Coffee and cancer: a prospective study of 43,000 Norwegian men and women

A systematic review and dose-response meta-analysis of prospective cohort studies on coffee consumption and risk of lung cancer

Studies on the association between coffee consumption and risk of lung cancer have been conflicting. The aim of this study was to systematically review the current evidence on the association between coffee consumption and risk of lung cancer and to quantify this association by performing a meta-analysis. A comprehensive systematic search was performed on online databases up to July 2023 investigating the association between coffee consumption and risk of lung cancer. All prospective cohort studies reporting odds ratios (ORs), rate or risk ratios (RRs), or hazard ratios (HRs) and 95% confidence intervals (CIs) in this context were included. The overall effect size was calculated using the random-effects model and statistical between-studies heterogeneity was examined using Cochrane's Q test and I2. A total of 14 prospective cohort studies were included in this systematic review and meta-analysis. We found a significant positive association between coffee consumption and risk of lung cancer (RR: 1.28; 95% CI: 1.12, 1.47). This association remained significant when we included a pooled analysis paper and excluded 5 cohort studies (RR: 1.37; 95% CI: 1.12, 1.66). We observed no proof of significant publication bias using Egger's test (P = 0.58). Moreover, dose-response analysis showed that each one cup/day increase in coffee consumption was related with a 6% higher lung cancer risk (RR: 1.06; 95% CI: 1.03, 1.09). In conclusion, we found a significant positive association between coffee consumption and risk of lung cancer.

Coffee Consumption and Risk of Lung Cancer: A Meta-Analysis of Prospective Cohort Studies

The association between coffee consumption and lung cancer risk remains inconsistent. To quantitatively assess this association, we conducted a meta-analysis of prospective cohort studies. We searched PubMed and Web of Science databases along with hand searches for eligible studies published up to July 2023. A total of 26 prospective studies, including 30,305 lung cancer cases and 1,795,158 participants, were included in the meta-analysis. The pooled RR for high vs. low coffee consumption was 1.30 (95% CI: 1.11-1.53) with significant heterogeneity (I2 = 72.0%, p < .001). For never smokers, however, the pooled RR was 1.18 (95% CI: 0.999-1.38) with no evidence of heterogeneity (I2 = 0.0%, p = .53). By adjustment for body mass index (BMI), there was no significant association between coffee consumption and lung cancer risk in studies that adjusted for BMI (RR = 1.06; 95% CI: 0.87-1.30) (Pdifference = .01). Further analysis of studies that adjusted for BMI in never smokers found that coffee consumption was not associated with lung cancer risk. In conclusion, the association of high coffee consumption with lung cancer risk was attenuated when the confounding effects caused by smoking and BMI were controlled. Our results, therefore, imply that coffee consumption does not seem to be a risk factor for lung cancer incidence.

Coffee consumption and risk of renal cancer: a meta-analysis of cohort evidence

PURPOSE

There is increasing evidence that coffee consumption is related to reduced risks for some cancers, but the evidence for renal cancer is inconclusive. Therefore, we conducted a meta-analysis to summarize the cohort evidence of this relationship.

METHODS

A literature search was performed in PubMed and Embase through February 2021. Meta-analyses using a random effects model were conducted for reported relative risk estimates (RRs) relating coffee intake and renal cancer incidence or mortality. We also performed a two-stage random effects exposure-response meta-analysis. Between-study heterogeneity was assessed.

RESULTS

In a meta-analysis of the ten identified cohort studies, we found a summary RR of 0.88 [95% confidence interval (CI) 0.78-0.99] relating the highest vs. the lowest category of coffee intake and renal cancer, with no significant between-study heterogeneity observed (I² = 35%, p = 0.13). This inverse association remained among studies of incident cancers (RR 0.85, 95% CI 0.76-0.96) and studies adjusting for smoking and body mass index (RR 0.87, 95% CI 0.77-0.99).

CONCLUSIONS

Our findings from this meta-analysis of the published cohort evidence are suggestive of an inverse association between coffee consumption and renal cancer risk.

Coffee consumption and breast cancer risk: a narrative review in the general population and in different subtypes of breast cancer

PURPOSE

Most of the existing literature reports no association or a slight negative association between coffee consumption and the risk of developing breast cancer. However, the level of risk differs when considering various subgroups, such as menopausal status, hormonal status of the tumor or genetic mutations. The present review based on a literature search sets the point on the potential influence of a common daily drink, coffee, on the risk of developing breast cancer in the general population, in different subgroups of women and the consequences of drinking coffee after breast cancer has been diagnosed and treated.

RESULTS

This review confirms that in the general population, there is no association between coffee intake and breast cancer risk or a slight protective effect, even at high dosages. Coffee is inversely associated with breast cancer risk in postmenopausal women and in women carrying a BRCA1 mutation. Possible risk differences exist between slow and fast caffeine metabolizers and with weight. Coffee consumption after breast cancer diagnosis and surgery, associated with tamoxifen and/or radiotherapy, reduced the occurrence of early events. The effects of coffee intake are less clear in other subgroups, mainly premenopausal women, women carrying a BRCA2 mutation and tumors with variable hormonal status (positive or negative for ER/PR) and would need additional studies.

Coffee consumption and risk of prostate cancer: a systematic review and meta-analysis

OBJECTIVES

To conduct a systematic review with meta-analysis of cohort studies to evaluate the association of coffee consumption with the risk of prostate cancer.

DATA SOURCES

PubMed, Web of Science and Embase were searched for eligible studies up to September 2020.

STUDY SELECTION

Cohort studies were included.

DATA EXTRACTION AND SYNTHESIS

Two researchers independently reviewed the studies and extracted the data. Data synthesis was performed via systematic review and meta-analysis of eligible cohort studies. Meta-analysis was performed with the "metan" and "glst" commands in Stata 14.0.

MAIN OUTCOMES AND MEASURES

Prostate cancer was the main outcome. It was classified as localised prostate cancer which included localised or non-aggressive cancers; advanced prostate cancer which included advanced or aggressive cancers; or fatal prostate cancer which included fatal/lethal cancers or prostate cancer-specific deaths.

RESULTS

Sixteen prospective cohort studies were finally included, with 57 732 cases of prostate cancer and 1 081 586 total cohort members. Higher coffee consumption was significantly associated with a lower risk of prostate cancer. Compared with the lowest category of coffee consumption, the pooled relative risk (RR) was 0.91 (95% CI 0.84 to 0.98), I²= 53.2%) for the highest category of coffee consumption. There was a significant linear trend for the association (p=0.006 for linear trend), with a pooled RR of 0.988 (95% CI 0.981 to 0.995) for each increment of one cup of coffee per day. For localised, advanced and fatal prostate cancer, the pooled RRs were 0.93 (95% CI 0.87 to 0.99), 0.88 (95% CI 0.71 to 1.09) and 0.84 (95% CI 0.66 to 1.08), respectively. No evidence of publication bias was indicated in this meta-analysis.

CONCLUSIONS

This study suggests that a higher intake of coffee may be associated with a lower risk of prostate cancer.

Therapeutic strategies and potential implications of silver nanoparticles in the management of skin cancer

Skin cancer (SC) is the most common carcinoma affecting 3 million people annually in the United States and millions of people worldwide. It is classified as melanoma SC (MSC) and non-melanoma SC (NMSC). NMSC represents approximately 80% of SC and includes squamous cell carcinoma and basal cell carcinoma. MSC, however, has a higher mortality rate than SC because of its ability to metastasize. SC is a major health problem in the United States with significant morbidity and mortality in the Caucasian population. Treatment options for SC include cryotherapy, excisional surgery, Mohs surgery, curettage and electrodessication, radiation therapy, photodynamic therapy, immunotherapy, and chemotherapy. Treatment is chosen based on the type of SC and the potential for side effects. Novel targeted therapies are being used with increased frequency for large tumors and for metastatic disease. A scoping literature search on PubMed, Google Scholar, and Cancer Registry websites revealed that traditional chemotherapeutic drugs have little effect against SC after the cancer has metastasized. Following an overview of SC biology, epidemiology, and treatment options, this review focuses on the mechanisms of advanced technologies that use silver nanoparticles in SC treatment regimens.

Coffee Consumption and Pancreatic Cancer Risk: A Meta-Epidemiological Study of Population-based Cohort Studies

OBJECTIVE

Previous systematic reviews evaluating the association between coffee consumption and pancreatic cancer showed inconsistent results. The aim was to conduct a meta-epidemiological study to explore further the association between coffee consumption and the incidence of pancreatic cancer.

