Table 2.
Hazard ratios (HR) for reproductive history reported at baseline and lung cancer risk in a cohort of female textile workers, 1989–2000
| Reproductive Factor | Person-years at risk |
Cases (N=824) |
HRa | 95% CI |
|---|---|---|---|---|
| Pregnancy | ||||
| Never | 104,010 | 42 | 1.00 | referent |
| Ever | 2,373,840 | 782 | 0.77 | (0.56–1.05) |
| Number of Pregnancies | ||||
| 1 | 426,541 | 62 | 1.08 | (0.72–1.61) |
| 2 | 636,989 | 85 | 0.70 | (0.48–1.02) |
| 3 | 481,407 | 149 | 0.80 | (0.56–1.12) |
| 4 | 362,584 | 174 | 0.78 | (0.55–1.09) |
| ≥5 | 466,268 | 312 | 0.73 | (0.53–1.01) |
| p trend* | 0.17 | |||
| Live Birth History | ||||
| 0 (never pregnant or past pregnancy, no live birth) | 121,123 | 50 | 1.00 | referent |
| 1 | 1,160,760 | 112 | 0.88 | (0.61–1.28) |
| 2 | 407,151 | 130 | 0.72 | (0.52–1.01) |
| 3 | 324,115 | 201 | 0.80 | (0.59–1.10) |
| 4 | 238,347 | 156 | 0.71 | (0.51–0.98) |
| ≥5 | 226,343 | 175 | 0.70 | (0.51–0.95) |
| p trend* | 0.15 | |||
| Age at First Live Birth (years)a,b | ||||
| <19 | 118,183 | 80 | 1.03 | (0.80–1.31) |
| 20–24 | 691,690 | 387 | 1.00 | referent |
| 25–29 | 1,135,467 | 230 | 0.92 | (0.77–1.10) |
| 30+ | 411,355 | 77 | 0.91 | (0.69–1.20) |
| p trend | 0.29 | |||
| Duration of Breastfeeding (months)a,b | ||||
| Never (with live birth) | 360,434 | 69 | 1.00 | referent |
| <6 | 331,819 | 42 | 0.96 | (0.65–1.41) |
| 7–12 | 686,130 | 119 | 1.13 | (0.84–1.52) |
| 13–24 | 369,764 | 143 | 1.12 | (0.83–1.52) |
| 25–36 | 238,511 | 153 | 1.21 | (0.892013;1.65) |
| 37–48 | 160,534 | 109 | 1.11 | (0.80–1.55) |
| ≥49 | 209,525 | 139 | 0.87 | (0.62–1.21) |
| p trend* | 0.18 | |||
| IUD | ||||
| Never | 1,299,050 | 675 | 1.00 | referent |
| Ever | 1,178,779 | 149 | 1.01 | (0.81–1.24) |
| Tubal Ligation | ||||
| Never | 2,023,403 | 582 | 1.00 | referent |
| Ever | 454,458 | 242 | 0.83 | (0.72–0.97) |
| Age at Menarche (years) | ||||
| ≤13 | 254,133 | 60 | 1.00 | referent |
| 14 | 453,581 | 107 | 1.00 | (0.73–1.38) |
| 15 | 550,942 | 142 | 0.98 | (0.73–1.33) |
| 16 | 529,477 | 204 | 1.22 | (0.92–1.63) |
| ≥17 | 689,107 | 311 | 1.16 | (0.88–1.53) |
| p trend | 0.06 | |||
| Reproductive window (years) | ||||
| ≤30 | 195,349 | 123 | 1.00 | referent |
| 31–33 | 292,332 | 206 | 1.13 | (0.90–1.41) |
| 34–36 | 221,336 | 153 | 1.12 | (0.88–1.42) |
| ≥37 | 185,166 | 126 | 1.08 | (0.84–1.39) |
| p trend | 0.37 | |||
| Cause of Menopause | ||||
| Premenopausal | 1,456,443 | 121 | 1.00 | referent |
| Natural | 952,215 | 655 | 1.35 | (0.84–2.18) |
| Surgical | 67,402 | 48 | 1.64 | (0.96–2.79) |
| Age at Menopause (years) | ||||
| ≤48 | 385,073 | 235 | 1.00 | referent |
| 49–51 | 399,116 | 298 | 1.22 | (1.03–1.46) |
| ≥52 | 233,042 | 169 | 1.16 | (0.95–1.42) |
| p trend | 0.10 | |||
| Hysterectomy c | ||||
| Never | 947,255 | 649 | 1.00 | referent |
| Ever | 72,298 | 54 | 1.21 | (0.91–1.61) |
| Oophorectomyc | ||||
| Never | 954,705 | 652 | 1.00 | referent |
| Ever | 56,362 | 45 | 1.27 | (0.93–1.72) |
| Unilateral | 20,803 | 13 | 1.10 | (0.63–1.92) |
| Bilateral | 35,558 | 32 | 1.35 | (0.95–1.93) |
| Reproductive Surgical Procedurec,d | ||||
| None | 935,048 | 640 | 1.00 | referent |
| Hysterectomy only | 19,639 | 12 | 1.03 | (0.57–1.83) |
| Oophorectomy only | 10,290 | 8 | 1.14 | (0.57–2.30) |
| Hysterectomy and oophorectomy | 46,062 | 37 | 1.30 | (0.93–1.82) |
| Hysterectomy and unilateral oophorectomy | 13,405 | 7 | 1.02 | (0.47–2.18) |
| Hysterectomy and bilateral oophorectomy | 32,656 | 30 | 1.39 | (0.96–2.00) |
a
Adjusted for age (using linear splines with knots at 5 year periods) and smoking (ever/never)
b
Adjusted for parity
c
Postmenopausal women only
d
Excluded subjects missing information for one procedure or for unknown number of ovaries removed
*
Trend does not include referent group