The genetics of tea and coffee drinking and preference for source of caffeine in a large community sample of Australian twins

Whole Exome Sequencing Study Identifies Novel Rare Risk Variants for Habitual Coffee Consumption Involved in Olfactory Receptor and Hyperphagia

Habitual coffee consumption is an addictive behavior with unknown genetic variations and has raised public health issues about its potential health-related outcomes. We performed exome-wide association studies to identify rare risk variants contributing to habitual coffee consumption utilizing the newly released UK Biobank exome dataset (n = 200,643). A total of 34,761 qualifying variants were imported into SKAT to conduct gene-based burden and robust tests with minor allele frequency <0.01, adjusting the polygenic risk scores (PRS) of coffee intake to exclude the effect of common coffee-related polygenic risk. The gene-based burden and robust test of the exonic variants found seven exome-wide significant associations, such as OR2G2 (PSKAT = 1.88 × 10−9, PSKAT-Robust = 2.91 × 10−17), VEZT1 (PSKAT = 3.72 × 10−7, PSKAT-Robust = 1.41 × 10−7), and IRGC (PSKAT = 2.92 × 10−5, PSKAT-Robust = 1.07 × 10−7). These candidate genes were verified in the GWAS summary data of coffee intake, such as rs12737801 (p = 0.002) in OR2G2, and rs34439296 (p = 0.008) in IRGC. This study could help to extend genetic insights into the pathogenesis of coffee addiction, and may point to molecular mechanisms underlying health effects of habitual coffee consumption.

Validation of the Turkish Version of the Caffeine Use Disorder Questionnaire in an Adult Population

The aim of this study was to examine the reliability and validity of the Turkish version of the Caffeine Use Disorder Questionnaire (CUDQ) in an adult population. In this instrument validation study, a total of 310 individuals (253 female, 57 males), with a mean age of 25.96 ± 6.29 years were included. The questionnaire consisted of 4 parts, comprising the sociodemographic characteristics, CUDQ, caffeine withdrawal symptoms, and caffeine consumption. For the evaluation of the data, confirmatory factor analysis (CFA), descriptive statistics, and the t test were used. In the reliability analysis, the Cronbach alpha internal consistency coefficient was 0.86, and the intraclass correlation coefficient was 0.83 for CUDQ. The CMIN/df was 0.54, and the model generally fits well to the structure (RMSEA = 0.08, CFI = 1, NFI = 1, GFI = 0.99, AGFI = 0.99, TLI = 1, NNFI = 1, RFI = 0.98). The findings suggested that the CUDQ has validity of structure, internal consistency, and construct validity for assessing Caffeine Use Disorder the tendency in the Turkish adult population.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s11469-021-00688-8.

Investigating the genetic and causal relationship between initiation or use of alcohol, caffeine, cannabis and nicotine

BACKGROUND

Caffeine, alcohol, nicotine and cannabis are commonly used psychoactive substances. While the use of these substances has been previously shown to be genetically correlated, causality between these substance use traits remains unclear. We aimed to revisit the genetic relationships among different measures of SU using genome-wide association study (GWAS) summary statistics from the UK Biobank, International Cannabis Consortium, and GWAS & Sequencing Consortium of Alcohol and Nicotine use.

METHODS

We obtained GWAS summary statistics from the aforementioned consortia for ten substance use traits including various measures of alcohol consumption, caffeine consumption, cannabis initiation and smoking behaviours. We then conducted SNP-heritability (h²) estimation for individual SU traits, followed by genetic correlation analyses and two-sample Mendelian randomisation (MR) studies between substance use trait pairs.

RESULTS

SNP h² of the ten traits ranged from 0.03 to 0.11. After multiple testing correction, 29 of the 45 trait pairs showed evidence of being genetically correlated. MR analyses revealed that most SU traits were not causally associated with each other. However, we found evidence for an MR association between regular smoking initiation and caffeine consumption 40.17 mg; 95 % CI: [24.01, 56.33] increase in caffeine intake per doubling of odds in smoking initiation). Our findings were robust against horizontal pleiotropy, SNP-outliers, and the direction of causality was consistent in all MR analyses.

CONCLUSIONS

Most of the substance traits were genetically correlated but there is little evidence to establish causality apart from the relationship between smoking initiation and caffeine consumption.

Quantile-Specific Heritability may Account for Gene-Environment Interactions Involving Coffee Consumption

Estimated heritability of coffee intake ranges from 0.36 to 0.58, however, these point estimates assume that inherited effects are the same throughout the distribution of coffee intake, i.e., whether consumption is high or low relative to intake in the population. Quantile regression of 4788 child-parent pairs and 2380 siblings showed that offspring-parent and sibling concordance became progressively greater with increasing quantiles of coffee intake. Each cup/day increase in the parents' coffee intake was associated with an offspring increase of 0.020 ± 0.013 cup/day at the 10th percentile of the offsprings' coffee intake (slope ± SE, NS), 0.137 ± 0.034 cup/day at their 25th percentile (P = 5.2 × 10^-5), 0.159 ± 0.029 cup/day at the 50th percentile (P = 5.8 × 10^-8), 0.233 ± 0.049 cup/day at the 75th percentile (P = 1.8 × 10^-6), and 0.284 ± 0.054 cup/day at the 90th percentile (P = 1.2 × 10^-7). This quantile-specific heritability suggests that factors that distinguish heavier vs. lighter drinkers (smoking, male sex) will likely manifest differences in estimated heritability, as reported.

