Table 2.
Adjusted HRs and 95% CIs for cardiovascular disease mortality in relation to reproductive history among non-smoking female textile workers in Shanghai, China (1989–2000)
| Ischaemic heart disease |
Ischaemic stroke |
Haemorrhagic stroke |
||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Reproductive characteristic | Person- years at risk | Numbera | HR (95% CI) | P trend | Numbera | HR (95% CI) | P trend | Numbera | HR (95% CI) | P trend |
| Number of livebirthsb,c,d | ||||||||||
| 0 | 120 932 | 22 | 1.17 (0.66–2.10) | 0.20 | 37 | 1.15 (0.72–1.82) | 0.01 | 87 | 1.31 (0.98–1.76) | 0.05 |
| 1 | 1 193 771 | 33 | 1.00 (referent) | 45 | 1.00 (referent) | 133 | 1.00 (referent) | |||
| 2 | 412 279 | 67 | 0.98 (0.62–1.57) | 69 | 0.70 (0.46–1.04) | 278 | 1.07 (0.84–1.35) | |||
| 3 | 319 960 | 100 | 0.99 (0.62–1.57) | 124 | 0.78 (0.53–1.15) | 385 | 1.03 (0.82–1.31) | |||
| 4 | 230 629 | 89 | 0.97 (0.60–1.55) | 121 | 0.78 (0.53–1.15) | 349 | 1.07 (0.84–1.36) | |||
| ≥5 | 211 391 | 131 | 1.23 (0.78–1.95) | 216 | 1.10 (0.76–1.59) | 438 | 1.22 (0.96–1.55) | |||
| Age at first livebirth (years)b,c | ||||||||||
| ≤19 | 110 194 | 43 | 0.93 (0.67–1.28) | 0.11 | 75 | 1.23 (0.96–1.59) | 0.06 | 178 | 1.09 (0.92–1.28) | 0.0002 |
| 20–24 | 676 422 | 239 | 1.00 (referent) | 309 | 1.00 (referent) | 850 | 1.00 (referent) | |||
| 25–29 | 1 160 345 | 101 | 0.75 (0.59–0.95) | 141 | 0.88 (0.72–1.07) | 423 | 0.84 (0.74–0.94) | |||
| ≥30 | 421 047 | 37 | 0.85 (0.60–1.20) | 50 | 0.95 (0.71–1.29) | 132 | 0.81 (0.67–0.97) | |||
| First pregnancy outcomec,e | ||||||||||
| Livebirth | 2 191 094 | 394 | 1.00 (referent) | 554 | 1.00 (referent) | 1496 | 1.00 (referent) | |||
| Spontaneous abortion | 124 332 | 22 | 1.23 (0.78–1.94) | 15 | 0.58 (0.33–1.01) | 61 | 0.90 (0.68–1.17) | |||
| Stillbirth | 27 523 | 6 | 0.89 (0.40–2.01) | 8 | 0.80 (0.40–1.61) | 29 | 1.17 (0.81–1.69) | |||
| Induced abortion | 38 767 | 1 | 0.61 (0.08–4.44) | 2 | 0.94 (0.22–3.97) | 7 | 1.04 (0.49–2.22) | |||
| Other | 3094 | 2 | 2.04 (0.45–9.26) | 0 | – | 3 | 0.86 (0.26–2.82) | |||
| History of stillbirthc,f | ||||||||||
| No | 2 321 098 | 408 | 1.00 (referent) | 0.78 | 550 | 1.00 (referent) | 0.25 | 1517 | 1.00 (referent) | 0.34 |
| Single | 55 934 | 13 | 0.76 (0.43–1.31) | 21 | 0.86 (0.55–1.33) | 68 | 1.09 (0.86–1.40) | |||
| Multiple | 7744 | 4 | 1.02 (0.38–2.73) | 8 | 1.36 (0.68–2.75) | 11 | 0.80 (0.44–1.44) | |||
| History of spontaneous abortionc,f | ||||||||||
| No | 2 092 348 | 350 | 1.00 (referent) | 0.16 | 482 | 1.00 (referent) | 0.90 | 1303 | 1.00 (referent) | 0.69 |
| Single | 233 896 | 51 | 0.88 (0.66–1.19) | 72 | 0.87 (0.68–1.12) | 224 | 1.06 (0.92–1.22) | |||
| Multiple | 58 565 | 24 | 1.27 (0.84–1.92) | 25 | 0.90 (0.60–1.35) | 69 | 1.01 (0.80–1.29) | |||
| History of induced abortionc,f | ||||||||||