METHODS

The selection criteria were defined as a population-based prospective cohort study reporting adjusted relative risk (RR) and their 95% confidence interval (95%CI) of pancreatic cancer occurrence according to coffee consumption. Adjusted RR for the highest versus the lowest level of coffee consumption in each study was extracted. A fixed-effect model was applied to calculate a summary RR (sRR) and its 95%CI. Two-stage random-effects dose-response meta-analysis (DRMA) was performed to estimate the incidence risk per unit dose (cup per day).

RESULTS

Twelve cohort studies were selected for meta-analysis. The total number of cohort participants was 3,230,053, and pancreatic cancer incidents were 10,587. The sRR of pancreatic cancer risk for the highest versus the lowest level of coffee consumption indicated no statistical significance (sRR=0.98, 95% CI: 0.88-1.10; I-squared=0.0%). Two-stage random-effect DRMA showed the non-linear relationship between the amount of coffee consumption and pancreatic cancer risk. And the RR for an increment of one cup per day of coffee consumption was 0.97 (95%CI: 0.91-1.04, P=0.42), without statistically significant.

CONCLUSION

There was no association between coffee consumption habits and pancreatic cancer risk. And there was no statistical significance in the dose-response relationship between the amount of coffee consumption and pancreatic cancer risk. Finding the turning point would be important because it can be critical information for the prevention of pancreatic cancer. 
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Association between dietary intake and risk of ovarian cancer: a systematic review and meta-analysis

PURPOSE

It is unclear how dietary intake influences the ovarian cancer. The present paper sets out to systematically review and meta-analyze research on dietary intake to identify cases having high- or low-risk ovarian cancer.

METHODS

Scopus, PubMed, and Wiley Online Libraries were searched up to the date November 24, 2019. Two reviewers were requested to independently extract study characteristics and to assess the bias and applicability risks with reference to the study inclusion criteria. Meta-analyses were performed to specify the relationship between dietary intake and the risk of ovarian cancer identifying 97 cohort studies.

RESULTS

No significant association was found between dietary intake and risk of ovarian cancer. The results of subgroup analyses indicated that green leafy vegetables (RR = 0.91, 95%, 0.85-0.98), allium vegetables (RR = 0.79, 95% CI 0.64-0.96), fiber (RR = 0.89, 95% CI 0.81-0.98), flavonoids (RR = 0.83, 95% CI 0.78-0.89) and green tea (RR = 0.61, 95% CI 0.49-0.76) intake could significantly reduce ovarian cancer risk. Total fat (RR = 1.10, 95% CI 1.02-1.18), saturated fat (RR = 1.11, 95% CI 1.01-1.22), saturated fatty acid (RR = 1.19, 95% CI 1.04-1.36), cholesterol (RR = 1.13, 95% CI 1.04-1.22) and retinol (RR = 1.14, 95% CI 1.00-1.30) intake could significantly increase ovarian cancer risk. In addition, acrylamide, nitrate, water disinfectants and polychlorinated biphenyls were significantly associated with an increased risk of ovarian cancer.

CONCLUSION

These results could support recommendations to green leafy vegetables, allium vegetables, fiber, flavonoids and green tea intake for ovarian cancer prevention.

Associations between tea and coffee beverage consumption and the risk of lung cancer in the Singaporean Chinese population

BACKGROUND

Tea and coffee are widely consumed beverages. Tea flavonoids have been shown to inhibit lung tumorigenesis using in vitro and in vivo models. Conversely, coffee contains complex mixtures of biochemically active compounds, some of which may have genotoxic and mutagenic properties. However, previous epidemiologic studies have shown inconsistent results on tea and coffee in relation to lung cancer risk.

METHODS

The Singapore Chinese Health Study is a population-based prospective cohort of 63,257 Singaporean Chinese men and women, with an average of 17.7 years of follow-up. Information on tea and coffee consumption and other lifestyle factors was collected through in-person interviews at baseline. Multivariable Cox regression models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the associations with adjustment for potential confounders.

RESULTS

There were 1486 incident lung cancer cases. Compared to non-daily coffee drinkers, HRs (95% CIs) of lung cancer risk for those consuming one, two, and three or more cups of coffee per day were 1.18 (1.02-1.36), 1.21 (1.05-1.40), and 1.32 (1.08-1.62) respectively (P for trend = 0.0034). The highest category of black tea consumption (at least 2 cups per day) was inversely associated with risk of lung cancer [HR (95% CI) = 0.73 (0.53-0.99)], particularly among men [HR (95% CI) = 0.67 (0.47-0.95)], compared to less-than-weekly black tea drinkers, although the interaction by sex was not statistically significant.

CONCLUSIONS

Coffee beverage consumption was associated with higher risk of developing lung cancer. On the other hand, black tea intake was associated with lower risk of lung cancer among men in our cohort, and further studies are needed to confirm this association.

Caffeine, Type of Coffee, and Risk of Ovarian Cancer: A Dose-Response Meta-Analysis of Prospective Studies

CONTEXT

Prospective studies on caffeine and different types of coffee intake in relation to the risk of ovarian cancer have shown conflicting results.

OBJECTIVE

The aim of the present study was to perform a dose-response meta-analysis of cohort studies on the association between dietary caffeine intake, different types of coffee consumption, and the risk of ovarian cancer.

DATA SOURCES

PubMed/Medline, ISI Web of Science, Scopus, and EMBASE were searched to identify relevant studies reported until October 2018.

STUDY SELECTION

Prospective cohort studies that had considered caffeine or different types of coffee as the exposure variable and ovarian cancer as the main outcome variable or as one of the outcome variables were included in our systematic review and meta-analysis. Two of us independently screened 9344 publications. A total of 14 cohort studies were included in the meta-analysis.

DATA EXTRACTION

Two of us independently extracted the data. Any disagreements were resolved in consultation with the principal investigator.

RESULTS

Combining 13 effect sizes, we found no substantial association between coffee consumption and risk of ovarian cancer [risk ratio (RR), 1.08; 95% CI, 0.89 to 1.33]. Also, one additional cup daily of coffee consumption was marginally associated with an increased risk of ovarian cancer (RR, 1.02; 95% CI, 0.99 to 1.05; P = 0.21; I2 = 0.0%; Pheterogeneity = 0.68). No statistically significant association was observed between caffeine intake or caffeinated or decaffeinated coffee consumption and the risk of ovarian cancer.

CONCLUSIONS

We found no statistically significant association between caffeine intake or different types of coffee and the risk of ovarian cancer.

Mediterranean dietary pattern and skin cancer risk: A prospective cohort study in French women

BACKGROUND

The Mediterranean diet (MD) has been reported to be associated with lower cancer risk. However, while previous studies explored major single components of the MD, only 1 previous study has investigated adherence to the MD in relation to melanoma risk.

OBJECTIVE

The aim of this study was to explore the relations between adherence to the MD and the risk of skin cancer, including melanomas, basal cell carcinomas (BCCs), and squamous cell carcinomas (SCCs).

DESIGN

Etude Epidémiologique auprès de femmes de la Mutuelle Générale de l'Education Nationale (E3N) is a prospective cohort of 98,995 French women aged 40-65 y in 1990. Dietary data were collected via a validated food questionnaire in 1993. Adherence to the MD was assessed using a 9-unit dietary score that incorporates intakes of fruit, vegetables, legumes, cereal products, olive oil, fish, dairy products, meat products, and alcohol. We used Cox proportional hazards regression models to compute HRs and 95% CIs adjusted for age and main known skin cancer risk factors.

RESULTS

From 1993 to 2008, a total of 2003 skin cancer cases were ascertained among 67,332 women, including 404 melanomas, 1367 BCCs, and 232 SCCs. Score of adherence to the MD was associated with lower risk of skin cancer (HR: 0.83; 95% CI: 0.73, 0.93 for high compared with low score, Ptrend = 0.001). MD score was also inversely and linearly associated with risks of melanoma (HR: 0.72; 95% CI: 0.54, 0.96; Ptrend = 0.02) and BCC (HR: 0.77; 95% CI: 0.66, 0.90; Ptrend = 0.0006) but not SCC (HR: 1.08; 95% CI: 0.75, 1.55; Ptrend = 0.68), although with no heterogeneity across skin cancer types (Pheterogeneity = 0.23).

CONCLUSION

These findings suggest that adherence to the MD is associated with a lower skin cancer risk in women, particularly melanoma and BCC. If confirmed in future research, these findings may have important implications in skin cancer prevention.

