Heterogeneity in assessing self-reports of caffeine exposure: implications for studies of health effects

Caffeine intake during pregnancy and adverse outcomes: An integrative review

Caffeine intake during pregnancy is common. Caffeine crosses the placenta, raising concerns about its possible deleterious effects on the developing embryo/fetus. Studies on this subject show conflicting results, and still there is no consensus on the recommended dose of caffeine during pregnancy. We performed an integrative review with studies from six databases, using broad MESH terms to allow the identification of publications that addressed the outcomes of caffeine use during pregnancy, with no date limit for publications, in English and Portuguese language. The research returned 16,192 articles. After removing duplicates, screening by title, abstract and full-text, we evaluated 257 and included 59 articles. We found association between caffeine intake and pregnancy loss, low birth weight, cardiac and genital anomalies, higher body mass, and neurodevelopmental and neurobehavioral outcomes. The effects were often dose dependent. No association with prematurity has been demonstrated, but one study showed a small reduction in gestational age with increasing doses of caffeine intake. Defining a safe dose for caffeine intake during pregnancy is a challenging task due to the heterogeneity in study designs and results, as well as the difficulty of reliably assessing the amount of caffeine consumed. In some studies, exposures below the recommended level of caffeine intake during pregnancy (200 mg/day), as suggested by the guidelines, were associated with pregnancy loss, low birth weight, cardiac and genital anomalies, higher body mass, and neurodevelopmental and neurobehavioral outcomes. Well-designed studies with reliable quantification of caffeine intake are needed to assess the safety of low doses during pregnancy.

Maternal chronic caffeine intake impairs fertility, placental vascularization and fetal development in mice

Caffeine is commonly consumed by pregnant women to avoid fatigue or as a habit. However, it is not clearly determined its side effects to the conceptuses. This study evaluated placental morphofunctional alterations after maternal chronic caffeine intake and the effects on fetal growth. Female Swiss mice received, via gavage, caffeine doses (either 60, 120 or 240 mg/kg/day) seven days before mating until gestational days-(GD) 11.5 or 17.5. Fetal biometrical parameters were assessed, and placentae were either submitted to histomorphometrical or molecular evaluation of angiogenesis (placental growth factor-1[PlGF-1]), apoptosis (Caspase-3) and proliferation (Ki-67) markers (evaluated in Swiss dams) and to intravital microscopy (evaluated in C57BL/6 dams). Caffeine exposed fetuses exhibited intrauterine growth restriction in a sex-dependent manner, with greater commitment of female fetuses (P < 0.05). In addition, placentae from dams that received 120 mg/kg/day showed less irrigation by maternal blood and greater development of fetal vasculature, characterized by higher number of larger vessels (P < 0.05). Although no effects on apoptosis (Caspase-3) and angiogenesis (PlGF-1) were observed, dams treated with 60 mg/kg/day showed greater placental cell proliferation (Ki-67 staining) at GD 11.5 (P < 0.05). The group treated with 240 mg/kg/day exhibited only one pregnant dam for each gestational age, suggesting that this high caffeine consumption may compromise fertility. Taken together, even in the doses currently ingested by many pregnant women, caffeine has detrimental effects on placental vasculature and fetal development in mice. Therefore, our results strongly suggest that caffeine consumption in human pregnancies greater than the recommended doses should be avoided.

Association of caffeine and caffeine metabolites with obesity among children and adolescents: National Health and Nutrition Examination Survey (NHANES) 2009-2014

The effect of caffeine exposure on children's health remains poorly understood. We aimed to characterize the associations of caffeine and caffeine metabolites with adiposity outcomes among children and adolescents. We performed cross-sectional analyses of 1,447 children and adolescents aged 6-19 years from the 2009-2014 National Health and Nutrition Examination Survey. The linear regression and weighted quantile sum (WQS) regression were used to explore the associations of urinary caffeine and 14 caffeine metabolites with adiposity outcomes, including body mass index (BMI) z-score, waist circumference (WC), obesity, and overweight. In linear regression models, compared with the participants who consumed low caffeine, higher BMI z-score, WC, and risks of obesity and overweight were more likely among those who consumed high caffeine (P < 0.05). In WQS regression models, an interquartile range increase in the weighted caffeine index was significantly associated with increased BMI z-score (β = 0.10, 95% CI = 0.01, 0.17) and WC (β = 1.20, 95% CI = 0.31, 2.09), and risks of obesity (OR = 1.09, 95% CI = 1.02, 1.17). Totally, no modification effect of age or gender was observed in the linear regression model. Nonetheless, in WQS models, the positive associations of caffeine exposure with WC and risks of obesity and overweight were significant in children aged 6-11 years rather than 12-19 years. When stratified by gender, caffeine exposure was significantly associated with BMI z-score and WC in both boys and girls. These results add novel evidence that caffeine exposure might be associated with adverse adiposity outcomes among children and adolescents.

Association of Coffee, Tea, and Caffeine Consumption With All-Cause Risk and Specific Mortality for Cardiovascular Disease Patients

Aim

The aim of the study was to examine the relationship between coffee, tea, caffeine consumption and risk of all-cause death and cardiovascular disease (CVD) death in CVD population.

Methods

This cohort study included 626 CVD participants aged ≥18 years old who derived from the National Health and Nutrition Examination Surveys (NHANES) database 2003–2006. The end time of follow-up was 2015, and with a median follow-up time of 113.5 (63, 133) months. CVD death was defined as a death caused by congestive heart failure (CHF), coronary heart disease (CHD), angina pectoris, heart attack or stroke. Cox model and competitive-risk model were used to explore the relationship of coffee, tea, caffeine, decaffeinated coffee/tea on the risk of the all-cause death and CVD death for CVD population, respectively. Additionally, we explored the effect of urinary caffeine and caffeine metabolites on all-cause death.

Results

All patients were divided into survival group (n = 304), non-CVD death group (n = 223), and CVD death group (n = 99). The incidence of all-cause death and CVD death was ~51.44 and 15.81% in the study. After adjusting age, body mass index (BMI), cancer, estimated glomerular filtration rate (eGFR), energy, the history of CVD medications, carbohydrate and family income to poverty ratio (PIR), the results suggested coffee, caffeine, iced tea and hot tea consumption (≥4 cups per day) were associated with an increased risk of the all-cause death in CVD patients; while hot tea (1–3 cups per day), decaffeinated coffee/iced tea/hot tea could reduce the risk of the all-cause death. Likewise, coffee, caffeine, iced tea (≥4 cups per day), hot tea, decaffeinated iced tea/ hot tea (Always) could enhance the risk of the CVD death in CVD population. We also found that 1-methylxanthine showed a significant positive association on the risk of all-cause death in CVD population.

Conclusion

Our study indicated that higher consumption of coffee, tea and caffeine could increase the risk of all-cause and CVD death for CVD patients.

Lifestyle in Pregnancy and Hypospadias in Sons: A Study of 85,923 Mother-Son Pairs from Two Danish Pregnancy Cohorts

Purpose

Hypospadias is one of the most frequent male congenital malformations. It remains controversial whether maternal lifestyle during pregnancy may affects the risk of having a son with hypospadias, especially for smoking with many suggesting lower risk. We assessed the individual and joint associations between maternal cigarette smoking, pre-pregnancy body mass index (BMI), alcohol consumption, binge drinking, and caffeine consumption and occurrence of hypospadias in sons.

Patients and Methods

This cohort study utilized the Danish National Birth Cohort and the Aarhus Birth Cohort, holding detailed information on lifestyle factors in early pregnancy between 1989 and 2012. The Danish health registers were used to identify boys with hypospadias, according to International Classification of Diseases. Potential confounders and covariates were identified by literature search and use of directed acyclic graphs. Missing data were handled by multiple imputation and Cox proportional hazards models were applied to analyse data.

Results

In total, 85,923 live-born singleton boys were included in the study of whom 502 (0.6%) were diagnosed with hypospadias. Maternal smoking in early pregnancy was associated with lower occurrence of hypospadias. An increase of one cigarette smoked per day was associated with lower risk of having a son with hypospadias (adjusted hazard ratio (HR) 0.97 (95% confidence interval (CI) 0.94, 1.00)). However, sub-analyses suggested that the results may be prone to unadjusted confounding. We found no association between pre-pregnancy BMI, alcohol consumption, binge drinking, or caffeine consumption and hypospadias.

Conclusion

Maternal smoking during pregnancy was associated with lower occurrence of hypospadias but we cannot exclude uncontrolled confounding. The other investigated maternal lifestyle factors were not associated with hypospadias in sons.