| No | 1 114 138 | 270 | 1.00 (referent) | 0.14 | 385 | 1.00 (referent) | 0.52 | 1009 | 1.00 (referent) | 0.04 |
| Single | 889 671 | 120 | 1.00 (0.80–1.24) | 138 | 0.86 (0.71–1.05) | 400 | 0.86 (0.76–0.96) | |||
| Multiple | 381 000 | 35 | 0.76 (0.53–1.08) | 56 | 0.96 (0.72–1.27) | 187 | 1.03 (0.88–1.20) | |||
| Breastfeeding history (months)c,e,g | ||||||||||
| Never (with livebirth) | 368 108 | 54 | 1.00 (referent) | 0.23 | 47 | 1.00 (referent) | 0.08 | 143 | 1.00 (referent) | 0.35 |
| <6 | 340 530 | 21 | 0.70 (0.42–1.16) | 25 | 1.02 (0.63–1.66) | 69 | 0.84 (0.63–1.12) | |||
| 7–12 | 702 203 | 37 | 0.50 (0.33–0.76) | 64 | 1.05 (0.72–1.54) | 198 | 0.98 (0.79–1.22) | |||
| 13–24 | 372 338 | 74 | 0.67 (0.46–0.97) | 76 | 0.90 (0.62–1.31) | 302 | 1.01 (0.82–1.24) | |||
| 25–36 | 234 664 | 60 | 0.53 (0.36–0.79) | 98 | 1.15 (0.79–1.67) | 257 | 0.88 (0.71–1.09) | |||
| 37–48 | 155 294 | 61 | 0.71 (0.48–1.06) | 88 | 1.21 (0.83–1.77) | 234 | 1.02 (0.82–1.28) | |||
| ≥49 | 194 892 | 113 | 0.78 (0.53–1.14) | 177 | 1.20 (0.84–1.72) | 380 | 1.05 (0.84–1.30) | |||
| Age at menarche (years)c,h | ||||||||||
| ≤13 | 256 455 | 47 | 1.44 (1.00–2.05) | 0.007 | 50 | 1.05 (0.75–1.45) | 0.49 | 130 | 0.97 (0.79–1.19) | 0.06 |
| 14 | 459 130 | 63 | 1.06 (0.76–1.47) | 71 | 0.82 (0.61–1.09) | 251 | 1.03 (0.88–1.22) | |||
| 15 | 556 680 | 83 | 1.00 (referent) | 123 | 1.00 (referent) | 336 | 1.00 (referent) | |||
| 16 | 531 148 | 107 | 1.09 (0.82–1.45) | 143 | 0.97 (0.76–1.23) | 361 | 0.92 (0.79–1.07) | |||
| ≥17 | 684 948 | 142 | 0.85 (0.65–1.12) | 225 | 0.87 (0.70–1.09) | 592 | 0.90 (0.79–1.03) | |||
| Age at natural menopause (years)c,h | ||||||||||
| <40 | 16 029 | 7 | 1.10 (0.52–2.34) | 0.48 | 13 | 1.18 (0.68–2.05) | 0.31 | 30 | 1.21 (0.84–1.75) | 0.55 |
| 40–44 | 46 200 | 20 | 1.12 (0.70–1.77) | 24 | 0.78 (0.52–1.19) | 63 | 0.90 (0.69–1.16) | |||
| 45–49 | 347 760 | 156 | 1.18 (0.95–1.46) | 182 | 0.82 (0.68–0.99) | 524 | 1.00 (0.89–1.12) | |||
| 50–54 | 450 359 | 175 | 1.00 (referent) | 295 | 1.00 (referent) | 691 | 1.00 (referent) | |||
| ≥55 | 44 349 | 23 | 1.24 (0.81–1.92) | 26 | 0.83 (0.55–1.23) | 85 | 1.17 (0.94–1.47) | |||
| Cause of menopausec,d | ||||||||||
| Pre-menopausal | 1 479 020 | 32 | 1.00 (referent) | 25 | 1.00 (referent) | 157 | 1.00 (referent) | |||
| Natural | 906 697 | 381 | 1.35 (0.73–2.50) | 542 | 1.97 (0.99–3.93) | 1397 | 1.14 (0.86–1.51) | |||
| Surgical | 101 652 | 27 | 1.23 (0.61–2.48) | 44 | 2.08 (1.00–4.33) | 113 | 1.18 (0.85–1.63) | |||
aNumber of mortalities.
bTrend includes only women who have had one or more livebirths.
cAdjusted for age.
dAdjusted for age-squared.
eAdjusted for number of livebirths.
fTrend from single to multiple outcome.
gTrend includes only women who have breastfed.
hTrend includes women in all age categories.