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 I (2) 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, I (2) = 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, I (2) = 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.
Department of Social Medicine and Health Management, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, No. 13 Hangkong Road, Wuhan, 430030, Hubei, China. liliqing_lily@163.com.|School of Economics and Management, Jiangxi Science and Technology Normal University, Nanchang, Jiangxi, China. liliqing_lily@163.com.
Liqing
L
Li
Department of Social Medicine and Health Management, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, No. 13 Hangkong Road, Wuhan, 430030, Hubei, China. scswj2008@163.com.
Yong
Y
Gan
Department of Social Medicine and Health Management, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, No. 13 Hangkong Road, Wuhan, 430030, Hubei, China. 88907576@qq.com.
Chunmei
C
Wu
School of Health Management, Hangzhou Normal University, Hangzhou, Zhejiang, China. quxianguo@163.com.
Xianguo
X
Qu
Department of Social Medicine and Health Management, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, No. 13 Hangkong Road, Wuhan, 430030, Hubei, China. sunhoney163@163.com.
Gang
G
Sun
Department of Social Medicine and Health Management, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, No. 13 Hangkong Road, Wuhan, 430030, Hubei, China. zuxunlu@yahoo.com.
Zuxun
Z
Lu
D003069:Coffee; D014943:Global Health; D006801:Humans; D015994:Incidence; D011446:Prospective Studies; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors; D013274:Stomach Neoplasms / Q000453:epidemiology* / Q000209:etiology*
D003069:Coffee