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) |