TABLE 2.
Descriptive Statistics on Variables Used in the Study by Sex
| All | Male | Female | |
|---|---|---|---|
| 47,727 | 22,010 | 25,714 | |
| Total number | n (%) | n (%) | n (%) |
| Background information | |||
| Age during the survey | |||
| 14 y | 15,880 (33.3) | 7533 (34.2) | 8347 (32.5) |
| 16 y | 15,885 (33.3) | 7320 (33.3) | 8565 (33.3) |
| 18 y | 15,982 (33.5) | 7167 (32.6) | 8815 (34.3) |
| Age at the end of the follow-up (y) (mean; SD) | 42.7 (4.3) | 42.7 (4.3) | 42.7 (4.3) |
| Family SES at age 15 | |||
| Both upper white-collar | 7775 (16.3) | 3677 (16.7) | 5776 (22.5) |
| Either one upper white-collar | 11,899 (24.9) | 5456 (24.8) | 1319 (5.1) |
| Either one lower white-collar | 15,184 (31.8) | 7093 (32.2) | 8091 (31.5) |
| Either on blue-collar | 10,423 (21.8 | 4647 (21.1) | 4098 (16.0) |
| Both unknown | 2466 (5.2) | 1147 (5.2) | 6443 (25.1) |
| Explanatory variables | |||
| Smoking in adolescence | 11,564 (24.2) | 5690 (25.9) | 5874 (22.8) |
| Drunk once or more a month | 9048 (19.0) | 4892 (22.2) | 4156 (16.2) |
| Physical activity in adolescence | |||
| High | 11,315 (23.7) | 5588 (25.3) | 5727 (22.3) |
| Medium | 13,467 (28.2) | 6324 (28.7) | 7143 (27.8) |
| Low | 22,280 (46.7) | 9681 (44.0) | 12,599 (49.0) |
| Unknown | 662 (1.4) | 417 (1.9) | 245 (1.0) |
| High BMI in adolescence | 4839 (10.1) | 2838 (12.9) | 2001 (7.8) |
| Chronic diseases in adolescence | 4222 (8.8) | 1819 (8.2) | 2403 (9.3) |
| Outcome variables in adulthood | |||
| Low back pain hospitalizations | 5538 (11.6) | 2524 (11.5) | 3014 (11.7) |
| LDH hospitalizations | 2104 (4.4) | 1084 (4.9) | 1020 (4.0) |
| Spine surgeries | 913 (1.9) | 490 (2.2) | 423 (1.6) |
BMI indicates body mass index; LDH, lumbar disc herniation; SES, socioeconomic status.