Occupational Medicine Advance Access originally published online on November 2, 2005
Occupational Medicine 2006 56(2):89-93; doi:10.1093/occmed/kqi195
© The Author 2005. Published by Oxford University Press on behalf of the Society of Occupational Medicine. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org
Work ability of workers in western China: reference data
Sihao Lin,
Zhiming Wang and
Mianzhen Wang
Occupational and Environmental Medicine, Sichuan University, No. 17 Renmin South Road, Chengdu, Sichuan 610041, People's Republic of China
Correspondence to: Sihao Lin, Occupational and Environmental Medicine, Sichuan University, No. 17 Renmin South Road, Chengdu, Sichuan 610041, People's Republic of China. e-mail: sihaoll{at}yahoo.com.cn
 |
Abstract
|
|---|
Background The Work Ability Index (WAI) is a validated and widely
used research tool. Reference data for Chinese workers by age,
gender and work content are poorly documented or lacking.
Objective To provide reference data for work ability among workers in western China.
Methods A random sample of 10 218 workers (including manual, professional, clerical and semi-skilled workers) in western China, aged 16–69 years, was taken from several studies and the WAI questionnaire was administered.
Results All the WAI scores were distributed continuously and nearly normally. The WAI for female workers was significantly higher than for males (P < 0.01) and the ‘poor’ WAI category only accounted for 3% of females, against 6% of males. WAI scores declined with age and changed variably among workers according to work content and age. Mean WAI scores of manual workers declined rapidly beyond the age of 35 years, and beyond age 45 years for professional and clerical workers. WAI scores were distributed differently according to work content and age group (P < 0.01). WAI categories differed by work content and age group both for male and female workers.
Conclusion WAI is validated in Chinese occupational practices. Some reference data are different from Finnish data. This study provides gender, age and work-content-specific WAI reference values that will help enable comparison and intervention evaluation in further studies.
Keywords Cross-sectional study; reference data; western China; Work Ability Index
|
Introduction
|
|---|
The concept of ‘work ability’ is to measure how
capable the worker is at present and in the near future, and
how able he or she is to do his or her work given his or her
work demands, individual health conditions and mental resources.
During the last decade, thanks to the scientific efforts of
members in the Finnish Institute of Occupational Health, the
Work Ability Index (WAI) [
1] was developed and applied to assess
an individual's work ability. In recent years, the WAI questionnaire
has been widely used in scientific studies on occupational health
[
2–
5]. For instance, WAI results at the group level were
used as primary outcome variables for the identification of
occupational and personal risk factors for poor work ability
[
6]. The questionnaire has been used to evaluate the effects
of intervention programmes on work ability [
7] and to identify
prognostic factors for work disability [
8]. This questionnaire
has also been used as a screening instrument for stress [
4].
In addition, the WAI can be applied by occupational physicians
as a simple instrument to assess individual work ability in
cross-sectional and follow-up surveys. Making use of reference
data, occupational health personnel can determine which health
measures are the most effective to promote or maintain an individual's
work ability [
9,
10].
Maintaining good or excellent work ability among workers is important with the rapid development of China and the WAI questionnaire has been increasingly used in studies of Chinese workers. For example, the WAI was used to assess workers in primary and high schools, chemical plants, petroleum companies, hospitals and mine companies [11–14]. Most of these studies have been cross-sectional and lack a reference standard with which to compare results. The developers of the WAI generated reference values compiled from previous research and described the WAI values of workers aged 50, 55 and 58 years [1]. These reference values can be used to determine the work ability of workers in other environments in comparison with the average work ability of Finnish municipal workers and other occupational groups of the same age. Nevertheless, since the cultures of China and Europe are quite different, China requires its own work ability reference data. In this study we focus on whether the Chinese WAI reference standard differs from other research reports, while also investigating WAI variation by gender, age group and work content among a large number of workers in western China. The objectives of this paper are to investigate the work ability of workers in western China using the WAI and to obtain reference data for comparing and evaluating the effectiveness of any measure implemented.
|
Methods
|
|---|
One hundred and sixteen employment organizations in three provinces
of western China (Sichuan, Xinjiang and Gangshu) were randomly
selected by computer using the registered code number of the
organization in a bureau of personnel. We contacted these employers
by telephone and 112 organizations responded. According to the
Chinese classification of occupations there are three main subgroups:
physically demanding work, mentally demanding work and a combination
of physical and mentally demanding work. First we conducted
a random selection of occupation based on the three subgroups,
then a cluster selection of individuals. The manual worker subgroup
included construction workers, street sweepers, sanitation workers,
cleaners, hospital aides, cooks, painters, unskilled labourers,
miners and installation workers. The professional and clerical
worker subgroup included all types of teachers, department directors,
inspectors, senior nurses, secretaries, accountants, doctors,
office workers, technicians, engineers and managers. The semi-skilled
subgroup included drivers, salespeople, guards, all types of
nurses, dental technicians, shop clerks, storage keepers, foremen,
traffic and crime policemen. Questionnaires were administered
in the workplace by trained health professionals.
