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Congratulations with a well-conducted and well reported study.
I concur with the reviewers that this is an important study but that there are a few minor amendments that would improve the clarity of the presentation.
" No comments"
Please provide reference to the HUSK study.
Did the participants fill out the questionnaire before or after the examination? Please provide a little bit more information about the data collection.
Please provide more information on the validity of the one item self-reported health question as well as reference(s).
Were the results that women and those living alone in this age group had poorer health surprising or were these results in line with previous research?
In the discussion line 136: With reference to the study by Naess et al from 2005; this study is to old to be characterized as “recent”. Please change to “previous” as only the study by Riise et al from 2014 is recent.
In the limitations part it should be discussed how the population aged 40-44 might limit the generalizability of the results from this study. This in particular in respect to implications regarding relationship to diseases as few in this age population had any of the diseases. In addition it should be discussed that diseases might have different impact on self-reported health depending on one’s age group.
The conclusion should state what new knowledge this paper adds; e.g. the associations between lifestyle and health in a relatively young population where the consequences of poor lifestyle to a quite small extent have resulted in severe diseases.
Congratulations with a well written and well performed study.
Line 141: “extra-personal explanatory factors”: I easily understand what you mean, but is there a more common expression for this? I suggest rephrasing the sentence.
Line 161: The common expression is “units of alcohol”, not “units of spirits”. The latter is also misleading to the behavior of interest.
Line 203-205: The word “demonstration” is wrong.
Table 2: Look to the rows explaining physical activity: The data do not correspond to the correct labels in the left column.
Design is adequate.
The authors found that being a former smoker actually implied better self-rated health compared to those who had never smoked (reference group). The change in OR is small, although statistically significant at least in the univariate model. This may surprise some readers (me included), and a reflection from the authors would be welcome. One perspective on this is that we expect to see almost a linear inverse relationship between smoking and self-rated health. Another question that may arise is related to the validity of the rawdata: What is a former smoker? Did the questionnaire provide a definition of this? Are those who smoked occasionally at college twenty years ago in this category? I acknowledge the complexity of this and assume there is no straight forward answer, but if the authors have any opinion, that could be included in the Discussion.
The authors anticipate some criticism concerning that the data origins from the late nineties. I do not find this a limitation to a study with this aim and design. The authors' comments explaining recent changes in tobacco use, alcohol consumption and physical activity are strictly not necessary, but of course of interest when deducing secondary information from the study to say something about how the situation is today.
I question the use of Meyer & Tverdals paper on body weight as long as you only use this to refer to BMI and prevalence. There is more recent data on this, e.g. Midthjell et al. "Trends in overweight and obesity over 22 years in a large adult population" (2013) which also is based upon a representative sample.
I have spent some time thinking about the authors’ use of the term ‘prediction’. In line 134-137 they refer to how self-rated health is a predictor of mortality, diabetes and lung cancer. Is this use of the term correct? Doesn’t this imply some causal relationship between the variable and the outcome? Yes, there is solid basis to say there is a relationship, but prediction for me is also about causality. And does the studies you refer to give a basis to say there is?
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