Review for 10.1186/1471-230X-9-25 (2009)

Reviewer's report
Title:Decreasing Incidence of Peptic Ulcer Complications Despite Increasing
Sales of Prescribed NSAID:s, a study of the Swedish Population from
1974-2002.
Version: 2Date:24 June 2008
Reviewer: Henrik Sorensen
Reviewer's report:
Thank you very much for the revised paper which covers important public health
information. The paper has been substantially improved but a number of
limitations remain which the authors need to address:
1. In the Abstract: In the results section it remains strange that a paper involving
incidence does not report the incidence rates. The authors should do so.
2. In the Abstract: The conclusion is very speculative and is longer than the
results. The conclusion of the study is simple – there is a decrease in the
incidence of ulcus complications.
3. Based on the figures in the text, it is difficult to ascertain that the data follow a
linear regression model. Other regression models, such as spline, would
probably be much better at describing the data. If you look at the figure regarding
perforated peptic ulcer in males, the decrease in incidence actually does not
occur until about 1992. A number of new statistical programs such as STATA can
do a spline regression model unproblematically.
The authors can also receive a quick introduction on how to describe incidence
data with spline regression model by reading e.g. Greenland S. Dose-response
and trend analysis in epidemiology: Alternative to categorical analysis.
Epidemiology 1995: 6:356-65, as well as the newest edition of Modern
Epidemiology: Rothman KJ, Greenland S, Lash TL (eds). Modern Epidemiology,
3rd edition. Philadelphia: Lippincott Williams & Wilkins. 2008.
4. In general, the paper would benefit if, instead of p-values, confidence intervals
were listed, which is much more informative and in accordance with the Uniform
Requirements for Manuscripts Submitted to Biomedical Journals. “Despite a
widespread belief that many journals require significance tests for publication, the
Uniform Requirements for Manuscripts Submitted to Biomedical Journals
discourages them, and every worthwhile journal will accept papers that omit them
entirely. ln Epidemiology, we do not publish them at all.” Please see Rothman KJ.
Writing for Epidemiology. Epidemiology. 1998;9:333-7.
5. The paper furthermore needs a thorough language revision. For instance, in
the Abstract abbreviations such as ASA and NSAIDs are used but the
abbreviations are not defined until the first page of the Background section. On
the other hand, proton pump inhibitors are not abbreviated in the Background
section but become abbreviated in the Discussion section. In the first paragraph
of the Discussion, a definition of an abbreviation, which was also defined in the
Introduction, is repeated.
In other places, NSAIDs are abbreviated with or without the lower case ‘s’. The
authors ought to stick to “NSAIDs”.
6. On the first page of the Discussion, second to last line, the authors refer to
‘several studies’. These studies are not numbered and the reader has no chance
of examining which they are.
In sum, the paper entails robust and interesting data on the development of
peptic ulcer complications in the Swedish population over a large period of time.
These results are very much of interest to an international readership.
However, the paper needs a much better statistical analysis to describe the
development of the incidence. A lot of information is lost by simply dichotomising
the time periods from 1988 and onwards.
Moreover, the paper needs a thorough technical editing.
If the above two problems are solved, I am confident that the paper will be of
interest to your readership.