In this study, the effect of an ergonomic intervention (i.e. ergonomic modification and training) on cognitive function was assessed in office workers. Wechsler working memory and Stroop tests were used to assess cognitive function before and after ergonomic intervention in female office workers. The results showed that forward visual memory, response time and interference time were significantly changed after the intervention, and some demographic and occupational variables, especially age, significantly affected the participants' response after the intervention.
To assess short-term and active working memory, memory span was measured using Wechsler working memory test. This test can assess forward visual memory, backward visual memory and memory span based on the golden digit (7 ± 2), and its score is usually between 5 and 9 in the adults. Greater score of working memory shows a better memory function. Some previous studies have assessed the effect of different variables on working memory. Barella et al. (2010) found that posture modification positively affects working memory. Chang et al. in a systematic review found a positive effect of exercise on short-term memory (Chang et al. 2012).
In this study, consistent with Russel et al. study (2018) the score of all aspects of working memory (i.e. memory span, and forward and backward visual memory) were increased after the intervention, but the difference was significant only for forward visual memory which was consistent with the study of Bantoft et al. (2016); although the level of significance for memory span was near significance and increasing sample size may lead to a significant difference. Working memory is a part of cognitive system which stores information and also holds some information while performing mental tasks (Bantoft et al. 2016). Working memory affects attention and concentration as well (Alloway et al. 2010; Hill et al. 2010). So, its deficit may lead to errors in the workplace.
In the current study, attention and response time were assessed by Stroop test. This test has been designed to measure attention and cognitive flexibility by visual processing. Interference score shows attention, and response score shows response or reaction time. Usually, response time to congruent words is shorter than incongruent ones. When interference time is shorter, the time of stimulus control is shorter and the participant can differentiate between the color and the meaning in a shorter duration of time. Interference score is an index of human brain capability in the management of new tasks. Lower interference score shows a better performance, less errors and higher attention. In the current study, interference score was decreased after the intervention, although this decrease was not statistically significant.
Test duration was significantly decreased after the intervention which shows higher speed of the participants in response and reaction. This result was consistent with the results of Mohammadi et al. (2018) and inconsistent with the studies conducted by Shwartz et al. (2018; 2019); although it should be considered that in all of these studies the intervention was different with the current study. Response time significantly reduced after the intervention, but the change in the number of errors was not statistically significant. Zhang et al. (2018) in a study on students found that dynamic workstation cannot affect the results of Stroop test, although again the intervention was different from our study and the results cannot be compared.
Interference score in the current study was decreased after the intervention which shows a lower probability of error and a better performance in the workplace; although the decrease was not statistically significant, the difference was large and a larger sample size may lead to a significant difference. Mohammadi et al. (2018) found that interference score and selective attention in the standard sitting position was better than other positions. Russell et al. (2016) found that after their intervention, attention was improved. Unfortunately, we couldn't find a study with a similar intervention with the current study.
In this study, interference time after the intervention was significantly decreased, which shows a higher speed and lower response time, which was inconsistent with the results of Schwartz et al. (2018). Most studies on the effects of ergonomic modification in the workplace have been conducted on the musculoskeletal complaints and disorders (Torbeyns et al. 2014; Mehrparvar et al. 2–14).
Some factors may affect cognitive function in the workplace. Working hours, shift work, work posture, and some environmental exposures are among the factors which have been assessed in different studies (Esmaily et al. 2020; Schwartz et al. 2019; Schwartz et al. 2018; Zeydabadi et al. 2019). Ergonomic interventions to improve work posture, workplace arrangement, micro-breaks and stretching exercises have been shown to improve discomfort, fatigue and musculoskeletal complaints in different jobs (Torbeyns et al. 2014; Pronk et al. 2011; Lee et al. 2021), but the effect of interventions on workers’ cognitive function is controversial by now. Most studies in this regard have assessed the effect of changing work posture on cognitive function. Schwartz et al. in two different studies found that sit-stand work posture as an ergonomic modification cannot affect cognitive function in short and medium-term durations (Schwartz et al., 2019; Schwartz et al., 2018). They showed that intermittent work posture did not affect response time, concentration and work speed (Schwartz et al., 2018), which was inconsistent with the results of the current study, although our modification was ergonomic modification of the workplace and training, but they compared two different work postures. Russel et al. couldn't find a significant effect of intermittent sitting and standing postures on cognitive function in office workers (Russell et al., 2016). Mohammadi et al. (2018) conversely found that work posture can significantly affect cognitive function. Bantoft et al. assessed the effect of standing and walking during work on cognitive function and didn't find a significant effect (Bantoft et al., 2016). Magnon et al. in a systematic review found that interventions to reduce sedentary behavior is not associated with changes in cognitive function (Magnon et al. 2018). Sohrabi & Babamiri (2021) found a significant effect of an ergonomic training intervention on musculoskeletal complaints of office workers, but this effect was not observed on productivity and some variables of quality of work-life.
In the current study, marital status significantly affected the difference after the intervention, so as the impact of intervention was higher in single individuals than married ones, which is probably due to family or social preoccupations in married individuals. Age and work history did not affect working memory, but it was affected by daily working hours. Response time was significantly increased by age. Increased daily working hours significantly increased the number of errors after the intervention.
Limitations: This study had some limitations. The participants were only females, so the results cannot be generalized to males. The assessment was done one month after the intervention, so the long-term effects of the intervention could not be assessed. The small sample size may have affected the significance of some differences. We couldn't change any non-ergonomic equipment due to monetary constraints, and our modification consisted only of standard arrangement and adjustment of different equipment in the workstation.