Long Sleep Duration and Stroke—Highly Linked, Poorly Understood
Round 1
Reviewer 1 Report
Dear Authors,
I hope this letter finds you well. I recently came across your paper titled "Long sleep duration and stroke—highly linked, poorly understood" and I wanted to express my appreciation for the valuable insights and research you have presented in your work.
Your paper sheds light on an important and often overlooked aspect of sleep and its potential impact on stroke risk. The comprehensive review of existing research, as outlined in the abstract, provides a clear understanding of the association between long sleep duration and stroke incidence and mortality.
I was particularly impressed with the identification of potential links between long sleep duration and stroke, such as the increased prevalence of conditions like diabetes and atrial fibrillation, as well as elevated levels of inflammation, arterial stiffness, and blood pressure variability. These insights contribute significantly to our understanding of the mechanisms behind this relationship.
Furthermore, your emphasis on considering long sleep duration as a marker and a plausible risk factor for stroke in future risk stratification and stroke prevention efforts is of great importance. It highlights the need for healthcare professionals to take sleep duration into account when assessing stroke risk and designing preventive strategies.
I commend your meticulous research and analysis, as well as the clarity with which you have presented the findings in your paper. The information you have shared has the potential to make a significant impact on both the scientific community and public health practices.
Once again, I would like to express my gratitude for your valuable contributions to the field. Your work serves as an inspiration for researchers and healthcare professionals alike. I eagerly anticipate further research in this area and the potential implications it may have on stroke prevention.
Thank you for your dedication and commitment to advancing our understanding of sleep and stroke. I wish you continued success in your future endeavors.
Sincerely,
The Reviewer
Author Response
We greatly appreciate the reviewer’s positive feedback.
Reviewer 2 Report
The authors discussed the problem of long sleep duration and stroke. The subject presented by the authors is relevant and critical from a theoretical and clinical point of view. The paper is comprehensive, well-written, and up to nowadays knowledge - unfortunately, the knowledge is still far from perfect, what the authors acknowledged. The paper is worth to be published.
I have no essential comments on the paper.
Maybe just two minor shortcomings
Line 26: “Stroke accounts… ranking fifth among all causes 26 of death”. It is true, but it could be worth adding that regarding DALYs stroke constituting second place in GBD trail.
Based on the Global Burden of Disease (GBD), the percent of changes in Numbers of DALYs, in cerebrovascular diseases for both sexes combined moved from fifth place in 1990 to third in 2005 and second in 2015 [Lancet 2016; 388: 1603–58].
For complete pictures of the problem, the authors could comment on some differences concerning optimal sleep duration between men and women (it seems that women (at least younger) could sleep longer without harm). See, for example, the Fang et al. study (Ref 22). It seems that in terms of hypertension for younger women (i.e., 18-44 years of age) correlation between hypertension and longer sleep occurred just after sleep ≥ 10 hours, without any harm for that sleeping 7, 8, or even 9 hours, what is not valid for younger men.
Author Response
Point 1: The authors discussed the problem of long sleep duration and stroke. The subject presented by the authors is relevant and critical from a theoretical and clinical point of view. The paper is comprehensive, well-written, and up to nowadays knowledge - unfortunately, the knowledge is still far from perfect, what the authors acknowledged. The paper is worth to be published.
I have no essential comments on the paper.
Maybe just two minor shortcomings
Response 1: We greatly appreciate the reviewer’s positive feedback.
Point 2: Line 26: “Stroke accounts… ranking fifth among all causes 26 of death”. It is true, but it could be worth adding that regarding DALYs stroke constituting second place in GBD trail.
Based on the Global Burden of Disease (GBD), the percent of changes in Numbers of DALYs, in cerebrovascular diseases for both sexes combined moved [Lancet 2016; 388: 1603–58].
Response 2: We greatly appreciate the reviewer’s suggestion and we have added “Stroke is also a major contributor to global disability-adjusted life-years, moving from the fifth place in 1990 to the third in 2005 and the second in 2015 [4].”
Point 3: For complete pictures of the problem, the authors could comment on some differences concerning optimal sleep duration between men and women (it seems that women (at least younger) could sleep longer without harm). See, for example, the Fang et al. study (Ref 22). It seems that in terms of hypertension for younger women (i.e., 18-44 years of age) correlation between hypertension and longer sleep occurred just after sleep ≥ 10 hours, without any harm for that sleeping 7, 8, or even 9 hours, what is not valid for younger men.
Response 3: We agree with the reviewer that there might be gender difference in the relationship between sleep duration and stroke. We carefully reviewed all the references we cited with the following findings.
- In retrospective cohort studies, 9 studies (19, 21, 23, 24, 28. 29, 30, 37, 38) performed subgroup analysis on gender difference. Seven (19, 21, 23, 24, 28. 29, 37) of the 9 studies showed a stronger association between long sleep duration and stroke prevalence in men than in women. Two (30, 38) of the 9 studies showed a stronger association between long sleep duration and stroke prevalence in women than in men.
- In prospective cohort studies, 4 studies (41, 46, 49, 58) performed subgroup analysis on gender difference. Two (41, 49) of the 4 studies showed a stronger association between long sleep duration and stroke incidence in women than in men. The other two (46, 58) studies showed no association between long sleep duration and stroke incidence in either women or men.
- In mortality cohort studies, 3 studies (18, 69, 70) performed subgroup analysis on gender difference. Two (18, 69) of the 3 studies showed a stronger association between long sleep duration and stroke mortality in women than in men. The other (70) study showed similar association between long sleep duration and stroke mortality in women and men.
Overall, retrospective studies showed a stronger association for men, but prospective studies showed a stronger association for women. Therefore, gender influence is inconclusive. We have added “The impact of gender on the association between long sleep duration and stroke needs to be further explored given conflicting data from retrospective and prospective studies [18, 28, 29, 41, 49, 69]” in the Future Directions section.
