Research proposal advanced epidemiology

Elevated physiological symptoms related to
air-conditioning use while sleeping: a longitudinal
cohort study in NUS
Research proposal
Ying Chen, Xiaohe Li, Divya Balasubramanian
Saw Swee Hock School of Public Health
National University of Singapore
A0078002, A0123847, A0120163
April 15, 2015
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Abstract
Background
Cross-sectional studies have consistently shown that health problems are related to air-conditioning
use in tropical regions. We intend to conduct our study with students in the residences of Na-
tional University of Singapore. We are interested in the night exposure to air-conditioning as
CO2 levels are found to be higher in air-conditioned rooms and suspected to cause elevated
physiologic symptoms. We hypothesize that exposure to air-conditioning during sleep is a risk
factor for health conditions in terms of respiratory systems and central nervous systems, skin
problems. We also hypothesize there could be a dose-response relationship between the inten-
sity and temperature of the exposure and health conditions.
Method
A longitudinal cohort study will be conducted in two cohorts of residents from National Uni-
versity School. Participants will be followed up for a semester where exposure, potential
confounders, and outcomes will be measured repeatedly. Logistic regression and poisson re-
gression will both be used for analysis. To account for the time correlation between outcomes
from the same subject and adjust for time-varying covariates, generalized linear mixed model
will be applied.
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Contents
1 Introduction 1
2 Problem Statement 2
2.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2.2 Research Question/Hypothesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
3 Objectives and Aims 3
3.1 Overall Objective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.2 Speciﬁc Aims . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4 Background and Signiﬁcance 4
5 Research Design and Methods 5
5.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.2 Population and Study Sample . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.3 Inclusion and Exclusion Criterion . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5.4 Sample Size and Selection of Sample . . . . . . . . . . . . . . . . . . . . . . . . 6
5.5 Sources of Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5.6 Collection of Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
5.7 Exposure Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
5.8 Outcome Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5.9 Missing Data Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5.10 Data Analysis Strategies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5.11 Ethics and Human Subjects Issues . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.12 Timeframes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
6 Strength and Weakness of the Study 10
6.1 Strengths . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
iii

6.2 Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
6.2.1 Selection bias . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
6.2.2 Information bias . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
6.2.3 Reverse causality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
6.2.4 Generalizability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
6.3 Public Health Signiﬁcance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Appendices 14
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1 Introduction
Lifestyle of the urban population has been changing radically in the last two decades. The invasion
of air-conditioners has made air-conditioning almost inescapable in our daily life. Particularly in
Singapore, air-conditioning can be everywhere when we are going out by buses, trains, visiting
clinics, having classes in the university, staying within stations, shopping at malls, working at
offices and so on. Most of our day time are spent in an air-conditioned environment. Interestingly,
health problems and discomforts, referred to as sick building syndrome or tight building syndrome,
has been recognized to be related to the quality of indoor air along the changes for over fifteen
years [1].
Problems associated with indoor air quality is considered to be a common environmental health
issue faced by clinicians, because the factors associated with the perceived indoor air quality or
indoor air problems are not fully understood. It can be said with certainty that no known toxins are
found to be causing these symptoms. And there have not been any standardized tests or instruments
used to define this as a syndrome [2]. This has made it all the more difficult to clearly identify the
associations and the causal inference from the associations.
There are studies that have compared the indoor air quality while sleeping in the air-conditioned
and the naturally ventilated buildings. The results from such studies suggest an association between
the air-conditioner use and the symptoms of the respiratory or central nervous systems. The sug-
gested causal relationship is that the air-conditioning leads to an increased carbon dioxide levels
inside the room due to changes in humidity, temperature and ventilation rates and this could in
turn lead to discomfort or even health problems [3]. The most important factors that have been
attributed to affect indoor air quality is the presence of heating, ventilation and air-conditioning
systems. There are analyses that showed an increase in the mentioned symptoms of about 30% to
200% in air-conditioned buildings compared to natural ventilation [5].
A weakness identified in such studies are the difficulties in finding a perfect control group
where there is absolutely no exposure to air-conditioning given surroundings are almost always
air-conditioned. The other difficulties include controlling for potential confounders that might
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bias the conclusions. In view of all these, we are motivated to restrict our study to a relatively
homogenous population and examine the effect of air-conditioning only during sleep on health
problems.
