Country
| Finland | Finland | Sweden | Canada | USA | Denmark |
Design
| Cross sectional + follow up | Cross sect. + follow up | Cross sectional | Longitudinal (8 yrs) | Longitudinal (3 m/3 yrs) | Cross sectional + follow up |
Study sample
| Pupils from 19 primary schools | Population register. All Finns born on adjacent dates in summer | Randomized cluster sample of pupils | Non-institutionalized civilian population | Girls/boys initially 11 yrs randomly selected in GH database | Primary/secondary school. 38 state schools in one municipality |
Response rate
| 83% | 77% | 97% | ? | 49% | 62%, 57%, 58% |
Valid sample size
| 1756 | 62677 | 1121 | 2488 | 1333 | 479, 439, 443 |
Data collection
| Questionnaire | Questionnaire | Questionnaire | Computer ass. Interview + Questionnaire | Telephone survey + Questionnaire | Interview + Questionnaire |
Age group
| 9, 12 (mean: 9.8, 11.8) | 12,14,16,18 (mean: 12.6, 14.6, 16.6, 18.6) | 6-13 | 10-18 | 11-14 | 9,13,15 (mean: 9.7, 13.1, 15.7) |
Definition of back pain
| Pain/ache in neck, upper back (UB), low back (LBP) | Back or neck pain the past half a year | Backache last 6 months | Backache past 6 months | Back pain a whole day or more in the past 3 months | Any spinal pain: |
Recall period
| 3 months | 6 months | 6 months | 6 months | 3 months | 1 month |
Prevalence estimates never/seldom
| BP (UB, LBP) | BP + NP (12y) | BP (6-13y) | BP (12-13y) | BP (11-14y) 78% | BP (9y, 13y, 15y) 67% |
Overall: monthly
| | | | | | 33%, 28%, 48% |
Frequency
| Weekly | Weekly | ≥ 1 Weekly: | Weekly | Low/high | |
Once
| | | | | 10% (low prob.) | |
Several/frequently/continually
| 12.7% (Only mentioned in the discussion section) | Girls: 6-16% Boys: 4-10% | Grade 0: 2% Grade 1: 3% Grade 2: 3% Grade 3: 6% Grade 4: 7.5% Grade 5: 14% Grade 6: 17% | 17.6% | 1,3% (high prob.) | |