Reports in the scientific literature and lay press have suggested that computer users are at increased risk of upper extremity musculoskeletal disorders (MSDs). Early studies often found elevated rates of MSD outcomes among keyboard users when compared to non-users. Attention soon focused on specific aspects of keyboard work that might be responsible for the observed rate increase. In this review, the epidemiological evidence examining associations between MSD outcomes and computer user posture and keyboard use intensity (hours of computer use per day or per week) are examined.

Results of epidemiological studies of posture and MSD outcomes have not been entirely consistent. Reasons for the inconsistency in results include cross-sectional study design (with possible failure to assure that measured exposure preceded health effect), imprecision of posture measures used, and difficulties involved in analyzing multiple related variables. Despite the inconsistencies, it appears from the literature that posture is an independent risk factor of modest magnitude for MSDs among computer users. It appears that lowering the height of the keyboard to or below the height of the elbow and resting the arms on the desk surface or chair armrests is associated with reduced risk of neck and shoulder MSDs.

Results of epidemiological studies examining computer use (hours keying per day or per week) are more consistent than those examining posture, although some inconsistency is observed. Reasons for the inconsistency include possible selective survival bias resulting from cross-sectional study design, differences in exposure categorization, and possible interaction with other exposure variables. Overall, the literature shows that daily or weekly hours of computer use is more consistently associated with hand and arm MSDs than with neck and shoulder MSDs.

The objectives of this study were to examine the association between work-related upper limb disorders (WRULDs) and duration of computer and mouse use, to investigate differences in these associations between men and women, and to examine whether a possible relationship between duration of computer use and WRULDs was explained by physical or psychosocial risk factors. The study population in this cross-sectional questionnaire study consisted of 5400 office employees. Participants had filled out a questionnaire on job characteristics, job content, physical workload, psychosocial workload and musculoskeletal symptoms.

Working with a computer during more than 6 h/day was associated with WRULDs in all body regions. Stratified analyses showed that the strength of the associations differed between men and women. In men, only moderate associations were seen for computer use more than 6 h/day. In women, moderately increased ORs were observed for a duration of computer use of more than 4 h/day and strongly increased risks for a computer use during more than 6 h/day.

Frequent computer users who often used a mouse did not report more WRULDs or neck or shoulder disorders than frequent computer users who did not use a mouse. Only for arm, elbow or wrist or hand problems a moderately increased OR among the mouse users was observed, but this was not statistically significant.
Relevance to industry

Recent increases in the number of employees working with computers and in the durations of computer and mouse use coincide with a huge prevalence increase of work-related disorders of neck and upper limb (WRULDs) and sick leave, which poses financial burdens on companies. Research on risk factors and preventive measures is relevant for these companies.