Figure 1Flow of study selection process.
Figure 2Forest plot of relative risks or odds ratios from eighteen observational studies on green tea consumption and stomach cancer. The black squares and horizontal lines correspond to the RRs or ORs and 95% confidence intervals. The area of the black squares reflects the weight each trial contributes to the meta-analysis. The diamond at the bottom of the graph represents the combined odds ratio and its 95% confidence interval, indicating 14% reduction in the risk of stomach cancer. The solid vertical line corresponds to no effect of green tea consumption (odds ratio 1.0), the dotted vertical line to the combined odds ratio (0.86). The graph was produced in STATA.
Figure 3
Begg's funnel plot of studies on green tea consumption and stomach cancer risk. The solid line in the center is the natural logarithm of pooled odds ratio (OR), and two oblique lines are pseudo 95% confidence limits.
SE, standard error.
Table 1Characteristics of studies on green tea consumption and stomach cancer risk
Author, year |
Design |
Region, country |
No. of cases/ No. of noncases |
No. of exposure level |
Lowest consumption level |
Highestconsumptionlevel |
RR/OR (95%CI) for the highest vs. the lowest level |
Galanis DJ, 1998[35]
|
Cohort |
Hawaii, USA |
108/11,799 |
3 |
None |
≥ 2 cups/day |
1.5 (0.9-2.3) |
|
|
|
64 men |
|
|
|
1.6 (0.9-2.9) |
|
|
|
44 women |
|
|
|
1.3 (0.6-2.6) |
Nakachi K, 2000[37]
|
Cohort |
Saitama, Japan |
140/8,412 |
3 |
≤ 3 cups/day |
≥ 10 cups/day |
0.70 (0.23-1.88) |
Tsubono Y, 2001[13]
|
Cohort |
Miyagi, Japan |
419/25,892 |
4 |
<1 cup/day |
≥ 5 cups/day |
1.2 (0.9-1.6) |
|
|
|
296 men |
|
|
|
1.5 (1.0-2.1) |
|
|
|
123 women |
|
|
|
1.1 (0.6-2.0) |
Nagano J, 2001[16]
|
Cohort |
Hiroshima & Nagasaki, |
901/37,639 |
3 |
<1 time/day |
≥ 5 times/day |
0.95 (0.76-1.20) |
|
|
Japan |
|
|
|
|
|
Koizumi Y, 2003[12]
|
Cohort |
Japan |
314/39,290 |
4 |
<1 cup/day |
≥ 5 cups/day |
1.19 (0.89-1.59)* |
Sasazuki S, 2004[28]
|
Cohort |
Japan |
892/72,051 |
4 |
<1 cup/day |
≥ 5 cups/day |
|
|
|
|
665 men |
|
|
|
0.97 (0.77-1.22)†
|
|
|
|
227 women |
|
|
|
0.70 (0.47-1.05)†
|
Kono S, 1988[19]
|
Case-control |
Saga, Japan |
139/278 |
3 |
≤ 4 cups/day |
≥ 10 cups/day |
0.36 (0.16-0.80)‡
|
Kato I, 1990[33]
|
Case-control |
Aichi, Japan |
427/3,014 |
3 |
<1 cup/day |
≥ 5 cups/day |
|
|
Hospital based |
|
289 men |
|
|
|
1.01 (0.70-1.47) |
|
|
|
138 women |
|
|
|
0.81 (0.51-1.27) |
Hoshiyama Y, 1992[34]
|
Case-control |
Saitama, Japan |
294/294 |
3 |
≤ 4 cups/day |
≥ 8 cups/day |
0.8 (0.5-1.3) |
Yu G, 1995[17]
|
Case-control |
Shanghai, China |
711/711 |
3 |
None |
≥ 4 new batches/day |
0.54 (0.33-0.88) |
|
|
|
453 men |
|
|
(≥ 15 cups/day) |
0.53 (0.31-0.90) |
|
|
|
258 women |
|
|
|
0.44 (0.07-2.97) |
Ji BT, 1996[22]
|
Case-control |
Shanghai, China |
1,124/1,451 |
5 |
None |
>3000 g/yr |
|
|
|
|
684 men |
|
|
(> 2 cups/day) |
0.76 (0.55-1.27) |
|
|
|
345 women |
|
|
>1200 g/yr |
0.81 (0.46-1.43) |
|
|
|
|
|
|
(>1 cup/day) |
|
Inoue M, 1998[36]
|
Case-control |
Nagoya, Japan |
869/21,128 |
5 |
Rarely |
≥ 7 cups/day |
0.69 (0.48-1.00) |
|
Hospital based |
|
613 men |
|
|
|
0.98 (0.80-1.20)§
|
|
|
|
280 women |
|
|
|
1.09 (0.79-1.49)§
|
Setiawan VW, 2001[23]
|
Case-control |
Yangzhong, China |
132/423 |
3 |
None |
>21 cups/wk |
0.39 (0.15-1.01) |
|
|
|
|
|
|
(>3 cups/day) |
|
Hoshiyama Y, 2004[27]
|
Nested case- |
Japan |
151/265 |
5 |
<1 cup/day |
≥ 10 cups/day |
1.2 (0.6-2.5) |
|
control |
|
|
|
|
|
|
Mu LN, 2005[11]
|
Case-control |
Taixing, China |
193/397 |
4 |
None |
≥ 250 g/month |
0.39 (0.17-0.91) |
|
|
|
|
|
|
(≥ 2 cups/day) |
|
Table 2Subgroup analysis of green tea consumption and stomach cancer risk
Characteristics |
Subgroup |
No. of studies |
Summary RR/OR (95% CI)* |
p for heterogeneity |
All studies |
NA |
18 |
0.86 (0.74-1.00) |
0.06 |
Country |
China studies |
5 |
0.61 (0.47-0.81) |
0.43 |
|
Japan studies |
12 |
0.92 (0.80-1.05) |
0.10 |
Study design |
Case control studies |
11 |
0.74 (0.63-0.86) |
0.20 |
|
Cohort studies |
7 |
1.03 (0.92-1.16) |
0.13 |
Gender |
Males |
7 |
1.00 (0.82-1.24) |
0.02 |
|
Females |
7 |
0.89 (0.74-1.07) |
0.53 |
Year of publication |
Published before 2000 |
9 |
0.80 (0.63-1.00) |
0.06 |
|
Published on and after 2000 |
9 |
0.93 (0.77-1.12) |
0.06 |
Difference between the highest and lowest |
Less than 5 |
12 |
0.94 (0.81-1.10) |
0.04 |
consumption level |
5 or more |
6 |
0.68 (0.54-0.85) |
0.30 |