Table 1

Baseline characteristics of the study population after exclusion of study subjects who were pensioned at baseline

PopulationCases (operated subjects)Control subjectsDifference
Total500810 148NR
Grouped by sex
 Female (percent within group)3921 (78.3)7974 (78.6)NS
 Male (percent within group)1087 (21.7)2174 (21.4)
Grouped by age group
 (18–30) years (percent within group)943 (18.8)1785 (17.6)p=0.048
 (30–40) years (percent within group)1900 (37.9)3765 (37.1)
 (40–50) years (percent within group)1553 (31.0)3239 (31.9)
 (50–60) years (percent within group)612 (12.2)1359 (13.4)
Grouped by education
 Short education or unskilled (percent of group)1673 (36.4)2247 (23.9)p<1−10
 Craftsmen or office (percent of group)1084 (23.6)2513 (26.8)
 Bachelor or master degree (percent of group)677 (14.7)2345 (25.0)
 Interdisciplinary (percent of group)1163 (25.3)2279 (24.3)
  • The study population is grouped by sex, age group and vocational education.

  • NR, not relevant; NS, not significant.