- Email: [email protected]
Associations between work ability, health-related quality of life, physical activity and fitness among middle-aged men
ARTICLE IN PRESS
Applied Ergonomics 39 (2008) 786–791 www.elsevier.com/locate/apergo
Associations between work ability, health-related quality of life, physical activity and fitness among middle-aged men Lars E. So¨rensena,, Mika M. Pekkonenb, Kaisa H. Ma¨nnikko¨c, Veikko A. Louhevaarad, Juhani Smolandere, Markku J. Ale´nf a Suomen Terveystalo Oy, Va¨ino¨nkatu 6, FIN-40100 Jyva¨skyla¨, Finland Peurunka—Medical Rehabilitation Center, Peurungantie 85, FIN-41340 Laukaa, Finland c Department of Biology of Physical Activity, Jyva¨skyla¨ University, Box 35, FIN-40014 Jyva¨skyla¨, Finland d Finnish Institute of Occupational Health, University of Kuopio, Box 93, FIN-70701 Kuopio, Finland e ORTON Orthopedic Hospital, Tenholantie 10, FIN-00280 Helsinki, Finland f Department of Medical Rehabilitation, Oulu University Hospital and University of Oulu, BOX 10, FIN-90029 OYS b
Received 4 October 2006; accepted 17 November 2007
Abstract The Work ability of ageing work force is a matter of major concern in many countries. The aim of this study was to examine the relationship between perceived work ability and health-related quality of life (HRQoL), and to investigate their associations with age, physical activity and physical fitness in middle-aged men working in blue-collar occupations. The study population consisted of 196 middle-aged (aged 40–60 years) men (construction and industrial work) attending occupationally orientated early medical rehabilitation. They were mostly healthy having only symptoms of musculoskeletal or psychological strain. Perceived work ability was assessed with the work ability index (WAI) and HRQoL with the Rand, 36-item health survey (Rand-36). Information on physical activity was obtained with a structured questionnaire. Cardiorespiratory fitness was estimated with a submaximal exercise test on a cycle-ergometer. The WAI was significantly (po0.001) associated with the total score of Rand-36, and with all its domains. Age, physical activity and cardiorespiratory fitness were neither associated with the WAI, nor did physical activity predict any of the dimensions of Rand-36. Cardiorespiratory fitness was associated with the physical functioning dimension of the Rand-36 whilst age was positively associated with the dimensions of the energy, emotional well being and social functioning of the Rand-36. The present study on middle-aged men showed a close relationship between perceived work ability and the HRQoL. It is suggested that the promotion of work ability may have beneficial effects on quality of life. r 2007 Elsevier Ltd. All rights reserved. Keywords: Work ability; Quality of life; Ageing
1. Introduction Perceived health, health-related quality of life (HRQoL) and work ability are associated with future health status, functioning, and even mortality (Kaplan et al., 1996; Tuomi et al., 1997). Therefore, the assessment of a person’s perspective of these parameters, combined with objective findings, is important to detect early declines for initiating preventive and corrective occupational health-care measures. Today, this work is even more important because the Corresponding author. Tel.: +358 20 7453490; fax: +358 20 7453491.
E-mail address: lars.sorensen@fimnet.fi (L.E. So¨rensen). 0003-6870/$ - see front matter r 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.apergo.2007.11.001
work force is ageing rapidly in many countries (Ilmarinen, 1999). Several instruments are available for assessing HRQoL (Cieza and Stucki, 2005), but very few are specific to functioning at work. The Finnish Institute of Occupational Health has developed a questionnaire-based work ability index (WAI) to define a person’s work ability (Ilmarinen and Tuomi, 2004). In an 11-year follow-up study on 6259 older municipal workers a poor WAI score was a strong predictor of future work disability (Tuomi et al., 1997). Because work and employment are important parts of adult life, one could assume that measures of work ability should correlate positively with measures of HRQoL.
ARTICLE IN PRESS L.E. So¨rensen et al. / Applied Ergonomics 39 (2008) 786–791
The available data, however, is scarce. During an occupational intervention program de Boer et al. (2004) found that when work ability (assessed with the WAI) decreased, HRQoL (assessed with Nottingham Health Profile) also decreased. Chiu et al. (2003) assessed the relationship between HRQoL and WAI in 2173 subjects (aged 20–67 years), who were working in construction, manufacture, restaurant and hospital sectors in Taiwan. WAI scores correlated significantly with every domain of the ‘‘Quality of life questionnaire’’ developed by WHO (Saxena et al., 2001). There is strong evidence on the protective effects of regular leisure-time physical activity against major chronic diseases such as coronary heart disease, hypertension, stroke, non-insulin-dependent diabetes mellitus, osteoporosis, depression and anxiety (Weyer and Kupfer, 1994; Dunn et al., 2001; Kesa¨niemi et al., 2001). In line with this, increased physical activity and improved fitness are shown to result in better quality of life in older adults (Rejeski and Mihalko, 2001). The relationship between regular physical activity/improved fitness and perceived work ability are less clear. In a 2-year follow-up study by Smolander et al. (2000), the WAI showed no changes due to increased physical activity and cardiorepiratory fitness. In contrast, physical exercise carried out in work units improved physical capacity and prevented the early decline in WAI among home care workers (Pohjonen and Ranta, 2001). Theoretically, increased physical activity may increase the person’s capacities to cope with the demands of everyday life, but the pathways to global improvement of work ability or HRQoL may be very complicated due to many factors influencing these concepts. The purpose of this cross-sectional study was to examine the relationship between perceived work ability (assessed by the WAI) and HRQoL (assessed using the RAND-36), and to investigate their associations with age, physical activity and physical fitness in middle-aged men working in blue-collar occupations.
787
hypertension, but none of them had other cardiovascular diseases. The local ethics committee approved the study plan and a written informed consent was obtained from each subject.
2.2. Assessments Perceived work ability was assessed using the WAI. The WAI is a self-administered questionnaire derived as the sum scores of seven items (Table 1). The score derived from the WAI ranges from 7 to 49, and it is categorized into one of four categories: poor (7–27 points), moderate (28–36 points), good (37–43 points) and excellent (44–49 points). The reliability and validity of the WAI is well documented (Ilmarinen and Tuomi, 2004). HRQoL was assessed with the Rand 36-item Health Survey (RAND-36) (Hays et al., 1993). The RAND-36 assessed the following eight health dimensions: (i) general health perception, (ii) physical functioning, (iii) physical role functioning, (iv) bodily pain, (v) emotional role functioning, (vi) emotional wellbeing, (vii) social functioning, and (viii) energy vs. fatigue. The scale for each dimension of RAND-36 is from 0 to 100 (100 ¼ the best possible health-related quality of life). The first four health dimensions build up the physical summary score and the last four dimensions the mental summary score, e.g. the physical summary score is calculated simply by summing up the scores of four first dimensions of RAND-36 and dividing the sum with number four. In the same manner total summary score of RAND-36 can be calculated. The mental health summary score has been reported to have a strong relationship with global measures of life satisfaction (Ware et al., 1994). Extensive support for the reliability and validity of the RAND-36 has been provided by Hays and Morales (2001).
