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Occupational Medicine Advance Access originally published online on January 16, 2007
Occupational Medicine 2007 57(2):126-130; doi:10.1093/occmed/kql157
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© The Author 2007. Published by Oxford University Press on behalf of the Society of Occupational Medicine. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org

Inequality in the health status of workers in small-scale enterprises

Tsutomu Hoshuyama1, Yoshiyuki Hino2,3, Koutarou Kayashima2, Tetsuya Morita4, Hideyuki Goto5, Makiko Minami1,3, Sonoko Sakuragi1,6, Chieko Tanaka1 and Ken Takahashi1

1 Department of Environmental Epidemiology, University of Occupational and Environmental Health, Orio, Yahatanishiku, Kitakyushu, Japan
2 Occupational Health Training Center, University of Occupational and Environmental Health, Orio, Yahatanishiku, Kitakyushu, Japan
3 Nishinihon Occupational Health Service Center, Kitakyushu, Japan
4 Fukuoka Institute of Occupational Health, Fukuoka, Japan
5 Saga Occupational Health Association Foundation, Saga, Japan
6 Kyoto Industrial Health Association, Kyoto, Japan

Correspondence to: Tsutomu Hoshuyama, Department of Environmental Epidemiology, University of Occupational and Environmental Health, Orio, Yahatanishiku Kitakyushu City 807-8555, Japan. Tel: +81 93 691 7401; fax: +81 93 601 7324; e-mail: hoshuyam{at}med.uoeh-u.ac.jp


   Abstract
Top
 Abstract
Introduction
 Methods
 Results
 Discussion
 Conflicts of interest
 References
 
Background Small-scale enterprises (SSEs) usually share poorer resources for promoting occupational health.

Aim To investigate inequality of health status among SSEs in Japan.

Method A cross-sectional, multiple-centred study was carried out using the periodical health check-up data for the fiscal year 2000 to compare the age-adjusted proportions of workers with hypertension (HT), hyperlipidaemia, impaired glucose tolerance (IGT) and obesity and of current smokers by size of enterprise, i.e. ≤29, 30–49, 50–99, 100–299, 300–999 and ≥1000 employees in Japan.

Results From five leading occupational health organizations, data were collected for 9833 enterprises with a total of 436 729 subjects, 302 383 males and 134 346 females. The proportions of workers in SSEs with ≤49 employees with HT, IGT and obesity were 8.5, 5.0 and 3.5%, respectively, higher than those in enterprises with ≥50 male employees. The prevalence of smokers in SSEs with ≤49 employees was 61%, 2–6% higher than in enterprises with ≥50 male employees. These proportions showed a significantly increasing tendency with decreasing size of male workforce.

Conclusion Despite the cross-sectional design and only adjusting age as a potential confounder, higher proportions of HT, IGT, obesity and smoking in male workers were found in SSEs compared to larger organizations.

Keywords      Health check-up; hypertension; impaired glucose tolerance; obesity; prevalence; small-scale enterprises; smoking


   Introduction
Top
 Abstract
 Introduction
Methods
 Results
 Discussion
 Conflicts of interest
 References
 
Small-scale enterprises (SSEs), usually defined as companies with <50 employees, are a key issue in occupational health. Such companies share common characteristics such as poor resources, including monetary, personnel and technological resources; ageing and less flexibility for fitness for work, unfavourable factors for the promotion of occupational health [1]. It is also recognized that SSEs account for the majority of employed workers. In 2004, the proportions of SSEs and their employees of all enterprises were 97.5% (5 580 709 among a total of 5 721 150 enterprises) and 63.5% (33 103 101 among a total of 52 067 396) of workers in Japan [2].

The actual provision of occupational health among SSEs is not well known in Japan. SSEs are exempt from some of the legal obligations regarding occupational health regulated by the Japanese Industrial Health Law, e.g. they are not required to submit a report of periodical health check-ups to the chief of the Labour Standards Inspection Office or appoint an occupational physician, health officer or health committee [3,4]. Previous studies have found the health status of workers in SSEs to be worse than that of workers in larger scale enterprises [5,6].

This study aimed to explore the health status among workers in SSEs using information obtained from the periodical general health check-up (PGHC) and to compare the health levels by scale of enterprises in Japan.


   Methods
Top
 Abstract
 Introduction
 Methods
Results
 Discussion
 Conflicts of interest
 References
 
From the five occupational health organizations (OHOs), which broadly cover the western area of Japan, the authors collected data of the PGHC of 436 729 Japanese workers (302 383 males and 134 346 females). The information included was age at the PGHC, gender, systolic and diastolic blood pressures (SBP and DBP, respectively), total cholesterol (TC), triglycerides (TG), high density lipoprotein-cholesterol (HDL), fasting blood sugar (FBS), urine sugar (US), haemoglobin A1c (HbA1c) and smoking status (current smoker, ex-smoker or non-smoker). Screening for hypertension (HT), hyperlipidaemia (HL), impaired glucose tolerance (IGT) and obesity was conducted by applying the following criteria to individual PGHC data—HT: SBP ≥160 or DBP ≥95 (mmHg); HL: TC ≥250, TG ≥400 or HDL ≤30 (mg/dl); IGT: FBS ≥200 (mg/dl), HbA1c ≥6.5 (%) or US +1 or higher score in qualitative analysis; obesity: body mass index (BMI) (body weight per square of body height) ≥25 (kg/m2). All the PGHCs were conducted from April 2000 through March 2001.

