Table 4

Case-referent evaluations of data on reproduction and breast feeding in women (179 cases of RA and 259 referents) from southeastern Sweden, 1980–95, with adjustment for age

Exposed cases/referents OR4-150 95% CI4-150 95%
Menarche
 Early20/281.10.6 to 2.1
 Normal4-151 109/1631.0Reference
 Late35/331.61.0 to 2.8
Menopause
 Early15/131.60.7 to 3.7
 Normal4-152 48/631.0Reference
 Late20/151.60.7 to 3.4
Fertile period
 Short23/132.51.1 to 5.4
 Normal4-153 43/601.0Reference
 Long13/101.50.6 to 3.9
Current OC4-150use4-155 7/310.30.1 to 0.8
Other exogenous sex hormones4-154 7/160.50.2 to 1.2
Never parous32/311.0Reference
Ever parous4-160 145/2210.50.3 to 0.9
First child at age (years)4-160
 ⩽19 18/191.80.9 to 3.6
 20–29106/1801.0Reference
 ⩾30 21/221.40.7 to 2.7
Breast feeding4-164
 Never4-161 22/161.0Reference
 Ever123/2050.40.2 to 0.8
 Duration (months)
  <526/280.40.1 to 1.1
  5–1466/1080.40.2 to 0.9
  15–2419/510.30.1 to 0.7
  ⩾2512/180.40.1 to 1.3
p for trend = 0.063
  • 4-150 OC = oral contraceptive; OR = Mantel-Haenszel odds ratio; CI = confidence interval as outlined by Robins et al.36

  • 4-151 Menarche at age 13–15.

  • 4-152 Menopause at age 48–53.

  • 4-153 Fertile period of 34–40 years.

  • 4-155 At time of diagnosis of RA.

  • 4-154 Before onset of RA symptoms.

  • 4-160 Adjustment also for marital status.

  • 4-164 Adjustment also for marital status and socioeconomic status.

  • 4-161 Parous women having never breast fed.