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Table 1 Association of reproductive factors and overall lung cancer risk (highest vs. lowest category)

From: Reproductive factors and lung cancer risk: a comprehensive systematic review and meta-analysis

Reproductive factors Highest category Lowest category (reference) No. of studies Phet a I2 value (%) OR (95% CI)b
Menstrual-related factors
 Age at menopause ≥50 to ≥55 Premenopausal or < 50 22 < 0.001 64.3 0.99 (0.88, 1.12)
 Age at menarche ≥15 to ≥18 < 11 to ≤15 20 0.032 40.4 1.03 (0.96, 1.10)
Non-natural menopause Non-natural Natural / premenopausal 11 0.013 55.3 1.52 (1.25, 1.86)
Ovariectomy yes no 5 0.487 0.0 1.38 (1.16, 1.64)
 Hysterectomy yes no 4 0.171 40.1 1.21 (0.98, 1.49)
 Ovariectomy and Hysterectomy yes no 4 0.405 0.0 1.22 (0.95, 1.58)
Menstrual cycle length > 30 days < 27 to ≤ 30 days 7 0.106 42.7 0.79 (0.65, 0.96)
Menopausal status Post-menopausal Pre-menopausal 6 0.057 53.4 1.26 (0.92, 1.73)
Length of menstrual flow (days) ≥5 to > 6 ≤3 to < 5 4 0.712 0.0 1.01 (0.84, 1.23)
Other factors
 Hormone use ever never 38 < 0.001 56.6 0.95 (0.90, 1.01)
Oral contraceptive use ever never 26 0.003 48.2 1.01 (0.94, 1.09)
 OC use duration (years) ≥2 to ≥12 0 to < 2 12 0.012 54.5 0.99 (0.87, 1.14)
Parity ≥3 to ≥ 7 0 to 2 24 < 0.001 75.4 0.83 (0.72, 0.96)
 Number of pregnancy ≥ 4 to ≥7 0 to 2 10 0.002 66.3 0.91 (0.73, 1.15)
Age at first birth ≥25 to ≥ 31 Nulliparous or < 25 19 < 0.001 62.7 0.85 (0.74, 0.98)
Reproductive period (years) ≥36 to ≥41 ≤30 to < 33 8 0.048 50.6 0.95 (0.78, 1.17)
Breastfeeding ever never 6 0.330 13.2 0.94 (0.83, 1.06)
Miscarriage ever never 4 0.063 58.9 1.20 (0.93, 1.56)
Tubal sterilization use ever never 4 0.019 69.7 1.05 (0.84, 1.33)
Intrauterine device use ever never 4 0.097 52.5 0.83 (0.66, 1.04)
  1. aHeterogeneity P-value
  2. bAdjusted odds ratio (OR) and 95% confidence interval (CI). Highest non-reference category as compared to the lowest reference group