Table 2
Summary of bidirectional variables
| Variable | Number of studies | Number of studies: Increased risk | Number of studies: Decreased risk | Number of studies not significant | Strength of association (95% CI) |
|---|---|---|---|---|---|
| Physical activity/work | 10 | 6 | 0 | 4 | Playing sport OR 9.5 (1.9, 48.2) [11] White collar work OR 4.9 (1.7, 14.2) [13] Vigorous intensity physical activity: OR 1.2 (1.0–1.4) (diagnostic spinal pain) OR 1.3 (1.0–1.5) (traumatic) [15] High level sports activity RR 1.6 (1.1, 2.3) [24], Part-time work RR 1.5 (1.1, 2.1) [24] Provoked by manual work: OR 9.2 (2.9, 28.8) [33] Increased physical activity OR 1.9 (1.2, 2.8) [34] |
| Psychological factors | 7 | 4 | 0 | 3 | High level of peer problems: RR 2.3 (1.3, 4.2) [23] High level of psychological factors: RR 1.6 (1.1, 2.3) [24] Externalising behaviour: RR 1.5 (1.3, 1.7) (boys), RR 1.4 (1.3, 1.5) (girls), RR 3.6 (1.5, 8.5) (girls 18) [28] High levels of aggressive behaviour OR 1.4 (1.2, 1.6) [34] High level of somatic complaints OR 1.3 (1.1, 1.5) [34] |
| Higher BMI | 8 | 3 | 0 | 5 | OR 1.3 (1.0, 1.5) [11] RR 1.1 (1.0, 1.2) (girls), RR 1.1 (1.0, 1.3) (boys) [29] OR 2.9 (1.7, 5.1) (9 yr), 2.2 (1.4, 3.5) (10 yr), 1.6 (1.2, 2.1) (13 yr) [32] |
| Smoking | 6 | 6 | 0 | 0 | OR 2.2 (1.4, 3.5) [4] OR 2.4 (1.3, 6.0) [14] OR 3.1 (1.1, 9.2) (MB), 1.8 (1.2, 2.8) (BP) [17] OR 1.7 (1.4, 2.1) [19] HR 1.6 (1.4, 1.9) [27] OR 2.5 (1.4, 4.5) (females) [30] |
| Illness | 4 | 3 | 0 | 1 | Asthma OR 1.4 (1.1, 1.7) (female) [20] Headache OR 1.6 (1.1, 2.1) (female), OR 2.4 (1.2, 4.7) (male) [20] Abdominal pain RR 1.8 (1.1, 3.0) [24] Headache OR 2.4 (1.8, 3.1) [26] |
| Posture/sitting position | 4 | 4 | 0 | 0 | No LB support: OR 1.7 (1.2, 2.6), OR 2.9 (1.1, 3.5) (persistent LBP) [25] Provoked by sitting OR 3.8 (1.3, 11.3) [33] Non-neutral standing posture OR 2.2 (1.3, 3.6) [34] Uncomfortable school desk OR 6.0 (3.7, 9.7) [35] |
| Insufficient sleep | 3 | 3 | 0 | 0 | OR 2.9 (1.7, 5.2) (girls), OR 2.4 (1.3, 4.5)(boys) [10] OR 2.2 (1.7, 3.8) [35] OR 1.2 (1.1, 1.4) [36] |
| Flexibility | 3 | 2 | 0 | 1 | Decreased flexibility: hamstrings OR 1.1 (1.0, 1.1) [4] Decreased flexibility: quad muscles: OR 1.7 (1.1, 2.8) [25] |
| Screen time | 3 | 1 | 0 | 2 | Increased TV time OR 2.0 (1.4, 2.9) [35] |
| Backpack factors | 3 | 1 | 0 | 2 | Heavy school satchel OR 2.2 (1.0, 4.8) [36] |
| Muscle endurance | 1 | 1 | 0 | 0 | Poor back muscle endurance OR 1.9 (1.2, 3.0) [34] |