Abstract
BackgroundPrevious studies showed that high dose of caffeine intake may induce some specific human reproductive system diseases, even lead to infertility.ObjectivesIn consideration of the high consumption of caffeine according to the latest population-based survey, this review is aimed to systematically review the evidence from all controlled clinical studies of caffeine intake for infertility.DesignsRelevant randomized/quasi-randomized controlled trials, non-randomized clinical studies, cohort studies, and case-control studies will be included in this review. Participants will be either those without a history of infertility who are willing to have a baby (for prospective studies) or infertile patients with confirmed diagnosis (for retrospective studies). Caffeine or caffeine-containing beverage will be observed as the exposure factor. The key outcome will be the diagnosis of infertility in participants. All relevant published/unpublished or ongoing studies will be searched from seven databases and four online systems until December 2015. Two authors will screen the literatures and extract the data independently. Methodological quality of the included studies will be assessed by two authors according to either Risk of Bias Assessment or Newcastle-Ottawa Scale. We will use R software to analyze the data. Dose of caffeine will be quantified on a daily basis, and relative risk with their 95 % confidence interval will be measured. If data permit, meta-analysis and dose-response analysis will be conducted. Summary of findings tables will be generated using Guideline Development Tool online.Systematic review registrationPROSPERO CRD42015015714Electronic supplementary materialThe online version of this article (doi:10.1186/s13643-016-0221-9) contains supplementary material, which is available to authorized users.
Highlights
Previous studies showed that high dose of caffeine intake may induce some specific human reproductive system diseases, even lead to infertility
For the negative effect of caffeine intake on reproductive system diseases, we only found a systematic review [8] with observational studies that showed high dose caffeine intake may induce specific adverse events during pregnancy
The effects of caffeine consumption on delayed conception were evaluated in a European multicenter study on risk factors of infertility, which issued that women in the highest level of caffeine consumption had an increase of 11 % in the time leading to the first pregnancy
Summary
Previous studies showed that high dose of caffeine intake may induce some specific human reproductive system diseases, even lead to infertility. Infertility is a disease of the reproductive system defined by the failure to achieve a clinical pregnancy after 12 months or more of regular unprotected sexual intercourse without a certain reason, such as breast feeding or postpartum menorrhea [1]. Caffeine is present in many drinks and foods consumed during pregnancy and most notably in tea, coffee, colas, energy drinks, and chocolate [8]. Caffeine can have both positive and negative health effects. It may confer a modest protective effect against some diseases of the cardiovascular system and of the metabolism of carbohydrates and lipids, including the various forms of arterial cardiovascular disease, arrhythmia, heart insufficiency, diabetes, liver disease [9], and even Parkinson’s disease [10]
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