2. Subjects and methods 2.1. Subjects The subjects comprised of 196 men aged 40–60 (mean 48.3, SD 4.5) years who attended occupationally oriented early rehabilitation courses between October 2000 and October 2001. Their selection criteria were given by the Finnish Social Insurance Institution as follows: (i) at least 3 years experience in the current job and intention to continue, (ii) no diseases causing sick leave for more than 60 days during the past 2 years, (iii) no diseases preventing physically active rehabilitation, (iv) motivation to continue in the job, and (v) voluntary participation in the course. The subjects worked mostly in physically demanding jobs like construction and industrial work. Participants were healthy having only mild symptoms of musculoskeletal or psychological strain. However, 14% of the subjects had
Table 1 Work ability index (WAI) questionnaire items Item
Scale
(1) Subjective estimation of present work ability compared with lifetime best (2) Subjective work ability in relation to both physical and mental demands of the work (3) Number of diagnosed diseases (4) Subjective estimation of work impairment due to diseases (5) Sickness absenteeism during the past year (6) Own prognosis of work ability after 2 years (7) Psychological resources (enjoying daily tasks, activity and life spirit, optimistic about the future)
1–10 2–10 1–7 1–6 1–5 1, 4, 7 1–4
The items are explained as follows: (1) 1 ¼ very poor, 10 ¼ very good; (2) 2 ¼ very poor, 10 ¼ very good; (3) 1 ¼ five or more diseases, 7 ¼ no diseases; (4) 1 ¼ fully impaired, 6 ¼ no impairment; (5) 1 ¼ 100 days or more, 5 ¼ 0 days; (6) 1 ¼ hardly able to work, 4 ¼ not sure, 7 ¼ fairly sure; and (7) 1 ¼ very poor, 4 ¼ very good.
ARTICLE IN PRESS 788
L.E. So¨rensen et al. / Applied Ergonomics 39 (2008) 786–791
The present RAND-36 values were compared with the RAND-36 population values of Finnish men aged from 45 to 54 years (Aalto et al., 1999). The data on physical activity were collected with selfreported retrospective assessment. The data on last 12 months were asked for. Physical activity was rated with a questionnaire using the following five categories: (i) no regular physical activity, (ii) physical activity less than once a week, (iii) physical activity once a week, (iv) physical activity twice or three times a week, and (v) physical activity four times or more a week (modified from Oja, 1995). Summer and winter activity were assessed separately for (i) fitness or recreational activities (e.g., jogging, swimming, hiking or dancing), (ii) household activities (e.g., gardening, berry picking, errands on foot or by bicycle), and (iii) commuting to and from work (e.g., walking or bicycling). Cardiorespiratory fitness (maximal oxygen consumption, VO2max) was estimated with a standard submaximal incremental exercise test using an electronically braked cycle ergometer (Ergoline 900, Bitz, Germany) using the WHO extrapolation method (Lange-Andersen et al., 1971; Louhevaara et al., 1980). Body height and weight were measured with standard scales without shoes and subjects wearing only underwear pants. Body mass index (BMI) was calculated as body mass (kg) divided by height in meters squared (kg m2).
The results were considered statistically significant when p-values were o0.05. 3. Results 3.1. Physical characteristics, WAI, and RAND-36 The physical characteristics of the subjects and perceived work ability are given in Table 2. The factor analysis explained 41% of the total variance with the eigenvalue of 2.5. The mean value for the physical activity index was 0.23 (SD 0.88, range 2.35 to 1.61). Over one-third of the subjects (37%) were physically active at least twice a week at their leisure time, while 36% of them had leisure-time physical activity less than once a week. The WAI scores ranged from 21 to 47 with an average level of ‘good’ work ability (38.5). According to the 95% confidence intervals the subjects had significantly lower values for the dimension of bodily pain (i.e. more pain) than the Finnish men (Table 3). In other dimensions there were no significant differences between the subjects and the Finnish men. The age range of our subjects was 40–60 years and the population sample Table 2 Subjects’ physical characteristics and the work ability index (n ¼ 196) Variable
Mean
SD
Range
Age, years Body mass, kg Height, cm BMIa, kg m2 VO2maxb, l min1 VO2maxb, ml kg1min1 WAIc, points
48 85 176 27.3 3.0 36.1 38.5
5 13 7 3.9 0.45 6.4 5.1
40–60 56–130 162–200 16.9–45.5 2.1–4.4 19–58 21–47
2.3. Statistics Data were analyzed using SPSS (version 10.0, SPSS Inc., Chicago, IL, USA). The means and standard deviations were calculated for the physical characteristics and WAI. In addition, the means were calculated for each dimension of the RAND-36. Pearson’s correlation coefficient was used to examine the relationship between WAI, RAND-36, physical activity, and cardiorespiratory fitness. The data were further analyzed with multiple linear regression analysis. In the first analysis the age, WAI, physical activity and cardiorespiratory fitness were selected as the independent variables, and the dimensions of RAND-36 were selected as the dependent variables in each model. In the second analysis age, physical activity and cardiorespiratory fitness were selected as the independent variables and the WAI as the dependent variable. The power of each model to explain the dimensions of the RAND-36 or the WAI was determined in adjusted R square (R2) values. Standardised beta (beta) coefficients were determined for each independent variable to show its predictive value. For the comparison of the subjects and the random population sample of Finnish men aged 45–54 years, the confidence intervals were calculated. A physical activity index for the six items [fitness (both summer and winter), household activities (both summer and winter) and commuting to work (both summer and winter)] was calculated by means of a factor analysis (Principal axis factoring, Oblim) as an one-factor solution.
a
BMI ¼ body mass index. VO2max ¼ maximal oxygen consumption. c WAI ¼ work ability index. b
Table 3 Subjects’ health-related quality of life (n ¼ 196) in comparison with reference values representing the Finnish male population aged 45–54 years (n ¼ 180) RAND-36 dimension
General health perception Physical functioning Physical role functioning Bodily pain Emotional role functioning Emotional well-being Social functioning Energy a
Subjects
Finnish men
Meanb
95% CIa
Meanb
95% CIa
58.2 85.6 73.6 63.9 84.4 78.6 84.2 67.4
56.0–60.4 83.6–87.5 68.7–78.4 60.9–66.8 80.2–88.6 76.3–81.0 81.4–87.1 64.7–70.1
60.4 85.8 74.4 74.3 77.3 74.6 81.3 65.8
53.3–67.5 80.7–90.9 68.0–80.8 67.9–80.7 71.2–83.4 68.3–80.9 75.5–87.1 58.9–72.7
95% CI ¼ 95% confidence interval. The scale for each dimension is from 0 to 100 (100 ¼ the best possible health-related quality of life). b
ARTICLE IN PRESS L.E. So¨rensen et al. / Applied Ergonomics 39 (2008) 786–791
45–54 years. When we compared only the subjects aged 45–54 years (n ¼ 133) with the population sample, the pain was also the only dimension of RAND-36 where our subjects differed from the population sample significantly.
