Kumashiro M, Kadoya M, Kubota M, Yamashita T, Higuchi Y and Izumi H
Department of Ergonomics, IIES, University of Occupational and Environmental Health, Japan
Abstract
Factors affecting the work ability of Japanese workers from the perspective of work demands and physical and mental capacity were studied. The results suggested that those subjects with self-confidence in their physical strength demonstrated regular exercise habits and had fewer subjective fatigue symptoms. Further, those subjects with exercise habits had less symptoms of depression like acute stress reaction and less job dissatisfaction. At the same time, those subjects who have regular exercise habits with the stronger exercise activities had higher scores in WAI. Quantitative workload was identified as the primary factor for the decline in job satisfaction and it also functioned as the main stressor.
Key Term: Work Ability Index (WAI), exercise habits, job stress, fatigue
Introduction
The Work Ability Index (WAI) was created by FIOH (Finnish Institute of Occupational Health) in 1981 as a method of assessing the capacity for adaptation to work of moderately aging workers (1). WAI studies have begun in many countries since the English version of the Work Ability Index was published by FIOH in 1994. In Japan, the first ver-sion was translated into Japanese and registered with FIOH in 1998 by Kumashiro. This was later revised and reached its present form based on the WAI English language 2nd revised edition (FIOH, 1997) and the corrections to the Japanese language expressions identified through trial use. Full-fledged WAI research in Japan was started by the author and his group in 2000 at the factory of a major air-conditioner manu-facturer. The results were presented at several conferences organized by the ICOH SC (International Commission of Occupational Health Scientific Committee) for Aging and Work.
The theme taken for the first WAI study conducted in Japan was the “Influence of Worker Stress Moods on the WAI Score. It was also shown that workers with low WAI scores have a variety of strongly negative feelings about their work (2). Then, of the various stressors in the workplace to which workers were routinely exposed, the research group identified the stressors with the greatest affect on work ability.
They then studied the relationship between the WAI score and those people with Type A behavior pattern, who are said to be enthusiastic about work. The results indicated that the factors that positively affect work ability improvement were human relations, satisfaction with work, mental health, and degree of discretion at work while that with a nega-tive affect was a heavy workload. However, no meaningful relationship was found between people that demonstrate a Type A behavior pattern and work ability (3).
The third report was a comparative study of the follow-up results for the WAI (Work Ability Index) and mental stress conducted five times from 2000 to 2004. The results showed that over the relatively short span of five years, stable work ability can be maintained even for
elderly workers unless there is an extraordinary episode relating to quan-titative workload, intra-group conflict, or social support. Conversely, it was shown that WAI response differs during the busy work season and slow season even when the observation period is within a year.
In other words, it was observed that the WAI score tends to increase during the slow season (4).
As for long-term observation, the research monitoring the changes in work ability of the same individuals working at the same factory was conducted over the eight-year period of 2000 to 2007. During this eight-year period, the research group was successful during the study in tracking 571 of the original 1,004 individuals. Of these, 221 people filled out each and every WAI and the Japanese version of the NIOSH Generic Job Stress Questionnaire. The results from studying the data of these people showed a strong relationship between an increase in depression and poor social support and excessive quantitative workloads and that this was a major factor leading to lowered WAI scores (5).
As mentioned above, the research group was interested in WAI and mental health conditions. A review of WAI related reference works to date, however, shows that most of the studies were on the relationship between WAI and physiological function. For example, they showed a correlation between WAI and muscle strength (6) or the correlation with aerobic exercise, which is thought to show endurance strength (6,7). Regarding the relationship between physical exercise, which is thought to affect physical capability, and WAI, it has been reported that increased physical exercise supports increased WAI (8) and that deficient sports or leisure time (9) or deficient physical activity will lower the WAI score.
The daily workload at work affects the worker’s WAI. Occasional research results show that an excessive workload lowers the work ability of the worker (For example, 10, 11). This type of workload is thought to have the opposite effect of physical activity during leisure.
