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Table 1 Comparison of demographic and reproductive factors by birth year in Chinese women

From: Incidence of breast cancer in Chinese women exposed to the 1959–1961 great Chinese famine

 

Birth year

p value

1955–1958 (N = 25,836)

1959–1962 (N = 17,772)

1963–1966 (N = 15,452)

Participant rates (%)

68.7

61.2

54.6

 

Age (Mean ± SD)

52.7 ± 1.9

49.1 ± 1.9

45.2 ± 1.8

<0.0001

Educational level (N, %)

 Primary school or below

5448 (21.1)

2307 (13.0)

1521 (9.8)

 

 Junior high School

11,926 (46.2)

8669 (48.8)

9466 (61.3)

 

 Senior high school

637 (2.5)

511 (2.9)

3336 (21.6)

 

 Technical school

7334 (28.4)

5905 (33.2)

693 (4.5)

 

 College or above

491 (1.9)

380 (2.1)

436 (2.8)

<0.0001

Marriage status (N, %)

 Single

80 (0.3)

52 (0.3)

32 (0.2)

 

 Married

25,070 (97.0)

17,279 (97.2)

15,052 (97.4)

 

 Remarried

351 (1.4)

243 (1.4)

226 (1.5)

 

 Separate/divorced

163 (0.6)

119 (0.7)

111 (0.7)

 

 Widow

172 (0.7)

79 (0.4)

31 (0.2)

0.0005

Age at menarche <12 years (N, %)

66 (0.3)

50 (0.3)

46 (0.3)

0.41

Irregular cycle (N, %)

7040 (27.3)

3374 (19.0)

2488 (16.1)

<0.0001

Age at menopause ≥55 years (N, %)

96 (0.37)

32 (0.18)

12 (0.08)

<0.0001

Infertility (N, %)

446 (1.7)

282 (1.6)

241 (1.6)

0.17

Age at first birth >35 years (N, %)

122 (0.5)

90 (0.5)

42 (0.5)

0.86

Breastfeeding (N, %)

19,311 (74.7)

14,780 (83.2)

13,241 (85.7)

<0.0001

Estrogen use (N, %)

405 (1.6)

219 (1.2)

223 (1.4)

0.16

Family history of breast cancer (N, %)

297 (1.2)

136 (0.8)

101 (0.7)

<0.0001