Genetic determinants of beverage consumption: Implications for nutrition and health

Beverages make important contributions to nutritional intake and their role in health has received much attention. This review focuses on the genetic determinants of common beverage consumption and how research in this field is contributing insight to what and how much we consume and why this genetic knowledge matters from a research and public health perspective. The earliest efforts in gene-beverage behavior mapping involved genetic linkage and candidate gene analysis but these approaches have been largely replaced by genome-wide association studies (GWAS). GWAS have identified biologically plausible loci underlying alcohol and coffee drinking behavior. No GWAS has identified variants specifically associated with consumption of tea, juice, soda, wine, beer, milk or any other common beverage. Thus far, GWAS highlight an important behavior-reward component (as opposed to taste) to beverage consumption which may serve as a potential barrier to dietary interventions. Loci identified have been used in Mendelian randomization and gene×beverage interaction analysis of disease but results have been mixed. This research is necessary as it informs the clinical relevance of SNP-beverage associations and thus genotype-based personalized nutrition, which is gaining interest in the commercial and public health sectors.

Assessment of moderate coffee consumption and risk of epithelial ovarian cancer: a Mendelian randomization study

Background

Coffee consumption has been shown to be associated with various health outcomes in observational studies. However, evidence for its association with epithelial ovarian cancer (EOC) is inconsistent and it is unclear whether these associations are causal.

Methods

We used single nucleotide polymorphisms associated with (i) coffee and (ii) caffeine consumption to perform Mendelian randomization (MR) on EOC risk. We conducted a two-sample MR using genetic data on 44 062 individuals of European ancestry from the Ovarian Cancer Association Consortium (OCAC), and combined instrumental variable estimates using a Wald-type ratio estimator.

Results

For all EOC cases, the causal odds ratio (COR) for genetically predicted consumption of one additional cup of coffee per day was 0.92 [95% confidence interval (CI): 0.79, 1.06]. The COR was 0.90 (95% CI: 0.73, 1.10) for high-grade serous EOC. The COR for genetically predicted consumption of an additional 80 mg caffeine was 1.01 (95% CI: 0.92, 1.11) for all EOC cases and 0.90 (95% CI: 0.73, 1.10) for high-grade serous cases.

Conclusions

We found no evidence indicative of a strong association between EOC risk and genetically predicted coffee or caffeine levels. However, our estimates were not statistically inconsistent with earlier observational studies and we were unable to rule out small protective associations.

Coffee consumption is positively related to insulin secretion in the Shanghai High-Risk Diabetic Screen (SHiDS) Study

Background

It has been proved that coffee consumption was associated with a lower risk of type 2 diabetes mellitus. But the benefit effect of coffee on hyperglycemia in Chinese population was largely unknown. Besides, the relationship of coffee intake and diabetic pathogenesis was still unclear.

Methods

The study population was selected from the Shanghai High-Risk Diabetic Screen (SHiDS) project. A total of 1328 individuals over 18 years of age who have the information of coffee intake were enrolled in the study from 2012 to 2016. Each participant finished a five-point 75 g oral glucose tolerance test and finished a standard questionnaire. Insulin resistance was evaluated by HOMA-IR and insulin secretion was evaluated by HOMA-β, Stumvoll first phase and second phase indexes.

Results

Coffee consumption group had lower plasma glucose levels at 2-h and 3-h and higher insulin levels at fasting, 30-min and 1-h during OGTT after adjustment with age, fat%, BMI, waist, tea intake, smoking habit, alcohol intake, diabetes family history and educational status (P for PG2h = 0.002; P for PG3h = 0.010; P for FIN = 0.010; P for IN30min = 0.001; P for IN1h = 0.002). Both HOMA-β and Stumvoll formula indexes were positively related to coffee consumption (P for HOMA-β = 0.033; P for Stumvoll first phase = 0.003; P for Stumvoll second phase = 0.001). Logistic regression analysis further confirmed that coffee intake was independently associated with higher levels of HOMA-β and Stumvoll insulin secretion indexes [OR (95% CI) for HOMA-β = 2.270 (1.456–3.538); OR (95% CI) for Stumvoll first phase = 2.071 (1.352–3.173); OR (95% CI) for Stumvoll second phase = 1.914 (1.260–2.906)].

Conclusions

Coffee intake is independently and positively related to pancreatic beta cell function in a large high-risk diabetic Chinese population.