Urine caffeine metabolites and hearing threshold shifts in US adults: a cross-sectional study

Previous studies have reported the relationship between effect of caffeine and many diseases. However, studies to evaluate the association between caffeine and hearing loss are contradictory. To examine the relationship of urinary caffeine metabolites with the hearing threshold in US adults, a total of 849 adults aged 20–69 years who participated in the National Health and Nutrition Examination Survey (NHANES, 2011–2012) were enrolled in this study. Urinary caffeine and its 14 metabolites were applied as biomarkers to assess caffeine exposure. Hearing loss was defined as mean pure tone averages > 25 dB HL at 500, 1000, and 2000 Hz in both ears (low frequency); and 3000, 4000, and 6000 Hz in both ears (high frequency). Univariate and multivariate linear regression analyses were conducted to examine the associations of urinary caffeine metabolites with low- and high-frequency hearing thresholds, respectively. Low-frequency hearing loss were 5.08% and 6.10% in male and female participants, respectively; and high-frequency hearing loss were 31.81% and 15.14% in male and female participants, respectively. In the unadjusted model, the P value for trend shows that urinary caffeine metabolites 137X and AAMU were significantly associated with low-frequency PTA, and that 17X, 137X, AAMU were significantly associated with high-frequency PTA, but when the model was adjusted for sex, age, education level, firearm noise exposure, occupational noise exposure, recreational noise exposure, serum cotinine, body mass index, diabetes, hypertension, these were no longer statistically significant. In conclusion, urinary caffeine metabolites were not associated with the hearing threshold shifts in US adults.

Characteristics of Women with Urinary Tract Infection in Pregnancy

Background: Urinary tract infection (UTI) is the most common bacterial infection in pregnancy. Known risk factors for UTI in pregnancy include diabetes and certain urologic conditions. Other maternal characteristics might also be associated with risk and could provide clues to the etiology of UTI in pregnancy. Our objective was to identify maternal characteristics associated with UTI in pregnancy. Materials and Methods: We used data from pregnant women participating in the National Birth Defects Prevention Study, a population-based study of risk factors for major structural birth defects in 10 U.S. sites, from 1997 to 2011. In cross-sectional analyses, we used multivariable log-binomial regression to estimate prevalence ratios (PRs) and 95% confidence intervals (CIs) for associations between self-reported maternal characteristics and UTI in pregnancy. Results: In our sample of 41,869 women, the overall prevalence of reported UTI in pregnancy was 18%, but ranged from 11% to 26% between study sites. In adjusted models, diabetes was moderately associated with higher UTI prevalence (PR 1.39, 95% CI: 1.24-1.57). Higher UTI prevalence was associated even more strongly with low educational attainment (PR 2.06, 95% CI: 1.77-2.40 for some high school vs. graduate school), low household income (PR 1.64, 95% CI: 1.46-1.84 for <$10,000 vs. ≥$50,000), and race/ethnicity (PR 1.45, 95% CI: 1.13-1.80 for American Indian or Alaska Native vs. White women). Conclusions: About one in six women reported UTI in pregnancy but the prevalence varied markedly by geography and maternal characteristics. This variability could provide clues to the causes of UTI in pregnancy.

Environment-wide association study on childhood obesity in the U.S

BACKGROUND

Childhood obesity is a national public health issue with increasing prevalence. It has been linked to diet, lack of physical activity, and genetic susceptibility, with more recent evidence that it could also result from environmental factors. Studies linking it to environmental factors are limited, unsystematic, incomprehensive, and inconclusive.

OBJECTIVE

To conduct an environment-wide association study (EWAS) to comprehensively investigate all the environmental factors available in a nationally representative sample of children to determine factors associated with childhood obesity.

METHODS

We utilized the 1999-2016 National Health and Nutrition Examination Survey (NHANES) datasets and included all children/adolescents (6-17 years). Obesity was measured using body mass index and waist to height ratio. A multinomial and binary logistic regression were used adjusting for age, sex, race/ethnicity, creatinine, calorie intake, physical activity, screen time, limitation to physical activities, and socioeconomic status. We then controlled for multiple hypothesis testing and validated our findings on a different cohort of children.

RESULTS

We found that metals such as beryllium (OR: 3.305 CI: 1.460-7.479) and platinum (OR: 1.346 CI: 1.107-1.636); vitamins such as gamma-tocopherol (OR: 8.297 CI: 5.683-12.114) and delta-tocopherol (OR: 1.841 CI:1.476-2.297); heterocyclic aromatic amines such as 2-Amino-9H-pyrido (2,3-b) indole (OR: 1.323 CI: 1.083-1.617) and 2-Amino-3-methyl-9H-pyriodo(2,3-b)indole (OR: 2.799 CI: 1.442-5.433); polycyclic aromatic amines such as 9- fluorene (OR: 1.509 CI: 1.230-1.851) and 4-phenanthrene (OR: 2.828 CI: 1.632-4.899); and caffeine metabolites such as 1,3,7-trimethyluric acid (OR: 1.22 CI: 1.029-1.414) and 1,3,7-trimethylxanthine (OR: 1.258 CI: 1.075-1.473) were positively and significantly associated with childhood obesity.

CONCLUSION

Following the unique concept of EWAS, certain environmental factors were associated with childhood obesity. Further studies are required to confirm these associations while investigating their mechanisms of action.

Modulation of CYP2E1 metabolic activity in a cohort of confirmed caffeine ingesting pregnant women with preterm offspring

Background

To ascertain interactions of caffeine ingestion, food, medications, and environmental exposures during preterm human gestation, under informed consent, we studied a cohort of Mexican women with further preterm offspring born at ≤ 34 completed weeks. At birth, blood samples were taken from mothers and umbilical cords to determine caffeine and metabolites concentrations and CYP1A2 (rs762551) and CYP2E1 (rs2031920, rs3813867) polymorphisms involved in caffeine metabolism.

Results

In 90 pregnant women who gave birth to 98 preterm neonates, self-informed caffeine ingestion rate was 97%, laboratory confirmed rate was 93 %. Theobromine was the predominant metabolite found. Consumption of acetaminophen correlated significantly with changes in caffeine metabolism (acetaminophen R² = 0.637, p = 0.01) due to activation of CYP2E1 alternate pathways. The main caffeine source was cola soft drinks.

Conclusion

Environmental exposures, especially acetaminophen ingestion during human preterm pregnancy, can modulate CYP2E1 metabolic activity.

Maternal, but not paternal or grandparental, caffeine intake is associated with childhood obesity and adiposity: The Lifeways Cross-Generation Cohort Study

BACKGROUND

Maternal caffeine intake is associated with adverse birth outcomes, but its long-term influence on offspring adiposity outcomes is not well studied. Furthermore, few studies have investigated paternal and grandparental caffeine intake in relation to offspring outcomes.

OBJECTIVE

To study the associations between maternal, paternal, and grandparental caffeine intake and offspring childhood adiposity.

DESIGN

The core study sample consists of 558 mother-child pairs from the Lifeways Study. Caffeine intake was derived from relevant food items in a self-administered validated food frequency questionnaire in early pregnancy. Children's body mass index (BMI) and waist circumference (WC) were measured at 5- and 9-y follow-up. Childhood overall and central obesity were defined as age- and sex-specific BMI z-score > International Obesity Task Force cut-off and WC z-score > 90th percentile, respectively. Multiple linear and logistic regressions were used to assess associations.

RESULTS

Study mothers had a mean age of 30.8 y and a mean prepregnancy BMI (kg/m2) of 23.7. In adjusted models, maternal caffeine intake was associated with a higher offspring BMI z-score [β (95% CI): 0.13 (0.06, 0.21) for year 5 and 0.17 (0.04, 0.29) for year 9; per 100 mg/d increment in maternal caffeine intake], WC z-score [β (95% CI): 0.09 (0.01, 0.17) for year 5 and 0.19 (0.05, 0.32) for year 9], and a higher risk of offspring overall obesity [OR (95% CI): 1.32 (1.11, 1.57) for year 5 and 1.44 (1.10, 1.88) for year 9] and central obesity [1.28 (1.02, 1.60) for year 5 and 1.62 (1.12, 2.34) for year 9]. The influence was stronger for coffee caffeine than tea caffeine. No consistent associations were observed for paternal and grandparental caffeine intake.

CONCLUSIONS

Maternal antenatal, but not paternal or grandparental, caffeine intake is associated with higher offspring adiposity and obesity risk at age 5 and 9 y, with stronger associations observed for coffee caffeine. This prospective observational study was registered at the ISRCTN Registry as ISRCTN16537904.

The association between coffee consumption and bladder cancer in the bladder cancer epidemiology and nutritional determinants (BLEND) international pooled study

Background

Inconsistent results for coffee consumption and bladder cancer (BC) risk have been shown in epidemiological studies. This research aims to increase the understanding of the association between coffee consumption and BC risk by bringing together worldwide case–control studies on this topic.

