Table 1 Selected international literature regarding symptoms or disorders in employees working at VDT workstations, in chronological order.

Eltayeb et al. 2007 [11] (Netherlands)

cross-sectional

264 computer workers

not indicated (n.i.)

not indicated (n.i.)

- Prevalence of musculoskeletal complaints: neck: 33%, shoulder: 31%, upper arm: 12%, elbow: 6%, lower arm: 8%, wrist: 8%, hand: 11% (complaints during the previous year that lasted at least one week).

- Higher prevalence of musculoskeletal symptoms in women than in men.

Ye at al. 2007 [12] (Japan)

cross-sectional

2,327 VDT users

n.i.

mean: 19.3 days/month

- Age less than 40 years, not receiving breaks during VDT work, and the presence of eyestrain and musculoskeletal pain were significantly associated with poor general health status (high GHQ scores).

- Using a VDT for more than 5 h/day was also marginally associated with high GHQ scores in women (p < 0.1).

- In conclusion, the management of physical health as well as work duration is important for good general health status among VDT users.

Thomsen et al. 2007 [13] (Denmark)

case-control

18 cases (VDT-workers with symptoms); 20 controls (VDT-workers without symptoms)

cases: 47.0 h/week controls: 35.5 h/week

cases: 28.6 h/week controls: 23.9 h/week

- Computer users with forearm pain and moderate to severe palpation tenderness had diminished forearm extensor muscle fatigue response.

- Additional studies are necessary to determine whether this result reflects an adaptive response to exposure without any pathophysiological significance, or represents a part of a causal pathway leading to pain.

Kubo et al. 2006 [14] (Japan)

cross-sectional

2,161 office workers

n.i.

n.i.

- Positive relationship between VDT work and sick building syndrome (SBS) in men.

- Association between prevalence of SBS an duration of VDT work in women.

- Positive relationship between use of VDT and general symptoms, eye symptoms, respiratory symptoms, and skin rash.

- The authors suggested that extended hours of VDT use might be related to increased SBS symptoms. Moreover, psychosocial distress related to VDT work might mediate the relationship between VDT use and SBS symptoms in women.

Gerr et al. 2005 [15] (USA)

intervention study (3 years)

3 intervetion groups

nA = 122

nB = 125

nC = 115

n.i.

n.i.

- No differences in risk of musculoskeletal symptoms were observed among participants randomly assigned to two workstation and postural interventions in comparison to participants who received no workstation or pos-tural intervention.

- The study provides no empirical basis for recommendation of one posture versus another for prevention of musculoskeletal symptoms among computer users.

Juul-Kristensen & Jensen 2005 [16] (Denmark)

cohort study

3,361 office workers in 11 Danish companies

n.i.

n.i.

- Working as much as 75% of the work time at the computer increased the probability of musculoskeletal disorders in the neck/shoulder and elbow/hand.

- The speed of work was a prognostic factor for symptoms in the lower back.

Lassen et al. 2004 [17] (Denmark)

cohort study

6,943 technical assistants and machine technicians with VDT

69.5% full time work

24.3 h/week

- Detailed examination of self-reported exposures showed that mouse and keyboard-related work time predicted elbow and wrist/hand pain from low exposure levels without a threshold effect.

- Mouse and keyboard-related work time were no predicting factors for clinical conditions.

Kryger et al. 2003 [18] (Denmark)

cohort study

same sample as in the study of Lassen et al. [17]

- Intensive use of a mouse device and (to a lesser extent) keyboard usage, were the main risk factors for forearm pain.

- The occurrence of clinical disorders was low, suggesting that computer use is not commonly associated with any severe occupational hazard to the forearm.

Sillanpää et al. 2003 [19] (Finland)

cross-sectional

office workers (n = 298), customer service workers (n = 238) and designers (n = 247)

n.i.

total sample < 2 h/day: 2.3%; 2–4 h/day: 15.3%; 4–6 h/day: 23.0% > 6 h/day: 47.4%

- For all the occupations combined, the 12-month prevalence of musculoskeletal symptoms in the neck, shoulders, elbows, lower arms and wrists, and fingers were 63, 24, 18, 35 and 16%, respectively.

- The study indicated that musculoskeletal pain is common among computer workers in offices.

- There was no strong association between the duration of computer work and pain or between the duration of mouse use and pain, but workers' perception of their workstation as being ergonomically poor was strongly associated with an increased prevalence of pain.

