominant hand and the severity of neck/shoulder pain (Analysis 1). We also examined the relationship between the dominant hand and the onset of neck/shoulder pain at the follow-up among workers without neck/shoulder pain at baseline (Analysis 2).
2. Methods
2.1. Study design and participants
This prospective cohort study was part of the Work, Well-Being and Safety for Occupational Health Practice and Management II Study (W2S-Ohpm II). This study was approved by the Ethics Committee of the University of Occupational and Environmental Health, Japan (approval number: R4-077). Informed consent was obtained from all participants via an online form at the start of the self-administered online questionnaire. We conducted the baseline survey in March 2023 and the follow-up survey in December 2023. Details about the baseline study protocol are reported elsewhere.7 The data were collected through a self-administered online survey of people registered with Rakuten Insight, Inc (Tokyo, Japan). People registered with the survey company were able to answer this survey. We set the target sample size at about 10 000 participants.8 The target group was workers in Japan aged 20 and over. To ensure that the target population accurately represented workers in Japan, sampling was conducted by considering the sex, age, and region of residence of the actual Japanese workforce.9 A total of 10 000 workers responded to the baseline survey, of whom 549 were excluded due to fraudulent responses. A follow-up survey was conducted 9 months later and 6156 people responded (response rate, 65.1%). Analysis 1 was conducted on these subjects. Analysis 2 was restricted to workers who had no neck/shoulder pain at baseline. Among the 9451 respondents in the baseline survey, 3735 were included, after excluding 5716 individuals with a Numerical Rating Scale (NRS) of 3 or more. We followed up with these participants, and 2481 were included in Analysis 2. Pain occurrence was defined as the “onset of middle or high pain.” The details are shown in Figure 1.
Figure 1.
Flowchart for the selection of research participants.
2.2. Evaluation of the dominant hand at the baseline survey
We measured dominant hands in the baseline survey using 10 items from the Japanese version of the Flanders Questionnaire.10 Examples of items include, “Which hand do you hold the pen with when writing?” and “Which hand do you hold the spoon with when eating?” For each question, respondents chose 1 of 3 options—the right hand, the left hand, or neither—scored 1, −1, or 0 points, respectively. We summed the scores for all items to obtain a total score (from −10 to +10). Based on a previous study,10 we set 3 categories based on the total score: −10 to −5 = left-handed, −4 to +4 = mixed-handed, and +5 to +10 = right-handed.
2.3. Assessment of neck/shoulder pain
We used self-reported neck/shoulder pain as the outcome of this study. The questions assessing self-reported neck/shoulder pain were as follows: “Regarding your neck/shoulder pain, what is the average level of pain over the past two weeks?” Respondents selected their level of pain from 0 (not painful at all) to 10 (the most painful pain they ever experienced). An 11-point NRS ranging from 0 to 10 was used to assess the pain severity.11
2.4. Other covariates
We assessed age as a continuous variable, sex as a categorical variable (men and women), education in 3 categories (junior high or high school, vocational school or college, and university or graduate school), annual household income in 6 categories (<4.00 million Japanese Yen [JPY], 4.00-5.99 million JPY, 6.00-7.99 million JPY, 8.00-9.99 million JPY, 10.00-11.99 million JPY, and ≥12.00 million JPY), and marital status in 3 categories (married, never married, and divorced or widowed). We also assessed raising motion time and repetitive task time. We assessed the average daily working time spent with the elbow above the shoulder as raising motion time, and the daily duration of repetitive upper limb work as repetitive task time. Participants selected 1 of 11 options: not at all, less than 15 minutes, 15-30 minutes, 30 minutes-1 hour, 1-2 hours, 2-3 hours, 3-5 hours, 5-7 hours, 7-9 hours, 9-11 hours, more than 11 hours. We treated these 11 choices as continuous variables, applying them to the following time periods: 0, 15, 30, 45, 90, 150, 240, 360, 480, 600, and 720 minutes.