Methods

Data were collected from 13 case–control comprising of 5,911 cases and 16,172 controls. Pooled multivariate odds ratios (ORs), with corresponding 95% confidence intervals (CIs), were obtained using multilevel logistic regression models. Furthermore, linear dose–response relationships were examined using fractional polynomial models.

Results

No association of BC risk was observed with coffee consumption among smokers. However, after adjustment for age, gender, and smoking, the risk was significantly increased for never smokers (ever vs. never coffee consumers: OR_model2 1.30, 95% CI 1.06–1.59; heavy (> 4 cups/day) coffee consumers vs. never coffee consumers: OR_model2 1.52, 95% CI 1.18–1.97, p trend = 0.23). In addition, dose–response analyses, in both the overall population and among never smokers, also showed a significant increased BC risk for coffee consumption of more than four cups per day. Among smokers, a significant increased BC risk was shown only after consumption of more than six cups per day.

Conclusion

This research suggests that positive associations between coffee consumption and BC among never smokers but not smokers.

Impact of female daily coffee consumption on successful fertility treatment: a Danish cohort study

OBJECTIVE

To investigate whether female coffee consumption affects the chance of achieving a clinical pregnancy and a live birth among women and couples receiving medically assisted reproduction (MAR) treatment.

DESIGN

Cohort study with prospectively collected exposure data.

SETTING

Public fertility clinic.

PATIENT(S)

A total of 1,708 women and potential partners undergoing fertility treatment, contributing with 1,511 intrauterine insemination (IUI) cycles, 2,870 in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) cycles, and 1,355 frozen embryo transfer cycles.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Clinical pregnancy and live birth in consecutive treatment cycles in the Danish national health registries, enabling complete follow-up, and estimation of the cumulative chance of live birth for three consecutive treatment cycles.

RESULT(S)

Among women receiving IVF or ICSI treatment, coffee consumption did not seem to affect the chance of achieving a clinical pregnancy and a live birth. Women treated with IUI who had a daily coffee consumption of 1-5 cups were more likely to achieve a clinical pregnancy (adjusted relative risk 1.49; 95% confidence interval, 1.05-2.11) and live birth (adjusted relative risk 1.53; 95% confidence interval, 1.06-2.21) compared with the reference group of coffee abstainers.

CONCLUSION(S)

Women consuming 1-5 cups versus none had a 1.5-fold higher probability of achieving a pregnancy or a live birth when receiving IUI. No associations were found, however, between women's daily coffee consumption and achieving a pregnancy or a live birth from IVF/ICSI.

Misclassification of coffee consumption data and the development of a standardised coffee unit measure

Background

Associations of coffee consumption with multiple health outcomes have been researched extensively. Coffee consumption, usually reported in cups a day, is a heterogeneous measure due to numerous preparation methods and cup sizes, leading to misclassification. This paper develops a new ‘unit’ measure of coffee and uses coffee consumption data from a representative sample of the UK population to assess misclassification when cup volume and preparation type are not taken into account.

Methods

A coffee unit measure was created using published estimates of caffeine and chlorogenic acid concentrations, and applied across volumes and preparation types. Four-day food diary data in adults from the UK National Diet and Nutrition Survey (NDNS; 2012–2016) were used to quantify coffee intake. Participant self-reported cups a day were compared with cups a day standardised by (a) 227 mL volume and (b) 227 mL instant coffee equivalents (unit measure), and the degree of misclassification was derived. Sensitivity analyses were conducted to model coffee drinking preferences of different populations and caffeine:chlorogenic acid weighting assumptions of the unit measure.

Results

The NDNS sample consisted of 2832 adult participants. Coffee was consumed by 62% of participants. Types varied, with 75% of caffeinated coffee cups being instant, 17% filter, 3% latte, 2% cappuccino, 2% espresso and <1% other types. Comparing reported cups to volume-standardised cups, 84% of participants had correct classification, and 73% when using the coffee unit measure, 22% underestimated and 5% overestimated, largely by one cup. Misclassification varied by gender, age and income. Sensitivity analysis highlighted the benefits of using the unit measure over volume alone to cater for different populations, and stability of the unit composition assumption.

Conclusion

Cup volume and preparation type should be taken into account, through the application of a standardised coffee unit measure, when coffee consumption is classified in future research studies.

Coffee consumption and risk of pancreatic cancer: a systematic review and dose-response meta-analysis

The association between coffee consumption and pancreatic cancer risk has been extensively studied; however, there is no consistent conclusion. Therefore, this meta-analysis study sought to evaluate dose-response relationship between them. A search was conducted using the PubMed and Web of Science databases. Thirteen high-quality cohort studies were identified, involving in 959,992 study participants and 3831 pancreatic cancer cases. Comparing the highest with lowest categories of coffee intake, the pooled relative risk (RR) was 1.08 (95% CI 0.94-1.25). For dose-response analysis, no evidence of a nonlinear dose-response association between coffee consumption and pancreatic cancer (p for nonlinearity =0.171) was found. The risk of pancreatic cancer was increased by 5.87% (RR =1.06, 95% CI 1.05-1.07) with the increment of one cup/day. Coffee consumption was identified to be related with the increasing risk of pancreatic cancer in a dose-response manner. Nevertheless, further mechanistic studies are needed to clarify the concerned issues.

Potential nutraceutical and food additive properties and risks of coffee: a comprehensive overview

Coffee is a composite mixture of more than a thousand diverse phytochemicals like alkaloids, phenolic compounds, vitamins, carbohydrates, lipids, minerals and nitrogenous compounds. Coffee has multifunctional properties as a food additive and nutraceutical. As a nutraceutical, coffee has anti-inflammatory, anti-oxidant, antidyslipidemic, anti-obesity, type-2 diabetes mellitus (DM), and cardiovascular diseases (CVD), which can serve for the treatment and prevention of metabolic syndrome and associated disorders. On the other hand, as a food additive, coffee has antimicrobial activity against a wide range of microorganisms, inhibits lipid peroxidation (LPO), and can function as a prebiotic. The outcomes of different studies also revealed that coffee intake may reduce the incidence of numerous chronic diseases, like liver disease, mental health, and it also overcomes the all-cause mortality, and suicidal risks. In some studies, high intake of coffee is linked to increase CVD risk factors, like cholesterol, plasma homocysteine and blood pressure (BP). There is also a little evidence that associated the coffee consumption with increased risk of lung tumors in smokers. Among adults who consume the moderate amount of coffee, there is slight indication of health hazards with strong indicators of health benefits. Moreover, existing literature suggests that it may be cautious for pregnant women to eliminate the chances of miscarriages and impaired fetal growth. The primary purpose of this narrative review is to provide an overview of the findings of the positive impacts and risks of coffee consumption on human health. In conclusion, to date, the best available evidence from research indicates that drinking coffee up to 3-4 cups/day provides health benefits for most people.

Associations of maternal caffeine intake with birth outcomes: results from the Lifeways Cross Generation Cohort Study

Background

Maternal caffeine intake is associated with adverse birth outcomes, but in most studies the primary caffeine source is coffee; the influence of tea caffeine remains unclear.

Objective

The aim of the study was to examine the association between maternal caffeine intake and birth outcomes in a population with tea as the predominant caffeine source.

Design

Data from 941 Irish mother-child pairs of the Lifeways Cross Generation Cohort Study were examined. Maternal dietary intakes in early pregnancy were assessed using a validated food-frequency questionnaire. Caffeine intake was derived from coffee, tea, soft drinks, and cocoa-containing foods and beverages. Associations of maternal caffeine intake with continuous (birth weight, birth length, and gestational age) and binary [low birth weight (LBW) (<2500 g) and preterm birth (PB) (<37 wk gestational age)] birth outcomes were investigated using multiple linear and logistic regressions, respectively, with adjustment for potential confounders.

Results

Tea was the predominant caffeine source (48%), followed by coffee (39%). In the fully adjusted model, maternal caffeine intake was associated with lower birth weight [β (95% CI): -71.9 (-105.4, -38.4) g · 100 mg-1 · d-1 caffeine increment], shorter birth length [-0.30 (-0.49, -0.11) cm], smaller head circumference [-0.12 (-0.24, -0.01) cm], and shorter gestational age [-0.13 (-0.25, -0.02) wk]; higher risks for LBW [OR (95% CI): 1.47 (1.14, 1.90)] and PB [1.36 (1.07, 1.74)] were also observed (all P < 0.05). The associations were robust to the exclusion of participants with pregnancy complications and in never smokers. Similar higher risks of adverse birth outcomes were observed for the highest caffeine intake categories from coffee [ORLBW: 3.10 (1.08, 8.89); ORPB: 2.74 (1.05, 7.16)] and tea [ORLBW: 2.47 (1.02, 6.01); ORPB: 2.56 (1.14, 5.75)], compared with the lowest intake categories (all P < 0.05).