- Authors advise that more consideration should be paid to the ergonomics of workstations, the placing of the mouse, the postures of the upper extremities and the handling of the mouse.

Gerr et al. 2002 [20]; Marcus et al. 2002 [21] (USA)

cohort study

632 individuals with more than 15 h computer work per week.

38 h/week

mean 28 h/week

- Musculoskeletal symptoms (MSS) and disorders (MSD) in neck/shoulder (N/S) or hand/arm (H/A) were common among computer users.

- More than 50% of computer users reported MSS during the first year after starting a new job.

- The duration of keying (hours/week) was associated with H/A symptoms and disorders.

- The most common N/S MSD was somatic pain syndrome.

- Gender, age, ethnicity, and prior history of N/S pain were associated with N/S MSS and MSD. Gender, prior history of H/A pain, prior computer use, and children at home were associated with either H/A MSS or MSD.

- Authors suggested that the risk of musculoskeletal symptoms and musculoskeletal disorders may be reduced by encouraging specific seating postures.

Nakazawa et al. 2002 [22] (Japan)

cohort study

25,000 office workers

n.i.

21% < 1 h/day 29% 1–3 h/day 22% 5–5 h/day 28% > 5 h/day

- Physical symptoms became more severe with increased daily VDT use without a threshold value effect.

- Mental and sleep-related disorders in workers using VDT for more than 5 h/day were significantly higher than in groups using VDT for > 1, 1–3, and 3–5 h/day.

- Duration of daily VDT use was linearly related to physical symptoms, and was non-linearly related to mental and sleep-related symptoms with a threshold effect of 5 h/day.

Ariens et al. 2001 [4] (Netherlands)

cohort study

1,334 workers from 34 companies

mean: 39.2 h/week

n.i.

- Sitting at work for more than 95% of the working time seems to be a risk factor for neck pain.

- There tends to be a correlation between neck flexion and neck pain.

Bode & Isfort 2001 [23] (Germany)

cross-sectional

1,002 office workers (VDT ≥ 3 h/day)

n.i.

mean: 5 h/day

24-month prevalence: induration of the neck and shoulder area: 62%, muscle pain in the arm: 24%, paresthesia in the arm: 16%, paresthesia in the fingers or pain in the hand: 13% and 12% respectively (multiple answers possible).

- Only 1/3 reported no symptoms.

Hartmann & Guetschow 1999 [24] (Germany)

cross-sectional

205 female office workers

n.i.

n.i.

- Monthly prevalence of symptoms: neck: 40%, shoulders: 36%

- Hand/arm disorders seemed not to be the main issue of VDT users.

Ertel et al. 1997 [25] (Germany)

cross-sectional

352 female office workers

mean: 8.4 h/day

mean: 5.45 h/day

- Prevalence of symptoms during and after work: shoulder & neck: 62.7%, back: 53.0%, head: 45.3% and hands/arms/legs: 24.2%.

Michaelis et al. 1997 [26] (Germany)

cross-sectional

1,720 office workers

n.i.

n.i.

- Point prevalence of musculoskeletal symptoms: 62%.

- Point prevalence of symptoms in the thoracic/lumbar spine in employees working at desk: 23% to 58% (increasing with age). Working at VDT increased prevalence by an average of 8%.

- Point prevalence of symptoms in the cervical region is 20% to 36% (increasing with age). The prevalence was significantly higher in employees working at VDT compared to employees working only at desks.

Bergqvist et al. 1995 [27, 28] (Sweden)

cross-sectional

353 office workers

n.i.

n.i.

- No general differences between VDT and non-VDT users as to the occurrence of muscular problems.

- Combination of specific VDT work situations (e.g. typing work, work with a VDT for more than 20 h/week) and the presence of moderating factors was associated with excess risks of suffering from muscular problems.

Schwaninger et al. 1991 [29] (Germany)

cross-sectional

2,722 office workers in different companies

n.i.

33% 1/4, 27% 2/4, 27% 3/4, 13% 4/4 of work time

- Prevalence of musculoskeletal symptoms: neck pain: 38%, back pain: 38%, pain in the shoulders: 32%, pain in the arms/hands: 11% (no indication of reference period).

- Only 1/3 reported no symptoms.

- The authors recommended an optimal ergonomic configuration of the work place, multifaceted tasks and regular breaks at the VDT workstation.