2 Problem Statement
2.1 Overview
In Singapore, the usage of air-conditioners have been changed signiﬁcantly in the last decade due
to the huge economic development. The hot, humid and wet climates have led to increasing us-
age of air-conditioners in this fast developed island. Singapore is one of the tropical countries
where air-conditioning is of great concern because one study in energy consumption done in Na-
tional University of Singapore have reported that heating, ventilation and air-conditioning have
contributed up to 50% of the total energy consumption in whole Singapore [4]. Studies have
shown that there is potential association between respiratory systems related symptoms and other
sick building syndromes and exposure to air-conditioning. Step-down in performance of people
could be related to environmental conditions that cause an increase or decrease in the body core
temperature [5]. However there are only a few studies conducted in this area and we need more
studies to conﬁrm if there could be a causal relationship between exposure to air-conditioning and
related health problems. As described in introduction, our proposed cohort study has the advan-
tages that we could control for potential confounders by concentrating on a relatively homogenous
population and have a better control group with absolutely no exposure to air-conditioning by
studying the effect of exposure to air-conditioning during sleep.
2.2 Research Question/Hypothesis
1. Is usage of air-conditioners while sleeping associated with elevated levels of symptoms of
the upper and lower respiratory symptoms, central nervous system and skin?
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2. Is temperature, or the duration of use of air-conditioner while sleeping associated with any
of the above-mentioned symptoms?
3. Is there a dose-response relationship of the temperature and duration with the severity of the
symptoms?
3 Objectives and Aims
3.1 Overall Objective
We will conduct a longitudinal cohort study with one group consisting of users of air-conditioner
while sleeping (exposed) and the other group consisting of non-users of air-conditioners while
sleeping (non-exposed) among the residents of National University of Singapore by following
them up for a period of four months/ one semester.
3.2 Specific Aims
1. To investigate the relationship between the exposure (temperature and duration) of air-conditioner
use and the transient outcomes that includes
• Lower respiratory (tight chest, difficulty breathing, shortness of breath, wheeze and
flu-like symptoms)
• Upper respiratory/ mucous membrane (nose, throat and eye symptoms)
• Central nervous symptoms (head ache and lethargy)
• Skin (dry skin, itching skin and skin rash)
2. To identify the specific risk factors of the transient outcomes, including temperature of air-
conditioning setting, duration of air-conditioning setting.
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4 Background and Significance
A field study on the thermal comfort of Singapore subjects was conducted in 1988 and many other
studies in Jakarta and Bangkok to find the comfortable temperature for human beings. The study
has found that the comfortable temperature is around 27 C in both naturally ventilated setting and
air-conditioned setting but that in naturally ventilated setting is slightly higher [6].Air-conditioning
systems are deemed responsible for recirculating pathogens and spreading them throughout the
room like Mould, bacteria, dust mites, other micro-organisms; endotoxins and other microbial
products.
Reduced ventilation rates have been found inadequate to maintain the health and comfort of
residence occupants. Heating, ventilation and air-conditioning systems (HVAC systems) also have
been found to increase the indoor air pollution. In order to have an acceptable indoor air quality
(IAQ) with a minimum energy consumption, The American Society of Heating, Refrigeration
and Air-Conditioning Engineers (ASHRAE) has set ventilation standards to a minimum of 8.4 air
exchanges per 24 hours [7] [8] [9].
It becomes all the more important while sleeping because in addition to all these factors the
carbon dioxide levels are higher in an air-conditioned room and the brain signals the breathing
muscles to breathe faster in order to expire more carbon dioxide and inspire more oxygen. If
this regulatory mechanism is disrupted and the brain’s recognition of, or response to, oxygen and
carbon dioxide levels is impaired and sleep might be disturbed [9]. Thus the temperature and
intensity of air-conditioning use, leads in turn to change in temperature, humidity and carbon
dioxide levels and microbe concentration in the room while sleeping and these factors could be the
causal factors for the elevated symptoms that have been identified.