The WAI is based on subjective responses to questions comprising seven items as presented in Table 1. The index requires subjects to make subjective estimations of work ability in relation to physician-diagnosed diseases, job demands and mental resources. The index also contains questions about illnesses and work absenteeism. The total score ranges from 7 to 49. The higher the score, the better is the individual's work ability. According to the scores, work ability could be classified into four categories: poor (7–27 points), moderate (28–36), good (37–43) and excellent (44–49) [1].
Because the distribution of the sample mean is nearly normal
with the large sample size of this study, we used parametric
statistics on the index scores. Statistical procedures included
descriptive analysis, two-sided
t-test (independent samples),
Pearson chi-square statistics (categorical data), one-way analysis
of variance (ANOVA), multivariate analysis of variance (MANOVA),
internal consistency (Cronbach's alpha) and factor analysis
(principal components analysis with max variance rotation).
All tests were considered statistically significant at
P <
0.05. Analyses were performed using SPSS for Windows (version
10.0) software (SPSS, Inc.).
|
Results
|
|---|
Eighty-seven per cent of workers responded to the WAI. If only
one item was missing in the questionnaire, the value was replaced
by the rounded mean of the remaining items. If two or more items
were missing, the value would not be considered in the calculations.
This procedure yielded 10 218 completed questionnaires (97%)
available for further study.
Table 2 provides sociodemographic
information on the study participants.
Univariate analysis showed that the WAI score had a continuous,
nearly normal distribution. The highest score was 49 (115 subjects)
and the lowest score was 9 (2 subjects). The seven items were
correlated positively (0.05 <
r <0.52,
P < 0.01). Cronbach's
alpha was calculated to test for internal consistency; the coefficient
was 0.76. The exploratory factor analysis identified three common
factors (eigenvalues
1), capturing 66% of the variance and corresponding
to the hypothesized structure of the questionnaire. The W1 and
W2 items were loading on the self-estimation of ability, the
W3 and W4 items were loading on the diseases and the impairment
of diseases, and the W5 and W7 items were loading on the absenteeism
and mental resources. But W6 could not load on any of these
common factors.
The mean WAI in the 10 218 workers (mean age 36.8 years) was 38.6 (Table 3). Female workers had higher scores (mean = 39.0) on WAI than male workers (mean = 38.3, P < 0.01). Comparing the WAI of different age groups between male and female workers showed that female workers had statistically higher WAI scores than male workers, except for those aged 
29 years (P < 0.01). ANOVA indicated that differences existed among workers with different work content. Semi-skilled workers had the highest WAI scores (mean = 39.3), followed by professional and clerical workers (mean = 38.6) and manual workers (mean = 38.0). There was a tendency for WAI scores to decrease as age increased. The effect of age on WAI scores was modified by gender and work content. The mean WAI scores of manual workers declined rapidly beyond the age of 35 whereas professional and clerical workers' WAI scores declined beyond the age of 45. For semi-skilled workers, WAI scores began to decline as early as the age of 29.
WAI categories differed by work content and age group both for
men and for women (Pearson chi-square tests
P < 0.01) (
Tables 4 and
5). The percentage of WAI scores in the ‘poor’
category was highest among male manual workers (6%), and lowest
among female semi-skilled workers (2%). Male workers aged 50
or over were the most likely to be in the poor WAI category
(13%), while female workers aged 29 or younger were the least
likely (1%). With age, the percentage of individuals in the
poor WAI category increased while the percentage of individuals
in the ‘excellent’ WAI category decreased; the chi-square
test showed that this tendency was significant (
P < 0.01).
|
Discussion
|
|---|
Our study found that the work ability of workers aged 50 or
over as measured by the WAI is very similar to that of the reference
values developed by the Finnish Institute of Occupational Health
[
1]. For example, the average Finnish work ability value among
male manual workers at the age of 50 is 35, while that of Chinese
workers is 35.9, both of which fall into the category of ‘moderate’
work ability. However, the percentage of poor work ability in
this age group was lower than that of Finnish reference data:
13% in our study compared to 16% in Finland. One of the major
causes probably lies in the great difference in cultural background
and different labour policies (i.e. the retirement age is different
for the two countries). We also found that the work ability
of female workers was higher than that of male workers, and
this difference persisted after controlling for age except in
the
29 years group. This finding might relate to Chinese culture,
in which men receive more social pressure at work than women,
corresponding to decreased work ability [
15].