(b ¼ 0.06, p ¼ 0.49; b ¼ 0.03, p ¼ 0.23, respectively).
789
p ¼ 0.72;
b ¼ 0.11,
4. Discussion 3.2. Relationships between WAI, RAND-36, physical activity, fitness and age The correlation (r) between WAI and total RAND-36 score was 0.58 (po0.001). Highly significant correlations (all po0.001) were also obtained between WAI and the different domains of RAND-36: physical functioning (r ¼ 0.52), physical role functioning (r ¼ 0.54), bodily pain (r ¼ 0.52), emotional role functioning (r ¼ 0.43), emotional well-being (r ¼ 0.51), social functioning (r ¼ 0.45) and energy (r ¼ 0.65). The total RAND-36 scores did not correlate significantly with physical activity (r ¼ 0.05), and cardiorespiratory fitness (r ¼ 0.16). Corresponding correlation coefficients for WAI were 0.00 and 0.10, respectively. Self-reported physical activity correlated significantly with cardiorespiratory fitness (r ¼ 0.28, po0.01). In the regression analysis the WAI, physical activity, physical fitness and age explained 15–43% of the variance related to the dimensions of the RAND-36. The standardized beta coefficients for the WAI were significant in each dimension of the RAND-36 (b ¼ 0.38–0.64, po0.001). The standardized beta coefficients for physical activity were not significant in any of the dimensions of RAND-36. The standardized beta coefficients for age were significant in the dimensions of energy and emotional wellbeing (b ¼ 0.13–0.25, p ¼ 0.04–0.001), whilst approaching significance in the social functioning dimension (b ¼ 0.14, p ¼ 0.09). Cardiorespiratory fitness was significant in the physical functioning dimension (b ¼ 0.20, p ¼ 0.008) (Table 4). In the linear regression analysis age, physical activity and fitness explained 1% of the variance of WAI. The standardized beta coefficients for age, physical activity and physical fitness were not significant in respect of WAI
The main purpose of this study was to examine the relationship between perceived work ability and healthrelated quality of life (assessed with WAI and RAND-36), and their associations with physical activity and cardiorespiratory fitness in middle-aged men. The main finding was that there was a relatively close association between WAI and RAND-36 in this selected group of working men. Physical activity or fitness had no relationship to WAI in this study. This may be considered as rather surprising among men having physical jobs. The studied men primarily worked in physically demanding jobs like construction and industrial work. According to the selection criteria, the studied men had slight symptoms and signs (pain or slight restriction in the movements of joints or mild depression) that could lead to physical or psychological impairment and hamper work performance in the long run. Since 82% of the men in this study perceived their work ability according to the WAI as moderate or good having values between 28 and 43 points, the sample seemed to represent fairly well workers who needed early rehabilitation. The age, profession and WAI of the men in addition to the other selection criteria of the study seemed to indicate that the sample was homogeneous. When compared with the Finnish men of similar age, the men of this study felt more bodily pain. This may only reflect the fact that our subjects’ work was physically more demanding than in the general population. On the other hand, the difference in bodily pain between our subjects and Finnish men in general may be a true reflection of the selection criteria used. The Finnish men in the population sample were aged 45–54 years. WAI does not assess pain but the acute perceptions of pain may affect the perceived WAI as well as the perceived RAND-36. The cross-sectional study design limits the causal interpretation of the interactions between the WAI and RAND-36.
Table 4 Quality of life assessed by RAND-36 RAND dimensiona
R2 b
WAIa Beta
General health perception Physical functioning Physical role functioning Bodily pain Emotional role functioning Emotional well- being Social functioning Energy
0.30 0.33 0.25 0.27 0.18 0.28 0.15 0.43
0.53, 0.53, 0.50, 0.54, 0.43, 0.48, 0.38, 0.64,
po0.001 po0.001 po0.001 po0.001 po0.001 po0.001 po0.001 po0.001
Agea beta
Physical activitya beta
Physical fitnessa beta
0.10, p ¼ 0.156 0.03, p ¼ 0.721 0.02, p ¼ 0.810 0.04, p ¼ 0.584 0.05, p ¼ 0.965 0.25, p ¼ 0.001 0.14, p ¼ 0.090 0.13, p ¼ 0.044
0.02, p ¼ 0.755 0.04, p ¼ 0.585 0.06, p ¼ 0.431 0.01, p ¼ 0.939 0.04, p ¼ 0.622 0.03, p ¼ 0.742 0.08, p ¼ 0.349 0.09, p ¼ 0.203
0.11, p ¼ 0.159 0.20, p ¼ 0.008 0.07, p ¼ 0.375 0.01, p ¼ 0.901 0.08, p ¼ 0.316 0.00, p ¼ 0.973 0.03, p ¼ 0.708 0.03, p ¼ 0.643
a Results of the linear regression analysis for the eight dimensions are given. Work ability index (WAI), age, physical activity index and physical fitness (VO2max) are independent variables and different dimensions of the RAND-36 are dependent variables. The standardised beta (beta) coefficients are given for each independent variable to show their predictive value. b The power of the models for explaining the total variance are given in the adjusted R square (R2) values.
