Reviewer's report
Title:Psychological stress and coeliac disease in childhood: a cohort study
Version: 3Date:17 September 2009
Reviewer: Per Farup
Reviewer's report:
The paper describes surveys in children aged 1 and 2.5 years with focus on
stress after birth. These children have been followed up and 73 children have
developed biopsy-verified CD. The hypothesis is that stress is associated with
CD because stress has been related to autoimmune diseases.
The paper is well written and easy to read.
Major compulsory revisions that should be clarified.
1. Why is the research question of interest? Has it any importance? Is it of
theoretical interest only, or has it any practical consequences? Previous studies
have shown that stress during pregnancy is unrelated to CD (published by the
same group in Scand J Gastroenterol in 2003), why should stress after birth have
other effects? Is the paper written only because data are available from the ABIS
project and information about CD could easily be retrieved based on the previous
publication?
2. Stress might be related to autoimmune disorders, but is CD an autoimmune
disorder? Immune mechanisms are for sure involved in CD, but I don’t think it is
an autoimmune disorder like rheumatic diseases. The immune disturbances
normalize when gluten is withdrawn from the diet.
3. The analyses have been performed with asymptotic methods using SPSS. I
doubt that the method is correct. In table II the number of subjects with CD was 1
in the group with “A serious life event”. Such a low number (1) makes the method
unreliable, and exact methods are preferable. I have remade the calculation in
table II, row 1 and the results with exact statistics are OR 0.45 (as reported in the
paper), but the 95% CI is 0.011-2.6, and p=0.71 (a marked difference). Please
ask for statistical expertise, I am not a statistician.
4. The study concludes that psychological stress is unlikely to be a risk factor for
CD in childhood. This is probably correct, but in a negative trial like this one, a
discussion of a type II error is mandatory. In table II – row one, the prevalence of
CD in children with and without a serious life event are 0.224% and 0.495%
respectively, which means that CD is 2.21 times more common in children
without a serious life event. The 95% CI for the ratio is 0.39-12.72 (calculated
with asymptotic methods since the authors use this method). These findings
mean that CD might be 12.7 times more prevalent in children without stress. Is
really a 12.7 times reduction or a 2.56 (1/0.39) times increase in children with a
serious life event without importance?
Minor compulsory revisions.
Page 8 and 12. Why is breastfeeding excluded from the analyses when
breastfeeding has been shown to influence the risk of CD; it seems to be based
only on some unpublished data? Could stress reduce breastfeeding?
Level of interest: An article of limited interest
Quality of written English: Acceptable
Statistical review: Yes, and I have assessed the statistics in my report.
Declaration of competing interests:
I declare that I have no competing interests.
Reviewer's report
Title:Psychological stress and coeliac disease in childhood: a cohort study
Version: 3Date:17 September 2009
Reviewer: Per Farup
Reviewer's report:
The paper describes surveys in children aged 1 and 2.5 years with focus on
stress after birth. These children have been followed up and 73 children have
developed biopsy-verified CD. The hypothesis is that stress is associated with
CD because stress has been related to autoimmune diseases.
The paper is well written and easy to read.
Major compulsory revisions that should be clarified.
1. Why is the research question of interest? Has it any importance? Is it of
theoretical interest only, or has it any practical consequences? Previous studies
have shown that stress during pregnancy is unrelated to CD (published by the
same group in Scand J Gastroenterol in 2003), why should stress after birth have
other effects? Is the paper written only because data are available from the ABIS
project and information about CD could easily be retrieved based on the previous
publication?
2. Stress might be related to autoimmune disorders, but is CD an autoimmune
disorder? Immune mechanisms are for sure involved in CD, but I don’t think it is
an autoimmune disorder like rheumatic diseases. The immune disturbances
normalize when gluten is withdrawn from the diet.