The relationship between age and work ability is consistent with other studies [16–18], but quite different from our results that WAI score was nearly independent of age except for those over 50 years, where a strong decline in WAI was observed [4]. With regard to work content, different rates of decline for the WAI were demonstrated; manual workers' work ability declined earlier than that of professional and clerical workers. This indicates that measures should be taken to promote or maintain the work ability among manual workers earlier than for others.
The WAI is a viable instrument that has been widely used in occupational health research [2,3,5,11]. This study suggested that the WAI questionnaire was also a practical tool to use among Chinese workers. Questions on the survey were relatively easy for participants to answer and the questionnaire administration time was short. This research provided descriptive information on work ability according to gender, age group and work content. Using these data, we will be able to study the work ability of workers in a given workplace in comparison to the average work ability of workers in western China. It is of primary importance to determine how many workers have poor work ability in different occupations according to age group. Measures should be taken to help these workers with poor work ability, and then these workers should be followed to determine the success or failure of the relevant interventions. Although the present study provided the WAI score for different work content, reference values for specific occupations are still lacking and will require further research in order to provide a more detailed reference standard and comparison for future studies.
|
Conflicts of interest
|
|---|
None declared.
|
Acknowledgements
|
|---|
Financial support was given by the National Nature Science Committee
(No. 39970623). We are indebted to David Ganz and Michael Lin
for their assistance in preparing the manuscript.
|
References
|
|---|
- Tuomi K, Ilmarinen J, Jahkola A et al. Work Ability Index. Helsinki: Finnish Institute of Occupational Health, 1998.
- Williams SN, Crupton LL. Investigating the work ability of older workers. Int J Ind Ergon 1997;20:241–249.[CrossRef]
- Suzuki H, Kumashiro M, Kusanoi K et al. Comparison of work ability index and cognitive function tests. Sangyo Eiseigaku Zasshi 2004;46:71–77.[Medline]
- Kloimuller I, Karazman R, Geissler H et al. The relation of age, work ability index and stress-inducing factors among bus drivers. Int J Ind Ergon 2000;25:497–502.[CrossRef]
- de Zwart BCH, Frings-Dresen MHW, van Duivenbooden Jc. Test-retest reliability of the Work Ability Index questionnaire. Occup Med (Lond) 2002;52:177–181.
- Salonen P, Arola H, Nygard CH et al. Factors associated with employees. Occup Med (Lond) 2003;53:65–68.
- Tima P, Riikka R. Effects of worksite physical exercise intervention on physical fitness, perceived health status, and work ability among home care workers: five-year follow-up. Prev Med 2001;32:465–475.[Medline]
- Tuomi K, Luostatinen T. Work load and individual factors affecting work disability among aging municipal employees. Scand J Work Environ Health 1991;17(Suppl. 1):94–98.
- Sarch SB, Richaud L. Emotion health problems are the most important cause of disability in adult of working age: a study in the four countries of the old Oxford region. J Epidemiol Community Health 1997;51:250–256.
- Juhani I. Status and Promotion of Work Ability, Employability and Employment. Helsinki: Finnish Institute of Occupational Health, 1999; 142–162.
- Yang H, Wang M, Wang Z, Lan Y. Occupational stress effects on work ability in chemistry workers. Wei Sheng Yan Jiu 2004;33:130–133.[Medline]
- Yang X, Wang Z, Lan Y, Wang M. Appraisal of occupational stress and work ability. Wei Sheng Yan Jiu 2004;33:5–8.[Medline]
- Lin S, Wang Z, Tang W et al. A study on health status and work ability among production workers in paper plant. Hai Xia Yu Fang Yi Xue 2005;11:1–3.
- Lin S, Wang Z, Wang M et al. Study on work ability and its risk factors in health professionals. Zhonghua Lao Dong Wei Sheng Zhi Ye Bing Za Zhi 2005;23 in press.
- Wang Z, Wang M, Lan Y et al. Correlation between occupational stress and work ability in teachers. Zhongguo Gong Ye Yixue Za Zhi 2001;14:200–203.
- Yang X, Wang Z, Lan Y, Wang M. Relationship between the personal factors and work ability of different work category workers. Sichuan Da Xue Xue Bao Yi Xue Ban 2003;34:723–726.[Medline]
- Pohjonen T. Perceived work ability of home care workers in relation to individual and work-related factors in different age groups. Occup Med (Lond) 2001;51:209–217.
- Ilmarinen J, Tuomi K, Klockars M. Changes in the work ability of active employees as measured by the work ability index over an 11-year period. Scand J Work Environ Health 1997;23(Suppl. 1):49–57.
CiteULike 
Connotea 
Del.icio.us What's this?
Top
Abstract
Introduction