ARTICLE IN PRESS 790
L.E. So¨rensen et al. / Applied Ergonomics 39 (2008) 786–791
The assumed logical associations between WAI and RAND-36 should be investigated in a longitudinal study. RAND-36 is one of the most commonly used HRQoL survey methods both in research and practice (Hays and Morales, 2001) and WAI, to our knowledge, is the only survey method to predict work ability. This study was the first of its kind to explore their correlations. Some of the dimensions of RAND-36 and WAI are quite near each other (like ‘physical role functioning’ in RAND-36 and ‘estimated work impairment due to disease’ in WAI or ‘emotional well-being’ and ‘energy’ in RAND-36, and ‘mental resources’ in WAI) and the similarity of the different dimensions may explain the strong correlation of WAI to the different dimensions of the RAND-36. It has to be emphasized that WAI is tailored to assess perceived individual work ability related to job demands, health status (based on number of diagnosed sicknesses and sickleaves), mental resources and wellbeing related to the work. The WAI is a validated (Ilmarinen and Tuomi, 2004) standardized method with sum scale, which is widely used in many countries (Ilmarinen and Tuomi, 2004) and RAND-36 is a validated (Hays and Morales, 2001) standardized method which assesses various dimensions of the quality of life in general. Thus WAI is completely work-oriented method whereas the orientation of the RAND-36 covers the entire life. Therefore, the balanced work situation supports perceived work ability, and may also support the perceived quality of life. When the work situation is unbalanced the associations between WAI and RAND-36 may be reverse. Because many of the dimensions of RAND-36 not only reflect workload factors or individual resources, but also characteristics of social life and other factors outside the work environment, it is appropriate that the concept for promoting health and work ability should be supplemented by target areas outside the work environment, for e.g. family life. Interaction between work and family life may be strong and also important with respect to health, work ability and wellbeing (Jansen et al., 2006). Previous studies have also reported the modifying effect of leisure-time activities and satisfaction with life on the WAI (Seitsamo and Ilmarinen, 1997; Fujita and Kanaoka, 2003), and these observations confirm the need to develop the concept for promoting health and work ability even further. Physical activity or cardiorespiratory fitness had no relationship to WAI in the present study. Physical activity is a key determinant of physical fitness, but physical fitness is only one determinant of work ability and its impact may vary according to the job demands. The present observation that cardiorespiratory fitness was associated with perceived physical functioning domain of RAND-36 seems logical. Cieza and Stucki (2005) compared the contents of different HRQoL instruments by linking the items to the new WHO international classification of functioning, disability, and health. They found wide differences between instruments in breadth and coverage. SF-36, which is almost the same as RAND-36, contains nine items directly
related to physical performance (running, sports, lifting and carrying, climbing stairs, walking short and long distances), whereas most of the other instruments have less precise questions on mobility functioning. Thus, our finding may reflect the properties of the instrument, which was suitable for our subject group of physically working men. Physical activity was associated with no dimension of RAND-36. The major conclusion of the review by Rejeski and Mihalko (2001) was that physical activity positively influences various outcomes associated with the HRQoL. Their review mainly included studies with elderly individuals or individuals with different kinds of impairment, such as cardiovascular disease, osteoarthritis, pulmonary disease, cancer, and depression. Previous studies on the relationship between HRQoL and physical activity in middle-aged men in working life are not available. 5. Conclusions This study showed a close relationship between perceived work ability and quality of life in middle-aged men working in physically demanding jobs. It can be suggested that promoting work ability may also influence on quality of life in general. The rapidly growing interest in carrying out worksite physical activity interventions for promoting work ability did not receive much support in this crosssectional study. Therefore, measures targeting on work and the work environment, work community and organization, individual resources and professional competence, may have more potential in increasing work ability. References Aalto, A.M., Aro, A.R., Teperi, J., 1999. RAND-36 Terveyteen Liittyva¨n Ela¨ma¨nlaadun Mittarina. [RAND-36 as a Measure of Health Related Quality of Life]. Sosiaali-Ja Terveysalan Tutkimus-Ja Kehitta¨miskeskus, Tutkimuksia, 101. Gummerus, Saarija¨rvi, Finland. Chiu, M.-C., Wang, M.-J., Lu, C.-W., Pan, X.-M., Kumashiro, M., 2003. The work ability index and quality of life. J. Erg. Occup. Saf. Health 5 (Suppl. August), 67–69. Cieza, A., Stucki, G., 2005. Content comparison of health-related quality of life (HRQoL) instruments based on the international classification of functioning, disability, ad health (ICF). Qual. Life Res. 14, 1225–1237. de Boer, A.G.E.M., van Beek, J.-C., Durinck, J., Verbeek, J.H.A.M., van Dijk, F.J.H., 2004. An occupational health intervention programme for workers at risk for early retirement; a randomised controlled trial. Occup. Environ. Med. 61, 924–929. Dunn, A., Trivedi, M., O’Neal, H., 2001. Physical activity dose response effects on outcomes of depression and anxiety. Med. Sci. Sports Exerc. 33, 5587–5597. Fujita, D., Kanaoka, M., 2003. Relationship between social support, mental health and health care consciousness in developing the industrial health education of male employees. J. Occup. Health 45, 392–399. Hays, R.D., Sherbourne, C.D., Mazel, R.M., 1993. The RAND 36-item health survey 1.0. Health Econ. 2, 217–277. Hays, R.D., Morales, L.S., 2001. The RAND-36 measure of health-related quality of life. Ann. Med. 33, 350–357.
ARTICLE IN PRESS L.E. So¨rensen et al. / Applied Ergonomics 39 (2008) 786–791 Ilmarinen, J., 1999. Ageing Workers in the European Union–Status and Promotion of Work Ability, Employability and Employment. Finnish Institute of Occupational Health, Ministry of Social Affairs and Health, Ministry of Labour, Helsinki. Ilmarinen, J., Tuomi, K., 2004. Past, present and future of work ability. People Work Res. Rep. 65, 1–25. Jansen, N.W.H., Kant, I.J., van Amelswoort, G.P.M., Kristensen, T.S., Swaen, G.M.H., Nijhuis, F.J.N., 2006. Work–family conflict as a risk factor for sickness absence. Occup. Environ. Med. 6, 488–494. Kaplan, G., Goldberg, D., Everson, S., Cohen, R., Salonen, R., Tuomilehto, J., et al., 1996. Perceived health status and morbidity and mortality: evidence from the Kuopio ischaemic heart disease risk factor study. Int. J. Epidemiol. 25, 259–265. Kesa¨niemi, A., Danforth Jr., E., Jensen, M., Kopelman, P., Lefe´bvre, P., Reeder, P., 2001. Consensus statement concerning physical activity and health: an evidence-based symposium. Med. Sci. Sports Exerc. 33, 5351–5358. Lange-Andersen, K.L., Shephard, R.J., Denolin, H., Varnauskas, E., Masironi, R., 1971. Fundamentals of Exercise Testing. World Health Organization, Geneva. Louhevaara, V., Ilmarinen, J., Oja, P., 1980. Comparison of the A˚strand nomogram and the WHO extrapolation methods for estimating maximal oxygen uptake. Scand. J. Sports Sci. 2, 21–25. Oja, P., 1995. Descriptive epidemiology of health-related physical activity and fitness. Res. Quart. Exerc. Sport 66, 303–312.
791
Pohjonen, T., Ranta, R., 2001. 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. 32, 465–475. Rejeski, J.W., Mihalko, S.L., 2001. Physical activity and quality of life in older adults. J. Gerontol. (Ser. A) 56A, 23–35 (Special Issue II). Saxena, S., Carlson, D., Billington, R., WHOQOL Group, World Health Organisation Quality Of Life, 2001. The WHO quality of life assessment instrument (WHOQOL-Bref): the importance of its items for cross-cultural research. Qual. Life. Res. 10 (Suppl. 8), 711–721. Seitsamo, J., Ilmarinen, J., 1997. Life-style, aging and work ability among active Finnish workers in 1981–1992. Scand. J. Work Environ. Health 23 (Suppl. 1), 20–26. Smolander, J., Blair, S.N., Kohl, H.W., 2000. Work ability, physical activity, and cardiorespiratory fitness: 2-year results from project active. J. Occup. Environ. Med. 42, 906–910. Tuomi, K., Ilmarinen, J., Seitsamo, J., Huuhtanen, P., Martikainen, R., Nyga˚rd, C.-H., Klockars, M., 1997. Summary of the Finnish Research Project (1981–1992) to promote the health and work ability of aging workers. Scand. J. Environ. Health 23 (Suppl. 1), 66–71. Ware, J., Kosinski, M., Keller, S., 1994. Physical and Mental Health Summary Scales: A User’s Manual. The Health Institute, New England Medical Center, Boston. Weyer, S., Kupfer, B., 1994. Physical exercise and psychological health. Sports Med. 17, 108–116.