Understanding the role of bitter taste perception in coffee, tea and alcohol consumption through Mendelian randomization

Consumption of coffee, tea and alcohol might be shaped by individual differences in bitter taste perception but inconsistent observational findings provide little insight regarding causality. We conducted Mendelian randomization analyses using genetic variants associated with the perception of bitter substances (rs1726866 for propylthiouracil [PROP], rs10772420 for quinine and rs2597979 for caffeine) to evaluate the intake of coffee, tea and alcohol among up to 438,870 UK Biobank participants. A standard deviation (SD) higher in genetically predicted bitterness of caffeine was associated with increased coffee intake (0.146 [95%CI: 0.103, 0.189] cups/day), whereas a SD higher in those of PROP and quinine was associated with decreased coffee intake (-0.021 [-0.031, -0.011] and -0.081 [-0.108, -0.054] cups/day respectively). Higher caffeine perception was also associated with increased risk of being a heavy (>4 cups/day) coffee drinker (OR 1.207 [1.126, 1.294]). Opposite pattern of associations was observed for tea possibly due to the inverse relationship between both beverages. Alcohol intake was only negatively associated with PROP perception (-0.141 [-1.88, -0.94] times/month per SD increase in PROP bitterness). Our results reveal that bitter perception is causally associated with intake of coffee, tea and alcohol, suggesting a role of bitter taste in the development of bitter beverage consumption.

Interindividual Differences in Caffeine Metabolism and Factors Driving Caffeine Consumption

Most individuals adjust their caffeine intake according to the objective and subjective effects induced by the methylxanthine. However, to reach the desired effects, the quantity of caffeine consumed varies largely among individuals. It has been known for decades that the metabolism, clearance, and pharmacokinetics of caffeine is affected by many factors such as age, sex and hormones, liver disease, obesity, smoking, and diet. Caffeine also interacts with many medications. All these factors will be reviewed in the present document and discussed in light of the most recent data concerning the genetic variability affecting caffeine levels and effects at the pharmacokinetic and pharmacodynamic levels that both critically drive the level of caffeine consumption. The pharmacokinetics of caffeine are highly variable among individuals due to a polymorphism at the level of the CYP1A2 isoform of cytochrome P450, which metabolizes 95% of the caffeine ingested. Moreover there is a polymorphism at the level of another critical enzyme, N-acetyltransferase 2. At the pharmacodynamic level, there are several polymorphisms at the main brain target of caffeine, the adenosine A2A receptor or ADORA2. Genetic studies, including genome-wide association studies, identified several loci critically involved in caffeine consumption and its consequences on sleep, anxiety, and potentially in neurodegenerative and psychiatric diseases. We start reaching a better picture on how a multiplicity of biologic mechanisms seems to drive the levels of caffeine consumption, although much more knowledge is still required to understand caffeine consumption and effects on body functions.

The individual environment, not the family is the most important influence on preferences for common non-alcoholic beverages in adolescence

Beverage preferences are an important driver of consumption, and strong liking for beverages high in energy (e.g. sugar-sweetened beverages [SSBs]) and dislike for beverages low in energy (e.g. non-nutritive sweetened beverages [NNSBs]) are potentially modifiable risk factors contributing to variation in intake. Twin studies have established that both genes and environment play important roles in shaping food preferences; but the aetiology of variation in non-alcoholic beverage preferences is unknown. 2865 adolescent twins (18-19-years old) from the Twins Early Development Study were used to quantify genetic and environmental influence on variation in liking for seven non-alcoholic beverages: SSBs; NNSBs; fruit cordials, orange juice, milk, coffee, and tea. Maximum Likelihood Structural Equation Modelling established that beverage preferences have a moderate to low genetic basis; from 18% (95% CI: 10%, 25%) for orange juice to 42% (36%, 43%) for fruit cordials. Aspects of the environment that are not shared by twin pairs explained all remaining variance in drink preferences. The sizeable unique environmental influence on beverage preferences highlights the potential for environmental modification. Policies and guidelines to change preferences for unhealthy beverages may therefore be best directed at the wider environment.

Tea and coffee consumption in relation to DNA methylation in four European cohorts

Lifestyle factors, such as food choices and exposure to chemicals, can alter DNA methylation and lead to changes in gene activity. Two such exposures with pharmacologically active components are coffee and tea consumption. Both coffee and tea have been suggested to play an important role in modulating disease-risk in humans by suppressing tumour progression, decreasing inflammation and influencing estrogen metabolism. These mechanisms may be mediated by changes in DNA methylation. To investigate if DNA methylation in blood is associated with coffee and tea consumption, we performed a genome-wide DNA methylation study for coffee and tea consumption in four European cohorts (N = 3,096). DNA methylation was measured from whole blood at 421,695 CpG sites distributed throughout the genome and analysed in men and women both separately and together in each cohort. Meta-analyses of the results and additional regional-level analyses were performed. After adjusting for multiple testing, the meta-analysis revealed that two individual CpG-sites, mapping to DNAJC16 and TTC17, were differentially methylated in relation to tea consumption in women. No individual sites were associated with men or with the sex-combined analysis for tea or coffee. The regional analysis revealed that 28 regions were differentially methylated in relation to tea consumption in women. These regions contained genes known to interact with estradiol metabolism and cancer. No significant regions were found in the sex-combined and male-only analysis for either tea or coffee consumption.

