Table 2 Hazard ratios (HR) and 95% confidence intervals (CI) for the association between reproductive factors and the risk of lung cancer among postmenopausal women.

From: Female reproductive factors and the risk of lung cancer in postmenopausal women: a nationwide cohort study

 

Case no.

Duration (person-years)

IR per 100 000 person-years

HR (95% CI)

Model 1 (age-adjusted)

Model 2 (multivariablea)

Model 2 (multivariableb)

Age at menarche

 ≤14 y

1925

2,958,968.8

65.1

1 (ref.)

1 (ref.)

 

 15–16 y

6173

2,718,665.8

78.7

1.02 (0.97–1.07)

1.02 (0.97–1.08)

 

 17 y

3365

7,840,631.0

87.4

0.98 (0.93–1.04)

0.99 (0.93–1.05)

 

 ≥18 y

5093

9,111,375.6

96.8

1.03 (0.97–1.08)

1.03 (0.98–1.09)

 

Age at menopause

 <40 y

354

332,191.7

106.6

1 (ref.)

1 (ref.)

 

 40–44 y

1084

1,077,353.8

100.6

0.98 (0.87–1.11)

0.99 (0.88–1.12)

 

 45–49 y

4266

5,248,111.7

81.3

0.93 (0.83–1.03)

0.95 (0.85–1.06)

 

 50–54 y

8745

10,955,113.3

79.8

0.93 (0.84–1.04)

0.96 (0.87–1.07)

 

 ≥55 y

2107

2,298,204.9

91.7

0.98 (0.88–1.10)

1.02 (0.91–1.14)

 

Reproductive period

 <30 y

2615

2,578,602.2

101.4

1 (ref.)

 

1 (ref.)

 30–34 y

6775

7,951,785.0

85.2

0.97 (0.93–1.02)

 

0.98 (0.94–1.03)

 35–39 y

5879

7,911,853.1

74.3

0.97 (0.93–1.02)

 

0.99 (0.95–1.04)

 ≥40 y

1287

1,468,735.2

87.6

1.02 (0.96–1.10)

 

1.05 (0.98–1.12)

Parity

 Nulliparous

377

466,390.6

80.8

1 (ref.)

1 (ref.)

1 (ref.)

 1 child

970

1,410,842.3

68.8

0.95 (0.85–1.07)

1.00 (0.88–1.14)

1.00 (0.88–1.14)

 ≥2 children

15,209

18,033,742.6

84.3

0.84 (0.75–0.93)

0.95 (0.84–1.06)

0.95 (0.84–1.06)

Duration of breastfeeding

 Never

1062

1,520,411.3

69.9

1 (ref.)

1 (ref.)

1 (ref.)

 <0.5 y

837

1,458,435.9

57.4

0.86 (0.79–0.94)

0.91 (0.82–1.00)

0.91 (0.82–1.00)

 0.5 to <1 y

2439

3,478,988.5

70.1

0.88 (0.82–0.94)

0.95 (0.87–1.03)

0.95 (0.88–1.03)

 ≥1 y

12,218

13,453,139.8

90.8

0.87 (0.82–0.93)

0.95 (0.88–1.02)

0.95 (0.88–1.02)

Hormone therapy

 Never used

13,824

16,255,096.0

85.0

1 (ref.)

1 (ref.)

1 (ref.)

 <2 y

1203

1,744,475.1

69.0

1.05 (0.99–1.12)

1.05 (0.99–1.11)

1.05 (0.99–1.11)

 2 to <5 y

450

675,304.8

66.6

0.98 (0.89–1.07)

0.96 (0.88–1.06)

0.96 (0.88–1.06)

 ≥5 y

433

535,470.9

80.9

1.05 (0.96–1.16)

1.04 (0.95–1.15)

1.04 (0.95–1.15)

 Missing

646

700,628.7

92.2

1.09 (1.01–1.18)

1.07 (0.98–1.16)

1.07 (0.98–1.16)

Oral contraceptive use

 Never used

13,282

16,005,619.4

83.0

1 (ref.)

1 (ref.)

1 (ref.)

 <1 y

1345

176,6051.5

76.2

0.99 (0.94–1.05)

0.99 (0.94–1.05)

0.99 (0.94–1.05)

 ≥1 y

1043

1,171,489.9

89.0

1.07 (1.01–1.14)

1.06 (0.99–1.13)

1.06 (0.99–1.13)

 Missing

886

967,814.6

91.6

1.07 (1.00–1.15)

1.05 (0.97–1.13)

1.05 (0.97–1.13)

Pack years of smoking

 Never smoker

15,223

19,118,652.5

79.6

1 (ref.)

