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Table 1 Distributions of participants’ characteristics and their corresponding hazard ratio for breast cancer among women, the Singapore Chinese Health Study

From: Association between prediagnostic leukocyte telomere length and breast cancer risk: the Singapore Chinese Health Study

Characteristics

Non-cancer cases, N (%)

Breast cancer cases, N (%)

HR1 (95% CI)

P 1

Body mass index§, kg/m2

 < 18.5

992 (7.2)

24 (5.4)

1.00 (ref)

0.002

 18.5 to < 23.0

5700 (41.1)

159 (36.0)

1.09 (0.71, 1.68)

 23.0 to < 27.5

5521 (39.8)

195 (44.1)

1.43 (0.93, 2.18)

 ≥ 27.5

1650 (11.9)

64 (14.5)

1.56 (0.97, 2.49)

Level of education

 

 No formal education

4471 (32.3)

109 (24.7)

1.00 (ref)

0.013

 Primary school

5840 (42.1)

194 (43.9)

1.24 (0.97, 1.58)

 Secondary school and above

3552 (25.6)

139 (31.5)

1.42 (1.08, 1.86)

Alcohol consumption§ (drinks/week)

 

 None

12,403 (89.5)

385 (87.1)

1.00 (ref)

0.15

 < 7

1283 (9.3)

48 (10.9)

1.14 (0.84, 1.53)

 ≥ 7

177 (1.3)

9 (2.0)

1.57 (0.81, 3.05)

Physical activity (weekly)

 No

10,103 (72.9)

318 (72.0)

1.00 (ref)

0.91

 Yes

3760 (27.1)

124 (28.1)

1.01 (0.82, 1.25)

Smoking status§

 Never

12,639 (91.2)

414 (93.7)

1.00 (ref)

0.39

 Former/current

1224 (8.8)

28 (6.3)

0.84 (0.57, 1.24)

Age when period became regular§

 < 13

1918 (13.8)

70 (15.8)

1.61 (1.09, 2.38)

0.016

 13–14

4977 (35.9)

175 (39.6)

1.61 (1.14, 2.26)

 15–16

4435 (31.9)

143 (32.4)

1.53 (1.08, 2.16)

 ≥ 17

2045 (14.8)

42 (9.5)

1.00 (ref)

 Never regular

488 (3.5)

12 (2.7)

1.13 (0.59, 2.15)

Age at first live birth

 < 20.0

2363 (17.1)

57 (12.9)

1.00 (ref)

0.005

 21.0–25.0

5195 (37.5)

162 (36.7)

1.19 (0.88, 1.61)

 26.0–30.0

3840 (27.7)

122 (27.6)

1.15 (0.84, 1.59)

 ≥ 31

1475 (10.6)

51 (11.5)

1.27 (0.86, 1.86)

 Nulliparous

990 (7.1)

50 (11.3)

1.90 (1.29, 2.80)

Number of live births

 0

977 (7.1)

50 (11.3)

1.00 (ref)

0.0002

 1–2

4213 (30.4)

159 (36.0)

0.70 (0.51, 0.97)

 3–4

5591 (40.3)

157 (35.5)

0.54 (0.39, 0.74)

 ≥ 5

3082 (22.2)

76 (17.2)

0.54 (0.37, 0.79)

Age at menopause§

 ≤ 49

2371 (17.1)

54 (12.2)

1.00 (ref)

0.05

 50–54

3284 (23.7)

92 (20.8)

1.21 (0.86, 1.69)

 ≥ 55

8208 (59.2)

296 (67.0)

1.43 (1.00, 2.05)

Family history of breast cancer

 No

13,631 (98.3)

434 (98.2)

1.00 (ref)

0.96

 Yes

232 (1.7)

8 (1.8)

1.02 (0.51, 2.05)

Use of hormone therapy§

 Never

11,543 (83.3)

347 (78.5)

1.00 (ref)

0.10

 Ever

1540 (11.1)

62 (14.0)

1.26 (0.96, 1.65)

 Current

780 (5.6)

33 (7.5)

1.21 (0.84, 1.74)

Use of oral contraceptive

 Never

9586 (69.2)

302 (68.3)

1.00 (ref)

0.70

 Former/current

4277 (30.9)

140 (31.7)

0.98 (0.78, 1.18)

Sleeping hours

 ≤ 6 h

4737 (34.2)

134 (30.3)

0.84 (0.69, 1.04)

0.48

 7–8 h

8218 (59.3)

285 (64.5)

1.00 (ref)

 ≥ 8 h

908 (6.6)

23 (5.2)

0.75 (0.49, 1.15)

  1. Values are presented as frequency (%) or mean (SD). Percentages may not add up to 100% due to rounding
  2. CI confidence intervals, HR hazard ratio
  3. §Updated with data from the first follow-up interview
  4. 1Hazard ratios and P values for linear trend were derived from the Cox proportional hazard regression models that also included age at blood collection and dialect (Hokkien or Cantonese)