Ergonomic Studies and Treatment of Gender in Epidemiological Investigations

Friday, March 23, 2012: 11:00
Gran Cancun 2 (Cancun Center)

Karen Messing, Canada
Ergonomists are well versed in putting research into practice, the theme of this congress.  Our discipline is geared toward identifying aspects of the workplace that determine problems and can be changed (Guérin et al., 2009).   But how can an ergonomist put research on gender and work into practice?  Gender is not something that can be acted on like a poor work schedule or a wrong table height.  In this presentation I will argue that, during our interventions, ergonomists learn a lot about gender that is important when generating and testing hypotheses about the mechanisms that link workplace exposures to health outcomes. 

This presentation asks two questions:

1)     What do we learn about gender and occupational health when doing ergonomic interventions

2)     What are the potential implications of this knowledge for practice?

Note on terminology

Conceptually, “sex” refers to the biological specificity of women and men and “gender” to social factors. However, in empirical research with workplace populations we often find it hard to distinguish whether observed male-female differences are due to biological or social factors.

What do we learn about gender and occupational health when doing ergonomic interventions

A few years ago, Jeanne Stellman and I suggested that it would be important to examine the potential mechanisms linking sex, gender, the workplace and health (Messing and Stellman 2006).  Our work at the CINBIOSE  research centre provides us with some raw.  For over 20 years, we have participated in a research partnership with Québec’s three largest trade union confederations,on the theme of women’s occupational health.  CINBIOSE ergonomists have also collaborated with epidemiologists on a major occupational health survey in Chile, as well as with Canadian public health experts.  This presentation reflects what we have learned during those collaborations.

Same variable name, different exposure: Gender and sex as surrogates for exposure

The most obvious role for gender in the pathway linking workplace exposures and health is in determining exposure, both across and within job titles.  Gender segregation of the labour market is well documented and quite familiar to occupational health scientists, but within-job gender differences in task assignments are perhaps less well known.  I will give two examples relating to musculoskeletal health.  In 1994-95, we studied task requirements within hospital cleaning (Messing et al. 1998).  At that time, cleaning was divided into “light” work (dusting and cleaning surfaces, etc.), done mostly by women, and “heavy” work (mopping etc.) done mostly by men. Movements and manipulation of weights differed between the tasks and work accidents and illnesses also were different.  Partly as a result of our study, light and heavy work were merged.  However, when we returned to this job in 2007-2008, men and women assigned to the new merged job still performed somewhat different tasks and had somewhat different health problems (Calvet et al. in press).  Conversations with cleaners revealed that gender stereotyping was at the root of the informal re-division of tasks.  “I don’t clean toilets at home, why should I clean them at work?” asked one man.

Sex can also determine exposure differences within the same job.  Women and men have, on average, different shapes and the same work station may interact differently with male and female bodies, even if the work station is adjusted to the size of the worker (Won et al. 2009).   In our collaboration with epidemiologist Susan Stock relating prolonged standing to musculoskeletal disorders, we wanted to understand why women who usually stood at work reported more pain in their feet than men who usually stood at work.  Ph. D. candidate Ève Laperrière and colleagues (2006) carried out an observational study of women and men who worked in a standing position at factories, in restaurants and in retail stores.   We found that women took significantly more steps at work than men assigned to the same jobs, because of their shorter stride length.  The number of steps is of course related to the number of times the foot hits the floor surface, and may be related to musculoskeletal disorders.

Other aspects of gender that affect mechanisms linking exposures and outcomes

Gender potentially determines intrastratum confounding.  That is, we have observed that, although both male and female cleaners lifted weights regularly at work, men lifted somewhat heavier weights.  This means that if, for example, respondents are asked, “How often do you have to lift loads of more than 25 kg?”, men’s responses may refer (for example) to weights of 40 kg on average and women’s to 26 kg on average.  This may explain why, in some studies, men may appear to suffer more health problems than women from the same exposure to lifting weights (Hooftman et al. 2009).    In addition, women work fewer hours per week at their jobs and their seniority is lower on average (Vézina et al., 2011; chapter 4), so that exposure reports of the same intensity may correspond to a longer exposure duration. 