Tea consumption and its interactions with tobacco smoking and alcohol drinking on oral cancer in southeast China

BACKGROUND/OBJECTIVES

Epidemiological results on the association between tea consumption and oral cancer remain controversial. We aimed to evaluate the exact relationship between tea consumption and oral cancer in Chinese population.

SUBJECTS/METHODS

A large-scale case-control study was conducted on 586 oral cancer patients and 1024 controls frequency-matched by age and gender. Epidemiological data were collected through face-to-face interviews with a structure questionnaire. Unconditional logistic regression model was used to assess the effect of tea consumption on oral cancer stratified by smoking, alcohol drinking and demographics. Quantity of tea consumed (ml/day) was categorized into five subgroups based on quartiles and then its interactions was evaluated with tobacco smoking and alcohol drinking at each subgroup.

RESULTS

Tea consumption showed an inverse association with oral cancer for non-smokers or non-alcohol drinkers (the odds ratios (ORs) were 0.610 (95% confidence interval (CI): 0.425-0.876) and 0.686 (95% CI: 0.503-0.934), respectively). For smokers or alcohol drinkers, decreased risk was only observed in those who consumed >800 ml/day. Furthermore, oolong tea consumption was associated with decreased risk of oral cancer in smokers or alcohol drinkers but not in non-smokers or non-alcohol drinkers. Tea consumption combined with smoking or/and alcohol drinking had a greater risk than tea consumption alone, but the risk was roughly reduced from zero to Q4 (>800 ml/day). Additionally, when stratified by demographics, the protective effect of tea was especially evident in females, urban residents, normal body mass index population (18.5-23.9), farmers, office workers and those aged <60 years.

CONCLUSIONS

Tea consumption protects against oral cancer in non-smokers or non-alcohol drinkers, but this effect may be obscured in smokers or alcohol drinkers. Additionally, demographics may modify the association between tea consumption and oral cancer.

Cumulative neurobehavioral and physiological effects of chronic caffeine intake: individual differences and implications for the use of caffeinated energy products

The use of caffeine-containing energy products has increased worldwide in recent years. All of the top-selling energy drinks contain caffeine, which is likely to be the primary psychoactive ingredient in these products. Research shows that caffeine-containing energy products can improve cognitive and physical performance. Presumably, individuals consume caffeine-containing energy products to counteract feelings of low energy in situations causing tiredness, fatigue, and/or reduced alertness. This review discusses the scientific evidence for sleep loss, circadian phase, sleep inertia, and the time-on-task effect as causes of low energy and summarizes research assessing the efficacy of caffeine to counteract decreased alertness and increased fatigue in such situations. The results of a placebo-controlled experiment in healthy adults who had 3 nights of total sleep deprivation (with or without 2-hour naps every 12 hours) are presented to illustrate the physiological and neurobehavioral effects of sustained low-dose caffeine. Individual differences, including genetic factors, in the response to caffeine and to sleep loss are discussed. The review concludes with future directions for research on this important and evolving topic.

Phenotype refinement strengthens the association of AHR and CYP1A1 genotype with caffeine consumption

Two genetic loci, one in the cytochrome P450 1A1 (CYP1A1) and 1A2 (CYP1A2) gene region (rs2472297) and one near the aryl-hydrocarbon receptor (AHR) gene (rs6968865), have been associated with habitual caffeine consumption. We sought to establish whether a more refined and comprehensive assessment of caffeine consumption would provide stronger evidence of association, and whether a combined allelic score comprising these two variants would further strengthen the association. We used data from between 4,460 and 7,520 women in the Avon Longitudinal Study of Parents and Children, a longitudinal birth cohort based in the United Kingdom. Self-report data on coffee, tea and cola consumption (including consumption of decaffeinated drinks) were available at multiple time points. Both genotypes were individually associated with total caffeine consumption, and with coffee and tea consumption. There was no association with cola consumption, possibly due to low levels of consumption in this sample. There was also no association with measures of decaffeinated drink consumption, indicating that the observed association is most likely mediated via caffeine. The association was strengthened when a combined allelic score was used, accounting for up to 1.28% of phenotypic variance. This was not associated with potential confounders of observational association. A combined allelic score accounts for sufficient phenotypic variance in caffeine consumption that this may be useful in Mendelian randomization studies. Future studies may therefore be able to use this combined allelic score to explore causal effects of habitual caffeine consumption on health outcomes.