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Figure 1: diagram of relations
5 Research Design and Methods
5.1 Overview
Due to the short term occurring and recurring nature of symptoms of interest, we propose to do a
cohort study on residents in one of the local university in Singapore. Exposure to air-conditioning
use in sleep and symptoms of interest will be measured repeatedly four times in a monthly interval
between collection of measures
5.2 Population and Study Sample
Our study population is NUS residents, which is expected to be homogenous in terms of age (on an
average), environmental exposures, day-time exposure to air-conditioning (again on average) and
the food from the canteens (although their choices are different). We are going to use two cohorts
of residents one from the Prince George?s Park residence and second cohort from University-Town
residence. There are two types of rooms in these two residences, either provided with or without
air-conditioning. By selecting from the whole population, we can have a group of residents with
exposure to air-conditioning during sleep, and another without, the non-exposed group. Given that
accommodation contracts last for only one academic year including 2 semesters, and each semester
lasts for 4 months, excluding vacation, each of the cohort participants will be followed up from the
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beginning of move for the next 4 months, until the end of the semester.
5.3 Inclusion and Exclusion Criterion
Inclusion:
• Residents in Utown and PGP residents.
• Stay at their current accommodation through out the study period.
Exclusion:
• Residents who sleep at their room less than 80% of time.
• Residents with long term symptoms related to our outcome of interest.
• Residents who are below 18 years old.
Due to the short term nature of our symptoms of interest and the recurrences, participants who
already have symptoms will still be at risk immediately after they recover. In view of that, we will
still include participants with short term symptoms of interest.
5.4 Sample Size and Selection of Sample
To obtain an odds ratio of 2 in effect among groups with different exposures to air-conditioning,
we estimated the sample size for the non-exposed group to be 505 and for the exposed group to
be 101, if we assume the prevalence of symptoms in exposed group to be 0.40 and the prevalence
of symptoms in non-exposed group to be 0.25 and the sample size ratio be 1:5 between exposed
group and non-exposed group which is based on the literature review [1]. This estimated sample
sizes will give us at least 80% power and around we are able to control our type-I error rate at 0.05.
5.5 Sources of Data
Ofﬁce of hostel services (OHS) of the National University of Singapore
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5.6 Collection of Data
Data will be collected through questionnaires. To recruit participants into our study, questionnaire0
will be distributed where questions will be asked regarding stay time in residence, and conditions of
long term diseases including an injury, operation affecting chest, heart problems, bronchitis, pneu-
monia, pleurisy, asthma, other chest problems and hay fever.Once ineligible students are elim-
inated from the pool,, participants will be reached to distribute questionnaire1 to obtain basic
demographics, history of accommodation types (mainly whether exposed to air-conditioning use
in sleep), history of diseases, as well as history of symptoms of interest. At the end of each month,
a follow-up questionnaire2 will be distributed regarding the exposure to air-conditioning in sleep
over the past month. Information on potential confounders like day-time use of air-conditioning,
average sleeping time per night, type of air-conditioners using will be collected as well. Having
symptoms of interest and frequency of getting these symptoms will also be asked in this follow-up
questionnaire. The participants will be called and reminded of participating in the survey. The sec-
ond questionnaire is to gather data about the exposure and the outcome of that month. Participants
who do not respond will be called and enquired about the reasons for loss-to-follow up.
5.7 Exposure Assessment
When collecting exposure information, questions regarding the frequency of air-conditioning use
during sleep(number of days per week sleep with air-conditioning on), the duration of air-conditioning
use during sleep(number of hours per night sleep with air-conditioning on), the temperature setting
about air-conditioning during sleep will be asked. Apart from the exposure information, informa-
tion on potential confounders will be collected as well. Day-time exposure to air-conditioning is a
main confounder in the relationship because day-time exposure may be related to both the expo-
sure and outcome. Another important confounder is the sleeping time, because people who sleep
for very few hours might have used air-conditioning for the same duration compared to people
who sleep for very long time. But the effect of air-conditioning could be very different for them.
The third confounder could be the type of air-conditioner because different types of air-conditioner
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might have different effects. The other confounders include smoking, which could be a cause for
some of the respiratory symptoms.
5.8 Outcome Assessment
Symptoms of interest will be categorized into four groups: symptoms related to lower respiratory
systems (tight chest, difficulty in breathing, shortness of breath, wheeze, and flu-like symptoms);
symptoms related to upper respiratory/mucus membrane (nose, throat, and eye symptoms); symp-
toms related to central nervous systems (headache and lethargy); and symptoms related to skin
(dry skin, itching skin, and skin rash). The four categorized symptoms will be asked in a standard
questionnaire format, due to the short term occurrence and high risk of recurrences of the symp-
toms, participants who often have these symptoms will remember more clearly than those who
experience these symptoms at most only once in the one month period. The frequency of having
these symptoms asked will later be clustered to less than 2 times per month, 3-4 times per month,
and more than 4 times per month.
