The relationship between work stress and work ability among power supply workers in Guangdong, China: a cross-sectional study

Most western countries are experiencing the challenge of population ageing. Demographic projections of 27 European countries by Eurostat (2011) indicate that the old-age dependency ratio –the ratio of those outside the labor force to those of working age (15-64y)- will double from 25.9 % on average in 2010 to 50.2 % by 2050 [1]. The demographic projections in China are not different, with the population aged 65 and older expected to be almost 300 million by 2050 [2]. With the rapidly ageing population, it is of utmost importance to prevent disability and early retirement so that everybody can remain in the labor market for as long as possible. Promoting work ability is one of the effective ways to cope with the challenges to sustainability of workforce presented by population ageing. Prospective studies have demonstrated that a low score of work ability index (WAI), which is an instrument used in clinical occupational health and research to assess work ability, increased the risk of premature work exit due to disability pension or early retirement [3, 4].

Previous studies revealed that work ability was not only associated with individual characteristics but also with work-related factors [5, 6]. Epidemiologic studies have shown that work stress is related to work ability [7, 8]. The Job Content Questionnaire (JCQ) and Effort Reward Imbalance (ERI) Questionnaire have been widely used to assess work stress. The Job Content Questionnaire, based on the Job Demand-Control-Support model, demonstrates that employees who have high job demands while simultaneously having little control of their work are in a high job-strain situation. In addition, this model argues that work stress increases when the level of social support decreases. Previous studies showed that decreases of work ability were related to high job strain due to high demand and low control [8]. The Effort Reward Imbalance Questionnaire based on Effort Reward Imbalance model states that the experience of a lack of reciprocity in terms of high ‘cost’ and low ‘gains’ elicits negative emotions. The negative association between ERI and work ability have been supported by both cross-sectional and longitudinal studies [9, 10].

As a consequence of rapid economic development, domestic consumption of electricity in China has increased rapidly during the past decades. The total electricity consumption in China during 2014 was the highest in the world and accounted for 57 % of the consumption in Asia (https://?yearbook.?enerdata.?net/?). Chinese workers in the power supply industry have experienced increasing workload. As a result of the commercialization of the power industry in China, the labor market has undergone significant changes in the past several years. Deregulation, privatization and reduction of welfare programs have resulted in less job security. In addition, workers employed in the power supply industry are exposed to multiple stressors including electric shock, injury and trauma resulting from accidents, poor body posture, bad weather conditions, outdoor work and shift work [11]. Long-term stay in isolated regions also increases the level of work stress. It is of utmost importance to explore the relationship between work stress and work ability among power supply workers in China.

Most of the aforementioned studies concerning the relationship between work stress and work ability were conducted in western societies. However, work conditions in China are different from the ones in western societies. Long hours, rough conditions, and low pay have resulted in increased work stress. Besides, the Chinese workers are hardworking and obedient due to the culture of nationalism, stability, and harmony. This combination has created a uniquely motivated population. It is unclear whether the relationship between work stress and work ability in western societies could be generalized to China. In addition, despite that there were several studies explored the relationship between work stress and work ability in China [12, 13], few studies have applied a theoretical model to test the associations. The risk factors of work stress are correlated and individuals do not experience them in isolation. It is more appropriate to analyze effects of all these factors simultaneously by a theoretical model.

The job demands-resources (JD-R) model provides an opportunity for us to understand the work ability by a theoretical model [14, 15]. The basic premise of the JD-R model is that whereas every occupation may have its own specific risk factors associated with job stress, these factors can be classified into two general categories (i.e., job demands and job resources), thus constituting an overarching model that may be applied to various occupational settings, irrespective of the particular demands and resources involved [14, 15]. Evidence for this hypothesis would offer organizations a tool to maintain work ability by optimizing job demands and increasing job resources.

According to the JD-R model, job demands refer to those physical, social or organizational aspects of the job that require sustained physical or mental effort and are therefore associated with certain physiological and psychological costs [15]. Demands of the job have been linked to work ability in previous cross-sectional studies [6, 7, 16]. Both the mental and physical job demands are seen as having a negative relationship with work ability.

Job resources are defined as “those physical, psychological, social, or organizational aspects of the job that may be functional in achieving work goals, reduce job demands and the associated physical and psychological costs, and stimulate personal growth or development” [15]. Previous studies indicated that job resources were related to intrinsic motivational processes through fostering skill development and growth. In addition, they are instrumental in helping employees achieve work goals [17]. Therefore, some studies have examined the relationship between job resources and work ability [16]. Besides, according to the definition of job resources and previous study job resources may be correlated with job demands.

Consequently, we formulated three hypotheses in the present study. Firstly, it was supposed that job demands would be negatively related to perceived work ability. In addition, job resources would be positively related to perceived work ability. Thirdly, it was supposed that job demands would be correlated with job resources.

The aim of this study was to explore the relationship between work stress and work ability among Chinese power supply workers using a structural equation model. The findings of this study may help devise new strategies to improve ability.