2.5. Statistical analysis
We examined the relationship between one’s dominant hand and the self-reported degree of neck/shoulder pain. We applied a multiple regression model in Analysis 1 to assess the association between dominant hand and neck/shoulder pain severity among 6156 workers. The multivariate-adjusted model included age, sex, education, annual household income, marital status, raising motion time, repetitive task time, and NRS of neck/shoulder pain at the baseline survey as covariates. We calculated the unstandardized coefficient, SE, 95% CI, and P value. We compared right-handed with mixed-handed, and right-handed with left-handed using SD. Cohen’s d effect size was calculated for the t test.
We also examined the relationship between the dominant hand and the incidence rate ratio (IRR) of neck/shoulder pain in Analysis 2 (n = 2481). A modified Poisson regression analysis was applied. The multivariate-adjusted model was adjusted for age, sex, education, annual household income, marital status, raising motion time, repetitive task time, and NRS for neck/shoulder pain at the baseline survey. We calculated the IRR, 95% CI, and P value.
Two-tailed P values below .05 were considered statistically significant. All analyses were conducted using Stata Statistical Software, release 18.5 (MP) (Stata Corp LLC, College Station, TX, USA).
3. Results
Among the 9451 respondents surveyed, 6156 responded to the follow-up survey, and 3295 did not respond. Table S1 shows the characteristics of both respondents and nonrespondents. The demographic characteristics of the 3295 nonrespondents were compared with those of the 6156 respondents. Differences were observed in age, sex, and education.
Table 1 presents the characteristics of participants in Analysis 1. Among the participants, 5603 were right-handed, with a mean age of 48.1 years (SD 13.3); 57.8% were men, raising motion time (minutes/d) mean was 22.8 (SD 57.4), and repetitive task time (minutes/d) mean was 37.8 (SD 90.3). There were 311 mixed-handed participants, with a mean age of 45.7 years (SD 13.1); 67.5% were men, raising motion time (minutes/d) mean was 35.4 (SD 74.8), and repetitive task time (minutes/d) mean was 45.3 (SD 92.9). There were 242 left-handed participants, with a mean age of 43.2 years (SD 12.8); 66.1% were men, raising motion time (minutes/d) mean was 32.3 (SD 82.9), and repetitive task time (minutes/d) mean was 50.0 (SD 97.9).
Table 1.
Characteristics of participants in Analysis 1 (n = 6156).a
| Right-handed | Mixed-handed | Left-handed | |
|---|---|---|---|
| n | 5603 | 311 | 242 |
| Age, mean (SD), y | 48.1 (13.0) | 45.7 (13.1) | 43.2 (12.8) |
| Sex, women, n (%) | 2363 (42.2) | 101 (32.5) | 82 (33.9) |
| Education, n (%) | |||
| Junior high or high school | 1443 (25.8) | 74 (23.8) | 52 (21.5) |
| Vocational school or college | 1246 (22.2) | 67 (21.5) | 53 (21.9) |
| University or graduate school | 2914 (52.0) | 170 (54.7) | 137 (56.6) |
| Annual household income, n (%), JPY | |||
| <4.00 million | 1513 (27.0) | 71 (22.8) | 68 (28.1) |
| 4.00-5.99 million | 1347 (24.0) | 81 (26.0) | 63 (26.0) |
| 6.00-7.99 million | 1098 (19.6) | 64 (20.6) | 48 (19.8) |
| 8.00-9.99 million | 756 (13.5) | 45 (14.5) | 29 (12.0) |
| 10.00-11.99 million | 386 (6.9) | 21 (6.8) | 15 (6.2) |
| ≥12.00 million | 503 (9.0) | 29 (9.3) | 19 (7.9) |
| Marital status, n (%) | |||
| Married | 3077 (54.9) | 170 (54.7) | 106 (43.8) |
| Never married | 1662 (29.7) | 89 (28.6) | 99 (40.9) |
| Divorced or widowed | 864 (15.4) | 52 (16.7) | 37 (15.3) |
| Raising motion time,b mean (SD) | 22.8 (57.4) | 35.4 (74.8) | 32.3 (82.9) |
| Repetitive task time,c mean (SD) | 37.8 (90.3) | 45.3 (92.9) | 50.0 (97.9) |
Abbreviation: JPY, Japanese yen.
