Table 2.

Adjusted relative risks and 95% confidence intervals for associations between selected menstrual, hormonal and reproductive factors and risk of bladder cancer in the CTS

CharacteristicsAll womenNever smokersEver smokers
Total (N = 120,857)Cases (n = 196RR (95% CI)aTotal (N = 79,886)Cases (n = 82)RR (95% CI)bTotal (N = 40,971)Cases (n = 115)RR (95% CI)b
Pregnancy
 Never24,459481.0 (ref)17,026221.0 (ref)7,433261.0 (ref)
 Ever94,9441410.60 (0.43–0.83)61,927580.53 (0.32–0.87)33,017830.65 (0.42–1.01)
 Unknown or missing1,454793325215
Parityc
 Nulliparous31,511521.0 (ref)21,179231.0 (ref)10,332291.0 (ref)
 Parous87,7351370.69 (0.50–0.95)57,636570.61 (0.37–1.00)30,099800.76 (0.49–1.16)
 Unknown or missing1,61171,07125405
Age at first full-term pregnancyd
 <204,49150.78 (0.31–1.95)2,71541.77 (0.61–5.21)1,77610.24 (0.03–1.78)
 20–2534,828621.0 (ref)22,098211.0 (ref)12,730411.0 (ref)
 26–3032,603511.10 (0.76–1.62)22,213221.22 (0.66–2.25)10,390291.04 (0.64–1.68)
 >3014,992191.00 (0.59–1.71)10,030101.30 (0.58–2.82)4,96290.86 (0.41–1.80)
 Unknown or missing2,43271,65127815
Ptrend = 0.56Ptrend = 0.92Ptrend = 0.49
Total number of full-term pregnanciesd
 118,610241.0 (ref)12,141111.0 (ref)6,469131.0 (ref)
 238,878601.14 (0.71–1.86)25,808250.98 (0.49–2.00)13,070351.28 (0.68–2.43)
 319,235270.73 (0.42–1.27)12,49190.52 (0.22–1.26)6,744180.91 (0.44–1.89)
 4+10,193261.06 (0.61–1.87)6,617121.04 (0.46–2.56)3,576141.06 (0.49–2.30)
 Unknown or missing2,43071,65027805
Ptrend = 0.60Ptrend = 0.68Ptrend = 0.73
Breast-feedingd
 Never breast-fed19,684461.0 (ref)11,622191.0 (ref)8,062271.0 (ref)
 Ever breast-fed67,003910.93 (0.64–1.33)45,311380.79 (0.45–1.37)21,692531.05 (0.66–1.67)
 Unknown or missing2,65971,77428855
Age at menarche
 <1226,959411.0 (ref)17,878221.0 (ref)9,081191.0 (ref)
 1232,606551.08 (0.72–1.62)21,503190.68 (0.37–1.27)11,103361.51 (0.87–2.64)
 1335,116520.91 (0.60–1.38)23,263210.67 (0.37–1.22)11,853311.16 (0.65–2.06)
 14+24,432410.94 (0.61–1.46)16,107170.71 (0.37–1.35)8,325241.18 (0.64–2.16)
 Unknown or missing1,74471,13536094
Ptrend = 0.62Ptrend = 0.42Ptrend = 0.98
OC use
 Never user38,4081071.0 (ref)25,463481.0 (ref)12,945591.0 (ref)
 Ever user78,890791.05 (0.73–1.50)52,018290.92 (0.51–1.67)26,872501.09 (0.70–1.69)
 Unknown or missing3,559102,40551,1545
Menopausal status
 Pre- or perimenopausal50,226151.0 (ref)37,989101.0 (ref)12,23751.0 (ref)
 Postmenopausal, natural35,0451001.02 (0.48–2.19)20,202350.71 (0.25–2.04)14,843651.49 (0.46–4.82)
 Postmenopausal, surgicale10,172301.39 (0.63–3.09)6,200141.25 (0.42–3.69)3,972161.70 (0.50–5.80)
 Unknowne or missing25,4145115,495239,91928
Age at menopausef
 ≥5311,097351.0 (ref)6,614111.0 (ref)4,483241.0 (ref)
 47–5221,776641.02 (0.68–1.55)12,580261.41 (0.69–2.86)9,196380.85 (0.50–1.42)
 44–465,889150.94 (0.51–1.73)3,40971.44 (0.56–3.76)2,48080.71 (0.32–1.58)
 ≤436,455161.07 (0.59–1.93)3,79951.11 (0.38–3.23)2,656111.02 (0.50–2.10)
 Unknowng or missing25,4145115,495239,91928
Ptrend = 0.93Ptrend = 0.72Ptrend = 0.83
Hysterectomy
 Never90,1491061.0 (ref)60,875401.0 (ref)29,274661.0 (ref)
 Ever28,154811.29 (0.97–1.74)17,305391.61 (1.02–2.55)10,849421.09 (0.74–1.62)
 Unknown or missing2,55491,70638486
Ovary removed
 None98,9851381.0 (ref)66,549561.0 (ref)32,436821.0 (ref)