Much research has also been done on the relationship between WAI and musculoskeletal disorders, cardiac disease, etc. (For example, 12, 13). Many papers have reported that disorders lower the WAI
score. Further, Pohjonen (14) reported, using an odds ratio adjusted for age, that musculoskeletal disorders and psychological symptoms had a great effect on work ability, and similarly, Kiss and Walgraeve (15) reported that they found a correlation between musculoskeletal disorders, cardiac disease, and respiratory disorders and people with a low WAI score, with musculoskeletal disorders being the factor that had the greatest impact.
As stated above, the various WAI research that has been conducted by the authors mainly focused on mental capacity. This research there-fore aimed to clarify the relationship between physical capacity and WAI in addition to the relationship with mental capacity, which study has been continuously conducted at the same factory since 2000.
We sought to ascertain physical capacity from the state of regular exercise habits. In particular, we used a combination of exercise intensity and frequency as an exercise habits index. This exercise habits index was used to study the relationship between exercise habits and fatigue induced by work as well as to study the relationship between exercise habits and WAI score.
Method
The WAI, NIOSH job stress questionnaire, awareness survey regarding exercise habits and physical strength, and a questionnaire focusing on subjective fatigue symptoms were given to 1,200 employees working at a residential air-conditioner factory of a major Japanese manufacturer.
The intensity of daily exercise habits was surveyed by asking respon-dents to choose 1 of 5 levels. These were, “Almost none, just some light exercise such as calisthenics or stretching,” “Light to medium exercise, for example, slow walking for 30 minutes,” “Medium exercise, for example, walking quickly for over 30 minutes,” or “Heavy exercise, for example, jogging for over 30 minutes. For the subjective symptoms
of fatigue, the degree of fatigue felt was divided into 4 levels, “Very tired”, “A little tired”, “Not so tired” and “Not tired at all”.
The study was conducted in the summer of 2009. WAI stud-ies have been conducted at the factory studied since 2000, so WAI data has been accumulated for the past 9 years. The same company organization as in the past was used to distribute the mark sheet type questionnaire. The questionnaire can be completed at work or at home and the respondents place the questionnaire in an envelope and seal it. From past experience the respondents know that no one will know whose data it is.
The management, labor union, and employees of the subject fac-tory have been working on mental health measures since 2000 and this project was conducted as part of this initiative. Therefore, everyone except those that were away on business trips when the questionnaire was distributed completed and returned the questionnaire.
Results
1. Comparison of WAI scores from 2000 to 2009
A comparative observation of the WAI average score from 2000 to this project (2009) is shown in Fig. 1. The WAI average score range for the studied factory over 10 years is 35.8 to 38.5, and 2009 produced the highest score (38.5). Looking at the breakdown we see the share for Moderate has declined while that for Excellent has increased. This trend is the same for both men and women and for aging workers over 45 as well as for younger workers.
Figure 1. Change in WAI score at the studied factory from 2000 to 2009
2. Change in Occupational Stress Related Factors from 2007 to 2009 For the Japanese version of the NIOSH Generic Job Stress Question-naire, looking at the stress trend over the last 3 years gives the results shown in Table 1. Compared to the past 2 years, the greatest change seen during this year’s study was in Quantitative workloads and Depres-sion. There was a large burden in Quantitative workloads for workers in their 30’s and 40’s. A major trend was also seen in Depression for workers in their 20’s to 40’s compared to aging workers.