For these reasons, we and others have already suggested that epidemiologic studies refrain from adjusting for gender, since this procedure may result in over-adjusting (Messing et al. 2003; 2009).    We suggest that epidemiologic and other researchers generate hypotheses regarding how gender intervenes in the pathways linking exposures and outcome.  I refer the interested researcher to the very thorough review by Punnett and Herbert (2000) for an examination of a number of potential pathways.

Potential implications for practice

Making mistakes about handling gender has implications for equality in the workplace.   When we find that women in two non-traditional jobs have 2-3 times men’s rate of work accidents and illnesses, how do we think about this result?  A study that mistakenly reports that women are more susceptible to accidents may affect their access to employment. So in analyzing the data, we have to look at the re-division of labour that occurs after women enter a non-traditional job, to see if there are specific exposures of women.    We have to look at selection into these jobs – what is the process by which women become telecommunications technicians or day labourers. And we have to see whether the training women are given in how to carry out manual tasks is appropriate for their specific biology.

For men, equality means (among other things) protection of their health.  In some manual jobs, women do more physical tasks but men do more of the tasks with visible, dramatic risks (Messing and Elabidi 2003). In Québec, men, especially young men, are found more often in jobs with high noise levels, exposures to solvants and lifting heavy weights, for example (Vézina et al., 2011; Chapter 7).  So we have to look at whether these additional exposures are producing specific risks for men.

From the beginning of an epidemiologic study, researchers should examine the different workplace processes involving women and men, from the point of hiring: selection, task assignments, turnover, and how they experience, report and claim for compensation for health problems. This will lead to enhanced understanding of the data and better analyses.


I thank the Teasdale-Corti Global Health Research Partnership Program for funding  the project “Research, Policy and Practice with regard to Work–Related Mental Health Problems in Chile: A Gender Perspective”  and the Canadian Institutes of Health Research for its Gender, Environment and Health grant [GTA92108].

Guérin F., Laville, T., Daniellou, F., Durrafourg, J., Kerguelen, A. 2007. Understanding and transforming work. The practice of ergonomics. Lyon: ANACT Network Editions.

Laperrière, E., Ngomo, S., Thibault, M-C., Messing .  2006. Indicators for choosing an optimal mix of major working postures. Applied Ergonomics  37(3): 349-357.

Messing K, Elabidi D. 2003. Desegregation and occupational health:  How male and female hospital attendants collaborate on work tasks requiring physical effort.  Policy and Practice in Health and Safety 1(1): 83-103.

Messing, K., Stellman, J.M.  2006.  Sex, gender and health:  the importance of considering mechanism. Environmental Research 101(2):149-162.

Messing, K., Stock, S., Tissot, F. 2009. Should studies of risk factors for MSDs be stratified by gender?  Lessons from analyses of musculoskeletal disorders among respondents to the 1998 Québec Health Survey.  Scandinavian Journal of Work Environment and Health 35(2):96-112.

Punnett L, Herbert R. 2000.Work-related musculoskeletal disorders: Is there a gender differential, and if so, what does it mean? In: Goldman MB, Hatch MC, editors. Women and health. New York: Academic Press. p 474–492.

Vezina, M., Cloutier, E., Stock S., Lippel K., Fortin É. et al. 2011. Enquête québécoise sur des conditions de travail, d’emploi, et de santé et de sécurité du travail (EQCOTESST), Montréal : Institut de recherche Robert-Sauvé en santé et sécurité du travail - Institut national de santé publique du Québec et Institut de la statistique du Québec.

Won EJ, Johnson PW, Punnett L, Dennerlein JT. 2009.  Upper extremity biomechanics in computer tasks differ by gender.  J Electromyogr Kinesiol. 19(3):428-36.