 One removed5,610141.13 (0.66–1.97)3,36051.10 (0.74–2.76)2,25091.17 (0.58–2.33)
 Both removed14,470401.14 (0.81–1.63)8,840181.26 (0.74–2.16)5,630221.07 (0.66–1.71)
 Unknown or missing1,79241,13736551
BMI
 16–19.912,608140.80 (0.46–1.42)8,93860.83 (0.35–1.98)3,67080.82 (0.39–1.73)
 20–24.958,085941.0 (ref)38,526381.0 (ref)19,559561.0 (ref)
 25–29.929,009440.77 (0.54–1.10)18,689190.84 (0.48–1.45)10,320250.73 (0.45–1.16)
 ≥3016,370260.97 (0.64–1.50)10,724121.09 (0.58–2.11)5,646140.85 (0.47–1.53)
 Unknown or missing4,785183,00971,77611
Ptrend = 0.85Ptrend = 0.82Ptrend = 0.49
Ever use of menopausal HTh
 Never HT user16,713491.0 (ref)10,379241.0 (ref)6,334251.0 (ref)
 Ever HT user50,9281200.93 (0.66–1.31)29,781450.78 (0.47–1.28)21,147751.01 (0.64–1.60)
 Unknown or missing5,466163,30165,16510
Type of HT usedh
 Never HT user16,713491.0 (ref)10,379241.0 (ref)6,334251.0 (ref)
 Estrogen alone only user20,956751.18 (0.83–1.70)12,668300.98 (0.57–1.68)8,288451.31 (0.80–2.14)
 E + P only user20,524260.60 (0.37–0.98)11,66990.49 (0.22–1.10)8,855170.65 (0.35–1.24)
 E alone and E + P user7,010160.75 (0.42–1.32)3,91460.70 (0.28–1.73)3,096100.76 (0.36–1.58)
 P alone and E + P user2,17730.74 (0.23–2.41)1,363081431.41 (0.42–4.72)
 Unknown or missing5,727163,46862,25910
Past or current estrogen and progestin useh
 Never HT user16,713491.0 (ref)10,379241.0 (ref)6,334251.0 (ref)
 Past E + P user3,06370.93 (0.42–2.06)1,69630.98 (0.29–3.33)1,36740.87 (0.30–2.51)
 Current E + P user17,046190.55 (0.31–0.95)9,74060.40 (0.15–1.02)7,306130.62 (0.31–1.25)
 E alone user20,956751.18 (0.83–1.70)12,668300.98 (0.57–1.67)8.288451.31 (0.80–2.14)
 E alone and E + P or P alone and E + P user9,863190.72 (0.42–1.22)5,67760.55 (0.22–1.35)4,186130.82 (0.42–1.60)
 Unknown or missing5,466163,30162,16510
Duration of estrogen and progestin useh
 Never HT user16,713491.0 (ref)10,379241.0 (ref)6,334251.0 (ref)
 E + P only user, <1–2 y7,19690.73 (0.35–1.54)4,31240.70 (0.23–2.11)2,88450.72 (0.27–1.93)
 E + P only user, 3+ y12,448170.61 (0.35–1.08)6,86550.45 (0.17–1.22)5,583120.69 (0.34–1.40)
Ptrend = 0.11Ptrend = 0.13Ptrend = 0.35
 E alone, or E alone and E + P or P alone and E + P user31,284941.04 (0.73–1.47)18,604360.86 (0.52–1.44)12,680581.14 (0.71–1.82)
 Unknown or missing5,466163,30162,16510
  • aStratified on age at baseline and adjusted for smoking status (never, former, current), race/ethnicity (non-Hispanic white, African American, Hispanic white, Asian/Pacific Islander, mixed or other race, unknown), and BMI (<25, 25–29.9, 30+, unknown).

  • bStratified on age at baseline and adjusted for race/ethnicity (non-Hispanic white, African American, Hispanic white, Asian/Pacific Islander, mixed or other race, unknown) and BMI (<25, 25–29.9, 30+, unknown).

  • cNulliparous includes women who were never pregnant or did not have a full-term pregnancy.

  • dExcluding women with no full-term pregnancies.

  • eSurgical menopause was defined as undergoing a bilateral oophorectomy before occurrence of natural menopause.

  • fPre- and perimenopausal women excluded.

  • gIncludes women who underwent a hysterectomy before age 56 and were younger than 56 years at baseline, or had menopause due to chemotherapy or radiation, or had menopause due to other reasons, or had unknown menopausal status due to HT.

  • hPremenopausal women excluded.