Coffee and pancreatic cancer risk among never-smokers in the UK prospective Million Women Study

Reported associations between coffee consumption and an increased risk of pancreatic cancer could be due to residual confounding by smoking and/or biased recall of coffee consumption in retrospective studies. Studying associations prospectively in never smokers should minimize these problems, but thus far such studies have included relatively small numbers of cases. In our study, 309,797 never-smoking women self-reported typical daily coffee consumption at a mean age of 59.5 years (SD 5.0 years) and were followed up for a median of 13.7 years (IQR: 12.2-14.9) through record linkage to national health cancer and death registries. During this period, 962 incident cases of pancreatic cancers were registered. Cox regression was used to calculate adjusted relative risks [RRs] of incident pancreatic cancer with 95% confidence intervals [CIs] in relation to coffee consumption at baseline. After adjustment for potential confounding factors, including body mass index and alcohol consumption, RRs of pancreatic cancer in never-smokers who reported usually consuming 1-2, 3-4, and ≥ 5 cups of coffee daily, compared to nondrinkers of coffee, were 1.02 (CI 0.83-1.26), 0.96 (0.76-1.22), and 0.87 (0.64-1.18), respectively (trend p = 0.2). A meta-analysis of results from this cohort and 3 smaller prospective studies found little or no statistically significant association between coffee consumption and pancreatic cancer risk in never smokers (summary RR = 1.00, CI 0.86-1.17 for ≥2 vs. zero cups of coffee per day).

Association between coffee consumption and risk of bladder cancer in a meta-analysis of 16 prospective studies

Background

Current evidence remains equivocal as to whether and how consumption of coffee may be associated with risk of bladder cancer, and potential influence of confounding by smoking on this association is yet to be elucidated. We conducted an updated meta-analysis of prospective studies to address these issues.

Methods

Relevant studies were identified by searching PubMed and EMBASE databases from inception to April 2019. A random-effects model was used to estimate summary relative risk (RR) with corresponding 95% confidence interval (CI) of bladder cancer associated with coffee consumption.

Results

The final analysis included 16 prospective studies comprising 2,122,816 participants and 11,848 bladder cancer cases. Overall, coffee consumption was not associated with risk of bladder cancer (RR _high-vs-low = 1.07, 95% CI: 0.96–1.20). The lack of association persisted in the strata defined by sex or participants’ smoking status. Meta-regression analyses identified the number cases (P_difference = 0.06) and the degree of adjustment for smoking (P_difference = 0.04) as potential sources of heterogeneity. There was an increased risk of bladder cancer related to higher coffee consumption among studies with fewer cases (RR _high-vs-low = 1.38, 95% CI: 1.05–1.81) and among those with poorer adjustment for smoking (RR _high-vs-low = 1.48, 95% CI: 1.14–1.93). Results were similar in the dose-response analyses (RR _{1 cup/d} = 1.01, 95% CI: 0.98–1.03).

Conclusion

Best evidence available to date does not support an independent association between coffee consumption and bladder cancer risk. Some direct associations observed in individual studies may be a result of residual confounding by smoking.

Supplementary information

Supplementary information accompanies this paper at 10.1186/s12986-019-0390-3.

Association between coffee intake and the risk of oral cavity cancer: a meta-analysis of observational studies

The association between coffee intake and the risk of oral cavity cancer has been inconsistent in previous studies. Therefore, we conducted a meta-analysis to summarize the evidence regarding the strength of association between coffee intake and oral cavity cancer. PubMed, Embase, and Cochrane Library were searched to select studies on the relationship between coffee intake and oral cavity cancer conducted up to September 2018. Case-control or cohort studies and those that have reported about the effect estimates with 95% confidence intervals (CIs) of oral cavity cancer according to the different categories of coffee intake were included. The odds ratio (OR) and its corresponding 95% CI were calculated using the random-effects model. Fourteen case-control and five cohort studies that recruited 6456 patients with oral cavity cancer were included in the final quantitative meta-analysis. High versus low coffee intake was associated with a reduced risk of oral cavity cancer (OR: 0.68; 95% CI: 0.56-0.82; P < 0.001) in case-control studies (OR: 0.70; 95% CI: 0.55-0.90; P = 0.006) and cohort studies (OR: 0.65; 95% CI: 0.48-0.87; P = 0.004). Moreover, intermediate coffee intake was significantly associated with a reduced risk of oral cavity cancer (OR: 0.85; 95% CI: 0.77-0.94; P = 0.002), and such associations were mainly observed in case-control studies (OR: 0.86; 95% CI: 0.76-0.98; P = 0.021) but not in cohort studies (OR: 0.83; 95% CI: 0.67-1.02; P = 0.071). High or intermediate coffee intake might have protective effects against oral cavity cancer. However, the underlying mechanisms must be further evaluated in large-scale prospective cohort studies.

Coffee consumption and colorectal cancer risk: a dose-response meta-analysis on prospective cohort studies

Evidence regarding the influence of coffee drinking on colorectal cancer (CRC) is limited, and it remains unclear whether coffee consumption is associated with the risk of the disease. To clarify this association, a comprehensive meta-analysis was performed. The risk of CRC was compared between the categories of coffee consumption, and a dose-response relationship was studied using restricted cubic splines. We did not find evidence for the association between coffee consumption and CRC risk. Among alternative study inclusions, when using pooled projects, coffee consumption was related with a decreased risk of colon cancer in a subgroup analysis of never-smokers and in Asian countries, and with an increased risk of rectal cancer in an analysis of the general population and after restriction to women, never-smokers, and European countries. In conclusion, the association between coffee consumption and CRC risk is controversial and should be clarified in further cohort studies.

Coffee Consumption and Risk of Colorectal Cancer: A Systematic Review and Meta-Analysis of Prospective Studies

Coffee is a blend of compounds related to gastrointestinal physiology. Given its popularity and the epidemiology of colorectal cancer, the impact of this beverage on public health could be considerable. Our aim was to provide an updated synthesis of the relationship between coffee consumption and the risk of colorectal cancer. We conducted a systematic review and meta-analysis of 26 prospective studies. Regarding colorectal cancer, no significant relationship was detected. Stratifying for ethnicity, a protective effect emerged in US subjects. Concerning colon cancer, coffee proved to exert a protective effect in men and women combined and in men alone. Stratifying for ethnicity, a significant protective effect was noted in European men only and in Asian women only. Concerning rectal cancer, no association was found. Decaffeinated coffee exhibited a protective effect against colorectal cancer in men and women combined. Studies were appraised for their quality by means of the Newcastle-Ottawa Quality Assessment Scale for Cohort studies. Only one study proved to be of low quality. Ethnicity could explain the heterogeneity of the studies. However, little is known about the relationship between the genetic make-up and the risk of colorectal cancer associated with coffee. Further research is warranted.

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.

Foods and beverages and colorectal cancer risk: a systematic review and meta-analysis of cohort studies, an update of the evidence of the WCRF-AICR Continuous Update Project

Objective

As part of the World Cancer Research Fund International Continuous Update Project, we updated the systematic review and meta-analysis of prospective studies to quantify the dose-response between foods and beverages intake and colorectal cancer risk.

Data sources

PubMed and several databases up to 31 May 2015.

Study selection

Prospective studies reporting adjusted relative risk estimates for the association of specific food groups and beverages and risk of colorectal, colon and rectal cancer.

Data synthesis

Dose-response meta-analyses using random effect models to estimate summary relative risks (RRs).

Results

About 400 individual study estimates from 111 unique cohort studies were included. Overall, the risk increase of colorectal cancer is 12% for each 100 g/day increase of red and processed meat intake (95% CI = 4-21%, I2=70%, pheterogeneity (ph)<0.01) and 7% for 10 g/day increase of ethanol intake in alcoholic drinks (95% CI = 5-9%, I2=25%, ph = 0.21). Colorectal cancer risk decrease in 17% for each 90g/day increase of whole grains (95% CI = 11-21%, I2 = 0%, ph = 0.30, 6 studies) and 13% for each 400 g/day increase of dairy products intake (95% CI = 10-17%, I2 = 18%, ph = 0.27, 10 studies). Inverse associations were also observed for vegetables intake (RR per 100 g/day =0.98 (95% CI = 0.96-0.99, I2=0%, ph = 0.48, 11 studies) and for fish intake (RR for 100 g/day = 0.89 (95% CI = 0.80-0.99, I2=0%, ph = 0.52, 11 studies), that were weak for vegetables and driven by one study for fish. Intakes of fruits, coffee, tea, cheese, poultry and legumes were not associated with colorectal cancer risk.

Conclusions

Our results reinforce the evidence that high intake of red and processed meat and alcohol increase the risk of colorectal cancer. Milk and whole grains may have a protective role against colorectal cancer. The evidence for vegetables and fish was less convincing.

A Prospective Investigation of Coffee Drinking and Bladder Cancer Incidence in the United States

BACKGROUND

In 1991, coffee was classified as a group 2B carcinogen, possibly carcinogenic to humans, based on limited epidemiologic evidence of a positive association with bladder cancer. In 2016, the International Agency for Research on Cancer downgraded this classification due to lack of evidence from prospective studies particularly for never smokers.