The proportions of workers screened as ‘abnormal’ for HT, HL, IGT and obesity were compared according to the scale of enterprise, i.e. ≤29, 30–49, 50–99, 100–299, 300–999 and ≥1000 employees as well as the proportion of current smokers. To evaluate a linear trend, the test statistic {chi}2 was calculated [7]. All data analyses were performed using the SAS V8.02 statistical package. Difference in age was adjusted according to workforce size with PROC GLM in SAS.

This study was approved by the University of Occupational and Environmental Health, Japan, ethical committee in October 2002.


   Results
Top
 Abstract
 Introduction
 Methods
 Results
Discussion
 Conflicts of interest
 References
 
The total number of enterprises in which workers were employed was 9833. Although the proportion of enterprises varied among the OHOs, those with ≤29 employees were the most numerous, 6404 (65%), and enterprises with ≥1000 employees the least, 410 (4%) (Table 1).


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  		Table 1. Distribution of enterprises by five OHOs in a cross-sectional study on inequality of health status in SSEs in Japan (2002)

 
Table 2 shows the age and gender distributions according to size of enterprise. Overall, mean age (standard deviation) was 40.8 (12.3) years for males and 40.5 (13.3) years for females. The ranges of mean age were 40.1–42.1 years for males and 38.5–41.7 years for females among the OHOs. The numbers of workers in enterprises with ≤29 employees, 62 821 males (21%) and 25 371 females (19%), were similar to those with ≥1000 employees, 60 372 (20%) and 27 450 (21%), respectively.


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  		Table 2. Gender distribution of workers by scale of enterprise in a cross-sectional study on inequality of health status in SSEs in Japan (2002)

 
Table 3 shows the prevalence of current smokers according to the scale of enterprise. The age-adjusted prevalence tended to decrease in ascending order of scale of enterprise for males, but not for females.


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  		Table 3. Age-adjusted prevalences of current smokers according to scale of enterprise in a cross-sectional study on inequality of health status in SSEs in Japan (2002)

 
Table 4 shows the prevalences of the workers who were screened as suffering from HT, HL, IGT and obesity by applying the criteria to individual PGHC data. Age-adjusted prevalences of workers in SSEs with abnormal HT, HL, IGT and obesity in the PGHC were 8.3, 10.3, 5.0 and 3.5% males in enterprises with ≤29 employees and 8.6, 10.8, 4.4 and 3.6% males in enterprises with 30–49 employees. There were highly statistically significant trends in the age-adjusted prevalences of HT, IGT and obesity in ascending order of scale of company for males. For females, such trends were not clear.


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  		Table 4. Age-adjusted proportions of the workers screened as abnormal and of the current smokers according to scale of enterprise in a cross-sectional study on inequality of health status in SSEs in Japan (2002)

 

   Discussion
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
Conflicts of interest
 References
 
This study reveals the health status among workers in SSEs, in particular, those who work for enterprises with ≤49 employees. The health status of these workers was likely to be poorer, but partly statistically significant, than those in larger enterprises. Age-adjusted prevalences of workers in SSEs with ≤49 employees with abnormal blood pressure, glucose tolerance and BMI from the PGHC were 8.5, 5.0 and 3.5% males, respectively, which is slightly higher than for workers in enterprises with ≥50 employees. In addition, for males, there was a statistically significant tendency of increase in the prevalence of current smokers with decreasing scale of workplace. The difference in proportions of male smokers was ~6% between those in the enterprises with ≤29 employees and those with ≥1000 employees. These findings on the health status of the workers in SSEs in Japan are of great value since employers in SSEs with ≤49 employees are exempt from the legal obligation of reporting the results of health examinations.

Despite the fact that some studies report poorer provision of occupational health services in SSEs compared to larger enterprises [5,6,8], other studies have argued that the number of employees in SSEs showed no association with disadvantages in occupational health. Won et al. [9] reported that although prevalence of selected diseases appeared higher in SSEs than in the others using data from the medical examination of 26 324 manufacturing workers in the area limited to Kyung-in, South Korea, the relationship was reversed after standardization for sex and age. Morse et al. [10] reported that increased rates of occupational illness were seen in larger businesses in Connecticut, USA, and ‘company size in itself did not result in higher or lower injury or illness’, a finding that could be due to under-reporting among SSEs. Our study was multi-centred and carried out using a large data set broadly covering the western area of Japan. We believe that the data are not biased with regard to workers or enterprises with any specific characteristics which would skew the actual situation in occupational health.