Applied Ergonomics 39 (2008) 786–791 www.elsevier.com/locate/apergo
Associations between work ability, health-related quality of life, physical activity and fitness among middle-aged men Lars E. So¨rensena,, Mika M. Pekkonenb, Kaisa H. Ma¨nnikko¨c, Veikko A. Louhevaarad, Juhani Smolandere, Markku J. Ale´nf a Suomen Terveystalo Oy, Va¨ino¨nkatu 6, FIN-40100 Jyva¨skyla¨, Finland Peurunka—Medical Rehabilitation Center, Peurungantie 85, FIN-41340 Laukaa, Finland c Department of Biology of Physical Activity, Jyva¨skyla¨ University, Box 35, FIN-40014 Jyva¨skyla¨, Finland d Finnish Institute of Occupational Health, University of Kuopio, Box 93, FIN-70701 Kuopio, Finland e ORTON Orthopedic Hospital, Tenholantie 10, FIN-00280 Helsinki, Finland f Department of Medical Rehabilitation, Oulu University Hospital and University of Oulu, BOX 10, FIN-90029 OYS b
Received 4 October 2006; accepted 17 November 2007
Abstract The Work ability of ageing work force is a matter of major concern in many countries. The aim of this study was to examine the relationship between perceived work ability and health-related quality of life (HRQoL), and to investigate their associations with age, physical activity and physical fitness in middle-aged men working in blue-collar occupations. The study population consisted of 196 middle-aged (aged 40–60 years) men (construction and industrial work) attending occupationally orientated early medical rehabilitation. They were mostly healthy having only symptoms of musculoskeletal or psychological strain. Perceived work ability was assessed with the work ability index (WAI) and HRQoL with the Rand, 36-item health survey (Rand-36). Information on physical activity was obtained with a structured questionnaire. Cardiorespiratory fitness was estimated with a submaximal exercise test on a cycle-ergometer. The WAI was significantly (po0.001) associated with the total score of Rand-36, and with all its domains. Age, physical activity and cardiorespiratory fitness were neither associated with the WAI, nor did physical activity predict any of the dimensions of Rand-36. Cardiorespiratory fitness was associated with the physical functioning dimension of the Rand-36 whilst age was positively associated with the dimensions of the energy, emotional well being and social functioning of the Rand-36. The present study on middle-aged men showed a close relationship between perceived work ability and the HRQoL. It is suggested that the promotion of work ability may have beneficial effects on quality of life. r 2007 Elsevier Ltd. All rights reserved. Keywords: Work ability; Quality of life; Ageing
1. Introduction Perceived health, health-related quality of life (HRQoL) and work ability are associated with future health status, functioning, and even mortality (Kaplan et al., 1996; Tuomi et al., 1997). Therefore, the assessment of a person’s perspective of these parameters, combined with objective findings, is important to detect early declines for initiating preventive and corrective occupational health-care measures. Today, this work is even more important because the Corresponding author. Tel.: +358 20 7453490; fax: +358 20 7453491.
E-mail address: lars.sorensen@fimnet.fi (L.E. So¨rensen). 0003-6870/$ - see front matter r 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.apergo.2007.11.001
work force is ageing rapidly in many countries (Ilmarinen, 1999). Several instruments are available for assessing HRQoL (Cieza and Stucki, 2005), but very few are specific to functioning at work. The Finnish Institute of Occupational Health has developed a questionnaire-based work ability index (WAI) to define a person’s work ability (Ilmarinen and Tuomi, 2004). In an 11-year follow-up study on 6259 older municipal workers a poor WAI score was a strong predictor of future work disability (Tuomi et al., 1997). Because work and employment are important parts of adult life, one could assume that measures of work ability should correlate positively with measures of HRQoL.
ARTICLE IN PRESS L.E. So¨rensen et al. / Applied Ergonomics 39 (2008) 786–791
The available data, however, is scarce. During an occupational intervention program de Boer et al. (2004) found that when work ability (assessed with the WAI) decreased, HRQoL (assessed with Nottingham Health Profile) also decreased. Chiu et al. (2003) assessed the relationship between HRQoL and WAI in 2173 subjects (aged 20–67 years), who were working in construction, manufacture, restaurant and hospital sectors in Taiwan. WAI scores correlated significantly with every domain of the ‘‘Quality of life questionnaire’’ developed by WHO (Saxena et al., 2001). There is strong evidence on the protective effects of regular leisure-time physical activity against major chronic diseases such as coronary heart disease, hypertension, stroke, non-insulin-dependent diabetes mellitus, osteoporosis, depression and anxiety (Weyer and Kupfer, 1994; Dunn et al., 2001; Kesa¨niemi et al., 2001). In line with this, increased physical activity and improved fitness are shown to result in better quality of life in older adults (Rejeski and Mihalko, 2001). The relationship between regular physical activity/improved fitness and perceived work ability are less clear. In a 2-year follow-up study by Smolander et al. (2000), the WAI showed no changes due to increased physical activity and cardiorepiratory fitness. In contrast, physical exercise carried out in work units improved physical capacity and prevented the early decline in WAI among home care workers (Pohjonen and Ranta, 2001). Theoretically, increased physical activity may increase the person’s capacities to cope with the demands of everyday life, but the pathways to global improvement of work ability or HRQoL may be very complicated due to many factors influencing these concepts. The purpose of this cross-sectional study was to examine the relationship between perceived work ability (assessed by the WAI) and HRQoL (assessed using the RAND-36), and to investigate their associations with age, physical activity and physical fitness in middle-aged men working in blue-collar occupations.
787
hypertension, but none of them had other cardiovascular diseases. The local ethics committee approved the study plan and a written informed consent was obtained from each subject.
2.2. Assessments Perceived work ability was assessed using the WAI. The WAI is a self-administered questionnaire derived as the sum scores of seven items (Table 1). The score derived from the WAI ranges from 7 to 49, and it is categorized into one of four categories: poor (7–27 points), moderate (28–36 points), good (37–43 points) and excellent (44–49 points). The reliability and validity of the WAI is well documented (Ilmarinen and Tuomi, 2004). HRQoL was assessed with the Rand 36-item Health Survey (RAND-36) (Hays et al., 1993). The RAND-36 assessed the following eight health dimensions: (i) general health perception, (ii) physical functioning, (iii) physical role functioning, (iv) bodily pain, (v) emotional role functioning, (vi) emotional wellbeing, (vii) social functioning, and (viii) energy vs. fatigue. The scale for each dimension of RAND-36 is from 0 to 100 (100 ¼ the best possible health-related quality of life). The first four health dimensions build up the physical summary score and the last four dimensions the mental summary score, e.g. the physical summary score is calculated simply by summing up the scores of four first dimensions of RAND-36 and dividing the sum with number four. In the same manner total summary score of RAND-36 can be calculated. The mental health summary score has been reported to have a strong relationship with global measures of life satisfaction (Ware et al., 1994). Extensive support for the reliability and validity of the RAND-36 has been provided by Hays and Morales (2001).
