Table 1

Sample description for the cases and controls

Cases (n = 240)Controls (n = 285)P
Diagnosis categories for controls
  Traumatism (fractures, pounds, burns, …)151
  Osteo-articular diseases (arthritis, osteomyelitis, …)100
  Digestive, urinary and genital symptoms17
  Minor congenital disorders6
  Others11
Stratification variables
 Gendernsa
  Male166168
 Age (yrs)0.01
  <23351
  2–38451
  4–68379
  7–104163
  ≥113841
 Hospitalns
  Lille3826
  Lyon3635
  Nancy2321
  Paris182203
 Ethnic originns
  Caucasian243236
  North African1523
  Caribbean45
  African26
  Asian, Middle Eastern26
  Mixed, others139
Sociodemographic characteristics
 Maternal educationns
  ≤High school189176
  >High school90108
 Paternal educationns
  ≤High school181171
  >High school8799
 Socioprofessional categoriesns
  Professional, technical workers, administrators, and managers147160
  Clerical, sales, and services workers5549
  Factory and agricultural workers7776
Familial characteristics (means ± SD)
 Mean no. of family members
  First-degree3.3 (±1.1)3.2 (±1.0)ns
  Second-degree9.7 (±3.9)9.2 (±3.3)ns
  First- and second-degree12.9 (±4.3)12.4 (±3.6)ns
 Average age of the first-degree relatives (yrs)
  Parents30.0 (±5.4)30.2 (±5.5)ns
  Siblings8.7 (±6.0)8.9 (±5.8)ns
 Average age of the second-degree relatives (yrs)
  Grandparents58.3 (±9.0)58.4 (±9.4)ns
  Aunts and uncles29.9 (±9.5)29.5 (±9.7)ns
  • a ns, P > 0.05.