Table1. Change in stress survey results from 2007 to 2009
2007 2008 2009 Reference
Quantitative Workloads 32.6 33.0 37.5 36.34
Job Satisfaction 9.0 9.1 8.9 8.96
Depression 14.5 13.9 15.7 12.79
Job Control 44.1 44.5 43.9 45.52
Social Support from Supervisor 14.9 15.1 14.9 14.57 Social Support from Coworkers 15.2 15.2 15.0 15.15 Social Support from Family/Friends 15.1 15.1 15.1 15.24 Source: Research Report by the Ministry of Labor in Japan, 1997
(n=968) (n=929)
(n=906) (n=994)
(n=1049) (n=1156)
(n=1280) (n=1407)
(n=1138) (n=1030)
The Japanese version of the NIOSH Generic Job Stress Questionnaire was used. The number of subjects for the stress questionnaire in 2007 was 1,403 (1,227 men, 176 women), 1,133 in 2008 (1,009 men, 124 women), and 1,195 in 2009 (1,060 men, 135 women). The workplace consisted mostly of men because it is a manufacturing plant that handles medium to heavyweight objects.
3. Relationship between Daily Exercise Habits, Physical Strength, Fatigue, and WAI
In-depth study of the work ability index including physical capacity in relation to exercise habits, etc., was first conducted in 2009. The results shown below differ from the data in Figure 1 and Table 1 above and are cross-sectional results for one time only.
The relationship between WAI scores and the intensity of exercise habits which is divided into 5 levels is shown in Figure 2. Workers with no exercise habits had a lower WAI score compared to workers with exercise habits. Workers with a heavy exercise habit had a very high WAI score. At the same time, Figure 3 shows the relationship between depression and exercise habit intensity. It is apparent that the habit of daily exercise and its intensity greatly influence the occurrence and severity of depression in workers. As regards the exercise intensity in particular, the results indicated that an effect is obtained by light and moderate exercise, such as walking slowly for 30 minutes.
Figure 2. Relationship between exercise intensity divided into 5 levels, WAI and stress
Figure 3. Relationship between depression and the exercise habit inten-sity
(n=522) (n=326) (n=148) (n=94) (n=96)
12 13 14 15 16 17 18
(n=522) (n=326) (n=148) (n=94) (n=96)
Depression
0
1 6 .9 5r8 .5 9 0
1 5 .6 1r7 .9 4 4
1 3 .9 6r6 .9 7 01 4 .2 3r8 .5 11
1 3 .7 8r6 .4 2 7 Depression>16
1. Almost none 2. Some light exercise 3. Light to medium Exercise 4. Medium exercise 5. Heavy exercise
1 2 3 4 5
(n=522) (n=326) (n=148) (n=94) (n=96)
Further, a study of the relationship between exercise intensity and the item relating to “Mental resources” in the WAI questions showed that people with exercise habits demonstrated better mental health and that the higher the exercise intensity, the better the level of mental health (Figure 4).
Figure 4. Relationship between the State of Mental Health and Exercise Intensity.
Next, the relationship between exercise habits and the subjective feelings of fatigue induced by work was studied. The relationship between this and the daily fi tness habit intensity yielded the results shown in Figure5.
Looking at the percentage of people answering “Very tired” for each exercise intensity level showed that people with an exercise habit felt less fatigue from work than people without an exercise habit.
It was also shown that an exercise habit of light to medium or higher intensity reduced the degree of fatigue.
Figure 5. Relationship between Exercise Intensity and Degree of Fatigue Subjective Symptoms
The above mentioned results showed that the benefi t of daily exercise not only increase physical strength and reduced fatigue subjective symptoms during work but also increase work ability as expressed by WAI.
Discussion and conclusion
The result of the WAI-related studies conducted at the subject fac-tory for 10 years showed that negative feelings toward work and stress moods were strongly related to a decline in WAI score, and that there is a strong relationship between WAI score and mental stress (2). Here, looking at the relationship between stress and the high-score WAI group and the low-score WAI group showed that the poor group had marked receptivity to stressors while the excellent group had endurance against the stressors. The way in which depressive symptoms, which are a stress response, were expressed showed that for the poor group
there was a decrease in WAI prior to the appearance of the depressive symptoms. For the excellent group, however, applying the same load as was applied to the poor group was not immediately linked to a decline in WAI but that the depressive symptoms are expected to appear when the individuals can no longer endure the stress. In addition, it was demonstrated that causes for a decreased WAI score were an increase in quantitative workload as a stressor and increased depression as a stress response (5). Further, the current study demonstrated that the benefits of daily exercise had a markedly positive effect on the WAI score. This shows that the benefits of individual exercise habits and support for those habits from the company occupational health team will be an important key to increasing work ability. Therefore, since the intensity of exercise has a major affect on work ability, there is an urgent need to develop programs containing a suitable amount of exercise to increase work ability.