2. Subjects and methods 2.1. Subjects The subjects comprised of 196 men aged 40–60 (mean 48.3, SD 4.5) years who attended occupationally oriented early rehabilitation courses between October 2000 and October 2001. Their selection criteria were given by the Finnish Social Insurance Institution as follows: (i) at least 3 years experience in the current job and intention to continue, (ii) no diseases causing sick leave for more than 60 days during the past 2 years, (iii) no diseases preventing physically active rehabilitation, (iv) motivation to continue in the job, and (v) voluntary participation in the course. The subjects worked mostly in physically demanding jobs like construction and industrial work. Participants were healthy having only mild symptoms of musculoskeletal or psychological strain. However, 14% of the subjects had
Table 1 Work ability index (WAI) questionnaire items Item
Scale
(1) Subjective estimation of present work ability compared with lifetime best (2) Subjective work ability in relation to both physical and mental demands of the work (3) Number of diagnosed diseases (4) Subjective estimation of work impairment due to diseases (5) Sickness absenteeism during the past year (6) Own prognosis of work ability after 2 years (7) Psychological resources (enjoying daily tasks, activity and life spirit, optimistic about the future)
1–10 2–10 1–7 1–6 1–5 1, 4, 7 1–4
The items are explained as follows: (1) 1 ¼ very poor, 10 ¼ very good; (2) 2 ¼ very poor, 10 ¼ very good; (3) 1 ¼ five or more diseases, 7 ¼ no diseases; (4) 1 ¼ fully impaired, 6 ¼ no impairment; (5) 1 ¼ 100 days or more, 5 ¼ 0 days; (6) 1 ¼ hardly able to work, 4 ¼ not sure, 7 ¼ fairly sure; and (7) 1 ¼ very poor, 4 ¼ very good.
ARTICLE IN PRESS 788
L.E. So¨rensen et al. / Applied Ergonomics 39 (2008) 786–791
The present RAND-36 values were compared with the RAND-36 population values of Finnish men aged from 45 to 54 years (Aalto et al., 1999). The data on physical activity were collected with selfreported retrospective assessment. The data on last 12 months were asked for. Physical activity was rated with a questionnaire using the following five categories: (i) no regular physical activity, (ii) physical activity less than once a week, (iii) physical activity once a week, (iv) physical activity twice or three times a week, and (v) physical activity four times or more a week (modified from Oja, 1995). Summer and winter activity were assessed separately for (i) fitness or recreational activities (e.g., jogging, swimming, hiking or dancing), (ii) household activities (e.g., gardening, berry picking, errands on foot or by bicycle), and (iii) commuting to and from work (e.g., walking or bicycling). Cardiorespiratory fitness (maximal oxygen consumption, VO2max) was estimated with a standard submaximal incremental exercise test using an electronically braked cycle ergometer (Ergoline 900, Bitz, Germany) using the WHO extrapolation method (Lange-Andersen et al., 1971; Louhevaara et al., 1980). Body height and weight were measured with standard scales without shoes and subjects wearing only underwear pants. Body mass index (BMI) was calculated as body mass (kg) divided by height in meters squared (kg m2).
The results were considered statistically significant when p-values were o0.05. 3. Results 3.1. Physical characteristics, WAI, and RAND-36 The physical characteristics of the subjects and perceived work ability are given in Table 2. The factor analysis explained 41% of the total variance with the eigenvalue of 2.5. The mean value for the physical activity index was 0.23 (SD 0.88, range 2.35 to 1.61). Over one-third of the subjects (37%) were physically active at least twice a week at their leisure time, while 36% of them had leisure-time physical activity less than once a week. The WAI scores ranged from 21 to 47 with an average level of ‘good’ work ability (38.5). According to the 95% confidence intervals the subjects had significantly lower values for the dimension of bodily pain (i.e. more pain) than the Finnish men (Table 3). In other dimensions there were no significant differences between the subjects and the Finnish men. The age range of our subjects was 40–60 years and the population sample Table 2 Subjects’ physical characteristics and the work ability index (n ¼ 196) Variable
Mean
SD
Range
Age, years Body mass, kg Height, cm BMIa, kg m2 VO2maxb, l min1 VO2maxb, ml kg1min1 WAIc, points
48 85 176 27.3 3.0 36.1 38.5
5 13 7 3.9 0.45 6.4 5.1
40–60 56–130 162–200 16.9–45.5 2.1–4.4 19–58 21–47
2.3. Statistics Data were analyzed using SPSS (version 10.0, SPSS Inc., Chicago, IL, USA). The means and standard deviations were calculated for the physical characteristics and WAI. In addition, the means were calculated for each dimension of the RAND-36. Pearson’s correlation coefficient was used to examine the relationship between WAI, RAND-36, physical activity, and cardiorespiratory fitness. The data were further analyzed with multiple linear regression analysis. In the first analysis the age, WAI, physical activity and cardiorespiratory fitness were selected as the independent variables, and the dimensions of RAND-36 were selected as the dependent variables in each model. In the second analysis age, physical activity and cardiorespiratory fitness were selected as the independent variables and the WAI as the dependent variable. The power of each model to explain the dimensions of the RAND-36 or the WAI was determined in adjusted R square (R2) values. Standardised beta (beta) coefficients were determined for each independent variable to show its predictive value. For the comparison of the subjects and the random population sample of Finnish men aged 45–54 years, the confidence intervals were calculated. A physical activity index for the six items [fitness (both summer and winter), household activities (both summer and winter) and commuting to work (both summer and winter)] was calculated by means of a factor analysis (Principal axis factoring, Oblim) as an one-factor solution.
a
BMI ¼ body mass index. VO2max ¼ maximal oxygen consumption. c WAI ¼ work ability index. b
Table 3 Subjects’ health-related quality of life (n ¼ 196) in comparison with reference values representing the Finnish male population aged 45–54 years (n ¼ 180) RAND-36 dimension
General health perception Physical functioning Physical role functioning Bodily pain Emotional role functioning Emotional well-being Social functioning Energy a
Subjects
Finnish men
Meanb
95% CIa
Meanb
95% CIa
58.2 85.6 73.6 63.9 84.4 78.6 84.2 67.4
56.0–60.4 83.6–87.5 68.7–78.4 60.9–66.8 80.2–88.6 76.3–81.0 81.4–87.1 64.7–70.1
60.4 85.8 74.4 74.3 77.3 74.6 81.3 65.8
53.3–67.5 80.7–90.9 68.0–80.8 67.9–80.7 71.2–83.4 68.3–80.9 75.5–87.1 58.9–72.7
95% CI ¼ 95% confidence interval. The scale for each dimension is from 0 to 100 (100 ¼ the best possible health-related quality of life). b
ARTICLE IN PRESS L.E. So¨rensen et al. / Applied Ergonomics 39 (2008) 786–791
45–54 years. When we compared only the subjects aged 45–54 years (n ¼ 133) with the population sample, the pain was also the only dimension of RAND-36 where our subjects differed from the population sample significantly.
