Our goal was to understand associations between workers’ perception of ergonomic practices and self-reported symptoms of musculoskeletal disorders among patient care unit workers in two large academic hospitals, with the specific hypothesis that an increased ergonomic practice score has a protective association with musculoskeletal symptoms and limitations. All of our bivariate analysis and most of the multiple logistic regression analysis support this hypothesis. Increased scores of ergonomic practices were associated with lower odds of reporting musculoskeletal pain through the four body areas, low back, neck/shoulder, arms, and lower extremity, in the past 3 months, as well as pain severity and functional limitations in the past week in both bivariate and multiple logistic regression analyses.
Overall, our results indicate that indeed the workers’ perceptions about their unit's ergonomic practices are associated with self-reported musculoskeletal symptoms. The ergonomic practices scale asks workers how well work within their unit is designed to reduce lifting, pushing/pulling, and bending, reaching, and stooping, all of which are specific risk factors for musculoskeletal disorders [NRC/IOM 2001
]. These findings may suggest that workers in units with poor ergonomic practices may be at increased risk for musculoskeletal symptoms – across a range of body parts, for multiple parts of the body, and for higher severity of the pain levels. It is also possible that this association may be due to increased sensitivity of workers in pain noting specific ergonomic issues, that is, they may perceive their work environment differently than workers without pain. To those without pain, ergonomic practices may be perceived as acceptable. Those in pain can still benefit from ergonomic interventions and often secondary prevention efforts include as strong an emphasis on ergonomic practices and interventions as do primary prevention efforts [Snook 2004
]. Nonetheless, the associations indicate that these practices are important and support prevention efforts that incorporate employee involvements, such as participatory approaches [Hignett, et al. 2005
, Wilson 1995
The ergonomic practice scale, however, was not significantly associated with low back pain and work-interference in the multiple regression analysis that included psychosocial factors such as psychosocial demands and supervisor support (Model 2 in ). Studies have reported associations between psychosocial factors and low back pain in patient care workers (e.g. [Lipscomb, et al. 2002
, Mehrdad, et al. 2010
]); however, the relationships are complex and variable [van den Heuvel, et al. 2004
]. The psychological demands scale used in our questionnaire may capture some of the general physical demands of a job that are not captured by the specific ergonomic practice scale questions. The demands scale contains the questions, “my job requires me to work very hard” and “I am not asked to do an excessive amount of work”, both of which have general cognitive and physical constructs that may capture the identified physical risk factor of heavy physical work for low back pain [NRC/IOM 2001
]. Heavy physical work may not been identified for other body parts explaining why the association with the ergonomic practice scale remains significant for the other outcomes when the psychosocial demands scale is added to the model. A second factor may be that the activities associated with low back pain for patient care unit staff, mainly patient handling may not be perceived to be designed ergonomically in light of the job demands and the social support factors. Since, the original ergonomic practice scale was developed for manufacturing; hence, it may fail when respondents feel the question is not framed well for their work, such as the physical demands of a patient care worker. The ergonomic practice scale may better capture other types of work not involving patient handling, such as computer and office and hence why many of the other body parts were still associated strongly with ergonomic practices in the multiple logistic regression analyses with the psychosocial factors.
The people oriented scale was associated with the co-morbidity, work interference and functional limitations outcomes in multiple logistic regression without the psychosocial factors, which follows the intent of the organizational policies and practices scales to be a comprehensive scale for work-disability management [Amick, et al. 2000
]. Compared to the purely pain measures, work-interference and functional limitations outcomes include a component of disability – not being able to complete either work tasks or activities of daily living due to the pain. Only the association with work-interference remained when the psychosocial factors including supervisor and coworker support scales, which may be due to some similarity in the people oriented culture and the co-worker and supervisor support scales. The people oriented culture scale includes assessing “working relationships are cooperative” and “communications is open and employees feel free to voice concerns and make suggestions”.
The safety practice scales did not demonstrate any significant associations with the outcomes in the multiple logistic regressions, which may be due to the nature of outcomes being pain and disability rather than acute injuries more often associated with safety programs [Mark, et al. 2007
]. The safety practice scale has similar items in typical safety climate scales, which too have not been related to low back injuries in hospital nurses [Mark, et al. 2007
]. The organizational policies and practices scales were developed to capture factors related to disability management due to a range of causes including acute injuries and musculoskeletal disorders [Habeck, et al. 1998
]. Our study here has focused on symptoms of musculoskeletal disorders; hence, the safety scale may have better associations when the outcomes include acute injuries. In addition, the workers provided a higher safety scale than the ergonomic scales, which may indicate that current safety programs are more effective than current ergonomic practices.
The practice and culture scales were developed for examining injury incidence, disability, and return to work in a wide range of industries based on the conceptual model described by Amick et al., (2000)
. Amick et al. observed that better ergonomic practices and people oriented culture were associated with the 6-month post carpal tunnel release surgery return to work status. Often these scales have been used to examine different organizational factors with disability management [Ossmann, et al. 2005
, Westmorland, et al. 2005
, Williams, et al. 2005
, Williams, et al. 2007
]. To the best of our knowledge, these scales have not been associated with reported musculoskeletal pain and functional limitations before. Musculoskeletal pain may be a subset of all causes of injury-related work-disability and hence why some of the metrics, such as safety practices scale, which may be more related to acute injury, have non-significant associations with these pain outcomes. These data suggest that these organizational factors affect a continuum of worker outcomes that includes pain (shown here) to return to work (disability management) and hence demonstrate a potential for broader impact of ergonomics on prevention in this cohort.
As noted, the associations between the organizational practice and culture scales changed when the psychosocial factors were included in the multiple logistic regression analyses. As described above, the psychosocial factors have some overlap with the practice and culture scales. In addition, the psychosocial scales may be more comprehensive measures of the work environment. For example, the demands scale was developed to capture specific cognitive demands of a job across many different types of industries and jobs [Karasek and Theorell 1990
, Karasek, et al. 1998
]. While comprehensive, using psychosocial factors to inform intervention has proved to be difficult [Bourbonnais, et al. 2006
, Hannan, et al. 2005
]. Because, the concepts of the organizational practices are operational factors that can be implemented in a work place. the organizational practices scales provide opportunities for organizations to improve and develop prevention programs.
These findings rely on a cross-sectional survey; as with any cross-sectional assessment, it is not possible to determine the temporal sequence in these relationships, and we therefore do not infer causality. Data were collected from two academic teaching hospitals in the greater Boston area; we acknowledge that findings from this setting may not be generalized to all other patient care settings. Findings reported here are based on self-reports from the survey, and accordingly are subject to recall and social-desirability bias. Additionally, while we controlled for workload by grouping similar units, we recognize that work on patient care units is highly variable and unknown confounders or work characteristics may impact the outcomes. Despite these limitations, it is important to note the high response rate to this survey (79%), our reliance on measures previously tested in prior literature, and the use of multiple indicators of work experiences.
In conclusion, these findings suggest the importance of having clear ergonomic practices within a hospital may be important part of an MSD intervention program in the acute care work environment. While causality has not been determined further studies investigating these factors are warranted and will provide the evidence needed for adoptions of these types of practices within the health care sector.