Effect of Seasonal Ambient Temperature on Sleep and Thermal Comfort in Older People Living in Public Elderly Facilities

Round 1

Reviewer 1 Report

The topic is interesting and timely, but the methodology used is nothing remarkable. Authors could have used the opportunity to investigate deeper and recorded more indoor environmental parameters and physiological stress parameters.

Line 8 – define healthy. Healthy at 80 may not confirm to what is considered healthy otherwise.

“Both ambient temperature (Ta) and relative humidity (Rh) levels were found to be lower in the winter and higher in the summer, compared to those in the other seasons.” – this is an example of a trivial conclusion and need not be stated.

Table 2 – I am presuming there is a Japanese version? It would be a god reference for readers to have the Japanese version as well.

T and RH plots – provide box plots to provide the data over the entire observation period. It is not clear how this 24 hour was chosen. Are the authors using average temperature across the days of monitoring?

Why are authors using a 9 point thermal sensation scale?

Results should be discussed keeping in mind the small population size.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

The subject is important and worth investigating. My biggest concern is about the small sample size.

My comments and recommendations are:

Introduction:

• There are presented reasons why sleep quality is found to be poorer in elderly people. One missing reason is that many elderly people have all kind of sicknesses causing pain.
• You refer that older people have poorer sleep quality in summer. Is there some studies considering seasonal changes in sleep quality in general. Could one reason be that the day-light time is longer in summer?
• Quite interesting that the elder care facilities do not need to comply with Japanese Standard for Maintenance of Sanitation in Buildings. For instance, in Finland, temperature limit values are even tighter for retirement homes (Decree of the Ministry of Social Affairs and Health on Health-related Conditions of Housing and Other Residential Buildings). Indoor temperature action limits in retirement home are during heating season +20 °C – +26 °C (for other housing +18 °C – +26 °C) and outside heating season +20 °C – +32 °C (for other housing 18 °C – +32 °C). Is there a explanation why?

Methods:

• The sample size is quite small. How much the larger sample size could affected on reliability of the analysis?
• Table 1: please add daily operating hours of air conditioners.
• Did you check the distance between logger and mouth of occupant? Is it possible that breathing air effects on temperature and RH logging results? Was there any other loggers measuring average room conditions?
• The wrist actigraph is explained quite shortly, please explain operational principle more details. How does it measure sleep-wake patterns?
• It would be informative if the typical yearly outdoor conditions have been explained, how cold are the winters, how warm the summers.

Results:

• Also occupant presence in the room would increase the temperature and RH, but this should be seen every season. The most likely explanation of increased indoor temperatures during summer nights could be the heat storage of outer walls. Also I think that outdoor temperature is about the same whole summer night and decreases in other seasons.
• Figure 1 and 2: could you please add the average outdoor temperatures and RH in the figures. it would show how indoor T follows the outdoor T.
• Sleep parameter: did you investigate daytime (outdoor) activities and how they affect on sleep parameters?
• Table 5: Please add average sleep time, hours per night, to the table, it is easier to interpret. Is it possible to separate effective or recovering sleep time from total sleep time? Is it possible to conclude if the elderly people have enough sleep?
• Subjective sensation: sample size is quite small to analyse (Table 6), especially due lost of few men participants. How much this changes statistical credibility?

Discussion:

• It is very poor explanation of turning HVAC off during night due absence of facility managers!
• The neutral sensation is defined here by indoor temperature. Could you also define it by indoor relative humidity. The neutral sensation is a combination of T and RH, even the lower T could sensate appropriate if the RH is high.
• Page 13, sentence starting at the end of line 336, I could not understand what you meant by that?
• Line 338: it was stated that the sleep quality was not worse in summer for the women. Was the sleep quality worse in all seasons?
• I totally agree your conclusion in page 14/line 398!

Limitations to this study: this chapter could be include in introduction or discussion.

• Were there no loggers measuring air velocity and radiant temperature available?

Author Response

The authors' reply has been put in the attachment.