(b ¼ 0.06, p ¼ 0.49; b ¼ 0.03, p ¼ 0.23, respectively).
789
p ¼ 0.72;
b ¼ 0.11,
4. Discussion 3.2. Relationships between WAI, RAND-36, physical activity, fitness and age The correlation (r) between WAI and total RAND-36 score was 0.58 (po0.001). Highly significant correlations (all po0.001) were also obtained between WAI and the different domains of RAND-36: physical functioning (r ¼ 0.52), physical role functioning (r ¼ 0.54), bodily pain (r ¼ 0.52), emotional role functioning (r ¼ 0.43), emotional well-being (r ¼ 0.51), social functioning (r ¼ 0.45) and energy (r ¼ 0.65). The total RAND-36 scores did not correlate significantly with physical activity (r ¼ 0.05), and cardiorespiratory fitness (r ¼ 0.16). Corresponding correlation coefficients for WAI were 0.00 and 0.10, respectively. Self-reported physical activity correlated significantly with cardiorespiratory fitness (r ¼ 0.28, po0.01). In the regression analysis the WAI, physical activity, physical fitness and age explained 15–43% of the variance related to the dimensions of the RAND-36. The standardized beta coefficients for the WAI were significant in each dimension of the RAND-36 (b ¼ 0.38–0.64, po0.001). The standardized beta coefficients for physical activity were not significant in any of the dimensions of RAND-36. The standardized beta coefficients for age were significant in the dimensions of energy and emotional wellbeing (b ¼ 0.13–0.25, p ¼ 0.04–0.001), whilst approaching significance in the social functioning dimension (b ¼ 0.14, p ¼ 0.09). Cardiorespiratory fitness was significant in the physical functioning dimension (b ¼ 0.20, p ¼ 0.008) (Table 4). In the linear regression analysis age, physical activity and fitness explained 1% of the variance of WAI. The standardized beta coefficients for age, physical activity and physical fitness were not significant in respect of WAI
The main purpose of this study was to examine the relationship between perceived work ability and healthrelated quality of life (assessed with WAI and RAND-36), and their associations with physical activity and cardiorespiratory fitness in middle-aged men. The main finding was that there was a relatively close association between WAI and RAND-36 in this selected group of working men. Physical activity or fitness had no relationship to WAI in this study. This may be considered as rather surprising among men having physical jobs. The studied men primarily worked in physically demanding jobs like construction and industrial work. According to the selection criteria, the studied men had slight symptoms and signs (pain or slight restriction in the movements of joints or mild depression) that could lead to physical or psychological impairment and hamper work performance in the long run. Since 82% of the men in this study perceived their work ability according to the WAI as moderate or good having values between 28 and 43 points, the sample seemed to represent fairly well workers who needed early rehabilitation. The age, profession and WAI of the men in addition to the other selection criteria of the study seemed to indicate that the sample was homogeneous. When compared with the Finnish men of similar age, the men of this study felt more bodily pain. This may only reflect the fact that our subjects’ work was physically more demanding than in the general population. On the other hand, the difference in bodily pain between our subjects and Finnish men in general may be a true reflection of the selection criteria used. The Finnish men in the population sample were aged 45–54 years. WAI does not assess pain but the acute perceptions of pain may affect the perceived WAI as well as the perceived RAND-36. The cross-sectional study design limits the causal interpretation of the interactions between the WAI and RAND-36.
Table 4 Quality of life assessed by RAND-36 RAND dimensiona
R2 b
WAIa Beta
General health perception Physical functioning Physical role functioning Bodily pain Emotional role functioning Emotional well- being Social functioning Energy
0.30 0.33 0.25 0.27 0.18 0.28 0.15 0.43
0.53, 0.53, 0.50, 0.54, 0.43, 0.48, 0.38, 0.64,
po0.001 po0.001 po0.001 po0.001 po0.001 po0.001 po0.001 po0.001
Agea beta
Physical activitya beta
Physical fitnessa beta
0.10, p ¼ 0.156 0.03, p ¼ 0.721 0.02, p ¼ 0.810 0.04, p ¼ 0.584 0.05, p ¼ 0.965 0.25, p ¼ 0.001 0.14, p ¼ 0.090 0.13, p ¼ 0.044
0.02, p ¼ 0.755 0.04, p ¼ 0.585 0.06, p ¼ 0.431 0.01, p ¼ 0.939 0.04, p ¼ 0.622 0.03, p ¼ 0.742 0.08, p ¼ 0.349 0.09, p ¼ 0.203
0.11, p ¼ 0.159 0.20, p ¼ 0.008 0.07, p ¼ 0.375 0.01, p ¼ 0.901 0.08, p ¼ 0.316 0.00, p ¼ 0.973 0.03, p ¼ 0.708 0.03, p ¼ 0.643
a Results of the linear regression analysis for the eight dimensions are given. Work ability index (WAI), age, physical activity index and physical fitness (VO2max) are independent variables and different dimensions of the RAND-36 are dependent variables. The standardised beta (beta) coefficients are given for each independent variable to show their predictive value. b The power of the models for explaining the total variance are given in the adjusted R square (R2) values.