5.9 Missing Data Management
For participant with missing data, the answers from the previous questionnaire will be used by
assuming no changes for the recent month for that particular participant.
5.10 Data Analysis Strategies
Because our outcomes are dichotomous, logistic regression will be used to study the relationship
between exposure and each of the symptoms, as well as combination of symptoms. For the fre-
quency of outcomes, because it will be counts, poisson regression will be applied instead. In
a longitudinal study design, the correlation between repeated measurements at different timings
need to be considered and covariates might vary with time as well. To take into account of these
issues, generalized linear mixed model will be applied. Apart from specific symptoms, another set
8

of outcomes will be binary outcome of having symptoms of speciﬁc category for example, having
symptoms related to central nervous system or not. Two models will be tried out where the ﬁrst
one is a simpler model where only outcome will only be modelled with exposure variables. The
second model will be more complex where potential confounders will be adjusted for the relation-
ship between air-conditioning exposure in sleep and symptoms of interest. The adjusted variables
will include age, ethnicity, gender, day-time exposure to air-conditioning, ventilation rates, air-
conditioner type and sleeping time, smoking and income. In selecting the second model, step-wise
method will be applied to select the best model.
5.11 Ethics and Human Subjects Issues
In order to conduct an ethically valid research study among the participants, the approval of the
IRB shall be obtained prior to conducting the survey. Informed consent forms shall be provided
and signed by the participants before they are given the survey forms. The data collected shall be
stored in a private PC in the university that has been secured with a password and the access to it
requires unique IDs. The data shall be stored for six years for further investigation by the ethics
committee if necessary.
5.12 Timeframes
April 2015 to April 2016
Figure 2: timeframe chart
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6 Strength and Weakness of the Study
6.1 Strengths
By using the NUS cohort, where the population is homogenous in terms of many characteristics,
we could have avoided many unknown confounding effects. Conducting a longitudinal study and
collecting exposure and outcome measures concurrently help in providing information about onset
and dessistance, about continuity of harbouring the symptoms as well as about the within-subject
changes.
6.2 Limitations
In the study, although we made effort to adjust for potential confounders, we may still face some
risks.
6.2.1 Selection bias
Firstly, non-response bias is a serious problem. If we have a low response rate in both groups with-
out differentially distributed non-response reasons, the study will be inﬂuenced in terms of study
power. If the two groups have signiﬁcantly different response rate, and the reasons of people who
do not response are related to exposures and outcome, the study would be biased. To minimize
the non-response rate, at each follow-up point, participants are called to be reminded of the par-
ticipation. Secondly, we also face the problem of loss-to-follow-up bias. During the following up
period, people may leave the study due to various reasons. Similar to the non-response bias issue,
if the lost-to-follow-up rate is very high then our sample might have a larger chance to be different
from the source population, or if the lost-to-follow-up reason is related to the outcomes of interest,
then we will have a biased conclusion. In order to minimize the lost-to-follow-up bias, reasons for
leaving the study will be enquired when participants drop out.
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6.2.2 Information bias
In our study, information on both exposure and outcome collected through questionnaires are all
self-reported, which could have produced big risk for inaccurate information and different percep-
tions. Specifically, participants’ perception about symptoms might be very different. For instance,
participants might have different perceptions on lethargy. Another short-coming is that repeated
interviewing of the same subjects might influence their behavior.
6.2.3 Reverse causality
Symptoms resulted by air-conditioner usage will somehow influence the later on using of air-
conditioner which is the scenario of reverse causality in our study context. But under our as-
sumption that all the symptoms are short-term and they are unlikely to alter the habit of a regular
air-conditioner user, so we would say, reverse causality is not a big issue here.
6.2.4 Generalizability
Since our study will be done in NUS hostel occupants, so study subjects can not be representative
of larger population including people who are not students. We should be very considerate in
generalizing the result to larger population.
6.3 Public Health Significance
There may be several possible outcomes for our study.
One of the possibilities is that using air-conditioner during sleep is a risk factor for having
elevated symptoms. It is also possible that the association is not statistically significant. And it
may be that using air-conditioner during sleep is protective against elevated symptoms. (We think
this is not likely to be happen according to previous researches).