Influence of salty food preference on daily salt intake in primary care

PURPOSE

A salt preference questionnaire may be a convenient and cost-effective method for predicting salt intake; however, the influence of salt preference on daily salt intake is unclear. This study aimed at revealing the effectiveness of the salt preference question in determining the daily salt intake in primary care outpatients.

PATIENTS AND METHODS

This cross-sectional study included 1,075 outpatients (men, n=436, 40.6%) at six primary care institutions in Japan. Primary outcomes included a salty food preference assessed by using one question and a daily salt intake, assessed using early morning second urine samples. Multivariate analyses determined the relationships between the salt intake and the two salt preference levels.

RESULTS

The mean age was 67.6±14.6 years, and 594 (55.3%) preferred salty foods. The daily salt intake was 12.3±4.0 g per day and 11.4±3.7 g per day in the salt preference and nonsalt preference groups, respectively (P<0.001). A salt intake <10 g per day was consumed by 169 (28.5%) and 181 (37.6%) patients (P=0.001), respectively, and <6 g salt per day was consumed by 28 (4.7%) and 26 (5.4%) patients (P=0.606), respectively. The patients who preferred salty foods consumed a significantly larger amount of salt per day than those who did not prefer salty foods (β coefficient, 0.621; 95% confidence interval [CI], 0.146-1.095). There was no difference in the number of patients who consumed <10 g salt per day (adjusted odds ratio [ad-OR], 1.29; 95% CI, 0.99-1.69) or <6 g salt per day (ad-OR, 1.39; 0.90-1.69) between the groups.

CONCLUSION

Preference for salty foods was positively associated with daily salt intake. However, daily salt intake was not always appropriate, even in the patients who did not prefer salty foods. Behavioral interventions for salt restriction after an assessment of daily salt intake are necessary for primary care patients, regardless of their preference for salty foods.

Association analysis of bitter receptor genes in five isolated populations identifies a significant correlation between TAS2R43 variants and coffee liking

Coffee, one of the most popular beverages in the world, contains many different physiologically active compounds with a potential impact on people’s health. Despite the recent attention given to the genetic basis of its consumption, very little has been done in understanding genes influencing coffee preference among different individuals. Given its markedly bitter taste, we decided to verify if bitter receptor genes (TAS2Rs) variants affect coffee liking. In this light, 4066 people from different parts of Europe and Central Asia filled in a field questionnaire on coffee liking. They have been consequently recruited and included in the study. Eighty-eight SNPs covering the 25 TAS2R genes were selected from the available imputed ones and used to run association analysis for coffee liking. A significant association was detected with three SNP: one synonymous and two functional variants (W35S and H212R) on the TAS2R43 gene. Both variants have been shown to greatly reduce in vitro protein activity. Surprisingly the wild type allele, which corresponds to the functional form of the protein, is associated to higher liking of coffee. Since the hTAS2R43 receptor is sensible to caffeine, we verified if the detected variants produced differences in caffeine bitter perception on a subsample of people coming from the FVG cohort. We found a significant association between differences in caffeine perception and the H212R variant but not with the W35S, which suggests that the effect of the TAS2R43 gene on coffee liking is mediated by caffeine and in particular by the H212R variant.

No other significant association was found with other TAS2R genes. In conclusion, the present study opens new perspectives in the understanding of coffee liking. Further studies are needed to clarify the role of the TAS2R43 gene in coffee hedonics and to identify which other genes and pathways are involved in its genetics.

Genome-wide association analysis of coffee drinking suggests association with CYP1A1/CYP1A2 and NRCAM

Coffee consumption is a model for addictive behavior. We performed a meta-analysis of genome-wide association studies (GWASs) on coffee intake from 8 Caucasian cohorts (N=18 176) and sought replication of our top findings in a further 7929 individuals. We also performed a gene expression analysis treating different cell lines with caffeine. Genome-wide significant association was observed for two single-nucleotide polymorphisms (SNPs) in the 15q24 region. The two SNPs rs2470893 and rs2472297 (P-values=1.6 × 10(-11) and 2.7 × 10(-11)), which were also in strong linkage disequilibrium (r(2)=0.7) with each other, lie in the 23-kb long commonly shared 5' flanking region between CYP1A1 and CYP1A2 genes. CYP1A1 was found to be downregulated in lymphoblastoid cell lines treated with caffeine. CYP1A1 is known to metabolize polycyclic aromatic hydrocarbons, which are important constituents of coffee, whereas CYP1A2 is involved in the primary metabolism of caffeine. Significant evidence of association was also detected at rs382140 (P-value=3.9 × 10(-09)) near NRCAM-a gene implicated in vulnerability to addiction, and at another independent hit rs6495122 (P-value=7.1 × 10(-09))-an SNP associated with blood pressure-in the 15q24 region near the gene ULK3, in the meta-analysis of discovery and replication cohorts. Our results from GWASs and expression analysis also strongly implicate CAB39L in coffee drinking. Pathway analysis of differentially expressed genes revealed significantly enriched ubiquitin proteasome (P-value=2.2 × 10(-05)) and Parkinson's disease pathways (P-value=3.6 × 10(-05)).

