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. Author manuscript; available in PMC: 2007 May 24.
Published in final edited form as: Hum Reprod. 2004 Jun 24;19(8):1746–1754. doi: 10.1093/humrep/deh309

Table IV.

Risk of ultrasound- or hysterectomy-confirmed uterine leiomyomata in relation to caffeine consumption in 1995, according to age at start of questionnaire cycle: the Black Women’s Health Study, 1997–2001

Age <35 years
Age 35 + years
All women
P-value, test for age interaction
Cases Person- years Age-adjusted IRRa Multivariate IRR (95% CI)b Cases Person-years Age-adjusted IRRa Multivariate IRR (95% CI)b Multivariate IRR (95% CI)b
Coffee (caffeinated), cups/day 0.04
 Almost never 598 17 592 1.00c 1.00c 751 21 106 1.00c 1.00c 1.00c
 <1 134 5197 1.13 1.11 (0.92–1.34) 240 6262 1.07 1.04 (0.90–1.20) 1.06 (0.95–1.20)
 1 61 2200 1.15 1.11 (0.85–1.45) 165 4230 1.08 1.04 (0.88–1.23) 1.07 (0.92–1.23)
 2 26 1104 0.98 0.89 (0.60–1.32) 108 2745 1.10 1.06 (0.86–1.30) 1.03 (0.86–1.24)
 3 or more 31 768 1.67 1.53 (1.06–2.22) 63 2223 0.80 0.77 (0.59–1.00) 0.93 (0.75–1.15)
Coffee (decaffeinated), cups/day 0.69
 Almost never 774 34 032 1.00c 1.00c 1108 30 663 1.00c 1.00c
 <1 56 2073 1.12 1.12 (0.86–1.48) 128 3613 0.97 0.96 (0.80–1.15) 1.01 (0.87–1.18)
 1 or more 20 756 1.05 1.07 (0.69–1.68) 91 2290 1.12 1.11 (0.89–1.38) 1.11 (0.92–1.35)
Tea, cups/day 0.75
 Almost never 372 17 571 1.00c 1.00c 631 17 698 1.00c 1.00c 1.00c
 <1 313 13 112 1.12 1.10 (0.94–1.27) 438 12 026 1.02 1.01 (0.89–1.14) 1.05 (0.95–1.15)
 1 88 3354 1.19 1.16 (0.93–1.47) 133 3446 1.10 1.09 (0.90–1.31) 1.12 (0.97–1.30)
 2 34 1352 1.16 1.09 (0.76–1.54) 54 1590 0.95 0.94 (0.71–1.24) 0.99 (0.80–1.23)
 3 or more 43 1471 1.36 1.27 (0.93–1.75) 71 1806 1.11 1.12 (0.88–1.43) 1.18 (0.97–1.43)
Soft drinks, cans/day 0.66
 Almost never 350 15 651 1.00c 1.00c 657 17 812 1.00c 1.00c 1.00c
 <1 333 13 947 1.09 1.16 (1.00–1.35) 431 12 190 0.96 0.97 (0.86–1.10) 1.04 (0.95–1.14)
 1 84 3380 1.14 1.25 (0.98–1.59) 122 3276 1.00 1.04 (0.86–1.27) 1.11 (0.96–1.30)
 2 45 2107 0.96 1.07 (0.78–1.46) 62 1666 1.03 1.04 (0.80–1.35) 1.04 (0.85–1.27)
 3 or more 38 1776 1.00 1.14 (0.81–1.60) 55 1620 0.92 0.93 (0.70–1.22) 0.99 (0.80–1.23)
Caffeine, mg/day 0.01
 <50 359 17 799 1.00c 1.00c 470 13 422 1.00c 1.00c 1.00c
 50–149 300 11 382 1.27 1.27 (1.09–1.49) 408 10 974 1.06 1.05 (0.92–1.20) 1.14 (1.03–1.26)
 150–299 107 4528 1.12 1.13 (0.91–1.41) 235 5964 1.12 1.11 (0.94–1.30) 1.12 (0.99–1.28)
 300–499 42 2085 0.94 0.92 (0.67–1.28) 135 3689 1.03 1.00 (0.82–1.22) 1.00 (0.85–1.18)
 500 + 42 1068 1.79 1.70 (1.23–2.36) 79 2516 0.90 0.87 (0.68–1.11) 1.07 (0.88–1.30)

‘Almost never’ = <0.14 servings per day.

a

Adjusts for age at start of questionnaire cycle (1-year intervals) and time period (1997–1999 versus 1999–2001).

b

Adjusts for age, time period, age at menarche (years), parity (ever versus never), age at first birth (years), years since last birth (four knot restricted cubic spline), use of oral contraceptives (current, past, never), education (≤12, 13–15, 16, 17 + ), smoking (never, former, current), current alcohol consumption (<1, 1–6, 7 + per week) and BMI (kg/m2, four knot restricted cubic spline). Estimates for decaffeinated coffee, tea and soft drinks are additionally adjusted for caffeinated coffee (cups per day).

c

Reference group.