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The comments and suggestion to the paper have been adequate noticed and text modified.

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

The present work comprises of a study in which the thermal environment and thermal comfort of elderly who live in elder care facilities was studied. Comparisons in the quality of sleep was performed. The authors report changes in temperature and humidity between seasons, markedly in summer/winter. No significant difference was found between seasons in the sleep parameter; however, sex-related differences were found; in this line, it is reported that sleep efficiency index was significantly better for elderly women than men. The interest of the study is below average. It is well known that temperature and humidity affect sleep. In addition, the manuscript is quite descriptive and, in general, does not provide manoeuvres that could have improved sleep quality of elders. This is a major drawback of the study. This and other points, have called my attention after reading the manuscript and, thus, I have the next comments to the authors.

Comments:

Manoeuvres that could have improved sleep quality of elders should be implemented, analysed and discussed.

The manuscript by Caroline Hughes et al., 2019 (https://doi.org/10.1016/j.enpol.2019.110954) should be considered in the discussion.

Information about the diet and the timetable for dinner, that could be influencing sleep, is missing. Additionally, information about room illumination (direct or indirect, external, etc) or noise, which could also influence sleep, needs to be given.

In the Discussion, it is stated that “the hypothesis that sleep quality of elderly people was worse in summer due to the higher temperatures was not supported by this study”. However, it is mentioned that “significant differences were found in the total sleep time, wake time, sleep efficiency index, and sleep latency between women and men.” Later on, by the end of the discussion it is stated “However, sleep quality was worse for the men in summer” (line 457). This information seems contradictory to the reader, and needs clarification.

There are some spelling mistakes in the manuscript that need correction. For example, “indexes” in the abstract, line 22.

Reviewer 2 Report

Abstract – lines 13-16. If the values are not complying on temperature and RH, please formulate the sentence as such. Your current sentence seems to indicate first there is full compliance.

Also, as is apparent alter, air velocity was not measured so we cannot say for sure if it kept under 0.5 m/s as per requirements.

Abstract needs to contain information on how sleep quality was evaluated.

References 8 and 9 are specific to studies done in Japan and apart from summer temperature, there could also be an issue of longer daylight hours. It would be appropriate to introduce these qualifiers when quoting these references. We still do not have a generic idea on if summers are better for sleep or winters (globally). Indication would be thermal discomfort is bad for sleep.

Lines 92-93 – a few words on why the managers are qualified to evaluate dementia will be useful

Table 1  - how is grand floor area different from total floor area?

Table 2 – these are unusual questionnaires for assessing sleep quality and thermal comfort. Authors need to justify why these were used and not other standard questionnaires

Lines 142-145 – Is the implication that the investigators themselves did not check on the bedding/blankets etc. and relied on participant feedback to make their decisions on choosing a certain item on the check lists?

“The Ta and Rh did not change so much during the lights-out period from 21:00 to 6:00 because the central air conditioners were switched off by the guardians due to their absence.” – unclear. If they were absent, how were they switched off?

And this contradicts results put later that temperature drifted once AC was shut off

Figure 2 - 4 – data representation needs to improve quite a bit. At present, it just looks like a bunch of jumbled up points without any purpose.

Were any measurements made for luminance levels in the bedrooms?

Were any records kept about activities before sleep or typical everyday activities across seasons?

Was any feedback noted on the perception of fan use among participants?

Reviewer 3 Report

General comment

The article points to the very important issue of indoor air quality and sleep. The paper is well written, only minor corrections are needed.

Table 2 and 6 aren’t compatible, moreover the article doesn’t define what the numbers in Table 6 correspond to.

References should be formatted.

Specific comments in lines:

35 [8-9]

55 spacebar

128 spacebar

140 capital letter

167 Table no.?

228 spacebar

376 [8-9]

419 [5-7]

441 spacebars

480 degrees without spacebar

The article could be interesting for the readers, there are only few specific comments, which lead to the conclusion, that the manuscript can be considered for publication in the current form.