Conclusions

Maternal caffeine intake from both coffee and tea is associated with adverse birth outcomes. This prospective observational study was registered at ISRCTN Registry as ISRCTN16537904.

Residential mobility of pregnant women and implications for assessment of spatially-varying environmental exposures

Health studies on spatially-varying exposures (e.g., air pollution) during pregnancy often estimate exposure using residence at birth, disregarding residential mobility. We investigated moving patterns in pregnant women (n = 10,116) in linked cohorts focused on Connecticut and Massachusetts, U.S., 1988-2008. Moving patterns were assessed by race/ethnicity, age, marital status, education, working status, population density, parity, income, and season of birth. In this population, 11.6% of women moved during pregnancy. Movers were more likely to be younger, unmarried, and living in urban areas with no previous children. Among movers, multiple moves were more likely for racial/ethnic minority, younger, less educated, unmarried, and lower income women. Most moves occurred later in pregnancy, with 87.4% of first moves in the second or third trimester, although not all cohort subjects enrolled in the first few weeks of pregnancy. Distance between first and second residence had a median value of 5.2 km (interquartile range 11.3 km, average 57.8 km, range 0.0-4277 km). Women moving larger distances were more likely to be white, older, married, and work during pregnancy. Findings indicate that residential mobility may impact studies of spatially-varying exposure during pregnancy and health and that subpopulations vary in probability of moving, and timing and distance of moves.

Biases Inherent in Studies of Coffee Consumption in Early Pregnancy and the Risks of Subsequent Events

Consumption of coffee by women early in their pregnancy has been viewed as potentially increasing the risk of miscarriage, low birth weight, and childhood leukemias. Many of these reports of epidemiologic studies have not acknowledged the potential biases inherent in studying the relationship between early-pregnancy-coffee consumption and subsequent events. I discuss five of these biases, recall bias, misclassification, residual confounding, reverse causation, and publication bias. Each might account for claims that attribute adversities to early-pregnancy-coffee consumption. To what extent these biases can be avoided remains to be determined. As a minimum, these biases need to be acknowledged wherever they might account for what is reported.

Coffee consumption and risk of esophageal cancer incidence: A meta-analysis of epidemiologic studies

BACKGROUND

In epidemiologic studies, association between coffee consumption and esophageal cancer risk is inconsistent.

OBJECTIVE

The aim of tjis study was to evaluate the effect of coffee on esophageal cancer by combining several similar studies.

METHODS

We conducted a meta-analysis for association of coffee intake and esophageal cancer incidence. Eleven studies, including 457,010 participants and 2628 incident cases, were identified. A relative risk (RR, for cohort study) or odds ratio (OR, for case-control study) of heavy coffee drinkers was calculated, compared with light coffee drinkers or non-drinkers. The analysis was also stratified by cancer types (esophageal squamous cell carcinoma and esophageal adenocarcinoma), sex, and geographic region.

RESULTS

The summarized OR of having esophageal cancer in heavy coffee drinkers was 0.93 (95% confidence interval [CI]: 0.73-1.12), compared with light coffee drinkers. When stratified by sex, pathologic type of esophageal cancer, and type of epidemiologic study, we did not find any association of coffee consumption and esophageal cancer incidence. However, an inverse association between coffee consumption and incidence of esophageal cancer was found in East Asia participants with OR of 0.64 (95% CI: 0.44-0.83), but not in Euro-America participants (OR = 1.05; 95% CI: 0.81-1.29).

CONCLUSION

There is a protective role of coffee consumption against esophageal cancer in East Asians, but not in Euro-Americans.

Lifestyle in pregnancy and cryptorchidism in sons: a study within two large Danish birth cohorts

Purpose

Cryptorchidism is the most frequent congenital malformation in boys and is associated with low sperm count, infertility and testicular cancer. Unhealthy maternal lifestyle during pregnancy such as smoking, high prepregnancy body mass index (BMI) as well as alcohol and caffeine intake may constitute possible risk factors for cryptorchidism, but results from the few previous studies are conflicting. We aimed to explore the association between maternal lifestyle factors and occurrence of cryptorchidism in sons.

Patients and methods

The Danish National Birth Cohort and the Aarhus Birth Cohort provided information on maternal lifestyle from early pregnancy. Data were linked to several Danish health registers, multiple imputation was used to handle missing data and Cox proportional hazards models were used to adjust for potential confounders.

Results

In total, 85,923 boys were included, and of them, 2.2% were diagnosed with cryptorchidism. We observed the strongest associations between maternal tobacco smoking and prepregnancy BMI and cryptorchidism. Sons of women who smoked 10–14 cigarettes/day had the highest hazard ratio (HR) for cryptorchidism (1.37; 95% CI: 1.06–1.76), and for maternal BMI ≥30 kg/m², the HR was 1.32 (95% CI: 1.06–1.65). Binge drinking was associated with an HR <1, if the women had one or two episodes in pregnancy (HR: 0.81; 95% CI: 0.67–0.98). Average maternal alcohol intake and caffeine intake during pregnancy were not significantly associated with a higher occurrence of cryptorchidism detected at birth or later in life.

Conclusion

Maternal tobacco smoking, overweight and obesity in pregnancy were associated with higher occurrence of cryptorchidism in boys in this study.

Association between coffee or caffeine consumption and fecundity and fertility: a systematic review and dose-response meta-analysis

Objective

The aim was to investigate whether coffee or caffeine consumption is associated with reproductive endpoints among women with natural fertility (ie, time to pregnancy [TTP] and spontaneous abortion [SAB]) and among women in fertility treatment (ie, clinical pregnancy rate or live birth rate).

Design

This study was a systematic review and dose-response meta-analysis including data from case-control and cohort studies.

Methods

An extensive literature search was conducted in MEDLINE and Embase, with no time and language restrictions. Also, reference lists were searched manually. Two independent reviewers assessed the manuscript quality using the Newcastle-Ottawa Scale (NOS). A two-stage dose-response meta-analysis was applied to assess a potential association between coffee/caffeine consumption and the outcomes: TTP, SAB, clinical pregnancy, and live birth. Heterogeneity between studies was assessed using Cochrane Q-test and I² statistics. Publication bias was assessed using Egger's regression test.

Results

The pooled results showed that coffee/caffeine consumption is associated with a significantly increased risk of SAB for 300 mg caffeine/day (relative risk [RR]: 1.37, 95% confidence interval [95% CI]: 1.19; 1.57) and for 600 mg caffeine/day (RR: 2.32, 95% CI: 1.62; 3.31). No association was found between coffee/caffeine consumption and outcomes of fertility treatment (based on two studies). No clear association was found between exposure to coffee/caffeine and natural fertility as measured by fecundability odds ratio (based on three studies) or waiting TTP (based on two studies).

Conclusion

Results from this meta-analysis support the growing evidence of an association between coffee/caffeine intake and the risk of SAB. However, viewing the reproductive capacity in a broader perspective, there seems to be little, if any, association between coffee/caffeine consumption and fecundity. In general, results from this study are supportive of a precautionary principle advised by health organizations such as European Food Safety Authority (EFSA) and World Health Organization (WHO), although the advised limit of a maximum of two to three cups of coffee/200-300 mg caffeine per day may be too high.

Maternal Caffeine Consumption during Pregnancy and Behavioral Disorders in 11-Year-Old Offspring: A Danish National Birth Cohort Study

OBJECTIVE

To examine the association between maternal caffeine consumption from coffee and tea during pregnancy and offspring behavioral disorders.

STUDY DESIGN

We studied 47 491 children enrolled in the Danish National Birth Cohort between 1996 and 2002. Data on maternal coffee and tea consumption was collected at 15 and 30 weeks of gestation. When the child was 11 years old, the Strength and Difficulties Questionnaire was filled in by children, parents, and teachers. We estimated risk ratios (RRs) for offspring behavioral disorders.

RESULTS

At 15 weeks of gestation 3% and 4% of the pregnant women consumed ≥8 cups/d of coffee or tea, respectively. Maternal coffee consumption ≥8 cups/d at 15 weeks of gestation was associated with increased risk of hyperactivity-inattention disorder (RR 1.47; 95% CI 1.18-1.83), conduct-oppositional disorders (RR 1.22; 95% CI 1.01-1.48), and any psychiatric disorder (RR 1.23; 95% CI 1.08-1.40). Maternal tea consumption ≥8 cups/d at 15 weeks of gestation was associated with increased risk of anxiety-depressive disorders (RR 1.28; 95% CI 1.09-1.52) and any psychiatric disorder (RR 1.24; 95% CI 1.11-1.40). An increased risk of hyperactivity-inattention disorder was observed with increasing daily caffeine consumption at 15 weeks of gestation.

