Epidemiology of musculoskeletal disorders among computer users: lesson learned from the role of posture and keyboard use
Introduction
Computers and computer workstations (also called video display terminals, VDTs) have become increasingly common in both workplaces and private residences over the past 20 years [23]. Reports in the scientific literature and lay press have suggested that computer users are at increased risk of upper extremity MSDs [10], [22]. Because of such widespread use, even relatively small risks associated with their use would have important public health implications. Characterization of those risks is necessary, ultimately, for the prevention of adverse health effects.
Early studies often found elevated risks of MSD among keyboard users when compared to non-users [9]. Attention soon focused on specific aspects of key board work that might be responsible for the increase in observed risk. In this review, the epidemiological evidence examining associations between upper extremity MSDs and computer user posture and keyboard use intensity (hours of computer use per day or per week) will be examined. Methodological issues that may have lead to inconsistencies in the literature will be discussed. The review is limited to field-based epidemiological investigations published in the peer-reviewed biomedical literature with sample sizes of 20 or more computer (VDT) users.
Section snippets
Posture and musculoskeletal outcomes among computer users
Review of the English language peer-reviewed literature identified six field-based, observational epidemiologic studies in which measures of operator posture were used as exposure variables in analyses relating VDT use to upper extremity MSDs. Only one study followed a cohort with a prospective design; the remaining five were of cross-sectional design. These six studies are described below.
Hunting et al. [11] performed a cross-sectional study of 162 workers using VDTs and 133 non-VDT using
Keyboard use and musculoskeletal outcomes among computer users
Fifteen epidemiological studies were identified in which associations between computer use (in units of hours per day or hours per week of keying) and MSD outcomes were investigated.
In a cross-sectional questionnaire study of 1742 VDT users, the percent of workers reporting “almost daily” neck discomfort increased monotonically with increasing hours of daily VDT use. The percent of workers reporting “almost daily” shoulder discomfort also appeared to increase with daily VDT use, however, those
Discussion and conclusions
A relatively modest number of field-based epidemiological studies have investigated associations between posture and MSD outcome among computer users and results from them have not been entirely consistent. It appears from the literature, however, that posture is an independent risk factor for MSDs among computer users. The most consistent finding is that locating the keyboard at or below the height of the elbow and resting the arms on the desk surface or chair armrests is associated with
Fred Gerr, MD, is Professor of Occupational and Environmental Health at the College of Public Health of the University of Iowa. Dr. Gerr is an occupational medicine physician who has collaborated on the design and conduct of several field-based epidemiological investigations of work-related musculoskeletal disorders. Dr. Gerr is also a practising clinician and provides clinical services to workers with musculoskeletal disorders.
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Fred Gerr, MD, is Professor of Occupational and Environmental Health at the College of Public Health of the University of Iowa. Dr. Gerr is an occupational medicine physician who has collaborated on the design and conduct of several field-based epidemiological investigations of work-related musculoskeletal disorders. Dr. Gerr is also a practising clinician and provides clinical services to workers with musculoskeletal disorders.
Michele Marcus, PhD, is Associate Professor of Epidemiology and Environmental and Occupational Health at the Rollins School of Public Health at Emory University. Dr. Marcus has collaborated on the design and conduct of field-based epidemiological investigations of work-related musculoskeletal disorders. Dr. Marcus is also involved in the epidemiological investigation of environmental effects on endocrine and reproductive outcomes.
Carolyn Monteilh, PhD, is Research Assistant Professor of Environmental and Occupational Health at the Rollins School of Public Health at Emory University. Dr. Monteilh is currently PI of a NIOSH-funded project to perform additional analyses of results from a large prospective study of musculoskeletal disorders among computer users. Dr. Monteilh has also investigated anthropometric effects on breast cancer survival among young women.