Analysis 1 corresponds to the overall analysis.
Raising motion time indicates mean working time (min/d) of upper limb motion with the elbows above the shoulders.
Repetitive task time means repetitive motion time (min/d) of upper limbs.
Table 2 presents the association between type of dominant hand and neck/shoulder pain using multiple regression analysis among participants in Analysis 1 (n = 6156). The unstandardized coefficient for mixed-handed was 0.57 (95% CI, 0.27-0.86; P < .001) in the age-sex–adjusted model, and 0.33(95% CI, 0.09-0.58; P = .008) in the multivariate-adjusted model, both of which were significant. For left-handed, the unstandardized coefficient was 0.23 (95% CI, −0.11 to 0.57) in the age-sex–adjusted model, and 0.25 (95% CI, −0.03 to 0.53) in the multivariate-adjusted model, showing no significant difference in both models. There was a statistically significant difference in neck/shoulder pain between right-handed (mean, 3.5; SD, 2.7) and mixed-handed (mean, 4.1; SD, 2.6) with P < .001. The effect size, measured by Cohen’s d, was 0.20, indicating a medium effect. On the other hand, there was no significant difference in neck/shoulder pain between right-handed and left-handed (mean, 3.8; SD, 2.7) with P = .143. The effect size, measured by Cohen’s d, was 0.10, indicating a low effect.
Table 2.
Association between type of dominant hand and neck/shoulder pain using multiple regression analysis among participants in Analysis 1 (n = 6156).a
| Neck/shoulder pain b | Age/sex adjusted | Multivariate adjusted c | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Mean | SD | B d | SE | 95% CI | P value | B d | SE | 95% CI | P value | |
| Right-handed | 3.5 | 2.7 | Reference | Reference | ||||||
| Mixed-handed | 4.1 | 2.6 | 0.57 | 0.15 | 0.27 to 0.86 | <.001 | 0.33 | 0.13 | 0.09 to 0.58 | .008 |
| Left-handed | 3.8 | 2.7 | 0.23 | 0.17 | −0.11 to 0.57 | .179 | 0.25 | 0.14 | −0.03 to 0.53 | .075 |
Analysis 1 corresponds to the overall analysis.
Neck/shoulder pain was evaluated using a numeric rating scale (0-10).
The multivariate model was adjusted for age, sex, education, annual household income, marital status, raising motion time, repetitive task time, and numeric rating scale of neck/shoulder pain at the baseline survey.
B represents an unstandardized coefficient.
Table 3 shows the characteristics of participants in Analysis 2 (n = 2481). Among them, 2278 were right-handed, with a mean age of 49.9 years (SD 13.5) and 66.9% were men. There were 107 mixed-handed participants, with a mean age of 47.9 years (SD 12.8) and 72.0% were men. There were 96 left-handed participants, with a mean age of 44.7 years (SD 13.1) and 70.8% were men.
Table 3.