CONCLUSION

High maternal caffeine consumption from coffee and tea at 15 weeks of gestation was associated with behavioral disorders in 11-year-old offspring. We hypothesize that caffeine exposure may affect the fetal brain and program for behavioral disorders later in life. The fetal brain seems to be more sensitive to caffeine exposure at 15 weeks of pregnancy compared with 30 weeks of gestation.

Maternal Smoking, Alcohol, and Caffeine Exposures and Risk of Hypospadias

BACKGROUND

We examined the association of hypospadias risk with maternal smoking and consumption of alcohol and caffeine.

METHODS

We analyzed data from mothers of 2437 moderate/severe cases and 5472 nonmalformed controls born from 1997 to 2011 who participated in the National Birth Defects Prevention Study (NBDPS). Exposures were assessed by maternal telephone interviews. Logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (95% CIs) adjusted for mother's age, parity, race-ethnicity, education, vitamin/mineral supplement intake, obesity, and study center.

RESULTS

Active smoking during the first month of pregnancy was associated with reduced risk, with smaller ORs for increasing quantity smoked; the OR for smoking >1/2 pack/day was 0.7 (95% CI, 0.5-0.9). Among nonsmokers, the OR for any secondhand smoke exposure was 0.8 (95% CI, 0.7-0.9). ORs for alcohol and caffeine consumption were near one and CIs included 1.0. In an analysis of joint exposures to smoking and alcohol and caffeine consumption, the only OR for which the 95% CI excluded 1.0 was for women who smoked, drank, and had low caffeine consumption (OR, 0.6; 95% CI, 0.4-0.8).

CONCLUSION

Maternal exposure to cigarette smoke was associated with reduced risk, and women who smoked, drank, and had low caffeine intake were at lowest risk. We do not interpret these results to suggest that these exposures have overall benefit to a pregnant woman or developing fetus. They may, however, offer clues to help us understand mechanisms that lead to hypospadias. Birth Defects Research 109:1127-1133, 2017. © 2017 Wiley Periodicals, Inc.

Coffee Consumption and the Risk of Thyroid Cancer: A Systematic Review and Meta-Analysis

An inverse association has been reported between coffee consumption and the risk of several cancers. However, the association between coffee and thyroid cancer is controversial. Thus, this study aimed to evaluate the association between coffee consumption and the risk of thyroid cancer through a systematic review and meta-analysis. Published studies were examined from PubMed, Embase, Cochrane Central, and the reference lists of the retrieved articles. The summary odds ratio (OR) for the association between coffee consumption was categorized as highest versus lowest consumption, and thyroid cancer risk was calculated using a fixed effects model. Subgroup analyses by study design, geographic location, source of controls, and adjusted variables were performed. A total of 1039 thyroid cancer cases and 220,816 controls were identified from five case-control studies and two cohort studies. The summary OR for the association between coffee consumption and thyroid cancer risk was 0.88 (95% confidence interval (CI) = 0.71-1.07). There was no significant heterogeneity among the study results (I² = 0%, p = 0.79). However, the beneficial effect of coffee consumption on thyroid cancer was found only in hospital-based case-control studies (OR= 0.59, 95% CI= 0.37-0.93). There was no significant association between coffee consumption and thyroid cancer risk according to our meta-analysis results. These findings should be interpreted with caution because of potential biases and confounding variables. Further prospective studies with a larger number of cases are encouraged to confirm these results.

Relation of 24-hour urinary caffeine and caffeine metabolite excretions with self-reported consumption of coffee and other caffeinated beverages in the general population

Background

Caffeine intake is generally estimated by self-reported consumption, but it remains unclear how well self-report associates with metabolite urinary excretion. We investigated the associations of self-reported consumption of caffeinated drinks with urinary excretion of caffeine and its major metabolites in an adult population.

Methods

We used data from the population-based Swiss Kidney Project on Genes in Hypertension (SKIPOGH) study. Consumption of caffeinated coffee, decaffeinated coffee and other caffeinated beverages was assessed by self-administered questionnaire. Quantification of caffeine, paraxanthine, theobromine and theophylline was performed by ultra-high performance liquid chromatography tandem mass spectrometry in 24-h urine. Association of reported consumption of caffeinated drinks with urinary caffeine derived metabolites was determined by quantile regression. We then explored the association between urinary metabolite excretion and dichotomized weekly consumption frequency of caffeinated coffee, with Receiver Operator Characteristic (ROC) analysis.

Results

In the present analysis, we included 598 individuals (52% women, mean age =46 ± 17 years). Self-reported caffeinated coffee intake was positively associated with 24-h urinary excretions of paraxanthine, theophylline and caffeine (p < 0.001), whereas reported intakes of decaffeinated coffee and other caffeinated beverages showed no association. In ROC analysis, optimal discrimination between individuals consuming less than one caffeinated coffee/week, vs. at least one coffee, was obtained for 24-h urinary paraxanthine (Area Under Curve (AUC) = 0.868, 95% Confidence Interval (CI) [0.830;0.906]), with slightly lower performance for theophylline and caffeine, whereas theobromine did not allow any discrimination.

Conclusion

Our results suggest that reported consumption of caffeinated coffee is positively associated with 24-h urinary excretion of caffeine, paraxanthine, and theophylline, and may be used as a marker of caffeine intake for epidemiological studies.

Electronic supplementary material

The online version of this article (doi:10.1186/s12986-016-0144-4) contains supplementary material, which is available to authorized users.

Prenatal Caffeine Exposure and Child IQ at Age 5.5 Years: The EDEN Mother-Child Cohort

BACKGROUND

Evidence from animal studies suggests maternal caffeine intake during pregnancy has detrimental effects on subsequent brain development in offspring. However, human data in this area are limited. The aim of this study was to assess whether caffeine intake by women during pregnancy is associated with impaired cognitive development in offspring at age 5.5 years.

METHODS

Multivariate modeling was conducted using data of 1083 mother-child pairs from a population-based birth cohort in France followed from pregnancy to age 5.5 years of the children. Measures included an estimate of maternal caffeine intake during pregnancy, children's IQ at age 5.5, and individual and family characteristics.

RESULTS

Prenatal caffeine exposure was common in the sample (91%) with 12% displaying an intake ≥200 mg/day (high). Multivariable modeling showed a significant negative relationship between caffeine intake and children's IQ at 5.5 years (-.94 [95% confidence interval = -1.70, -.17] full IQ unit per 100 mg daily caffeine intake). In particular, children of mothers consuming ≥200 mg/day were more likely to have borderline or lower IQ compared with children of mothers consuming <100 mg/day (13.5% vs. 7.3%; odds ratio = 2.30, 95% confidence interval = 1.13, 4.69).

CONCLUSIONS

We found an association between caffeine intake during pregnancy and impaired cognitive development in offspring, a result in line with animal data. More epidemiologic and biologically grounded research is needed to determine whether this association is causal. This finding suggests that conservative guidelines regarding the maximum caffeine intake recommended in pregnancy (i.e., 200 mg/day) should be maintained.

Assessment of CYP1A2 enzyme activity in relation to type-2 diabetes and habitual caffeine intake

BACKGROUND

Coffee consumption is a known inducer of cytochrome P450 1A2 (CYP1A2) enzyme activity. We recently observed that a group of type-2 diabetes patients consumed more caffeine (coffee) on a daily basis than non-type-2 diabetes controls. Here, we investigated whether type-2 diabetes cases may metabolize caffeine faster than non-type-2 diabetes controls.

METHODS

To estimate CYP1A2 enzyme activity, an established marker of caffeine metabolism, we quantified the paraxanthine/caffeine concentration ratio in saliva in 57 type-2 diabetes and 146 non-type-2 diabetes participants in a case-control field study. All participants completed validated questionnaires regarding demographic status, health and habitual caffeine intake, and were genotyped for the functional -163C > A polymorphism of the CYP1A2 gene.

RESULTS

In the diabetes group, we found a larger proportion of participants with the highly inducible CYP1A2 genotype. Furthermore, the paraxanthine/caffeine ratio, time-corrected to mitigate the impact of different saliva sampling times with respect to the last caffeine intake, was higher than in the control group. Participants who reported habitually consuming more caffeine than the population average showed higher CYP1A2 activity than participants with lower than average caffeine consumption. Multiple regression analyses revealed that higher caffeine intake was potentially an important mediator of higher CYP1A2 activity.

CONCLUSIONS

Estimated CYP1A2 enzyme activity, and thus speed of caffeine metabolism, was higher in our type-2 diabetes group; this was possibly due to higher intake of caffeine, a known inducer of CYP1A2 enzyme activity. Given the fairly small sample sizes, the results need to be considered as preliminary and require validation in larger populations.