The study has several limitations. First, the 9833 enterprises and the 436 729 workers in the study represented 11.2 and 3.8% of the enterprises/workers, respectively, of enterprises submitting a report of PGHC in 2000 [11]. The enterprises were selected in a non-random manner by the five OHOs, which may limit the generalization of our findings. The advantage was that the OHOs were certified by the National Federation of Industrial Health Organization of Japan which imposes several administrative requirements on occupational health services [12] and provided an adequate research field. The subjects, even in SSEs, may thus have received more reliable health services in comparison with the general working population. This may have led to an underestimation of the health status of the general population. Second, the data for PGHC were only available for one fiscal year 2000. Since no information was included concerning the employment or medical history of the workers before 1999, the workers in the SSEs may not necessarily have been in the same enterprises or in the same health condition from the time of first employment. In addition, since all the data were results of the PGHC, no unified measurement protocols for blood pressure or other items may be used among the OHOs. Therefore, attention should be paid to these aspects when interpreting the results of this study.

In conclusion, inequality in the health levels of workers in SSEs was found from the results of a cross-sectional study using large-size and multiple-centred data from routine health checks. With decrease in size of the company, there was a tendency towards poorer health indicators for blood pressure, glucose tolerance, and obesity. Moreover, a greater prevalence of current smokers among the smaller enterprises was shown with high statistical significance. However, caution should be exercised in interpreting the results because the study was cross-sectional and confounders other than age could not be adjusted. Also, the generalizability of the results was limited because of non-random sampling of the subjects. A longitudinal follow-up is needed to further clarify the disparity of health status according to the scale of enterprise.


Key points
  • The age-adjusted prevalences of employees abnormally screened for HT, IGT, obesity, and of smokers were 8.5, 5.0, 3.5 and 61% in SSEs, significantly higher than in larger scale enterprises for males.
  • These proportions showed a significantly increasing tendency with decreasing size of male workforce.
  • Inequality of health status in SSEs should be further investigated in Japan, where SSEs are exempt from some of the legal obligations regarding occupational health.

 


   Conflicts of interest
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 Conflicts of interest
References
 
None declared.


   Acknowledgements
 
This study was supported by a research grant from the Japan Foundation for Promoting Welfare of Independence Entrepreneurs.


   References
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 Conflicts of interest
 References
 

  1. Hirata M, Kumagai S, Tabuchi T, et al. (1999) Actual conditions of occupational health activities in small-scale enterprises in Japan: system for occupational health, health management and demands by small-scale enterprises. Sangyo Eiseigaku Zasshi 41:190–201 [in Japanese with English abstract].[Medline]

  2. 2004 Establishment Census of Japan. Statistics Bureau, Ministry of General Affairs. http://www.stat.go.jp/data/jigyou/2004/zenkoku/zuhyou/a014.xls (19 September 2006, date last accessed) [in Japanese].

  3. Takahashi K and Okubo T. (1994) Current status of occupational health in Japan. Occup Med (Lond) 44:66–69.

  4. Japan International Center for Occupational Safety and Health. Ordinance on Industrial Safety and Health. http://www.jicosh.gr.jp/english/law/IndustrialSafetyHealth_Ordinance/index.html (19 September 2006, date last accessed).

  5. Hino Y. (2002) Comprehensive activities on occupational safety and health for small-scale enterprises in occupational health organizations. In: Research Meeting for Occupational Safety and Health for Small-Scale Enterprises in Japan Society for Occupational Health (Rodochosakai, Tokyo, Japan)138–145 [in Japanese].

  6. Furuki K, Ashikaga K, Ishiwatari K, et al. (2002) Report on occupational health management and other activities among small-scale enterprises. Sangyo Igaku 25:21–28 [in Japanese].

  7. Altman DG. (1991) Practical Statistics for Medical Research(Chapman & Hall, London) pp. 229–276.

  8. Ukai H, Okamoto S, Takada S, Yamada C, Ikeda M. (2004) Lower vapor concentrations in solvent workplaces in larger-scale enterprises than in smaller-scale enterprises, and exceptions. Ind Health 42:252–259.[Web of Science][Medline]

  9. Won JU, Son J, Ahn YS, Roh J, Park CY. (2002) Analysis of factors associated with the workers' health status using periodic health examination data by size of enterprises. Yonsei Med J 43:14–19.[Web of Science][Medline]

  10. Morse T, Dillon C, Weber J, Warren N, Bruneau H, Fu R. (2004) Prevalence and reporting of occupational illness by company size: population trends and regulatory implications. Am J Ind Med 45:361–370.[CrossRef][Web of Science][Medline]

  11. Fukuoka Labour Bureau. National Statistics of the Annual General Health Check-ups, 1999 –2004 http://www.fukuoka.plb.go.jp/7eisei/eisei16.html (19 September 2006, date last accessed) [in Japanese].

  12. Obata Y, Narisada H, Fujishiro K, et al. (2003) Actual situation of medical check-ups carried out by Industrial Health Organizations in Japan—manpower and service. J UOEH 25:109–122 [in Japanese with English abstract].[Medline]


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