METHODS

Baseline coffee drinking was assessed with a food frequency questionnaire in the NIH-AARP prospective cohort study. Among 469,047 US adults, who were cancer free at baseline, 6,012 bladder cancer cases (5,088 men and 924 women) were identified during >6.3 million person-years of follow-up. Multivariable-adjusted Cox proportional hazards models were used to estimate hazard ratios (HR) and 95% confidence intervals (CI), with non-coffee drinkers as the reference group.

RESULTS

Coffee drinking was positively associated with bladder cancer in models adjusted for age and sex (HR for ≥4 cups/d relative to coffee nondrinkers = 1.91, 95% CI = 1.70, 2.14; P trend < 0.0001). However, the association was substantially attenuated after adjustment for cigarette smoking and other potential confounders (HR for ≥4 cups/d relative to coffee nondrinkers = 1.18, 95% CI = 1.05, 1.33; P trend = 0.0007). Associations were further attenuated after additional adjustment for lifetime smoking patterns among the majority of the cohort with this available data (P trend = 0.16). There was no evidence of an association among never smokers (P trend = 0.84).

CONCLUSIONS

Positive associations between coffee drinking and bladder cancer among ever smokers but not never smokers suggest that residual confounding from imperfect measurement of smoking or unmeasured risk factors may be an explanation for our positive findings.

Coffee Drinking and the Risk of Endometrial Cancer: An Updated Meta-Analysis of Observational Studies

BACKGROUND

Several compounds contained in coffee have been found to suppress carcinogenesis in experimental studies. We conducted a dose-response meta-analysis to assess the impact of coffee consumption on the risk of endometrial cancer.

MATERIALS AND METHODS

We searched MEDLINE and EMBASE databases for studies published up to August 2016. Using random effects models, we estimated summary relative risks (RR) for cohort studies and odds ratios (OR) for case-control studies with 95% confidence intervals (CI). Dose-response analyses were conducted by using generalized least square trend estimation.

RESULTS

We identified 12 cohort studies and 8 case-control studies eligible for inclusion, contributing with 11,663 and 2,746 endometrial cancer cases, respectively. The summary RR for highest compared with lowest coffee intake was 0.74 (95% CI: 0.68-0.81; pheterogeneity = 0.09, I2 = 32%). The corresponding summary RR among cohort studies was 0.78 (95% CI: 0.71-0.85; pheterogeneity = 0.14, I2 = 31.9%) and 0.63 (95% CI: 0.53-0.76; pheterogeneity = 0.57, I2 = 0%) for case-control studies. One-cup increment per day was associated with 3% risk reduction (95% CI: 2-4%) in cohort studies and 12% (95% CI: 5-18%) in case-control studies. After pooling the results from 5 cohort studies, the association remained significant only in women with body mass index over 30 (RR = 0.71, 95% CI: 0.61-0.81).

CONCLUSION

The results from our meta-analysis strengthen the evidence of a protective effect of coffee consumption on the risk of EC and further suggest that increased coffee intake might be particularly beneficial for women with obesity.

Coffee consumption and risk of rare cancers in Scandinavian countries

Studies on the association between heavy coffee consumption and risk of less frequently diagnosed cancers are scarce. We aimed to quantify the association between filtered, boiled, and total coffee consumption and the risk of bladder, esophageal, kidney, pancreatic, and stomach cancers. We used data from the Norwegian Women and Cancer Study and the Northern Sweden Health and Disease Study. Information on coffee consumption was available for 193,439 participants. We used multivariable Cox proportional hazards models to calculate hazard ratios (HR) with 95% confidence intervals (CI) for the investigated cancer sites by category of total, filtered, and boiled coffee consumption. Heavy filtered coffee consumers (≥ 4 cups/day) had a multivariable adjusted HR of 0.74 of being diagnosed with pancreatic cancer (95% CI 0.57-0.95) when compared with light filtered coffee consumers (≤ 1 cup/day). We did not observe significant associations between total or boiled coffee consumption and any of the investigated cancer sites, neither in the entire study sample nor in analyses stratified by sex. We found an increased risk of bladder cancer among never smokers who were heavy filtered or total coffee consumers, and an increased risk of stomach cancer in never smokers who were heavy boiled coffee consumers. Our data suggest that increased filtered coffee consumption might reduce the risk of pancreatic cancer. We did not find evidence of an association between coffee consumption and the risk of esophageal or kidney cancer. The increased risk of bladder and stomach cancer was confined to never smokers.

Association of coffee consumption with risk of colorectal cancer: a meta-analysis of prospective cohort studies

A meta-analysis was performed to assess the association of coffee consumption with colorectal cancer and to investigate the shape of the association. Relevant prospective cohort studies were identified by a comprehensive search of the PubMed, Embase and Web of Science databases from their inception through August 2015. Either a random-effects model or fixed-effects model was used to compute the pooled risk estimates when appropriate. Linear and nonlinear dose-response meta-analyses were also performed. Nineteen prospective cohort studies involving 2,046,575 participants and 22,629 patients with colorectal cancer were included. The risk of colon cancer was decreased by 7% for every 4 cups per day of coffee (RR=0.93, 95%CI, 0.88-0.99; P=0.199). There was a threshold approximately five cups of coffee per day, and the inverse association for colorectal cancer appeared to be stronger at a higher range of intake. However, a nonlinear association of rectal cancer with coffee consumption was not observed (P for nonlinearity = 0.214). In conclusion, coffee consumption is significantly associated with a decreased risk of colorectal cancer at ≥ 5 cups per day of coffee consumption. The findings support the recommendations of including coffee as a healthy beverage for the prevention of colorectal cancer.

Coffee is protective against oral and pharyngeal cancer: A systematic review and meta-analysis

OBJECTIVES

Coffee is one of the most popular and consumable drinks worldwide. However, there are conflicting results on the influence of this drink in oral and pharyngeal cancer risk. To clarify this, we aimed to systemically review and carry out a meta-analysis of the relevant literature on the association between coffee and oral and pharyngeal cancer.

STUDY DESIGN

We carried out an electronic search of publications up to August 2016 from PubMed, National Library of Medicines Medline, Embase, Science Direct and the Cochrane Central Register. The Newcastle-Ottawa scale was used to address the quality of the studies a meta-analysis was carried out using random-effects models.

RESULTS

From the 22,515 entries identified in the search, 13 case-control and 4 cohort studies were selected. With regards to quality on the Newcastle-Ottawa scale, an overall value of 6.06 was obtained. The analysis for oral and pharyngeal cancer grouped together indicated a pooled OR of .69 (95% CI of .57-.84; p<.001) for high versus low coffee consumption with a moderate heterogeneity (I2: 50.3%; p=.009). Regarding studies on oral cavity cancers we observed a pooled OR of 0.82; 95% CI =.58-1.16; p=.257) and for pharyngeal cancers a pooled OR of .72 (95% CI of 0.54-.95; p=.019). There was no significant publication bias.

CONCLUSION

The results show an inverse association between high coffee consumption and the risk of oral and pharyngeal cancers, which indicates that coffee may have a protective role against these cancers. Further larger prospective observational cohort studies are needed to address any effect of other possible co-factors.

A genome-wide analysis of gene-caffeine consumption interaction on basal cell carcinoma

Animal models have suggested that oral or topical administration of caffeine could inhibit ultraviolet-induced carcinogenesis via the ataxia telangiectasia and rad3 (ATR)-related apoptosis. Previous epidemiological studies have demonstrated that increased caffeine consumption is associated with reduced risk of basal cell carcinoma (BCC). To identify common genetic markers that may modify this association, we tested gene-caffeine intake interaction on BCC risk in a genome-wide analysis. We included 3383 BCC cases and 8528 controls of European ancestry from the Nurses' Health Study and Health Professionals Follow-up Study. Single nucleotide polymorphism (SNP) rs142310826 near the NEIL3 gene showed a genome-wide significant interaction with caffeine consumption (P = 1.78 × 10-8 for interaction) on BCC risk. There was no gender difference for this interaction (P = 0.64 for heterogeneity). NEIL3, a gene belonging to the base excision DNA repair pathway, encodes a DNA glycosylase that recognizes and removes lesions produced by oxidative stress. In addition, we identified several loci with P value for interaction <5 × 10-7 in gender-specific analyses (P for heterogeneity between genders < 0.001) including those mapping to the genes LRRTM4, ATF3 and DCLRE1C in women and POTEA in men. Finally, we tested the associations between caffeine consumption-related SNPs reported by previous genome-wide association studies and risk of BCC, both individually and jointly, but found no significant association. In sum, we identified a DNA repair gene that could be involved in caffeine-mediated skin tumor inhibition. Further studies are warranted to confirm these findings.