If we get significant results showing using air-conditioner during sleep is a risk factor, we will
come up with a suggestion regarding the proper usage of air-conditioner which at best doesn’t
11

result in elevated symptoms(e.g., no more than 30 minutes, higher than 26 C), so students in the
cohort as well as other occupants in the residences will ﬁrst beneﬁt.
Then our cohort study can serve as a pilot study in probing the association between air-
conditioner usage and risk of getting elevated symptoms in general population in Singapore.
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References
[1] Mendell, M. J. Smith, A. H. (1990). Consistent pattern of elevated symptoms in air-conditioned
office buildings: a reanalysis of epidemiologic studies. American journal of public health,
80(10), 1193-1199.
[2] Wong, N. H., Huang, B. (2004). Comparative study of the indoor air quality of naturally ven-
tilated and air-conditioned bedrooms of residential buildings in Singapore. Building and Envi-
ronment, 39(9), 1115-1123.
[3] Mendell, M. J., Lei Gomez, Q., Mirer, A. G., Seppnen, O.,Brunner, G. (2008). Risk factors in
heating, ventilating, and air?conditioning systems for occupant symptoms in US office build-
ings: the US EPA BASE study. Indoor air, 18(4), 301-316.
[4] Yap, C., Cai, W.J., Ooi, K.T., Toh, K.C., Calavarro, G., Pillai, E.K. (2011). Air-con system
efficiency primer. National Climate Change Secretariat and National Research Foundation.
Retrieved from https://www.nccs.gov.sg/sites/nccs/files/Aircon%20Primer.pdf
[5] Okamoto-Mizuno, K., Tsuzuki, K., Mizuno, K. (2005). Effects of humid heat exposure in
later sleep segments on sleep stages and body temperature in humans. International journal of
biometeorology, 49(4), 232-237.
[6] Antic NA. Global warming and increased sleep disordered breathing mortality,rising carbon
dioxide levels are a serial pest. Respirology. 2012;17(6):885-886.
[7] Babatsikou FP. The Sick Building Syndrome (SBS). Health Science Journal.2011;5(2):72.
[8] Ruhl RA, Chang CC, Halpern GM, Gershwin ME. The Sick Building Syndrome. Journal of
Asthma. 1993;30(4):297-308.
[9] Skov P. The sick building syndrome. Annals of the New York Academy of Sciences.
1992;641(1 Sources of In):17-20.
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[10] Wong NH, Khoo SS. Thermal comfort in classrooms in the tropics. Energy Buildings.
2003;35(4):337-351.
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Elevated symptoms related to air-conditioner use during sleep: a cohort study in Singapore. 1
Questionnaire 0
Welcome to this study which we researchers want to look at possible associations between elevated symptoms
and air-conditioning usage during sleep. Thanks for your participation!
Please note that this is questionnaire number 0, which is intended to recruit participants to our study.
1. Your name:
2. Which residence do you live in? 2 PGP Residence 2 UT Residence
3. How long have you stayed in your current accommodation? years.
4. Approximately how many days in a week do you sleep in your current accommodati-
on? days.
5. Have you ever had, or been told that you have had any of these disease?
2 An injury, or operation a↵ecting your chest 2Heart trouble
2 Bronchitis 2Pneumonia 2 Pleurisy 2 Asthma
2Other chest trouble 2 Hay fever 2 Long term skin symptoms
2 None

Elevated symptoms associate with air-conditioner use during sleep: a cohort study in Singapore. 1
Questionnaire 1
Please note that this is questionnaire number 1, which is intended to collect basic/baseline information from
participants
About you
1. Your name:
2. Your gender: 2 Female 2 Male
3. How old are you? I am years old.
4. Which country are you from? I am from .
5. How long have you been in Singapore? years .
6. What is your ethnicity? 2 Chinese 2 Malay 2 Indian 2 Others, please specify
7. Are you a graduate student or undergraduate student? 2 graduate 2 undergraduate, which
year? .
8. Which faculty are you from? I am from .
9. Which residence do you live in? 2 PGP Residence 2 UT Residence
Please specify your room type .
10. How long have you stayed in your current accommodation? years.
About your general air-conditioner usage
11. Do you usually stay in places with air-conditioning during day time?
2 Yes 2 No
12. Do you use air-conditioner in your previous accommodations?
2 Yes 2 No
13. Do you use air-conditioner in your current accommodation?
2 Yes 2 No
If No, please proceed to next section.