Common psychiatric disorders and caffeine use, tolerance, and withdrawal: an examination of shared genetic and environmental effects

BACKGROUND

Previous studies examined caffeine use and caffeine dependence and risk for the symptoms, or diagnosis, of psychiatric disorders. The current study aimed to determine if generalized anxiety disorder (GAD), panic disorder, phobias, major depressive disorder (MDD), anorexia nervosa (AN), or bulimia nervosa (BN) shared common genetic or environmental factors with caffeine use, caffeine tolerance, or caffeine withdrawal.

METHOD

Using 2,270 women from the Virginia Adult Twin Study of Psychiatric and Substance Use Disorders, bivariate Cholesky decomposition models were used to determine if any of the psychiatric disorders shared genetic or environmental factors with caffeine use phenotypes.

RESULTS

GAD, phobias, and MDD shared genetic factors with caffeine use, with genetic correlations estimated to be 0.48, 0.25, and 0.38, respectively. Removal of the shared genetic and environmental parameter for phobias and caffeine use resulted in a significantly worse fitting model. MDD shared unique environmental factors (environmental correlation=0.23) with caffeine tolerance; the genetic correlation between AN and caffeine tolerance and BN and caffeine tolerance were 0.64 and 0.49, respectively. Removal of the genetic and environmental correlation parameters resulted in significantly worse fitting models for GAD, phobias, MDD, AN, and BN, which suggested that there was significant shared liability between each of these phenotypes and caffeine tolerance. GAD had modest genetic correlations with caffeine tolerance, 0.24, and caffeine withdrawal, 0.35.

CONCLUSIONS

There was suggestive evidence of shared genetic and environmental liability between psychiatric disorders and caffeine phenotypes. This might inform us about the etiology of the comorbidity between these phenotypes.

Associations between polymorphisms in the AHR and CYP1A1-CYP1A2 gene regions and habitual caffeine consumption

BACKGROUND

Recent genome-wide association studies (GWASs) from populations of European descent identified single nucleotide polymorphisms (SNPs) in aryl-hydrocarbon receptor (AHR) and cytochrome P450 1A1 and 1A2 (CYP1A1-CYP1A2) genes that are associated with habitual caffeine and coffee consumption.

OBJECTIVE

We examined whether these SNPs (AHR: rs6968865 and rs4410790; CYP1A1-CYP1A2: rs2472297 and rs2470893) and 6 additional tag SNPs in the AHR gene were associated with habitual caffeine consumption in a Costa Rican population.

DESIGN

Subjects were from a case-control study of gene-diet interactions and myocardial infarction. Subjects with hypertension or missing information on smoking, caffeine intake, or genotype were excluded. Subjects were genotyped by using polymerase chain reaction with mass spectrometry-based detection, and caffeine intake was assessed by using a validated food-frequency questionnaire.

RESULTS

Compared with subjects who consumed <100 mg caffeine/d, subjects who consumed >400 mg caffeine/d were more likely to be carriers of the T, C, or T allele for rs6968865, rs4410790, and rs2472297, respectively. The corresponding ORs and 95% CIs were 1.41 (1.03, 1.93), 1.41 (1.04, 1.92), and 1.55 (1.01, 2.36). Multivariate-adjusted ORs (95% CIs) for rs6968865 were 1.44 (1.03, 2.00) for all subjects, 1.75 (1.16, 2.65) for nonsmokers, 1.15 (0.58, 2.30) for current smokers, 2.42 (1.45, 4.04) for subjects >57 y old, and 1.00 (0.65, 1.56) for subjects ≤57 y old. A similar effect modification was observed for rs4410790 but not for rs2472297.

CONCLUSION

Our findings show that previous associations between SNPs in AHR and CYP1A1-CYP1A2 and caffeine and coffee consumption from GWASs in European populations are also observed in an ethnically distinct Costa Rican population, but age and smoking are important effect modifiers.

Sleep-disordered breathing and caffeine consumption: results of a community-based study

BACKGROUND

Sleepiness is one of the most burdensome symptoms of sleep-disordered breathing (SDB). While caffeine is frequently used to avert sleepiness, the association between SDB and caffeine use has not been thoroughly explored. The current study examined whether SDB is associated with caffeine consumption and if factors such as sex, age, and daytime sleepiness explain or modify the association.

METHODS

Data from the Sleep Heart Health Study, a community-based study on the consequences of SDB, were used to characterize the association between SDB and caffeine intake. SDB was assessed with full-montage polysomnography. Caffeine use was quantified as the number of cans of soda or the cups of coffee or tea consumed daily. The Epworth Sleepiness Scale was used to assess daytime sleepiness. Multivariable negative binomial regression models were used to characterize the independent association between SDB and caffeine use.

