Table 1.
Study characteristics
| Author | Methodological Quality | Imaging | Study Design | Participant information |
|---|---|---|---|---|
| Arevalo et al. 2014 | 5 | MRI | Retrospective cohort study |
N = 652; 326 patients with established diagnosis of lumbar disc herniation on MRI and 326 patients without herniation. Age range was assessed but not reported. |
| Battie et al. 1995 | 6 | MRI | Cross sectional |
Monozygotic twin pairs from the Finnish Twin Cohort selected based on loading discordances. (n = 230 twins or 115 pairs) Age range from 35 to 69 years. |
| Biering-Sorense et al. 1985 | 4 | x-ray | Longitudinal cohort study |
666 participants taking part in a population study of 60-yerar-old inhabitants from the area around Glostrip Hospital in the suburbs of Copenhagen. All participants were either 50 or 60 years of age. |
| Brinckmann et al. 1998 | 5 | x-ray | Retrospective cohort study |
355 subjects with long term exposure to heavy physical load (from different professions) and 737 healthy controls compiled from healthy unexposed subjects. Participants were between 17 to 57 years old. |
| Elfering et al. 2002 | 3 | MRI | longitudinal cohort study |
46 asymptomatic patients from a group of 2000 trauma patients presenting to the university trauma clinic with minor extremity injuries with complete recovery. Participants were between 20 and 50 years of age. |
| Frymoyer et al. 1984 | 3 | x-ray | Cross sectional (retrospective) |
321 random patients from a sample of 1221 from a previous study. Only 285 were included in the occupation vs imaging study due to reasons such as imaging quality Participants were between 18 an d55 years of age. |
| Han et al. 2017 | 6 | MRI and x-ray | Cross sectional |
210 patients with low back pain attending the hospital. All underwent imaging evaluation and responded to questionnaires about workload. Age ranged from 40 to 60 years. |
| Hangai et al. 2008 | 4 | MRI | cross sectional |
Recruited over 50 year old to participate in a health promotion program though newspapers in Japan. Those with imaging were recruitment. N = 270 (1350 discs) All participants were between 51 and 86 years. |
| Hartwig et al. 1997 | 4 | MRI | Cross sectional |
Recruited 142 participants from 35 to 50 years old that were either nurse (n = 54), construction workers (n = 51) or controls (n = 37). Unclear how controls were selected All patients were between 35 and 50 years old. |
| Hung et al. 2014 | 6 | MRI | Cross sectional |
553 workers that carry heavy loads (fruit market workers) versus walk in clinic patients (most commonly diagnosis was common cold). After that all participants were assessed using questionnaires and functional assessment for the amount of lifting load and then categorized into either low, intermediate, or high lifting loads. Participants were between 20 and 65 years old. |
| Luoma et al. 1998 | 8 | MRI | cross sectional |
Patients were extracted from a cohort participating in a study evaluating occupational effects of LBP. (n = 164, 53 drivers, 51 carpenters and 60 office workers). Participants were between 40 and 45 years old. |
| Munoz-Gomez et al. 1980 | 5 | x-ray | Cross sectional |
Workers from an industry All participants were between 19 to 63 years of age. |
| Riihimaki et al. 1990 | 6 | x-ray | cross sectional |
N = 417 Male workers. 216 concrete reinforcement workers of an specific area were included and 201 house painters from a local union. Painters were matched with concrete workers based on a 5-year strata. Participants were between 25 to 54 years of age. |
| Savage et al. 1997 | 4 | MRI | cross sectional (only 60% participated in the longitudinal cohort) |
Volunteers from different occupations. N = 149 (24 ambulance men, 16 hospital porters, 40 car production workers, 12 brewery drayman and 57 office workers). All participants were between 20 and 58 years of age and were divided in two groups 20–30 and 31 to 58 years. |
| Schenk et al. 2006 | 7 | MRI | Cross sectional - case control |
N = 109 staff of local hospital that worked at least 20 h per week. (57 nurses and 52 administration workers) All participants were between 45 and 62 years old. |
| Videman et al. 2006 | 7 | MRI | longitudinal cohort study |
Monozygotic twin pairs from the Finnish Twin Cohort selected based on smoking, exercise or occupational loading discordance. (n = 140 twins or 70 pairs). All participants were between 35 to 69 years of age. |
| Videman et al. 2007 | 7 | MRI | restrospective cohort study |
N = 600 patients from the Finnish Twin Cohort. 474 were included in the model for disc signal and 513 in the model for disc height (inclusion was dependent on availability or imaging and occupational data) All participants were between 35 to 70 years of age. |
Methodological quality was assessed using the Newcastle Ottowa Assessment Scale for case control studies or cohort studies accordingly. Scores are given in starts with a maximum (higher quality) of 9 starts