Review for 10.1186/1471-230X-13-82 (2013)

Reviewer's report
Title:Barrett's esophagus and the risk of obstructive sleep apnea: A case-control
study
Version: 1Date:17 September 2012
Reviewer: William C Orr
Reviewer's report:
This research addresses the issue of the risk of obstructive sleep apnea (OSA) in
patients with Barrett’s Esophagus (BE). Ostensibly, I cannot see any reason to
suspect OSA in anyone who has a diagnosis of BE except insofar as they might
share certain risk factors such as obesity which is a well know risk factor for
OSA. In such cases the risk is most likely attributable to obesity not the presence
or absence of BE. There appears to be nothing unique to BE which contributes to
OSA and the presence of obesity is no more likely to contribute to OSA in the BE
group than in the colonoscopy control group (COL.)
1. Major compulsory revisions:
a. The authors must be more convincing regarding why BE should be considered
a major risk for OSA. I do not conclude this from my interpretation of these data.
To rephrase this, why would a patient with BE be more likely to have OSA than
either the EGD or COL control group? For example the authors use the rationale
that patients with BE will be subjected to more instances of sedation and perhaps
longer sedation due to surveillance issues with BE patients. Is this not also the
case with a patient who would have an adenomatous polyp on colonoscopy?
Furthermore the results of the multivariate logistic regression controlling for age
did not reveal any significant association between BE and the Berlin
Questionnaire. This seems to provide evidence that the authors primary
hypothesis should be rejected.
b. It would be helpful to know what percentage of the COL group were referred
for screening colonoscopy as opposed to those who were referred for clinical
evaluations. The groups could be stratified to assess the OR with each since the
screening colonoscopy group would seem to be the perfect control group.
c. The odds ratio for the BE group is not presented in the results or the abstract.
In the results the authors state that “BE was therefore associated with an
increased risk for OSA compared with COL controls.” I do not note that there are
any statistics to support this conclusion. Is the OR for the BE group significantly
greater that for the COL group? The authors state only that 56% of BE patients
and 37% of COL patients were at high risk for OSA according to the Berlin
Questionnaire.
d. In the Introduction the authors attribute reflux related to OSA as resulting from
the negative intrapleural pressure noted with an obstructed upper airway. They
cite a study by Ing et.al. as support for this. In point of fact this study does not
document this rationale and the Ing study reports that only 18% of reflux events
were associated with an upper airway obstruction. and in fact numerous studies
have been done to address this issue and I am unaware of a single study that
documents reflux secondary to negative intrapleural pressure.
e. In the last sentence of the introduction the authors state, “We hypothesize that
nocturnal gastroesophageal reflux may be associated with an increased risk for
OSA due to potential effects on sleep quality.” This is a statement which
essentially says the disturbed sleep quality is the cause of OSA; a statement
which is entirely without any evidence in the literature. Furthermore the statement
has nothing to do with patients with BE, and therefore seems somewhat
tangential to the main thrust of this study.
f. Regarding the inclusion/exclusion criteria the authors include in the BE group
“…cases diagnosed at endoscopy.” I assume this diagnosis is made without
pathologic evidence and this is not optimal for inclusion in a study based on an
experimental group with BE. I feel all study patients included should have
definitive pathological evidence of BE.
2. Minor essential revisions:
a. Pg 9 3rd par in Results add “significantly” to the sentence “Although EDG
patients had a “significantly” lower…” Similarly add “significant” to the sentence
beginning “BE patients were “significantly” more likely…” Add (Table 1) to the
end of that sentence.
b. Consider eliminating the data presented in the sentence on pg 9 in the Results
beginning with “In addition,…” I think all of these data are tangential and not
relevant to the main topic of this study.
c. The presentation of specific responses to the Berlin Questionnaire is of
questionable validity. It should be considered that this instrument was validated
as a whole and not each individual question. I leave it to the authors do decide
whether or not to include these data.
d. On pg 11 end of the first paragraph, the significance of this result is not noted
in Fig 2.
Level of interest: An article of limited interest
Quality of written English: Acceptable
Statistical review: No, the manuscript does not need to be seen by a
statistician.
Declaration of competing interests:
I declare that I have no competing interests.