The consumption of coffee and black tea and the risk of lung cancer

PURPOSE

Coffee and black tea are among the most consumed beverages worldwide. Although their potential role in lung cancer occurrence has been investigated in several studies, results have been inconclusive. We investigated the associations between intake of coffee and black tea with lung cancer in a population-based case-control study in Montreal, Canada.

METHODS

These analyses included 1130 cases and 1483 controls. Adjusted odds ratios (ORs) were estimated between four metrics of coffee and black tea consumption (frequency, average daily amount, duration, and cumulative amount) and lung cancer, using unconditional logistic regression.

RESULTS

The adjusted ORs (95% confidence intervals) for lung cancer comparing daily to never consumers were 0.73 (0.49-1.10) for coffee and 1.05 (0.85-1.31) for black tea. Analyses of other metrics did not reveal any clear patterns of increasing or decreasing risk with increasing amounts or duration of consumption. There was no strong evidence of OR modification by sex or smoking level. The OR estimates did not materially differ by histological subtype for either of the beverages.

CONCLUSION

Our results do not provide strong support for associations between consumption of coffee and black tea and lung cancer.

Coffee and cancer risk: A meta-analysis of prospective observational studies

Meta-analyses on coffee and cancer incidence mainly restricted to limited cancers. We carried out a more comprehensive meta-analysis of cohort studies to explore association between coffee and most cancer types. We conducted comprehensive search and summarized relative risk (RR) and 95% confidence intervals for the highest versus lowest coffee intake and cancer using STATA12. We conducted dose-analysis if result suggested significant association. The publication bias was evaluated with begg's and egger's test. Finally, 105 individual prospective studies were included. Inverse associations were observed on oral, pharyngeal, colon, liver, prostate, endometrial cancer and melanoma, with RR 0.69 (95% CI = 0.48-0.99, I² = 73.4%, P = 0.044), 0.87 (95% CI = 0.78-0.96, I² = 28.4%, P = 0.007), 0.46 (95% CI = 0.37-0.57, I² = 0%, P = 0), 0.89 (95% CI = 0.84-0.93, I² = 30.3%, P = 0.003), 0.73 (95% CI = 0.67-0.80, I²  = 0%, P = 0) and 0.89 (95% CI = 0.80-0.99, I²  = 0%, P = 0.031) respectively. However, the relative risk for lung cancer is 2.18 (95% CI = 1.26-3.75, I²  = 63.3%, P = 0.005). The summary relative risk for increment of 2 cups of coffee were RR = 0.73, 95% CI = 0.67-0.79 for liver cancer, RR = 0.97, 95% CI = 0.96-0.98 for prostate cancer and RR = 0.88, 95% CI = 0.85-0.92 for endometrial cancer. Accordingly, coffee intake was associated with reduced risk of oral, pharynx, liver, colon, prostate, endometrial cancer and melanoma and increased lung cancer risk.

Coffee consumption and the risk of malignant melanoma in the Norwegian Women and Cancer (NOWAC) Study

Background

Coffee contains biologically-active substances that suppress carcinogenesis in vivo, and coffee consumption has been associated with a lower risk of malignant melanoma. We studied the impact of total coffee consumption and of different brewing methods on the incidence of malignant melanoma in a prospective cohort of Norwegian women.

Methods

We had baseline information on total coffee consumption and consumption of filtered, instant, and boiled coffee from self-administered questionnaires for 104,080 women in the Norwegian Women and Cancer (NOWAC) Study. We also had follow-up information collected 6–8 years after baseline. Multiple imputation was used to deal with missing data, and multivariable Cox regression models were used to calculate hazard ratios (HR) for malignant melanoma by consumption category of total, filtered, instant, and boiled coffee.

Results

During 1.7 million person-years of follow-up, 762 cases of malignant melanoma were diagnosed. Compared to light consumers of filtered coffee (≤1 cup/day), we found a statistically significant inverse association with low-moderate consumption (>1–3 cups/day, HR = 0.80; 95 % confidence interval [CI] 0.66–0.98) and high-moderate consumption of filtered coffee (>3–5 cups/day, HR = 0.77; 95 % CI 0.61–0.97) and melanoma risk (p_trend = 0.02). We did not find a statistically significant association between total, instant, or boiled coffee consumption and the risk of malignant melanoma in any of the consumption categories.

Conclusions

The data from the NOWAC Study indicate that a moderate intake of filtered coffee could reduce the risk of malignant melanoma.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2586-5) contains supplementary material, which is available to authorized users.

Caffeine Intake, Coffee Consumption, and Risk of Cutaneous Malignant Melanoma

BACKGROUND

Caffeine has been shown to prevent ultraviolet radiation-induced carcinogenesis and to inhibit growth of melanoma cells in experimental studies. We evaluated the association among caffeine intake, coffee consumption, and melanoma risk among three large cohort studies.

METHODS

The analysis used data from 89,220 women in the Nurses' Health Study II (1991-2009), 74,666 women in the Nurses' Health Study (1980-2008), and 39,424 men in the Health Professionals Follow-up Study (1986-2008). We used Cox proportional hazards models to estimate the hazard ratios (HR) with 95% confidence intervals (CIs) of melanoma associated with dietary intakes.

RESULTS

We documented 2,254 melanoma cases over 4 million person-years of follow-up. After adjustment for other risk factors, higher total caffeine intake was associated with a lower risk of melanoma (≥393 mg/day vs. <60 mg/day: HR = 0.78, 95% CI = 0.64, 0.96; Ptrend = 0.048). The association was more apparent in women (≥393 mg/day vs. <60 mg/day: HR = 0.70, 95% CI = 0.58, 0.85; Ptrend = 0.001) than in men (HR = 0.94, 95% CI = 0.75, 1.2; Ptrend = 0.81), and more apparent for melanomas occurring on body sites with higher continuous sun exposure (head, neck, and extremities; ≥393 mg/day vs. <60 mg/day: HR = 0.71, 95% CI = 0.59, 0.86; Ptrend = 0.001) than for melanomas occurring on body sites with lower continuous sun exposure (trunk including shoulder, back, hip, abdomen, and chest; HR = 0.90, 95% CI = 0.70, 1.2; Ptrend = 0.60). This pattern of association was similar to that for caffeinated coffee consumption, whereas no association was found for decaffeinated coffee consumption and melanoma risk.

CONCLUSIONS

Increasing caffeine intake and caffeinated coffee consumption is associated with decreased risk of cutaneous malignant melanomas.

Coffee Consumption and Melanoma: A Systematic Review and Meta-Analysis of Observational Studies

BACKGROUND

Laboratory and animals studies have suggested a possible protective effect of coffee consumption on the development of melanoma. However, the results of epidemiological studies investigating this association have been inconclusive.

OBJECTIVE

A systematic review and meta-analysis of published studies was conducted to evaluate any association between coffee consumption and melanoma.

METHODS

Observational studies were searched for in MEDLINE, EMBASE, and the Cochrane Central Register from inception to September 1, 2015. The Meta-analysis Of Observational Studies in Epidemiology (MOOSE) guidelines were followed in conducting this study.

RESULTS

We identified nine observational studies with a total of 927,173 study participants, of which 3787 had melanoma. With random-effects modeling, the pooled relative risks (RR) for melanoma among regular coffee drinkers was 0.75 (95 % confidence interval [CI] 0.63-0.89, p = 0.001) compared with controls. Visual inspection of a funnel plot suggested publication bias, although Egger's test (p = 0.981) delineated no small-study effects. The pooled relative risks for melanoma among decaffeinated coffee drinkers was, however, not statistically significant at 0.92 (95 % CI 0.82-1.05, p = 0.215).

CONCLUSION

There is some evidence for the beneficial effects of regular coffee consumption on melanoma. More prospective cohort studies with systematic quantification of coffee consumption would be necessary to further elucidate this association.

Coffee Consumption and Pancreatic Cancer Risk: An Update Meta-analysis of Cohort Studies

BACKGROUND & OBJECTIVE

The results of epidemiologic studies on the relationship between the coffee consumption and pancreatic cancer risk were inconsistent. Thus, we performed an update meta-analysis of cohort studies to quantitatively summarize the association between coffee consumption and pancreatic cancer risk.

METHODS

We searched CBM (China Biology Medicine disc) and MEDLINE for studies of coffee consumption and pancreatic cancer risk up to June 2015. A total of 20 cohort studies were identified in this meta-analysis, and we analyzed these studies using random effects model. The dose-response analysis was conducted too.

RESULTS

The overall relative risk (RR) for highest coffee consumption versus lowest coffee consumption was 0.75 (95% Confidence Interval (CI), 0.63-0.86). Statistic significant heterogeneity was found among these studies (I (2) =37.8%, P for heterogeneity =0.045). The pooled RR for increment of 1 cup/day of coffee consumption was 0.99 (95%CI, 0.96-1.03) for the nine studies, without statistically significant.