Pre-pregnancy caffeine and caffeinated beverage intake and risk of spontaneous abortion

PURPOSE

To investigate the relation between pre-pregnancy caffeine and caffeinated beverage intake and risk of spontaneous abortion (SAB).

METHODS

Our prospective cohort study included 15,590 pregnancies from 11,072 women with no history of SAB in the Nurses' Health Study II (1991-2009). Beverage intake was assessed every 4 years using a validated questionnaire. Pregnancies were self-reported with case pregnancies lost spontaneously at <20 weeks gestation. Multivariable log-binomial regression models with generalized estimating equations were used to estimate the relative risks (RRs) and 95 % confidence intervals (CIs).

RESULTS

There was a positive linear trend across categories of pre-pregnancy caffeine intake and risk of SAB such that women consuming >400 mg/day had 1.11 (95 % CI 0.98, 1.25) times the risk of SAB compared to women consuming <50 mg/day (p trend = 0.05). Total coffee intake had a positive, linear association with SAB. Compared to women with no pre-pregnancy coffee intake, women consuming ≥4 servings/day had a 20 % (6, 36 %) increased risk of SAB (p trend = 0.01). There was no difference in the association between caffeinated and decaffeinated coffee and risk of SAB. Pre-pregnancy intake of caffeinated tea, caffeinated soda, and decaffeinated soda had no association with SAB.

CONCLUSIONS

Pre-pregnancy coffee consumption at levels ≥4 servings/day is associated with increased risk of SAB, particularly at weeks 8-19.

Caffeine and caffeinated beverage consumption and fecundability in a preconception cohort

Caffeine is an adenosine receptor antagonist that may influence fertility by affecting ovulation, menstrual characteristics, or sperm quality. We studied the association between female and male preconception caffeine intake and fecundability in a North American prospective cohort study of 2135 pregnancy planners. Frequency of caffeinated beverage intake was self-reported at baseline. Outcome data were updated every 8 weeks until reported pregnancy; censoring occurred at 12 months. Adjusted fecundability ratios (FR) and 95% confidence intervals (CI) were estimated using proportional probabilities regression. Total caffeine intake among males, but not females, was associated with fecundability (FR for ≥300 vs. <100mg/day caffeine among males=0.72, 95% CI=0.54-0.96), although the association was not monotonic. With respect to individual beverages, caffeinated tea intake was associated with slight reductions in fecundability among females, and caffeinated soda and energy drink intake were associated with reduced fecundability among males.

Second-Trimester Maternal Serum Paraxanthine, CYP1A2 Activity, and the Risk of Severe Preeclampsia

OBJECTIVE

To measure the association between second-trimester maternal caffeine intake and caffeine metabolism through the CYP1A2 system and the risk of subsequent severe preeclampsia.

METHODS

This was a nested case-control study of women who had undergone second-trimester screening for fetal aneuploidy and had banked serum available for analysis. The outcome of interest was severe preeclampsia, and exposures were serum paraxanthine (1,7-dimethylxanthine), measured through high-performance liquid chromatography, and CYP1A2 activity, assessed by paraxanthine/caffeine ratios.

RESULTS

We identified 51 cases of severe preeclampsia from our population of 3,992 women (1.3%), of whom 33 had sufficient serum for analysis. These were compared with 99 healthy women. Median paraxanthine concentrations were not significantly higher in women in the control group than women in the case group (96.4 ng/mL compared with 38.0 ng/mL, P=.12), and higher serum paraxanthine was not associated with lower odds of severe preeclampsia (odds ratio [OR] 0.72, confidence interval [CI] 0.48-1.08). However, we found a significantly higher paraxanthine/caffeine ratio in women in the control group than women in the case group (0.37 compared with 0.23, P=.02) and a decreased risk of preeclampsia per every log standard deviation increase in paraxanthine/caffeine ratio (OR 0.53, 95% CI 0.31-0.90).

CONCLUSION

Faster caffeine metabolism in the second trimester, assessed by paraxanthine/caffeine ratios, is associated with a reduced risk of subsequent severe preeclampsia.

LEVEL OF EVIDENCE

II.

Caffeine: Friend or Foe?

The debate on the safety of and regulatory approaches for caffeine continues among various stakeholders and regulatory authorities. This decision-making process comes with significant challenges, particularly when considering the complexities of the available scientific data, making the formulation of clear science-based regulatory guidance more difficult. To allow for discussions of a number of key issues, the North American Branch of the International Life Sciences Institute (ILSI) convened a panel of subject matter experts for a caffeine-focused session entitled "Caffeine: Friend or Foe?," which was held during the 2015 ILSI Annual Meeting. The panelists' expertise covered topics ranging from the natural occurrence of caffeine in plants and interindividual metabolism of caffeine in humans to specific behavioral, reproductive, and cardiovascular effects related to caffeine consumption. Each presentation highlighted the potential risks, benefits, and challenges that inform whether caffeine exposure warrants concern. This paper aims to summarize the key topics discussed during the session.

Exploring maternal patterns of dietary caffeine consumption before conception and during pregnancy

We describe patterns of dietary caffeine consumption before and after pregnancy recognition in a cohort of women who recently gave birth. This study included 8,347 mothers of non-malformed liveborn control infants who participated in the National Birth Defects Prevention Study during 1997-2007. Maternal self-reported consumption of beverages (caffeinated coffee, tea, and soda) and chocolate the year before pregnancy was used to estimate caffeine intake. The proportions of prepregnancy caffeine consumption stratified by maternal characteristics are reported. In addition, patterns of reported change in consumption before and after pregnancy were examined by maternal and pregnancy characteristics. Adjusted prevalence ratios were estimated to assess factors most associated with change in consumption. About 97 % of mothers reported any caffeine consumption (average intake of 129.9 mg/day the year before pregnancy) and soda was the primary source of caffeine. The proportion of mothers reporting dietary caffeine intake of more than 300 mg/day was significantly increased among those who smoked cigarettes or drank alcohol. Most mothers stopped or decreased their caffeinated beverage consumption during pregnancy. Young maternal age and unintended pregnancy were associated with increases in consumption during pregnancy. Dietary caffeine consumption during pregnancy is still common in the US. A high level of caffeine intake was associated with known risk factors for adverse reproductive outcomes. Future studies may improve the maternal caffeine exposure assessment by acquiring additional information regarding the timing and amount of change in caffeine consumption after pregnancy recognition.

[Caffeine consumption during pregnancy and attention deficit hyperactivity disorder (ADHD): a systematic literature review]

This aim of this study was to conduct a systematic literature review on the association between maternal caffeine intake during pregnancy and attention deficit hyperactivity disorder (ADHD) in childhood. The systematic multiple-stage literature search in PubMed, LILACS, BIREME, and PsycINFO was limited to research in human subjects and published in Portuguese, English, and Spanish. A total of 373 references were retrieved. Of these, only five met the study's objectives and were kept in the review. Most of the studies employed a longitudinal design, were conducted in developed countries, and were published in the last five years. Only one study found a positive association. Studies on caffeine consumption during pregnancy and ADHD are scarce, with conflicting results and several methodological difficulties such as lack of standardized outcome measures.

Maternal caffeine consumption and small for gestational age births: results from a population-based case-control study

Caffeine is consumed in various forms during pregnancy, has increased half-life during pregnancy and crosses the placental barrier. Small for gestational age (SGA) is an important perinatal outcome and has been associated with long term complications. We examined the association between maternal caffeine intake and SGA using National Birth Defects Prevention Study data. Non-malformed live born infants with an estimated date of delivery from 1997-2007 (n = 7,943) were included in this analysis. Maternal caffeine exposure was examined as total caffeine intake and individual caffeinated beverage type (coffee, tea, and soda); sex-, race/ethnic-, and parity-specific growth curves were constructed to estimate SGA births. Crude and adjusted odds ratios (aORs) and 95% confidence intervals were estimated using unconditional logistic regression. Interaction with caffeine exposures was assessed for maternal smoking, vasoconstrictor medication use, and folic acid. Six hundred forty-eight infants (8.2%) were found to be SGA in this analysis. Increasing aORs were observed for increasing intakes of total caffeine and for each caffeinated beverage with aORs (adjusting for maternal education, high blood pressure, and smoking) ranging from 1.3 to 2.1 for the highest intake categories (300+ mg/day total caffeine and 3+ servings/day for each beverage type). Little indication of additive interaction by maternal smoking, vasoconstrictor medication use, or folic acid intake was observed. We observed an increase in SGA births for mothers with higher caffeine intake, particularly for those consuming 300+ mg of caffeine per day. Increased aORs were also observed for tea intake but were more attenuated for coffee and soda intake.

Urine excretion of caffeine and select caffeine metabolites is common in the U.S. population and associated with caffeine intake

BACKGROUND

Caffeine is a widely consumed psychoactive stimulant and is of epidemiologic interest. Major sources of caffeine are challenging to standardize, and the use of biomarkers is proposed as an alternative means of assessing intake.

