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Table 1 Characteristics and results of included studies concerned caffeine intake with infertility

From: Relationship between caffeine intake and infertility: a systematic review of controlled clinical studies

Study IDStudy TypeParticipantsExposure (Caffeine/coffee)ComparisonOutcomes
GenderAgeSample sizeDiseaseRelative Risk(95%CI)
Buiatti 1984Case-Control StudyMen20-54y239≥100 mg/d0 mg/dAzoospermia/oligospermiaOR = 0.91 (0.46–1.82)
Grodstein 1993Case-Control StudyWomenUnclear4883E1 100-167mg/d; E2 168-233mg/d;
E3>233mg/d
<100 mg/dPrimary infertilityOR1 = 1.00(0.79–1.25);
OR2 = 1.16(0.94–1.42);
OR3 = 1.36(1.16–1.60) a,b
Prazzini 1993Case-Control StudyMenMedian 31-33y216E1 200-300 mg/d; E2 ≥ 400 mg/d0-100 mg/dInfertile men with dyspermiaOR1 = 1.7(0.8–3.7);
OR2 = 5.4 (2.4–12.6) c
Liv2018Cohort StudyWomen20-29y7574Coffee:
E1 ≤ 200 ml/d
E2 200-400 ml/d
E3 ≥ 500 ml/d
0 ml/dInfertile womenHR1 = 0.86(0.70–1.06);
HR2 = 0.88(0.73–1.06);
HR3 = 0.89(0.72–1.10);
     Tea:
E1 ≤ 200 ml/d
E2 200-400 ml/d
E3 ≥ 500 ml/d
0 ml/d HR1 = 1.10(0.84–1.44);
HR2 = 1.10(0.84–1.46);
HR3 = 1.15(0.87–1.53);
     Caffeined:
E1 ≤ 1-168 mg/d
E2 169-333mg/d
E3 334-579mg/d
E4 ≥ 580 mg/d
0 mg/d HR1 = 0.93(0.58–1.49);
HR2 = 0.91(0.57–1.47);
HR3 = 0.97(0.60–1.55);
HR4 = 0.93(0.58–1.50)e
  1. Note: E Exposure, OR Odds ratio, HR Hazard ratio, CI Confidence interval
  2. a This study classified the participants into 5 groups according to their primary disease and calculated the estimate effect of them respectively. Details of the information were reported in the main text of this review
  3. b OR were adjusted for center, age, lifetime number of sexual partners, current and former cigarette smoking, and alcohol intake
  4. c Age-Adjust OR
  5. d Total caffeine calculated from consumption of both coffee and tea
  6. e Educational level (≤9, 10–11 or ≥ 12 years of schooling), Smoking (yes or no), Marital status (married/cohabiting or single), Weekly alcohol intake and Year of birth-Adjust HR.