RESULTS

Caffeinated soda, but not tea or coffee, intake was independently associated with SDB severity. Compared with participants without SDB, the relative ratios for caffeinated soda consumption in women with mild, moderate, and severe SDB were 1.20 (CI, 1.03-1.41), 1.46 (CI, 1.14-1.87), and 1.73 (CI, 1.23-2.42), respectively. For men, an association was only noted with severe SDB and caffeinated soda use. Age did not modify the SDB-caffeine association, and sleepiness could not explain the observed associations.

CONCLUSIONS

SDB is independently associated with caffeinated soda use in the general community. Identifying excessive caffeine used in SDB has potential significance given the cardiovascular effects of caffeine and untreated SDB.

Genome-wide meta-analysis identifies regions on 7p21 (AHR) and 15q24 (CYP1A2) as determinants of habitual caffeine consumption

We report the first genome-wide association study of habitual caffeine intake. We included 47,341 individuals of European descent based on five population-based studies within the United States. In a meta-analysis adjusted for age, sex, smoking, and eigenvectors of population variation, two loci achieved genome-wide significance: 7p21 (P = 2.4 × 10(-19)), near AHR, and 15q24 (P = 5.2 × 10(-14)), between CYP1A1 and CYP1A2. Both the AHR and CYP1A2 genes are biologically plausible candidates as CYP1A2 metabolizes caffeine and AHR regulates CYP1A2.

Genetics of caffeine consumption and responses to caffeine

RATIONALE

Caffeine is widely consumed in foods and beverages and is also used for a variety of medical purposes. Despite its widespread use, relatively little is understood regarding how genetics affects consumption, acute response, or the long-term effects of caffeine.

OBJECTIVE

This paper reviews the literature on the genetics of caffeine from the following: (1) twin studies comparing heritability of consumption and of caffeine-related traits, including withdrawal symptoms, caffeine-induced insomnia, and anxiety, (2) association studies linking genetic polymorphisms of metabolic enzymes and target receptors to variations in caffeine response, and (3) case-control and prospective studies examining relationship between polymorphisms associated with variations in caffeine response to risks of Parkinson's and cardiovascular diseases in habitual caffeine consumers.

RESULTS

Twin studies find the heritability of caffeine-related traits to range between 0.36 and 0.58. Analysis of polysubstance use shows that predisposition to caffeine use is highly specific to caffeine itself and shares little common disposition to use of other substances. Genome association studies link variations in adenosine and dopamine receptors to caffeine-induced anxiety and sleep disturbances. Polymorphism in the metabolic enzyme cytochrome P-450 is associated with risk of myocardial infarction in caffeine users.

CONCLUSION

Modeling based on twin studies reveals that genetics plays a role in individual variability in caffeine consumption and in the direct effects of caffeine. Both pharmacodynamic and pharmacokinetic polymorphisms have been linked to variation in response to caffeine. These studies may help guide future research in the role of genetics in modulating the acute and chronic effects of caffeine.

Coffee drinking in middle age is not associated with cognitive performance in old age

BACKGROUND

The lack of effective disease-modifying treatments highlights the need for research on the prevention of dementia. It has been suggested that coffee has a protective effect on cognitive performance in old age, but only some of the previous studies have shown this association.

OBJECTIVE

The aim of our study was to analyze the potential association between coffee drinking in middle age and cognitive performance in old age in a large sample of Finnish twins.

DESIGN

Coffee consumption and other baseline variables of 2606 middle-aged Finnish twins were assessed in 1975 and 1981 by postal questionnaires. After the median follow-up of 28 y, their cognitive status was measured by using a validated telephone interview questionnaire.

RESULTS

Coffee consumption was high and associated with educational level and several other baseline variables. After adjustment for these variables, linear regression analysis showed that coffee consumption was not an independent predictor of cognitive performance in old age (beta = -0.12 test score units per coffee cup; 95% CI: -0.27, 0.04). No consistent differences in coffee consumption and cognitive score were observed within discordant twin pairs. Also, coffee drinking did not affect the risk of mild cognitive impairment or dementia.

CONCLUSIONS

Coffee drinking is associated with many sociodemographic and health variables, but our results do not support an independent role of coffee in the pathogenesis of cognitive decline and dementia.

A genetic analysis of coffee consumption in a sample of Dutch twins

Caffeine is by far the most commonly used psychoactive substance. Caffeine is consumed regularly as an ingredient of coffee. Coffee consumption and coffee preference was explored in a sample of 4,495 twins (including 1,231 pairs) registered with the Netherlands Twin Registry. Twin resemblance was assessed by tetrachoric correlations and the influence of both genetic and environmental factors was explored with model fitting analysis in MX. Results showed moderate genetic influences (39%) on coffee consumption. The remaining variance was explained by shared environmental factors (21%) and unique environmental factors (40%). The variance in coffee preference (defined as the proportion of coffee consumption relative to the consumption of coffee and tea in total) was explained by genetic factors (62%) and unique environmental factors (38%).