OBJECTIVE

We described urine caffeine and caffeine metabolite concentrations (n = 2466) and excretion rates (n = 2261) in the US population ≥6 y by age, sex, race-ethnicity, and caffeine intake (from foods, beverages, and dietary supplements).

METHODS

We measured caffeine and 14 of its metabolites in spot urine samples from the cross-sectional NHANES 2009-2010 by use of LC-tandem mass spectrometry.

RESULTS

Caffeine and its metabolites were detectable in the urine of most persons, generally at concentrations ≥1 μmol/L. Median concentrations (95% CI) ranged from 0.560 (0.497, 0.620) μmol/L to 58.6 (48.6, 67.2) μmol/L; median excretion rates from 0.423 (0.385, 0.468) nmol/min to 46.0 (40.7, 50.2) nmol/min. Urine concentrations and excretion rates for 9 analytes (caffeine, theophylline, paraxanthine, 1-methylxanthine, 1-methyluric acid, 1,3-dimethyluric acid, 1,7-dimethyluric acid, 1,3,7-trimethyluric acid, and 5-acetylamino-6-amino-3-methyluracil) had moderate correlations with caffeine intake (Spearman ρ = 0.55-0.68, P < 0.0001); the remaining analytes had low correlations (ρ = 0.15-0.33, P < 0.0001). We observed larger differences in geometric mean concentrations and excretion rates between the highest vs. lowest quartiles of caffeine intake for these 9 compounds than the rest. Consistent with dietary caffeine intake, we observed that urine concentrations and excretion rates for most compounds were significantly (P < 0.05) higher in men than women, non-Hispanic whites than Hispanics and non-Hispanic blacks, and highest in persons aged 40-59 y.

CONCLUSION

Excretion of caffeine and its metabolites in urine is common in the US population. According to the observed associations between spot urine concentrations or excretion rates with caffeine intake, several of these compounds show promise as potential biomarkers of caffeine intake.

Caffeine and caffeinated beverage consumption and risk of spontaneous abortion

STUDY QUESTION

Is caffeine and caffeinated beverage consumption associated with the risk of spontaneous abortion (SAB)?

SUMMARY ANSWER

While preconceptional caffeine consumption was not materially associated with an increased risk of SAB, consumption during early pregnancy was associated with a small increased risk of SAB, although the relation was not linear.

WHAT IS KNOWN ALREADY

Caffeine has been hypothesized as a risk factor for SAB since the 1980s; however, results from previous studies have been conflicting.

STUDY DESIGN, SIZE, DURATION

This prospective cohort study included 5132 Danish women planning pregnancy and enrolled from 2007 to 2010.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Participants were women who conceived after entry into the Snart-Gravid cohort and who were aged 18-40, in a stable relationship with a male partner, and did not use fertility treatments to conceive. Women reported their daily caffeine and caffeinated beverage consumption on questionnaires before conception and during early pregnancy. All exposure measurements were prospective with respect to outcome ascertainment. We estimated hazard ratios (HRs) of SAB for categories of caffeine consumption in milligrams (mg) per day and the corresponding 95% confidence intervals (CIs) using Cox proportional hazards regression models with gestational weeks as the time scale.

MAIN RESULTS AND THE ROLE OF CHANCE

There were 732 women (14.3%) who were identified as having a SAB. In the preconceptional period, caffeine consumption was not materially associated with SAB risk (HR comparing ≥300 with <100 mg/day: 1.09; 95% CI: 0.89, 1.33). In early pregnancy, the HRs for 100-199, 200-299 and ≥300 mg/day of caffeine consumption were 1.62 (95% CI: 1.19, 2.22), 1.48 (95% CI: 1.03, 2.13) and 1.23 (95% CI: 0.61, 2.46), respectively, compared with that for <100 mg/day.

LIMITATIONS, REASONS FOR CAUTION

The observed results may be affected by non-differential exposure misclassification, reverse causation and residual confounding.

WIDER IMPLICATIONS OF THE FINDINGS

This is the largest study to date of prospectively measured, preconception caffeine consumption and risk of SAB. We were able to reduce the likelihood of differential left truncation bias and recall bias present in other analyses.

STUDY FUNDING/COMPETING INTERESTS

Snart-Gravid was funded by the NICHD (R21-050264). Dr. Hahn's work was funded in part by the BU Reproductive, Perinatal, and Pediatric Epidemiology Training Grant NIH #T32HD052458. There are no competing interests.

Coffee consumption and urologic cancer risk: a meta-analysis of cohort studies

OBJECTIVES

Controversial results were reported among several epidemiologic studies on the relationship between coffee consumption and urologic cancer risk. We, therefore, conducted this meta-analysis to clarify these associations.

METHODS

Electronic databases including Pubmed, Embase and Cochrane library were searched between January 1966 and August 2013 for eligible studies. Pooled relative risk (RR) and its 95 % confidence interval (CI) were calculated. All P values are two tailed.

RESULTS

Thirteen cohorts were eligible for inclusion. As to prostate cancer (PCa), significant reverse association was found among highest versus none/lowest analysis with acceptable heterogeneity (RR 0.86, 95 % CI 0.79-0.95; I(2) 25 %, P value for heterogeneity: 0.221). A pooled RR which assessed advanced PCa was 0.73 (with 95 % CI 0.50-1.07), and a slight stronger reverse association was found in fatal PCa. However, a slight insignificant reverse association, basing on 8 studies with 9 outcomes, was found in dose-response analysis (RR 0.98, 95 % CI 0.93-1.03). For kidney and bladder cancer, insignificant associations were found in both highest versus none/lowest analyses and dose-response analyses.

CONCLUSIONS

Our findings suggest that coffee consumption may reduce the risk of PCa. No associations were found with both bladder and kidney cancer. Further well-designed large-scaled cohort studies are warranted to provide more definitive conclusions.

Coffee consumption and prostate cancer risk: an updated meta-analysis

PURPOSE

Many epidemiological studies have been conducted to explore the association between coffee consumption and prostate cancer. However, the results remain inconsistent. We performed a large meta-analysis of relevant studies to derive a more precise estimation of this relationship.

METHODS

Systematic searches of PubMed and several other databases up to June 2013 were retrieved. All epidemiologic studies regarding coffee consumption and prostate cancer risk were included, and odds ratios (ORs) with 95 % confidence intervals (CIs) were calculated to estimate the strength of the association.

RESULTS

Twelve case-control studies involving 7,909 prostate cancer cases and 9,461 controls and nine cohort studies involving 455,123 subjects were included in our analysis. Compared with the lowest category, the unstratified highest category of coffee consumption showed a significance reduction in prostate cancer risk of a fixed-effects model (OR 0.91, CI 0.86-0.97). A borderline significant influence was also found when the stratified highest category (US ≥ 4, Europe ≥ 5) of coffee consumption was compared with the reference category (OR 0.96, CI 0.92-1.00), but no relationships were observed for the other two categories. In another analysis conducted by coffee consumption and prostate cancer stage and Gleason grade, our results showed a significant inverse association in all categories of prostate cancer except Gleason <7 grade in a fixed-effects model; the results remained the same, except for advanced prostate cancer, in a random-effects model.

CONCLUSIONS

Our meta-analysis suggests that high (e.g., highest ≥ 4 or 5 cups/day) coffee consumption may not only be associated with a reduced risk of overall prostate cancer, but also inversely associated with fatal and high-grade prostate cancer.

Validation of different instruments for caffeine measurement among premenopausal women in the BioCycle study

Effects of caffeine on women's health are inconclusive, in part because of inadequate exposure assessment. In this study we determined 1) validity of a food frequency questionnaire compared with multiple 24-hour dietary recalls (24HDRs) for measuring monthly caffeine and caffeinated beverage intakes; and 2) validity of the 24HDR compared with the prior day's diary record for measuring daily caffeinated coffee intake. BioCycle Study (2005-2007) participants, women (n = 259) aged 18-44 years from western New York State, were followed for 2 menstrual cycles. Participants completed a food frequency questionnaire at the end of each cycle, four 24HDRs per cycle, and daily diaries. Caffeine intakes reported for the food frequency questionnaires were greater than those reported for the 24HDRs (mean = 114.1 vs. 92.6mg/day, P = 0.01) but showed high correlation (r = 0.73, P < 0.001) and moderate agreement (К = 0.51, 95% confidence interval: 0.43, 0.57). Women reported less caffeinated coffee intake in their 24HDRs compared with their corresponding diary days (mean = 0.51 vs. 0.80 cups/day, P < 0.001) (1 cup = 237 mL). Although caffeine and coffee exposures were highly correlated, absolute intakes differed significantly between measurement tools. These results highlight the importance of considering potential misclassification of caffeine exposure.