ARTICLE IN PRESS 790
L.E. So¨rensen et al. / Applied Ergonomics 39 (2008) 786–791
The assumed logical associations between WAI and RAND-36 should be investigated in a longitudinal study. RAND-36 is one of the most commonly used HRQoL survey methods both in research and practice (Hays and Morales, 2001) and WAI, to our knowledge, is the only survey method to predict work ability. This study was the first of its kind to explore their correlations. Some of the dimensions of RAND-36 and WAI are quite near each other (like ‘physical role functioning’ in RAND-36 and ‘estimated work impairment due to disease’ in WAI or ‘emotional well-being’ and ‘energy’ in RAND-36, and ‘mental resources’ in WAI) and the similarity of the different dimensions may explain the strong correlation of WAI to the different dimensions of the RAND-36. It has to be emphasized that WAI is tailored to assess perceived individual work ability related to job demands, health status (based on number of diagnosed sicknesses and sickleaves), mental resources and wellbeing related to the work. The WAI is a validated (Ilmarinen and Tuomi, 2004) standardized method with sum scale, which is widely used in many countries (Ilmarinen and Tuomi, 2004) and RAND-36 is a validated (Hays and Morales, 2001) standardized method which assesses various dimensions of the quality of life in general. Thus WAI is completely work-oriented method whereas the orientation of the RAND-36 covers the entire life. Therefore, the balanced work situation supports perceived work ability, and may also support the perceived quality of life. When the work situation is unbalanced the associations between WAI and RAND-36 may be reverse. Because many of the dimensions of RAND-36 not only reflect workload factors or individual resources, but also characteristics of social life and other factors outside the work environment, it is appropriate that the concept for promoting health and work ability should be supplemented by target areas outside the work environment, for e.g. family life. Interaction between work and family life may be strong and also important with respect to health, work ability and wellbeing (Jansen et al., 2006). Previous studies have also reported the modifying effect of leisure-time activities and satisfaction with life on the WAI (Seitsamo and Ilmarinen, 1997; Fujita and Kanaoka, 2003), and these observations confirm the need to develop the concept for promoting health and work ability even further. Physical activity or cardiorespiratory fitness had no relationship to WAI in the present study. Physical activity is a key determinant of physical fitness, but physical fitness is only one determinant of work ability and its impact may vary according to the job demands. The present observation that cardiorespiratory fitness was associated with perceived physical functioning domain of RAND-36 seems logical. Cieza and Stucki (2005) compared the contents of different HRQoL instruments by linking the items to the new WHO international classification of functioning, disability, and health. They found wide differences between instruments in breadth and coverage. SF-36, which is almost the same as RAND-36, contains nine items directly
related to physical performance (running, sports, lifting and carrying, climbing stairs, walking short and long distances), whereas most of the other instruments have less precise questions on mobility functioning. Thus, our finding may reflect the properties of the instrument, which was suitable for our subject group of physically working men. Physical activity was associated with no dimension of RAND-36. The major conclusion of the review by Rejeski and Mihalko (2001) was that physical activity positively influences various outcomes associated with the HRQoL. Their review mainly included studies with elderly individuals or individuals with different kinds of impairment, such as cardiovascular disease, osteoarthritis, pulmonary disease, cancer, and depression. Previous studies on the relationship between HRQoL and physical activity in middle-aged men in working life are not available. 5. Conclusions This study showed a close relationship between perceived work ability and quality of life in middle-aged men working in physically demanding jobs. It can be suggested that promoting work ability may also influence on quality of life in general. The rapidly growing interest in carrying out worksite physical activity interventions for promoting work ability did not receive much support in this crosssectional study. Therefore, measures targeting on work and the work environment, work community and organization, individual resources and professional competence, may have more potential in increasing work ability. References Aalto, A.M., Aro, A.R., Teperi, J., 1999. RAND-36 Terveyteen Liittyva¨n Ela¨ma¨nlaadun Mittarina. [RAND-36 as a Measure of Health Related Quality of Life]. Sosiaali-Ja Terveysalan Tutkimus-Ja Kehitta¨miskeskus, Tutkimuksia, 101. Gummerus, Saarija¨rvi, Finland. Chiu, M.-C., Wang, M.-J., Lu, C.-W., Pan, X.-M., Kumashiro, M., 2003. The work ability index and quality of life. J. Erg. Occup. Saf. Health 5 (Suppl. August), 67–69. Cieza, A., Stucki, G., 2005. Content comparison of health-related quality of life (HRQoL) instruments based on the international classification of functioning, disability, ad health (ICF). Qual. Life Res. 14, 1225–1237. de Boer, A.G.E.M., van Beek, J.-C., Durinck, J., Verbeek, J.H.A.M., van Dijk, F.J.H., 2004. An occupational health intervention programme for workers at risk for early retirement; a randomised controlled trial. Occup. Environ. Med. 61, 924–929. Dunn, A., Trivedi, M., O’Neal, H., 2001. Physical activity dose response effects on outcomes of depression and anxiety. Med. Sci. Sports Exerc. 33, 5587–5597. Fujita, D., Kanaoka, M., 2003. Relationship between social support, mental health and health care consciousness in developing the industrial health education of male employees. J. Occup. Health 45, 392–399. Hays, R.D., Sherbourne, C.D., Mazel, R.M., 1993. The RAND 36-item health survey 1.0. Health Econ. 2, 217–277. Hays, R.D., Morales, L.S., 2001. The RAND-36 measure of health-related quality of life. Ann. Med. 33, 350–357.
ARTICLE IN PRESS L.E. So¨rensen et al. / Applied Ergonomics 39 (2008) 786–791 Ilmarinen, J., 1999. Ageing Workers in the European Union–Status and Promotion of Work Ability, Employability and Employment. Finnish Institute of Occupational Health, Ministry of Social Affairs and Health, Ministry of Labour, Helsinki. Ilmarinen, J., Tuomi, K., 2004. Past, present and future of work ability. People Work Res. Rep. 65, 1–25. Jansen, N.W.H., Kant, I.J., van Amelswoort, G.P.M., Kristensen, T.S., Swaen, G.M.H., Nijhuis, F.J.N., 2006. Work–family conflict as a risk factor for sickness absence. Occup. Environ. Med. 6, 488–494. Kaplan, G., Goldberg, D., Everson, S., Cohen, R., Salonen, R., Tuomilehto, J., et al., 1996. Perceived health status and morbidity and mortality: evidence from the Kuopio ischaemic heart disease risk factor study. Int. J. Epidemiol. 25, 259–265. Kesa¨niemi, A., Danforth Jr., E., Jensen, M., Kopelman, P., Lefe´bvre, P., Reeder, P., 2001. Consensus statement concerning physical activity and health: an evidence-based symposium. Med. Sci. Sports Exerc. 33, 5351–5358. Lange-Andersen, K.L., Shephard, R.J., Denolin, H., Varnauskas, E., Masironi, R., 1971. Fundamentals of Exercise Testing. World Health Organization, Geneva. Louhevaara, V., Ilmarinen, J., Oja, P., 1980. Comparison of the A˚strand nomogram and the WHO extrapolation methods for estimating maximal oxygen uptake. Scand. J. Sports Sci. 2, 21–25. Oja, P., 1995. Descriptive epidemiology of health-related physical activity and fitness. Res. Quart. Exerc. Sport 66, 303–312.
791
Pohjonen, T., Ranta, R., 2001. 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. 32, 465–475. Rejeski, J.W., Mihalko, S.L., 2001. Physical activity and quality of life in older adults. J. Gerontol. (Ser. A) 56A, 23–35 (Special Issue II). Saxena, S., Carlson, D., Billington, R., WHOQOL Group, World Health Organisation Quality Of Life, 2001. The WHO quality of life assessment instrument (WHOQOL-Bref): the importance of its items for cross-cultural research. Qual. Life. Res. 10 (Suppl. 8), 711–721. Seitsamo, J., Ilmarinen, J., 1997. Life-style, aging and work ability among active Finnish workers in 1981–1992. Scand. J. Work Environ. Health 23 (Suppl. 1), 20–26. Smolander, J., Blair, S.N., Kohl, H.W., 2000. Work ability, physical activity, and cardiorespiratory fitness: 2-year results from project active. J. Occup. Environ. Med. 42, 906–910. Tuomi, K., Ilmarinen, J., Seitsamo, J., Huuhtanen, P., Martikainen, R., Nyga˚rd, C.-H., Klockars, M., 1997. Summary of the Finnish Research Project (1981–1992) to promote the health and work ability of aging workers. Scand. J. Environ. Health 23 (Suppl. 1), 66–71. Ware, J., Kosinski, M., Keller, S., 1994. Physical and Mental Health Summary Scales: A User’s Manual. The Health Institute, New England Medical Center, Boston. Weyer, S., Kupfer, B., 1994. Physical exercise and psychological health. Sports Med. 17, 108–116.