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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)