Is peak exposure to computer use a risk factor for neck and upper-extremity symptoms?

OBJECTIVES: Epidemiologic studies on physical exposure during computer use have mainly focused on average exposure duration. In this study, we aimed to relate periods of high peak exposure during computer use with the occurrence of neck-shoulder (NS) and arm-wrist-hand (AWH) symptoms. METHODS: A prospective cohort study among 1951 office workers was carried out for two years, with periodical questionnaires and continuous measurements of computer input use. To define peak exposure, a distinction was made between peak days and weeks. Peak days were defined as days with a long duration of computer (ie, ≥4 hours) or mouse use (ie, ≥2.5 hours) or days with high frequency of mouse (ie, ≥20 clicks per minute) or keyboard use (ie, ≥160 keystrokes per minute). Weeks containing ≥3 peak days were considered peak weeks. Independent variables were numbers of peak days and peak weeks during a 3-month measurement period; dependent variables were self-reported NS and AWH symptoms during the following 3-month measurement period. RESULTS: Valid data were available for 2116 measurements of 774 office workers. No relation was found between any of the peak exposure parameters and AWH symptoms or with peak exposure in duration and NS symptoms. Most parameters referring to high frequency-related peak exposure were associated with less NS symptoms, but the effect estimates were very small and the confidence intervals close to the null. CONCLUSION: In this study, we found no indication that high peaks in computer use were related to the occurrence of NS or AWH symptoms.

Computer work duration and its dependence on the used pause definition.

Several ergonomic studies have estimated computer work duration using registration software. In these studies, an arbitrary pause definition (Pd; the minimal time between two computer events to constitute a pause) is chosen and the resulting duration of computer work is estimated. In order to uncover the relationship between the used pause definition and the computer work duration (PWT), we used registration software to record usage patterns of 571 computer users across almost 60,000 working days. For a large range of Pds (1-120 s), we found a shallow, log-linear relationship between PWT and Pds. For keyboard and mouse use, a second-order function fitted the data best. We found that these relationships were dependent on the amount of computer work and subject characteristics. Comparison of exposure duration from studies using different pause definitions should take this into account, since it could lead to misclassification. Software manufacturers and ergonomists assessing computer work duration could use the found relationships for software design and study comparison.