Characteristics of participants in Analysis 2 (n=2481).a
| Right-handed | Mixed-handed | Left-handed | |
|---|---|---|---|
| n | 2278 | 107 | 96 |
| Age, mean (SD), y | 49.9 (13.5) | 47.9 (12.8) | 44.7 (13.1) |
| Sex, women, n (%) | 754 (33.1) | 30 (28.0) | 28 (29.2) |
| Education, n (%) | |||
| Junior high or high school | 584 (25.6) | 20 (18.7) | 20 (20.8) |
| Vocational school or college | 469 (20.6) | 19 (17.8) | 17 (17.7) |
| University or graduate school | 1225 (53.8) | 68 (63.6) | 59 (61.5) |
| Annual household income, n (%), JPY | |||
| <4.00 million | 617 (27.1) | 22 (20.6) | 27 (28.1) |
| 4.00-5.99 million | 522 (22.9) | 27 (25.2) | 22 (22.9) |
| 6.00-7.99 million | 455 (20.0) | 22 (20.6) | 19 (19.8) |
| 8.00-9.99 million | 319 (14.0) | 14 (13.1) | 14 (14.6) |
| 10.00-11.99 million | 162 (7.1) | 9 (8.4) | 8 (8.3) |
| ≥12.00 million | 203 (8.9) | 13 (12.1) | 6 (6.2) |
| Marital status, n (%) | |||
| Married | 1288 (56.5) | 63 (58.9) | 40 (41.7) |
| Never married | 672 (29.5) | 29 (27.1) | 43 (44.8) |
| Divorced or widowed | 318 (14.0) | 15 (14.0) | 13 (13.5) |
| Raising motion time,b mean (SD) | 18.6 (49.3) | 25.0 (57.6) | 15.5 (42.0) |
| Repetitive task time,c mean (SD) | 32.1 (80.0) | 39.5 (82.6) | 33.8 (84.6) |
Abbreviation: JPY, Japanese yen.
Analysis 2 corresponds to the analysis of pain onset in the low-pain group.
Raising motion time indicates mean working time (min/d) of upper limb motion with the elbows above the shoulders.
Repetitive task time means repetitive motion time (mins/d) of upper limbs.
Table 4 presents the association between type of dominant hand and neck/shoulder pain using modified Poisson regression analysis among participants in Analysis 2 (n = 2481). The IRR for mixed-handed was 1.30 (95% CI, 1.02-1.65; P = .031) in the age-sex–adjusted model and 1.27 (95% CI, 1.01-1.61; P = .044) in the multivariate-adjusted model, both of which were significant compared with right-handed. The IRR for left-handed was 1.16 (95% CI, 0.89-1.51) in the age-sex–adjusted model and 1.19 (95% CI, 0.92-1.55) in the multivariate-adjusted model, showing no significant difference in both models.
Table 4.
Association between type of dominant hand and neck/shoulder pain using modified Poisson regression analysis among participants in Analysis 2 (n = 2481).a
| Neck/shoulder pain b | Age/sex adjusted | Multivariate adjusted c | ||||||
|---|---|---|---|---|---|---|---|---|
| n | % | IRR | 95% CI | P value | IRR | 95% CI | P value | |
| Right-handed | 683 | 30 | Reference | Reference | ||||
| Mixed-handed | 42 | 39 | 1.30 | 1.02-1.65 | .031 | 1.27 | 1.01-1.61 | .044 |
| Left-handed | 35 | 36 | 1.16 | 0.89-1.51 | .267 | 1.19 | 0.92-1.55 | .189 |
Abbreviation: IRR, incidence rate ratio.
Analysis 2 corresponds to the analysis of pain onset in the low-pain group.
Neck/shoulder pain was scored by using a numeric rating scale (0-10), and defined as having a score of 3 or more.
The multivariate model was adjusted for age, sex, education, annual household income, marital status, raising motion time, repetitive task time, and numeric rating scale of neck/shoulder pain at the baseline survey.
4. Discussion
This study examined the relationship between one’s dominant hand and the severity of neck/shoulder pain in workers. Mixed-handed workers reported more severe neck/shoulder pain than right-handed workers, whereas left-handed workers showed no significant difference compared with right-handed workers. These findings suggest a higher risk of work-related musculoskeletal complaints in mixed-handed individuals than in right-handed individuals. To the best of our knowledge, no previous studies have investigated this relationship, making these findings novel. In the modified Poisson regression analysis, workers with mixed-hand use also had a higher IRR for neck/shoulder pain. No previous studies have investigated this relationship, making these findings novel.