CONCLUSIONS

High coffee consumption is associated with a reduced pancreatic cancer risk. However, the result should be accepted with caution, due to the potential confounder and bias could not be excluded. Further well designed studies are needed to confirm the finding.

Coffee Drinking and Risk of Lung Cancer-A Meta-Analysis

BACKGROUND

Previous epidemiologic results on coffee consumption and lung cancer risk have not been consistent. Furthermore, not all studies have addressed the potential role of tobacco as a confounder in this association. A meta-analysis was conducted to assess the effect of coffee consumption on lung cancer risk independent of tobacco use.

METHODS

A systematic review and a meta-analysis based on random effects models were performed using studies from the PubMed and EMBASE databases, and the references from the retrieved articles. Included were 8 prospective cohorts and 13 case-control studies, which provided data for 19,892 cases and 623,645 non-cases, timeframe 1986-2015.

RESULTS

The meta-relative risk (RR) for coffee drinking, not controlling for tobacco smoking, was 1.09 [95% confidence interval (CI), 1.00-1.19], the reference group was never drinkers. There was significant heterogeneity among the study results (Q = 84.39, I² = 75.1%, Pheterogeneity < 0.001). Among non-smokers, coffee was not associated with lung cancer risk (RR, 0.92; 95% CI, 0.75-1.10), the reference group was never drinkers. The meta-RR for 1 cup per day increase, unadjusted for smoking, was 1.04 (95% CI, 1.03-1.05); the corresponding RR for non-smokers was 0.95 (95% CI, 0.83-1.09).

CONCLUSIONS

The pooled estimates indicated that when the potential confounding effect from smoking is controlled for, coffee drinking does not appear to be a lung cancer risk factor. Further pooled analyses, with larger non-smokers population size, are encouraged to confirm these results.

IMPACT

This study illustrates that the association between coffee consumption and lung cancer can be confounded by tobacco smoking. Cancer Epidemiol Biomarkers Prev; 25(6); 951-7. ©2016 AACR.

Coffee consumption and the risk of cancer in the Norwegian Women and Cancer (NOWAC) Study

An association between coffee consumption and cancer has long been investigated. Coffee consumption among Norwegian women is high, thus this is a favorable population in which to study the impact of coffee on cancer incidence. Information on coffee consumption was collected from 91,767 women at baseline in the Norwegian Women and Cancer Study. These information were applied until follow-up information on coffee consumption, collected 6-8 years after baseline, became available. Multiple imputation was performed as a method for dealing with missing data. Multivariable Cox regression models were used to calculate hazard ratios (HR) for breast, colorectal, lung, and ovarian cancer, as well as cancer at any site. We observed a 17 % reduced risk of colorectal cancer (HR = 0.83, 95 % CI 0.70-0.98, p trend across categories of consumption = 0.10) and a 9 % reduced risk of cancer at any site (HR = 0.91, 95 % CI 0.86-0.97, p trend = 0.03) in women who drank more than 3 and up to 7 cups/day, compared to women who drank ≤1 cup/day. A significantly increased risk of lung cancer was observed with a heavy coffee consumption (>7 vs. ≤1 cup/day HR = 2.01, 95 % CI 1.47-2.75, p trend < 0.001). This was most likely caused by residual confounding due to smoking, as no statistically significant association was observed in never smokers (>5 vs. ≤1 cup/day HR = 1.42, 95 % CI 0.44-4.57, p trend = 0.30). No significant association was found between coffee consumption and the risk of breast or ovarian cancer. In this study, coffee consumption was associated with a modest reduced risk of cancer at any site. Residual confounding due to smoking may have contributed to the positive association between high coffee consumption and the risk of lung cancer.

Higher Caffeinated Coffee Intake Is Associated with Reduced Malignant Melanoma Risk: A Meta-Analysis Study

Background

Several epidemiological studies have determined the associations between coffee intake level and skin cancer risk; however, the results were not yet conclusive. Herein, we conducted a systematic review and meta-analysis of the cohort and case-control studies for the association between coffee intake level and malignant melanoma (MM) risk.

Methods

Studies were identified through searching the PubMed and MEDLINE databases (to November, 2015). Study-specific risk estimates were pooled under the random-effects model.

Results

Two case-control studies (846 MM patients and 843 controls) and five cohort studies (including 844,246 participants and 5,737 MM cases) were identified. For caffeinated coffee, the pooled relative risk (RR) of MM was 0.81 [95% confidential interval (95% CI) = 0.68–0.97; P-value for Q-test = 0.003; I² = 63.5%] for those with highest versus lowest quantity of intake. In the dose-response analysis, the RR of MM was 0.955 (95% CI = 0.912–0.999) for per 1 cup/day increment of caffeinated coffee consumption and linearity dose-response association was found (P-value for nonlinearity = 0.326). Strikingly, no significant association was found between the decaffeinated coffee intake level and MM risk (pooled RR = 0.92, 95% CI = 0.81–1.05; P-value for Q-test = 0.967; I² = 0%; highest versus lowest quantity of intake).

Conclusions

This meta-analysis suggested that caffeinated coffee might have chemo-preventive effects against MM but not decaffeinated coffee. However, larger prospective studies and the intervention studies are warranted to confirm these findings.

Coffee consumption and the risk of incident gastric cancer--A meta-analysis of prospective cohort studies

As several epidemiological studies on the association of coffee consumption with gastric cancer risk have produced inconsistent results, this meta-analysis was designed to synthesize current evidence of this potential relationship. We searched PubMed, EMBASE, and the Cochrane Library up to September 2014 to retrieve relevant articles. Prospective cohort studies were included if the relative risks (RRs) or hazard ratios and 95% confidence intervals (CIs) for gastric cancer according to coffee consumption were reported. Fixed- or random-effects models were used based on heterogeneity. The search yielded 13 eligible cohort studies of 3484 incident gastric cancer patients from among 1,324,559 participants. A significantly increased risk was found between gastric cardia cancer and coffee consumption (RR = 1.50, 95% CI: 1.09-2.07). Compared with Europeans (RR = 1.12, 95% CI: 0.86-1.46) and Asians (RR = 0.96, 95% CI: 0.72-1.27), Americans (RR = 1.36, 95% CI: 1.06-1.74) demonstrated a significantly positive association. However, the significant differences of the pooled results vanished after adjusting for smoking or body mass index. Our meta-analysis results suggest that a high level of coffee consumption is a risk factor for gastric cancer. However, these results should not be overinterpreted because residual confounding effects of other factors could exist.

Coffee consumption and the risk of gastric cancer: a meta-analysis of prospective cohort studies

Background

Several observational studies suggest that coffee consumption may be associated with an increased risk of gastric cancer, but the results are inconsistent. We conducted a meta-analysis to evaluate the relationship of coffee consumption with gastric cancer risk and quantify the dose–response relationship between them.

Methods

Relevant prospective studies were identified by a search of PubMed, Embase, and Web of Science to May 2015 and by reviewing the references of retrieved articles. Two independent reviewers extracted data and performed the quality assessment. A random-effects model was used to calculate the pooled risk estimates and 95 % confidence intervals (CI). The heterogeneity was assessed using the I² statistic. Publication bias was assessed by using funnel plot, the Begg test and the Egger test.

Results

Thirteen prospective cohort studies with 20 independent reports involving 3,368 patients with gastric cancer and 1,372,811 participants during a follow-up period ranging from 4.3–8 years were included. Compared with the lowest consumption level of coffee, the pooled relative risk (RR) was 1.13 (95 % CI: 0.94–1.35). The dose–response analysis indicated that, the RR of gastric cancer was 1.03 (95 % CI; 0.95–1.11) for per 3 cups/day of coffee consumption. Any nonlinear association of gastric cancer risk with coffee consumption was not found (P for nonlinearity = 0.68). Subgroup analyses indicated that the pooled RR for participants from the United States comparing the highest with the lowest coffee consumption was 1.36 (95 % CI, 1.06–1.75, I² = 0 %). In addition, people with higher coffee consumption was associated with 25 % higher risk of gastric cancer in equal to or less than 10 years follow-up group (RR = 1.25; 95 % CI, 1.01–1.55, I² = 0 %). Visual inspection of a funnel plot and the Begg’s and the Egger’s tests did not indicate evidence of publication bias.

Conclusions

This meta-analysis does not support the hypothesis that coffee consumption is associated with the risk of gastric cancer. The increased risk of gastric cancer for participants from the United States and equal to or less than 10 years follow-up group associated with coffee consumption warrant further studies.