References
1. J. Ilmarinen and K. Tuomi. Past, present and future of work ability. Pro-ceedings of the 1st International Symposium on Work Ability. 1–25.
FIOH, Helsinki; 2004.
2. M. Kumashiro, S. Shazuki, A. Fujii, T. Hasegawa, W. Goedhard, J. Ilmar-inen. The improvement of stress moods and the increase in negative emotions toward work have a major impact on declines in WAI scores
~ The first WAI research in Japan ~. The 4th Conference on Aging and Work. Krakow; 2002.
3. M. Kumashiro, H. Suzuki, K. Yamamoto and S. Shazuki. Occupational Stress, Behavior Pattern and Work Ability. 2nd International Sym-posium on Work Ability. Verona; 2004.
4. M. Kumashiro, K. Yamamoto & K. Shirane. WAI and Job Stress, Five Years of Follow-up Research. IEA 2006, Maastricht; 2006.
5. M. Kumashiro, M. Kadoya, Y. Otsuki, M. Kubota, T. Yamasita and H.
Izumi. WAI and Mental Health Conditions ~ What was learned from following the changes in the same worker’s workability for 8 years?
~. International Workshop on postponing ageing “Contemporary Problems of Prolonging Work Ability. Age Management: Extending the Work Life. Tallinn; 2008.
6. Pohjonen T. Age-related physical fitness and the predictive values of fitness tests for work ability in home care work. J Occup Environ Med.
43(8): 723–30; 2001a.
7. Bugajska J, Makowiec-Dabrowska T, Jegier A, Marszalek A. Physical work capacity (VO2max) and work ability (WAI) of active employees (men and women) in Poland. International Congress Series. 1280: 156–
160; 2005.
8. Tuomi K, Vanhala S, Nykyri E, Janhonen M. Organizational practices, work demands and the well-being of employees: a follow-up study in the metal industry and retail trade. Occupational Medicine. 54(2):
115–21; 2004.
9. Estryn-Behar M, Kreutz G, Le Nezet O, Mouchot L, Camerino D, Salles RK, et al. for the NEXT Study Group. Promotion of work ability among French health care workers: value of the Work Ability Index.
International Congress Series. 1280: 73–78; 2005.
10. Parker T, Worringham CJ, Greig K. Woods SD Age-related changes in work ability and injury risk in underground and open-cut coal min-ers; 2006. Available; online: http://eprints.qut.edu.au/3854/1/3854.
11. Ilmarinen J, Tuomi K, Klockars M. Changes in the work ability of active employees over an 11-year period. Scand J Work Environ Health.
23 (s1): 49–57; 1997.
12. Walsh IAP, Corral S, Franco RN, Canetti EEF, Alen MER, Coury HJCG.
Work ability of Subjects with chronic musculoskeletal disorders. Rev Saude Publica. 38(2):149–156; 2004.
13. Walsh IA, Oishi J, Coury HJ. Clinical and functional aspect of work-related musculoskeletal disorders among active workers. Rev Saude Publica. 42(1):108–116; 2008.
14. Pohjonen T. Perceived work ability of home care workers in relation to individual and work related factors in different age groups. Occup med. 51(3): 209–217; 2001c.
15. Kiss P, Walgraeve M, Vanhoorne M. Assessment of work ability in aging fire fighters by means of the Work Ability Index Preliminary result.
Arch Public Health. 60: 233–243; 2002.