In our study, mixed-handed individuals experienced greater neck/shoulder pain than right-handed individuals did. Mixed-handedness typically results from sociocultural pressures that encourage left-handed individuals to adapt to right-hand use.12,13 However, personal variations exist in the hand that a mixed-handed person uses at work. Most workplace equipment is designed for right-hand use, which forces mixed-handed individuals to rely on their less familiar right hand. Neck/shoulder pain has multiple risk factors, including prolonged sitting, neck flexion, trunk twisting, and upper limb exertion, and is often related to poor posture and low physical activity (eg, extended computer use). 14-18 For mixed-handed workers, 2 mechanisms likely contribute to increased pain: differences in force application and movement patterns depending on hand dominance.19-22 First, mixed-handed individuals may apply excessive force compared with those using their dominant hand, especially when performing tasks designed for right-handed users. Mixed-handed individuals may not perform tasks as skillfully as right-handed individuals, potentially leading them to apply more force. Even if both right- and mixed-handed individuals use their right hand, strength and force may differ, with mixed-handed individuals exerting more effort.23,24 Second, mixed-handed workers may exhibit larger or less efficient movements, which can increase their physical demand. For instance, they may spend more time lifting their arms above shoulder height or repeating similar motions than right-handed users. By contrast, left-handed individuals reported less severe symptoms, which diverged from our initial hypothesis. Although handling right-handed equipment can be physically taxing for left-handed workers, their need for specific work adaptations may lead to more ergonomic accommodations, thereby reducing physical strain. Left-handed individuals spent more time lifting their arms than right-handed individuals but less time than mixed-handed individuals. Neck/shoulder pain significantly affects productivity, and neck/shoulder pain is the leading cause of presenteeism. Therefore, further research on dominant hands and productivity is necessary. Since the dominant hand is likely to affect movements and other factors, further research is needed on the relationship between the dominant hand and occupational accidents.25
Based on these findings, it is plausible that in the present study population the stress arising from the use of the nondominant hand may contribute to the development of depressive symptoms, which in turn could lead to the onset of pain.26
4.1. Practical applications
To mitigate the risk of neck/shoulder pain in mixed-handed workers, we propose strategies that focus on work environment management, occupational health education, and task design. First, adapting workstations to accommodate non–right-handed individuals is essential in terms of work environment and task design. Although large machinery is generally designed for right-handed individuals, providing flexibility in equipment layout, worker positioning, and table adjustments can reduce the strain caused by body twisting and hand crossing.17,18,27 Providing tools suited to individual hand dominance is recommended. Second, occupational health education is critical. In addition to a supportive environment, training can help mixed- and left-handed individuals work more efficiently with less physical strain. Educating workers on workplace-specific skills through consistent training may help reduce muscle fatigue and improve task efficiency. Third, efforts to reduce repetitive strain injuries have emphasized avoiding unilateral strain by encouraging the balanced use of both hands. However, our findings suggest that encouraging bilateral hand use may increase the risk of musculoskeletal disorders in certain contexts. Future research should investigate hand usage patterns during tasks and assess the physical load to inform occupational health guidelines.28
4.2. Strengths and limitations
This study has 2 strengths. First, it is the first study to show that mixed-handedness may increase the risk of neck/shoulder pain. Second, our stratified sampling method ensured sex, age, and regional representation of the Japanese workforce, thereby enhancing the generalizability of the study. However, this study has some limitations. The online survey format may have excluded those without internet access, which could limit representativeness and introduce volunteer bias. Additionally, although we adjusted for confounding variables based on prior research, unmeasured confounders may have influenced the findings. Another potential bias is response inconsistency: participants may underreport pain if the discomfort is unilateral. Finally, cultural differences in pain reporting and variations in neck/shoulder pain definitions across countries may limit the generalizability of our findings. The study also lacked detailed data on hand use patterns in mixed-handed individuals under real working conditions. Since the present study did not assess hand preference during work, this issue should be explored in future research. Further investigation is needed to determine whether the workplace environment is a contributing factor.