Long-Term Coffee Consumption and Risk of Gastric Cancer: A PRISMA-Compliant Dose-Response Meta-Analysis of Prospective Cohort Studies

Association between coffee consumption and gastric cancer risk remains controversial. Hence, we performed a meta-analysis to investigate and quantify the potential dose-response association between long-term coffee consumption and risk of gastric cancer.Pertinent studies were identified by searching PubMed and Embase from January 1996 through February 10, 2015 and by reviewing the reference lists of retrieved publications. Prospective cohort studies in which authors reported effect sizes and corresponding 95% confidence intervals (CIs) of gastric cancer for 3 or more categories of coffee consumption were eligible. Results from eligible studies were aggregated using a random effect model. All analyses were carried out using the STATA 12.0 software.Nine studies involving 15 independent prospective cohorts were finally included. A total of 2019 incident cases of gastric cancer were ascertained among 1,289,314 participants with mean follow-up periods ranging from 8 to 18 years. No nonlinear relationship of coffee consumption with gastric cancer risk was indentified (P for nonlinearity = 0.53; P for heterogeneity = 0.004). The linear regression model showed that the combined relative risk (RR) of every 3 cups/day increment of total coffee consumption was 1.07 (95% CI = 0.95-1.21). Compared with the lowest category of coffee consumption, the RR of gastric cancer was 1.18 (95% CI = 0.90-1.55) for the highest (median 6.5 cups/day) category, 1.06 (95% CI = 0.85-1.32) for the second highest category (median 3.5 cups/day), and 0.97 (95% CI = 0.79-1.20) for the third highest category (median 1.5 cups/day). Subgroup analysis showed an elevated risk in the US population (RR = 1.36, 95% CI = 1.06-1.75) and no adjustment for smoking (RR = 1.67, 95% CI = 1.08-2.59) for 6.5 cups/day.Current evidence indicated there was no nonlinear association between coffee consumption and gastric cancer risk. However, high coffee consumption (more than 6.5 cups/day) might increase the risk of gastric cancer in the US population. More high quality studies were warranted to further investigate the association.

Coffee consumption and risk of endometrial cancer: a dose-response meta-analysis of prospective cohort studies

This is a dose-response (DR) meta-analysis to evaluate the association of coffee consumption on endometrial cancer (EC) risk. A total 1,534,039 participants from 13 published articles were added in this meta-analysis. The RR of total coffee consumption and EC were 0.80 (95% CI: 0.74–0.86). A stronger association between coffee intake and EC incidence was found in patients who were never treated with hormones, 0.60 (95% CI: 0.50–0.72), and subjects with a BMI ≥25 kg/m², 0.57 (95% CI: 0.46–0.71). The overall RRs for caffeinated and decaffeinated coffee were 0.66 (95% CI: 0.52–0.84) and 0.77 (95% CI: 0.63–0.94), respectively. A linear DR relationship was seen in coffee, caffeinated coffee, decaffeinated coffee and caffeine intake. The EC risk decreased by 5% for every 1 cup per day of coffee intake, 7% for every 1 cup per day of caffeinated coffee intake, 4% for every 1 cup per day of decaffeinated intake of coffee, and 4% for every 100 mg of caffeine intake per day. In conclusion, coffee and intake of caffeine might significantly reduce the incidence of EC, and these effects may be modified by BMI and history of hormone therapy.

Caffeine promotes anti-tumor immune response during tumor initiation: Involvement of the adenosine A2A receptor

Epidemiologic studies depict a negative correlation between caffeine consumption and incidence of tumors in humans. The main pharmacological effects of caffeine are mediated by antagonism of the adenosine receptor, A2AR. Here, we examine whether the targeting of A2AR by caffeine plays a role in anti-tumor immunity. In particular, the effects of caffeine are studied in wild-type and A2AR knockout (A2AR(-/-)) mice. Tumor induction was achieved using the carcinogen 3-methylcholanthrene (3-MCA). Alternatively, tumor cells, comprised of 3-MCA-induced transformed cells or B16 melanoma cells, were inoculated into animal footpads. Cytokine release was determined in a mixed lymphocyte tumor reaction (MLTR). According to our findings, caffeine-consuming mice (0.1% in water) developed tumors at a lower rate compared to water-consuming mice (14% vs. 53%, respectively, p=0.0286, n=15/group). Within the caffeine-consuming mice, tumor-free mice displayed signs of autoimmune alopecia and pronounced leukocyte recruitment intocarcinogen injection sites. Similarly, A2AR(-/-) mice exhibited reduced rates of 3-MCA-induced tumors. In tumor inoculation studies, caffeine treatment resulted in inhibition of tumor growth and elevation in proinflammatory cytokine release over water-consuming mice, as depicted by MLTR. Addition of the adenosine receptor agonist, NECA, to MLTR resulted in a sharp decrease in IFNγ levels; this was reversed by the highly selective A2AR antagonist, ZM241385. Thus, immune response modulation through either caffeine or genetic deletion of A2AR leads to a Th1 immune profile and suppression of carcinogen-induced tumorigenesis. Taken together, our data suggest that the use of pharmacologic A2AR antagonists may hold therapeutic potential in diminishing the rate of cancer development.

Coffee consumption and the risk of lung cancer: an updated meta-analysis of epidemiological studies

BACKGROUND/OBJECTIVES

Coffee is one of the most popularly consumed beverages worldwide. Many epidemiological studies have investigated the association between coffee consumption and lung cancer risk, but the results are inconsistent. Hence, we conducted a systematic analysis of relevant population-based studies to examine this association and derive a more precise estimation.

SUBJECTS/METHODS

The Cochrane library, PubMed and Embase databases were searched to identify studies published through Mar 2015 that met the predetermined inclusion criterion. Seventeen studies (5 cohort and 12 case-control studies) involving 12 276 cases and 102 516 controls were included.

RESULTS

The summary odds ratio (OR) of lung cancer was 1.17 (95% confidence interval (CI): 1.03-1.33) for coffee drinkers compared with nondrinkers and 1.31 (95% CI: 1.11-1.55) for the highest category of coffee consumption compared with the lowest category. Compared with nondrinkers, the pooled ORs for lung cancer were 1.10 (95% CI: 0.92-1.31) for ⩽1 cup per day, 1.10 (95% CI: 0.93-1.30) for 2-3 cups per day and 1.20 (95% CI: 1.02-1.39) for ⩾3 cups per day. Further analysis showed that the ORs for hospital-based case-control studies, population-based case-control studies and prospective cohort studies were 1.36 (95% CI: 1.10-1.69), 0.99 (95% CI: 0.77-1.28) and 1.59 (95% CI: 1.26-2.00), respectively. Significant associations for high coffee intake with increased risk of lung cancer were observed in men (OR=1.41 95% CI: 1.21-1.63), but not in women (OR=1.16, 95% CI: 0.86-1.56), in American (OR=1.34 95% CI: 1.08-1.65) and Asian populations (OR=1.49 95% CI: 1.28-1.74), but not in European populations (OR=1.12, 95% CI: 0.74-1.67), and in smokers (OR=1.24, 95% CI: 1.00-1.54), but not in nonsmokers (OR=0.85, 95% CI: 0.64-1.11). Particularly over the last 5 years, studies have consistently indicated that lung cancer risk is significantly increased by 47% in the population with the highest category intake of coffee compared with that with the lowest category intake (OR=1.47, 95% CI: 1.21-1.79).

CONCLUSION

The present study suggested that coffee intake was associated with an increased risk of lung cancer.

Coffee consumption and incidence of lung cancer in the NIH-AARP Diet and Health Study

BACKGROUND

Coffee drinkers had a higher risk of lung cancer in some previous studies, but as heavy coffee drinkers tend to also be cigarette smokers, such findings could be confounded. Therefore, we examined this association in the nearly half a million participants of the US NIH-AARP Diet and Health Study.

METHODS

Typical coffee intake and smoking history were queried at baseline. During 4 155 256 person-years of follow-up, more than 9000 incident lung cancer cases occurred. We used Cox proportional hazards regression to estimate hazard ratios (HRs)and 95% confidence intervals for coffee intake and subsequent incidence of lung cancer. We also comprehensively adjusted for tobacco smoking and examined associations by detailed strata of tobacco use.

RESULTS

Coffee drinkers were far more likely to smoke than non-drinkers. Although coffee drinking was associated with lung cancer in age- and sex- adjusted models (HR for ≥ 6 cups/day compared with none: 4.56, 4.08-5.10), this association was substantially attenuated after adjusting for smoking (HR: 1.27, 1.14-1.42). Similar findings were observed for each different histological type of lung cancer, and for participants drinking predominantly caffeinated or decaffeinated coffee. Little evidence for an association was observed in our stratified analyses, either within never smokers or in most categories of tobacco use.

CONCLUSIONS

Coffee drinking was positively associated with lung cancer in our study, although the association was substantially attenuated after adjustment for tobacco smoking. As our adjustment for lifetime tobacco use was imperfect, it is likely that the remaining association is due to residual confounding by smoking, although other explanations are possible.