3. The analyses have been performed with asymptotic methods using SPSS. I
doubt that the method is correct. In table II the number of subjects with CD was 1
in the group with “A serious life event”. Such a low number (1) makes the method
unreliable, and exact methods are preferable. I have remade the calculation in
table II, row 1 and the results with exact statistics are OR 0.45 (as reported in the
paper), but the 95% CI is 0.011-2.6, and p=0.71 (a marked difference). Please
ask for statistical expertise, I am not a statistician.
4. The study concludes that psychological stress is unlikely to be a risk factor for
CD in childhood. This is probably correct, but in a negative trial like this one, a
discussion of a type II error is mandatory. In table II – row one, the prevalence of
CD in children with and without a serious life event are 0.224% and 0.495%
respectively, which means that CD is 2.21 times more common in children
without a serious life event. The 95% CI for the ratio is 0.39-12.72 (calculated
with asymptotic methods since the authors use this method). These findings
mean that CD might be 12.7 times more prevalent in children without stress. Is
really a 12.7 times reduction or a 2.56 (1/0.39) times increase in children with a
serious life event without importance?
Minor compulsory revisions.
Page 8 and 12. Why is breastfeeding excluded from the analyses when
breastfeeding has been shown to influence the risk of CD; it seems to be based
only on some unpublished data? Could stress reduce breastfeeding?
Level of interest: An article of limited interest
Quality of written English: Acceptable
Statistical review: Yes, and I have assessed the statistics in my report.
Declaration of competing interests:
I declare that I have no competing interests.
Please review this paper.
user
Reviewer's report
Title:Psychological stress and coeliac disease in childhood: a cohort study
Version: 3Date:17 September 2009
Reviewer: Per Farup
Reviewer's report:
The paper describes surveys in children aged 1 and 2.5 years with focus on
stress after birth. These children have been followed up and 73 children have
developed biopsy-verified CD. The hypothesis is that stress is associated with
CD because stress has been related to autoimmune diseases.
The paper is well written and easy to read.
Major compulsory revisions that should be clarified.
1. Why is the research question of interest? Has it any importance? Is it of
theoretical interest only, or has it any practical consequences? Previous studies
have shown that stress during pregnancy is unrelated to CD (published by the
same group in Scand J Gastroenterol in 2003), why should stress after birth have
other effects? Is the paper written only because data are available from the ABIS
project and information about CD could easily be retrieved based on the previous
publication?
2. Stress might be related to autoimmune disorders, but is CD an autoimmune
disorder? Immune mechanisms are for sure involved in CD, but I don’t think it is
an autoimmune disorder like rheumatic diseases. The immune disturbances
normalize when gluten is withdrawn from the diet.
3. The analyses have been performed with asymptotic methods using SPSS. I
doubt that the method is correct. In table II the number of subjects with CD was 1
in the group with “A serious life event”. Such a low number (1) makes the method
unreliable, and exact methods are preferable. I have remade the calculation in
table II, row 1 and the results with exact statistics are OR 0.45 (as reported in the
paper), but the 95% CI is 0.011-2.6, and p=0.71 (a marked difference). Please
ask for statistical expertise, I am not a statistician.
4. The study concludes that psychological stress is unlikely to be a risk factor for
CD in childhood. This is probably correct, but in a negative trial like this one, a
discussion of a type II error is mandatory. In table II – row one, the prevalence of
CD in children with and without a serious life event are 0.224% and 0.495%
respectively, which means that CD is 2.21 times more common in children
without a serious life event. The 95% CI for the ratio is 0.39-12.72 (calculated
with asymptotic methods since the authors use this method). These findings
mean that CD might be 12.7 times more prevalent in children without stress. Is
really a 12.7 times reduction or a 2.56 (1/0.39) times increase in children with a
serious life event without importance?
Minor compulsory revisions.
Page 8 and 12. Why is breastfeeding excluded from the analyses when
breastfeeding has been shown to influence the risk of CD; it seems to be based
only on some unpublished data? Could stress reduce breastfeeding?
Level of interest: An article of limited interest
Quality of written English: Acceptable
Statistical review: Yes, and I have assessed the statistics in my report.
Declaration of competing interests:
I declare that I have no competing interests.
assistant