Comments for “Sleep and subjective age: Protect your sleep if you want to feel young”
The paper addresses a very interesting topic and it is of interest to the readers of the journal as well as a large audience because it adds an important topic as sleep quality and its effect on well-being. The paper includes two studies: Study 1, a cross-sectional study including 429 participants and Study 2 aiming to examine how sleep during the last month and more acute sleep loss influence subjective age. the topic is intriguing but the conclusions are not solid and more analyses are needed to have a solid conclusion

Comments:
Abstract: The abstract is well-written and informative
Introduction: the introduction is well written and helps the reader to address the topic. The authors pointed to the beneficial effect of feeling young at the behavioural-psychological but also used as a biophysical marker of ageing. On line 51 I suggest changing “how old” to “how young”. The introduction is structured pointing to the beneficial effect of feeling young so I suggest being consistent.
Study 1 – procedure: the data were collected during one single day between 11:00 and 17:00?
When the study was conducted? Considering that sleep might be affected by hours of light and seasonal changes, I suggest being more specific on the exact time of testing.
Gender was not significant; can the authors comment on it for both studies?
Study 2 - It is not clear if the authors also measured the effect of sleep on subjective perception of tiredness. The authors commented that worse quality of sleep shaped participants’’ sense of age, but no other measures were collected to measure subjective feelings of tiredness or difficulties in dealing with everyday activities. It is possible that participants are simply tired and feel older because of it. Is there an effect of chronotype? Why did the authors ask participants to wear actigraphy but then they did not include that information in the analyses?