Effect of coffee consumption on the risk of gastric cancer: a systematic review and meta-analysis of prospective cohort studies

Background and Objectives

Results from observational epidemiologic studies on the relationship between coffee consumption and gastric cancer are inconsistent and inconclusive. To assess the association between coffee consumption and the risk of gastric cancer, we summarized evidence from prospective cohort studies.

Methods

Relevant studies were retrieved through computer searches (PubMed, EmBase and the Cochrane Library) and a review of references up to December 2014. The quality of the included studies was evaluated by Newcastle-Ottawa quality assessment scale. We used a meta-analytic approach to estimate overall hazard ratios (HRs) and 95% confidence intervals (CIs) for regular coffee drinkers versus individuals who seldom drank coffee. Sensitivity analysis and subgroup analysis were performed to assess the reliability of our results. A dose–response analysis was performed to assess the risk of gastric cancer based on the level of coffee consumption.

Results

Nine prospective cohort studies involving 1,250,825 participants and 3027 gastric cancer cases were included in this meta-analysis. The pooled HR of gastric cancer for the study-specific regularly versus seldom coffee drinking categories was 1.05 (95% CI, 0.88 to 1.25) with significant heterogeneity across studies (I² = 74.0%, P = 0.000). After the sensitivity analysis, three studies were deleted; however the association remained insignificant (HR, 0.99; 95% CI, 0.91 to 1.08). Subgroup analysis by anatomic location showed a risk for coffee consumption associated with cardia cancer (HR, 1.23; 95% CI, 1.04 to 1.45; heterogeneity, I² = 36.4, P = 0.207). In the dose–response analysis, there was no significant association between coffee intake (in cups) and the risk of gastric cancer (P for linearity trend and non-linearity > 0.05).

Conclusion

Our meta-analysis demonstrated that coffee consumption was not associated with overall gastric cancer risk; however, coffee consumption may be a risk factor for gastric cardia cancer.

Coffee consumption and risk of gastric cancer: an updated meta-analysis

OBJECTIVES

The aim of this study was to perform an updated review to evaluate the effect of coffee consumption on the risk of gastric cancer.

METHODS

We searched the PubMed and Embase database up to October 14th, 2013. Risk ratio (RR) and corresponding 95% confidence intervals (CIs) for the risk of gastric cancer were used as effect sizes. Overall effect sizes were derived using a fixed-effects model or a random-effects model when appropriate. Then in subgroup analyses, the data were reanalyzed, which were stratified by gender, area and follow-up time.

RESULTS

A total of 8 separate studies, including 312,993 volunteers (among them 1429 were diagnosed with gastric cancer in 10-18 years' follow-up), were considered in the meta-analysis. The overall estimate of coffee consumption on the risk of gastric cancer showed a pooled RR of 1.24 (95% CI: 1.03-1.49; P=0.026). In subgroup analyses, the pooled RR of gastric cancer was 1.36 (95% CI: 1.06-1.75) for USA volunteers and 1.29 (95% CI: 1.05-1.59) for people with more than 15-year follow-up time. The sensitivity analysis proved the stability and credibility of our results, and there was no significant bias (Begg's test P=0.640, Egger's test P=0.600) among the studies.

CONCLUSIONS

It indicated that coffee consumption was associated with the development of gastric cancer. More coffee drinking could result in the increased risk of gastric cancer.

Tea and coffee and risk of endometrial cancer: cohort study and meta-analysis

BACKGROUND

Previous reports, mostly from retrospective studies, suggested possible protective effects of both tea and coffee against endometrial cancer, but recent reports from prospective studies generally showed weaker or null associations.

OBJECTIVES

We investigated endometrial cancer risk in relation to tea and coffee consumption in a large prospective study and did a meta-analysis of published results.

DESIGN

Daily consumption of tea and coffee was recorded in 560,356 participants (without a hysterectomy) in the UK Million Women Study of whom 4067 women developed endometrial cancer during 5.2 million person-years of follow up (average: 9.3 y per woman).

RESULTS

With the use of Cox proportional hazards regression, we showed no significant association between endometrial cancer risk and consumption of either tea (multivariate adjusted RR per cup daily: 1.00; 95% CI: 0.98, 1.02) or coffee (RR per cup daily: 0.98; 95% CI: 0.96, 1.01). Our meta-analyses showed no significant association between endometrial cancer risk and tea consumption and a weak association for coffee consumption in prospective studies, but there may have been selective publication of only part of the evidence.

CONCLUSIONS

There is little or no association between tea consumption and endometrial cancer risk. If there is any association with coffee consumption, it appears to be weak.

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

This meta-analysis was conducted to assess the association between coffee consumption and prostate cancer risk. Thirteen cohort studies with 34,105 cases and 539,577 participants were included in the meta-analysis. The summary relative risks (RRs) with 95% confidence intervals (CIs) for different coffee intake levels were calculated. Dose-response relationship was assessed using generalized least square trend estimation. The pooled RR for the highest vs. lowest coffee intake was 0.90 (95% CI: 0.85-0.95), with no significant heterogeneity across studies (P = 0.267; I(2) = 17.5%). The dose-response analysis showed a lower cancer risk decreased by 2.5% (RR = 0.975; 95% CI: 0.957-0.995) for every 2 cups/day increment in coffee consumption. Stratifying by geographic region, there was a statistically significant protective influence of coffee on prostate cancer risk among European populations. In subgroup analysis of prostate cancer grade, the summary RRs were 0.89 (95% CI: 0.83-0.96) for nonadvanced, 0.82 (95% CI: 0.61-1.10) for advanced and 0.76 (95% CI: 0.55-1.06) for fatal diseases. Our findings suggest that coffee consumption may be associated with a reduced risk of prostate cancer and it also has an inverse association with nonadvanced prostate cancer. Because of the limited number of studies, more prospective studies with large sample size are needed to confirm this association.

Coffee drinking and cutaneous melanoma risk in the NIH-AARP diet and health study

BACKGROUND

Cutaneous melanoma is the fifth most common cancer in the United States. Modifiable risk factors, with the exception of exposure to ultraviolet radiation (UVR), are poorly understood. Coffee contains numerous bioactive compounds and may be associated inversely with melanoma. However, previous epidemiological evidence is limited.

METHODS

Coffee intake was assessed at baseline with a food frequency questionnaire in the National Institutes of Health-AARP prospective cohort study. Among 447 357 non-Hispanic whites who were cancer-free at baseline, 2904 incident cases of malignant melanoma were identified during 4 329 044 person-years of follow-up, with a median of 10.5 years of follow-up. Multivariable-adjusted Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for coffee intake and subsequent melanoma risk with non-coffee drinkers as the reference group. Statistical tests were two-sided, and P values less than .05 were interpreted as statistically significant.

RESULTS

The highest category of coffee intake was inversely associated with malignant melanoma (≥4 cups/day: HR = 0.80, 95% CI = 0.68 to 0.93, P trend = .01). This association was statistically significant for caffeinated (≥4 cups/day: HR = 0.75, 95% CI = 0.64 to 0.89, P trend = .01) but not for decaffeinated coffee (P trend = .55).

CONCLUSIONS

Higher coffee intake was associated with a modest decrease in risk of melanoma in this large US cohort study. Additional investigations of coffee intake and its constituents, particularly caffeine, with melanoma are warranted.

Tea, coffee, and caffeine and early-onset basal cell carcinoma in a case-control study

Tea and coffee are hypothesized to play a protective role in skin carcinogenesis through bioactive components, such as caffeine, yet the epidemiologic evidence is mixed. Existing data support an inverse association with basal cell carcinoma (BCC), more so than for melanoma or squamous cell carcinoma. To understand whether tea, coffee, and caffeine are related to early-onset BCC, we evaluated data from 767 non-Hispanic Whites under age 40 in a case-control study in Connecticut. BCC cases (n=377) were identified through Yale's Dermatopathology database. Controls (n=390) were randomly sampled from individuals in the same database with benign skin diagnoses and frequency matched to cases on age, sex, and biopsy site. Participants completed an in-person interview including assessment of caffeinated coffee and hot tea. We calculated multivariate odds ratios (ORs) and 95% confidence intervals (CIs) with unconditional logistic regression for regular consumption and frequency and duration measures. Combined regular consumption of caffeinated coffee plus hot tea was inversely associated with early-onset BCC (OR=0.60, 95% CI=0.38-0.96). Those in the highest category of caffeine from these sources had a 43% reduced risk of BCC compared with nonconsumers (OR=0.57, 95% CI=0.34-0.95, P-trend=0.037). Our findings suggest a modest protective effect for caffeinated coffee plus tea in relation to early-onset BCC that may, in part, be due to caffeine. This study adds to the growing body of literature suggesting potential health benefits from these beverages.