5. Conclusion
This study found that mixed-handed workers experienced a higher degree of neck/shoulder pain than right-handed workers did. Employers should consider these findings when designing work environments, managing tasks, and providing occupational health training to optimize worker comfort and safety.
Supplementary Material
Acknowledgments
The current members of the W2S-Ohpm Study, in alphabetical order, are as follows: Akiko Matsuyama, Asumi Yama, Ayaka Yamamoto, Ayana Ogasawara, Hideki Fujiwara, Juri Matsuoka, Kaufusi Matsuyama, Kenta Moriya, Kiminori Odagami, Koji Mori, Kosuke Sakai, Masako Nagata, Miho Omori, Mika Kawasumi, Mizuho Inagaki, Naoto Ito, Rina Minohara, Shunusuke Inoue, Suo Taira, Takahiro Mori, Takeru Tsutsumi, Tomohisa Nagata (present chairperson of the study group), and Tomoko Sawajima. All members are affiliated with the University of Occupational and Environmental Health in Japan. We thank Analisa Avila, MPH, ELS, of Edanz (https://jp.edanz.com/ac) for editing a draft of this manuscript.
Contributor Information
Yukiko Ogawa, Department of Occupational Health Nursing, School of Occupational Health Science, University of Occupational and Environmental Health, Japan, Kitakyushu, Japan.
Tomohisa Nagata, Department of Occupational Health Practice and Management, Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Japan, Kitakyushu, Japan.
Kiminori Odagami, Department of Occupational Health Practice and Management, Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Japan, Kitakyushu, Japan.
Takeshi Ebara, Department of Ergonomics, Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Japan, Kitakyushu, Japan.
Junko Nakatani, Department of Occupational Health Nursing, School of Occupational Health Science, University of Occupational and Environmental Health, Japan, Kitakyushu, Japan.
Koji Mori, Department of Occupational Health Practice and Management, Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Japan, Kitakyushu, Japan.
Author contributions
Y.O., T.N., K.O., T.E., J.N., and K.M. created the study hypothesis; T.N., K.O., and K.M. collected the data; Y.O. designed the analysis, analyzed the data, and wrote the draft of the manuscript. All authors advised on the data interpretation and reviewed, edited, and approved the final manuscript.
Supplementary material
Supplementary material is available at Journal of Occupational Health online.
Funding
This study was supported and partly funded by a research grant from the University of Occupational and Environmental Health, Japan (no grant number); Japanese Ministry of Health, Labour and Welfare (210401-01 and 20JA1005); JSPS KAKENHI (JP22K10543 and JP19K19471); Collabo-Health study group (no grant number), and DAIDO LIFE INSURANCE COMPANY (no grant number). The funders were not involved in the study design, collection, analysis, interpretation of data, writing of this article, or the decision to submit it for publication.
Conflicts of interest
The authors declare no conflicts of interest associated with this manuscript. T.N. has received personal fees from BackTech Inc, EWEL Inc, and Sompo Health Support Inc, outside of the submitted work. K.M. has received research grants from the DAIDO LIFE INSURANCE COMPANY, Komatsu Ltd, and HASEKO Corporation; scholarship grants from AORC, BackTech Inc, DAIDO LIFE INSURANCE COMPANY, EWEL Inc, iSEQ Inc, JMA Research Institute Inc, MEDIVA Inc, SMS Co., Ltd, Sompo Health Support Inc, and T-PEC CORPORATION; and personal fees from BackTech Inc and Sompo Health Support Inc, outside of the submitted work.
Data availability
The data are not publicly available due to privacy or ethical restrictions.
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Data Availability Statement
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