Table 1 Characteristics of the study population and comparison with rest of the NFBC1966 population. Variation of N is due to missing data
Excluded (n = 4297) | Included (n = 1505) | P value for difference | |
|---|---|---|---|
% (n) / Mean (SD) | % (n) / Mean (SD) | ||
Sex | 0.003 | ||
Men | 51.0 (4458) | 46.8 (703) | |
Women | 49.0 (4286) | 53.2 (799) | |
Body Mass Index (kg/m2) | 26.9 (5.0) | 26.7 (4.6) | 0.114 |
< 25 | 38.7 (1662) | 40.9 (614) | |
25–30 | 39.6 (1701) | 38.5 (578) | |
> 30 | 21.7 (932) | 20.5 (308) | 0.294 |
Smoking | < 0.001 | ||
Non-smoker | 50.8 (2634) | 54.0 (779) | |
Former | 25.9 (1344) | 29.5 (426) | |
Current | 23.2 (1205) | 16.5 (238) | |
Education years | 0.016 | ||
< 9 | 4.2 (221) | 3.3 (48) | |
9–12 | 68.3 (3574) | 72.0 (1053) | |
> 12 | 27.5 (1441) | 24.7 (361) | |
Leisure-time physical activity (times/week) | 0.377 | ||
< 1 | 28.1 (1470) | 26.5 (384) | |
1–3 | 56.4 (2955) | 56.8 (823) | |
> 4 | 15.5 (812) | 16.6 (241) | |
Occupational physical exposure | 0.053 | ||
Low | 62.7 (3148) | 59.8 (845) | |
High | 37.3 (1875) | 40.2 (567) | |
LBP category | – | ||
Bothersome-and-frequent pain | – | 15.2 (223) | |
Mild-to-moderate pain | – | 55.8 (820) | |
No pain | – | 29.0 (427) | |
LDD sum scorea (median with IQR) | – | 4 (2–6) | – |
Normal discs (sum score = 0, Pfirrmann = II) | – | 5.0 (75) | |
At least mild degeneration (sum score ≥ 1, at least one disc Pfirrmann ≥ III) | – | 95.0 (1427) | |
Modic changes | – | ||
No | – | 33.0 (492) | |
Yes | – | 67.0 (997) | |
Disc herniations | – | ||
No disc displacement or bulge | – | 80.3 (1195) | |
Protrusion, extrusion or sequester | – | 19.7 (294) |