Spontaneous abortion and a diet drug containing caffeine and ephedrine: a study within the Danish national birth cohort

Background

Medications may be consumed periconceptionally before a woman knows she is pregnant. In this study, the authors evaluate the association of a prescription diet drug (Letigen) containing ephedrine (20 mg) and caffeine (200 mg) with spontaneous abortion (SAB) in the Danish National Birth Cohort.

Methods

Women were recruited during their first prenatal visit from 1996–2002. Pre-conception and early pregnancy medication use was reported on the enrollment form, and pregnancy outcome was determined by linking the mother's Civil Registration Number to the Medical Birth Registry and the National Hospital Discharge Register. Of 97,903 eligible pregnancies, 4,443 ended in SAB between 5 and 20 completed gestational weeks, inclusive. Letigen use was reported for 565 pregnancies. Cox regression models accounting for left truncation were fit to estimate the effect of pre-conception and early pregnancy Letigen use on SAB.

Principal Findings

The estimated maternal age-adjusted hazard ratio for SAB was 1.1 (95% confidence interval 0.8–1.6) for any periconceptional Letigen use compared to no periconceptional use.

Conclusions

Although Letigen has high levels of caffeine (the recommended 3 pills/day are approximately equivalent to caffeine from 6 cups of coffee), periconceptional use does not appear to be associated with an appreciably increased hazard of clinically recognized SAB.

Coffee consumption and risk of gastric and pancreatic cancer--a prospective cohort study

Only few prospective studies have examined the association between coffee consumption and risk of gastric and pancreatic cancer. This study is designed to evaluate this relationship among Finns, whose coffee consumption is the highest in the world. A total of 60,041 Finnish men and women who were 26-74 years of age and without history of any cancer at baseline were included in the present analyses. Coffee consumption and other study parameters were determined at baseline using standardized measurements. Participants were prospectively followed up for onset of gastric and/or pancreatic cancer, emigration, death or until June 30, 2006. During a mean follow-up period of 18 years, 299 cases of gastric cancer and 235 cases of pancreatic cancer were found. There was a nonsignificant inverse association between coffee consumption and risk of gastric cancer among men but not in the women. The multivariate-adjusted hazard ratio of stomach and pancreatic cancer incidence for ≥ 10 cups of coffee per day compared with nondrinkers were 0.75 (95% CI, 0.40-1.41) (P for trend = 0.19) and 0.82 (95% CI, 0.38-1.76) (P for trend = 0.95) for the combined population of men and women, respectively. We did not find a significant association between coffee consumption and the risk of gastric and/or pancreatic cancers.

Maternal caffeine consumption and risk of congenital limb deficiencies

BACKGROUND

Animal studies have shown that high doses of caffeine might cause congenital limb deficiencies (LDs); however, no epidemiologic studies have explored this relation.

METHODS

This case-control study assessed associations between maternal dietary caffeine and congenital LDs using data from the National Birth Defects Prevention Study (NBDPS), with 844 LD cases and 8069 controls from 1997 to 2007. Caffeine intakes from beverages (coffee, tea, and soda) and chocolate combined and by beverage type were examined. Adjusted odds ratios (aORs) and 95% confidence intervals (CIs) were estimated for subtypes of isolated LDs (no additional major anomalies) and LDs with other major anomalies separately, comparing the odds of 10 to <100, 100 to <200, 200 to <300, and 300+ mg/day total caffeine intake to 0 to <10 mg/day.

RESULTS

All total dietary caffeine intake categories of 10 mg/day and above were marginally associated with odds of all isolated LDs combined (aOR, 1.4-1.7), isolated longitudinal LDs (aOR, 1.2-1.6), and isolated transverse LDs (aOR, 1.3-1.8) compared to the lowest intake category. A dose-response pattern for total dietary caffeine intake was not observed.

CONCLUSIONS

A weak increased risk of congenital LDs associated with maternal dietary caffeine consumption was observed in this study; however, risk did not vary by amount of caffeine consumed.

Caffeine intake during pregnancy and risk of problem behavior in 5- to 6-year-old children

BACKGROUND AND OBJECTIVE

Human studies that have investigated the association between caffeine intake during pregnancy and offspring's behavioral outcomes are scant and inconclusive. We prospectively investigated the association between maternal caffeine intake during pregnancy and children's problem behavior at age 5 to 6 years. Mediation by fetal growth restriction and gestational age as well as effect modification by the child's gender and maternal smoking was tested.

METHODS

In a community based multiethnic birth cohort, dietary caffeine intake (coffee, caffeinated tea, and cola) was measured (maternal self-report, n = 8202) around the 16th week of gestation. At age 5, children's overall problem behavior, emotional problems, conduct problems, hyperactivity/inattention problems, peer relationship problems, and prosocial behavior were rated by both mother and teacher (n = 3439) with the Strengths and Difficulties Questionnaire. Analyses were adjusted for maternal age, ethnicity, cohabitant status, education, smoking and alcohol consumption during pregnancy, child's gender, family size, and prenatal maternal anxiety.

RESULTS

Caffeine intake was not associated with a higher risk for behavior problems or with suboptimal prosocial behavior. No evidence was found for mediation by fetal growth restriction or gestational age, nor for effect modification by the child's gender.

CONCLUSIONS

Results did not provide evidence for developmental programming influences of intrauterine exposure to caffeine on offspring's problem behavior at age 5. Present results give no indication to advise pregnant women to reduce their caffeine intake to prevent behavior problems in their children.

Caffeinated beverage and soda consumption and time to pregnancy

BACKGROUND

Many epidemiologic studies have evaluated the association between caffeine and fertility, with inconsistent results. Some studies suggest that various caffeine-containing beverages may affect fertility differently.

METHODS

We evaluated the relation of caffeine, coffee, tea, and sodas with time to pregnancy in a prospective cohort study of 3628 women planning a pregnancy, in Denmark (2007-2010). Women reported beverage intake at baseline and every 8 weeks during follow-up until they became pregnant or for up to 12 cycles. We used discrete-time Cox proportional hazards regression to estimate fecundability ratios (FRs) and 95% confidence intervals (CIs), controlling for potential confounders.

RESULTS

There was little relation between fecundability and caffeine intake of 300+ mg/day compared with < 100 mg/day (FR = 1.04 [95% CI = 0.90-1.21]) or coffee intake of 3+ servings/day compared with none (1.05 [0.85-1.33]). Soda consumption was associated with reduced fecundability: for all types of sodas combined, the adjusted FRs were 0.89 (0.80-0.98), 0.85 (0.71-1.02), 0.84 (0.57-1.25), and 0.48 (0.21-1.13) for < 1, 1, 2, and 3+ servings per day, respectively, compared with none. Tea drinking was associated with a slight increase in fecundability, with FR = 1.27 (0.98-1.64) for 2+ servings/day versus none.

CONCLUSION

In this prospective study of time to pregnancy, the association between caffeine intake and fertility differed by beverage type. Although we controlled for many confounders, our findings of reduced fecundability among soda drinkers and increased fecundability among tea drinkers could have resulted from confounding by unmeasured lifestyle characteristics.

Maternal caffeine intake, blood pressure, and the risk of hypertensive complications during pregnancy. The Generation R Study

BACKGROUND

Caffeine intake has been suggested to be associated with the risk of hypertension. Less is known about the associations of caffeine intake on maternal cardiovascular adaptations during pregnancy. We examined the associations of caffeine intake in different trimesters of pregnancy with repeatedly measured blood pressure and the risks of pregnancy-induced hypertension and pre-eclampsia in a population-based cohort of 7,890 pregnant women.

METHODS

In each trimester caffeine intake and systolic and diastolic blood pressure were assessed by questionnaires and physical examinations, respectively. Information about hypertensive complications was obtained from medical records.

RESULTS

Our longitudinal analyses revealed no significant differences for both systolic and diastolic blood pressure. The cross-sectional analyses showed that higher caffeine intake tended to be associated with higher systolic blood pressure in first and third trimester (P trend <0.05), but not in second trimester. Caffeine intake was not consistently associated with diastolic blood pressure levels, or the risk of pregnancy-induced hypertension. As compared to women with caffeine intake of <2 units/day, those using 2-3.9 units/day had a lower risk of pre-eclampsia (odds ratio 0.63 (95% confidence interval: 0.40, 0.96)).

CONCLUSIONS

Higher caffeine intake during pregnancy seems to be associated with elevated systolic blood pressure levels in first and third trimester, but not with diastolic blood pressure levels. We did not find evidence of significant adverse associations of caffeine intake on maternal cardiovascular adaptations during pregnancy. The unexpected finding of a possible protective association with moderate caffeine intake deserves further investigation.