Reviewer's report
Title:Green tea consumption and risk of esophageal cancer: a meta-analysis of
epidemiologic studies
Version: 1Date:2 June 2012
Reviewer: Ellen E Kampman
Reviewer's report:
This paper bij Zheng et al describes a meta-analysis of the epidemiological
literature on green tea consumption and esophageal cancer. This is an important
topic given the incidence of esophageal cancer worldwide and the potential of
green tea to reduce the risk. The meta-analysis appears to be conducted
according to the rules, the paper is well written, however the english needs
considerable editing.
Major Compulsory Revisions
. Abstract should contain methods used as well as heterogeneity of study results
. Q statistic is described in the method while the I2 is given.
. Sensitivity analyses could possibly be added.
. Would a dose-response analysis be possible?
. Could a case-control study from Iran by Islami et al, 2009 be missed? If yes,
how could this have happened?
. Page 5 Highest versus lowest... heterogeneity should be discussed.
. method used for the assessment of tea consumption in the different studies
could be included and possibly used for stratification.
. Could the studies be stratified on the number and type of confounding variables
adjusted for?
. Could the exact similar finding between prospective versus case-control and
Japan versus China not simple be due to including the same studies in the
analyses? See also table 2.
. In the discussion, the authors try to provide a potential mechanism explaining
the protective effect in women and not in men. However, although estrogens may
influence esophageal cancer risk, it is not clear how green tea could be
associated with hormonal effects. Do women drink more green tea, is there more
variation in green tea drinking among women? Do women drink and smoke less,
etc etc?
. The discussion should include some discussion on reverse causation which
may explain the differences observed between case-control and cohort studies.
More detail needs to be provided about the fact that all studies among women
are case-control studies.
. Brief remark about population versus hospital based case-control studies in the
discussion is not clear and should be more focused on how this could have
influenced the results of this meta-analysis.
. Specific estimates on smoking and alcohol should be excluded from the
discussion.
Minor Essential Revisions
. Two decimals should be used instead of three
. References need editing, e.g. 10-12
. In the Discussion references 18 and 19 are focused on esophageal and not on
colorectal cancer.
Level of interest: An article whose findings are important to those with closely
related research interests
Quality of written English: Needs some language corrections before being
published
Statistical review: No, the manuscript does not need to be seen by a
statistician.
Reviewer's report
Title:Green tea consumption and risk of esophageal cancer: a meta-analysis of
epidemiologic studies
Version: 1Date:2 June 2012
Reviewer: Ellen E Kampman
Reviewer's report:
This paper bij Zheng et al describes a meta-analysis of the epidemiological
literature on green tea consumption and esophageal cancer. This is an important
topic given the incidence of esophageal cancer worldwide and the potential of
green tea to reduce the risk. The meta-analysis appears to be conducted
according to the rules, the paper is well written, however the english needs
considerable editing.
Major Compulsory Revisions
. Abstract should contain methods used as well as heterogeneity of study results
. Q statistic is described in the method while the I2 is given.
. Sensitivity analyses could possibly be added.
. Would a dose-response analysis be possible?
. Could a case-control study from Iran by Islami et al, 2009 be missed? If yes,
how could this have happened?
. Page 5 Highest versus lowest... heterogeneity should be discussed.
. method used for the assessment of tea consumption in the different studies
could be included and possibly used for stratification.
. Could the studies be stratified on the number and type of confounding variables
adjusted for?
. Could the exact similar finding between prospective versus case-control and
Japan versus China not simple be due to including the same studies in the
analyses? See also table 2.
. In the discussion, the authors try to provide a potential mechanism explaining
the protective effect in women and not in men. However, although estrogens may
influence esophageal cancer risk, it is not clear how green tea could be
associated with hormonal effects. Do women drink more green tea, is there more
variation in green tea drinking among women? Do women drink and smoke less,
etc etc?
. The discussion should include some discussion on reverse causation which
may explain the differences observed between case-control and cohort studies.
More detail needs to be provided about the fact that all studies among women
are case-control studies.
. Brief remark about population versus hospital based case-control studies in the
discussion is not clear and should be more focused on how this could have
influenced the results of this meta-analysis.
. Specific estimates on smoking and alcohol should be excluded from the
discussion.
Minor Essential Revisions
. Two decimals should be used instead of three
. References need editing, e.g. 10-12
. In the Discussion references 18 and 19 are focused on esophageal and not on
colorectal cancer.
Level of interest: An article whose findings are important to those with closely
related research interests
Quality of written English: Needs some language corrections before being
published
Statistical review: No, the manuscript does not need to be seen by a
statistician.
Please review this paper.
user
Reviewer's report
Title:Green tea consumption and risk of esophageal cancer: a meta-analysis of
epidemiologic studies
Version: 1Date:2 June 2012
Reviewer: Ellen E Kampman
Reviewer's report:
This paper bij Zheng et al describes a meta-analysis of the epidemiological
literature on green tea consumption and esophageal cancer. This is an important
topic given the incidence of esophageal cancer worldwide and the potential of
green tea to reduce the risk. The meta-analysis appears to be conducted
according to the rules, the paper is well written, however the english needs
considerable editing.
Major Compulsory Revisions
. Abstract should contain methods used as well as heterogeneity of study results
. Q statistic is described in the method while the I2 is given.
. Sensitivity analyses could possibly be added.
. Would a dose-response analysis be possible?
. Could a case-control study from Iran by Islami et al, 2009 be missed? If yes,
how could this have happened?
. Page 5 Highest versus lowest... heterogeneity should be discussed.
. method used for the assessment of tea consumption in the different studies
could be included and possibly used for stratification.
. Could the studies be stratified on the number and type of confounding variables
adjusted for?
. Could the exact similar finding between prospective versus case-control and
Japan versus China not simple be due to including the same studies in the
analyses? See also table 2.
. In the discussion, the authors try to provide a potential mechanism explaining
the protective effect in women and not in men. However, although estrogens may
influence esophageal cancer risk, it is not clear how green tea could be
associated with hormonal effects. Do women drink more green tea, is there more
variation in green tea drinking among women? Do women drink and smoke less,
etc etc?
. The discussion should include some discussion on reverse causation which
may explain the differences observed between case-control and cohort studies.
More detail needs to be provided about the fact that all studies among women
are case-control studies.
. Brief remark about population versus hospital based case-control studies in the
discussion is not clear and should be more focused on how this could have
influenced the results of this meta-analysis.
. Specific estimates on smoking and alcohol should be excluded from the
discussion.
Minor Essential Revisions
. Two decimals should be used instead of three
. References need editing, e.g. 10-12
. In the Discussion references 18 and 19 are focused on esophageal and not on
colorectal cancer.
Level of interest: An article whose findings are important to those with closely
related research interests
Quality of written English: Needs some language corrections before being
published
Statistical review: No, the manuscript does not need to be seen by a
statistician.
assistant