Genetics of coffee consumption and its stability

BACKGROUND

Coffee is a highly popular drink associated with the pathogenesis of several diseases and the use of tobacco and alcohol. Considering the worldwide consumption, coffee has a substantial effect on individual wellbeing and public health. The role of genetic factors contributing to interindividual differences and their stability in coffee use is not well known.

AIMS

We analysed the heritability of coffee consumption and its stability in a large population-based sample of Finnish twins.

DESIGN

In 1975 and 1981 a postal questionnaire on coffee consumption was sent to all Finnish same-sex twin pairs born before 1958. Responses were obtained from 10 716 complete twin pairs in 1975 (3409 monozygotic and 7307 dizygotic), of whom 8124 also responded in 1981. The data were analysed using classical twin modelling based on linear structural equations.

FINDINGS

Additive genetic and unique environmental factors affected coffee drinking, whereas shared environmental factors did not show any effect. Heritability of coffee consumption, adjusted for age and sex, was estimated as 0.56 in 1975 and 0.45 in 1981. Coffee consumption showed a moderate correlation between these two time-points (r = 0.58 in men and 0.55 in women). Genetic factors affecting coffee consumption were stable: additive genetic correlations were 0.84 in men and 0.83 in women, whereas unique environmental correlations were moderate (0.45 and 0.36). Additive genetic factors had the highest contribution in young adults.

CONCLUSIONS

Coffee consumption is affected by both additive genetic and unique environmental factors, each of which plays an almost equally important role. The long-term stability of coffee consumption is affected mainly by a stable set of additive genetic factors.

"No thanks, it keeps me awake": the genetics of coffee-attributed sleep disturbance

STUDY OBJECTIVES

Previous genetic investigations of sleep disturbance have shown various measures of sleep quality and sleep pattern to be heritable. But none of these studies have investigated the genetic predisposition to sleep disturbance attributed to caffeine. In this study, the heritability of coffee-attributed sleep disturbance and its relationship with other sleep measures were estimated, and chromosomal regions influencing this trait were identified.

DESIGN

A classical twin design was used to estimate the heritability of coffee-attributed sleep disturbance and its genetic covariance with other measures of sleep disturbance (e.g., due to anxiety, depression) and sleep quality (e.g., variability in sleep quality). To locate quantitative trait loci influencing coffee-attributed sleep disturbance, a genome-wide linkage screen of 1395 microsatellite markers was performed.

PARTICIPANTS

The study included 3808 Australian adult twin pairs (n = 1799 monozygous pairs; n = 2009 dizygous pairs). A subsample of 1989 individuals from 1175 families was used for the linkage analysis.

MEASUREMENTS AND RESULTS

The heritability of coffee-attributed sleep disturbance (measured by self report) was approximately 0.40, with three fourths of this genetic variance explained by genes unrelated to the general sleep disturbance factor. One region of significant linkage to coffee-attributed sleep disturbance was identified on chromosome 2q (LOD score of 2.9).

CONCLUSIONS

Although no candidate genes known to be related to caffeine metabolism or sleep disorder were identified in the significant linkage region, 2 candidates were found under a smaller peak on chromosome 17q.

Genetic polymorphism of the adenosine A2A receptor is associated with habitual caffeine consumption

BACKGROUND

Caffeine is the most widely consumed stimulant in the world, and individual differences in response to its stimulating effects may explain some of the variability in caffeine consumption within a population.

OBJECTIVE

We examined whether genetic variability in caffeine metabolism [cytochrome P450 1A2 (CYP1A2) -163A-->C] or the main target of caffeine action in the nervous system [adenosine A(2A) receptor (ADORA2A) 1083C-->T] is associated with habitual caffeine consumption.

DESIGN

Subjects (n=2735) were participants from a study of gene-diet interactions and risk of myocardial infarction who did not have a history of hypertension. Genotype frequencies were examined among persons who were categorized according to their self-reported daily caffeine intake, as assessed with a validated food-frequency questionnaire.

RESULTS

The ADORA2A, but not the CYP1A2, genotype was associated with different amounts of caffeine intake. Compared with persons consuming <100 mg caffeine/d, the odds ratios for having the ADORA2A TT genotype were 0.74 (95% CI: 0.53, 1.03), 0.63 (95% CI: 0.48, 0.83), and 0.57 (95% CI: 0.42, 0.77) for those consuming 100-200, >200-400, and >400 mg caffeine/d, respectively. The association was more pronounced among current smokers than among nonsmokers (P for interaction = 0.07). Persons with the ADORA2A TT genotype also were significantly more likely to consume less caffeine (ie, <100 mg/d) than were carriers of the C allele [P=0.011 (nonsmokers), P=0.008 (smokers)].

CONCLUSION

Our findings show that the probability of having the ADORA2A 1083TT genotype decreases as habitual caffeine consumption increases. This observation provides a biologic basis for caffeine consumption behavior and suggests that persons with this genotype may be less vulnerable to caffeine dependence.