1 (ref.)

1 (ref.)

 Former smoker & <10

152

168,394.2

90.3

1.30 (1.11–1.52)

1.27 (1.08–1.49)

1.27 (1.08–1.49)

 Former smoker & ≥10

107

44,052.2

242.9

2.65 (2.19–3.20)

2.59 (2.14–3.14)

2.59 (2.14–3.14)

 Current smoker & <10

485

376,445.3

128.8

2.03 (1.85–2.22)

1.98 (1.80–2.17)

1.98 (1.80–2.17)

 Current smoker & ≥10

589

203,431.2

289.5

3.48 (3.20–3.77)

3.40 (3.12–3.69)

3.40 (3.12–3.69)

Alcohol consumption

 None

14,660

17,293,429.6

84.8

1 (ref.)

1 (ref.)

1 (ref.)

 Mild (<30 g/d)

1816

2,525,463.6

71.9

1.13 (1.08–1.19)

1.03 (0.98–1.09)

1.03 (0.98–1.09)

 Heavy (≥30 g/d)

80

92,082.2

86.9

1.53 (1.23–1.91)

1.05 (0.84–1.31)

1.05 (0.84–1.31)

Regular physical activity

 No

10,683

11967393.3

89.3

1 (ref.)

1 (ref.)

1 (ref.)

 Yes

5873

7943582.1

73.9

0.96 (0.93–0.99)

0.97 (0.94–1.00)

0.97 (0.94–1.00)

Body mass index (kg/m2)

 <18.5

455

427,226.4

106.5

1.07 (0.97–1.17)

1.02 (0.93–1.12)

1.02 (0.93–1.12)

 18.5 to <23 kg/m2

5796

6,953,966.4

83.4

1 (ref.)

1 (ref.)

1 (ref.)

 23 to <25 kg/m2

4198

5,253,687.4

79.9

0.94 (0.90–0.98)

0.95 (0.91–0.99)

0.95 (0.91–0.99)

 25 to <30 kg/m2

5355

6,390,031.5

83.8

0.94 (0.90–0.97)

0.94 (0.91–0.98)

0.94 (0.91–0.98)

 ≥30

752

886,063.8

84.9

0.97 (0.90–1.04)

0.96 (0.88–1.03)

0.96 (0.88–1.03)

Co-morbidity

Hypertension

 No

8046

11,397,844.2

70.6

1 (ref.)

1 (ref.)

1 (ref.)

 Yes

8510

8,513,131.2

100.0

1.03 (1.00–1.07)

1.05 (1.01–1.08)

1.05 (1.01–1.08)

Diabetes mellitus

 No

13,797

17,214,825.2

80.2

1 (ref.)

1 (ref.)

1 (ref.)

 Yes

2759

2,696,150.2

102.3

1.04 (1.00–1.09)

1.04 (0.99–1.08)

1.04 (0.99–1.08)

Dyslipidaemia

 No

10,380

12,762,248.2

81.3

1 (ref.)

1 (ref.)

1 (ref.)

 Yes

6176

7,148,727.3

86.4

1.00 (0.97–1.03)

0.98 (0.95–1.02)

0.98 (0.95–1.02)

Income

 Q1 (lowest)

4488

5,481,769.8

81.9

1.04 (1.00–1.09)

1.00 (0.96–1.04)

1.00 (0.96–1.04)

 Q2

3371

4,452,819.7

75.7

0.98 (0.94–1.03)

0.96 (0.92–1.00)

0.96 (0.92–1.00)

 Q3

3994

4,749,847.9

84.1

0.98 (0.94–1.03)

0.97 (0.93–1.01)

0.97 (0.93–1.02)

 Q4 (highest)

4703

5,226,537.9

90.0

1 (ref.)

1 (ref.)

1 (ref.)

  1. IR incidence rate, HR hazard ratio, CI confidence interval.
  2. aAdjusted for age, age at menarche and menopause, parity, duration of breastfeeding, duration of HRT, duration of oral contraceptive use, alcohol consumption, smoking, regular exercise, income, BMI, hypertension, diabetes mellitus, dyslipidaemia and cancer.
  3. bAdjusted for age, reproductive period, parity, duration of breastfeeding, duration of HRT, duration of oral contraceptive use, alcohol consumption, smoking, regular exercise, income, BMI, hypertension, diabetes mellitus, dyslipidaemia and cancer.
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