14. What kind of air-conditioner do you use in your current accommodation?
2Residence set air-conditioner 2 Portable air-conditioner
2 Others, please specify
15. Generally speaking, how frequently do you use air-conditioner in your accommodation?
very often 2—2—2—2—2 very rare
16. Do you open the window when the air-conditioner is not on?
2 Yes 2 No 2 Sometimes
17. Do you use air-conditioner during sleeping time in your current accommodation?
2 Yes 2 No
18. On average how many days in a week do you use air-conditioner during sleep?
About days.
19. On average how many hours do you keep your air-conditioner on during sleep?
About hours.
20. How many degrees do you usually set for your air-conditioner during sleep?
I set C.
21. Do you use fan simultaneously with air-conditioner during sleep?
2 Yes 2 No 2 Sometimes

22. Do you open the window during sleep when the air-conditioner is on?
2 Yes 2 No. 2 Sometimes
23. Do you set other functions of air-conditioner during sleep?
2 No 2 Yes I set .
About smoking status
24. Do you smoke?
2 Yes 2 No
If No, then
25. Have you ever smoked as much as one cigarette a day for as long as one year?
2 Yes 2 No
If No to either of previous two questions, please proceed to next section.
26. How old were you when you started smoking regularly? years old.
About the conditions on elevated symptoms
0.1 Central Nervous System
27. Do you have headache?
2 Yes 2 No
28. Do you get lethargy(feeling of slowness, sluggishness, tiredness, or lack of energy, and in-
cluding fatigue, drowsiness, lethargy, tiredness, malaise, listlessness)?
2 Yes 2 No
0.2 Upper Respiratory/Mucus Membrane
29. Do you have any of these nose symptoms?
2 Blocked nose 2 Runny nose
2 Others, please specify 2 None
30. Do you cough?
2 Yes 2 No
31. Do you usually bring up phlegm?
2 Yes 2 No
32. Do you have any of these throat symptoms?
2 Dry throat 2Sore throat 2 Others, please specify
2 None
33. Do you have any of these eye symptoms?
2 Itching eyes 2 Irritated eyes 2 Dry eyes
0.3 Lower Respiratory
34. Do you have tight chest?
2 Yes 2 No
35. Do you wheeze?
2 Yes 2 No
36. Do you feel short of breath?
2 Yes 2 No
37. Do you have ﬂu-like symptoms?
2 Yes 2 No

0.4 Skin
38. Do you have any of these skin symptoms?
2 Dry skin 2 Itching skin 2 Rash

Elevated symptoms related with air-conditioner use during sleep: a cohort study in Singapore. 1
Questionnaire 2
Please note that this is questionnaire number 2, which is intended to collect your current elevated symptoms
condition and your air-conditioner usage during the past month
1. Your name/Participation number:
2. Approximately how many days in a week do you sleep in your current accommodati-
on? days.
3. On average how many hours do you sleep everyday? hours.
4. Have you ever had, or been told that you have had any of these disease?
2 An injury, or operation a↵ecting your chest 2Heart trouble
2 Bronchitis 2Pneumonia 2 Pleurisy 2 Asthma
2Other chest trouble 2 Hay fever 2 Long term skin symptoms
2 None
About your air-conditioner usage during the past month
During the past month:
5. Do you usually stay in places with air-conditioning during day time?
2 Yes 2 No
6. Have you ever used air-conditioner in your accommodation?
2 Yes 2 No
7. What kind of air-conditioner do you use in your accommodation?
2Residence set air-conditioner 2 Portable air-conditioner
2 Others, please specify
8. Generally speaking, how frequently did you use air-conditioner in your accommodation?
very often 2—2—2—2—2 very rare
9. Did you open the window when the air-conditioned is not on?
2 Yes 2 No
10. Have you ever used air-conditioner during sleeping time in your accommodation?
2 Yes 2 No
11. On average how many days in a week did you use air-conditioner during sleep?
About days.
12. On average how many hours did you keep your air-conditioner on during sleep each day?
About hours.
13. How many degrees did you usually set for your air-conditioner during sleep?
I set C.
14. Did you use fan simultaneously with air-conditioner during sleep?
2 No 2 Yes 2 Sometimes
15. Did you open window when air-conditioner is on during sleep?
2 No 2 Yes 2 Sometimes
16. Did you set other functions of air-conditioner during sleep?
2 No 2 Yes I set .
About smoking status
17. Have you smoked over the past month?
2 Yes 2 No

Elevated symptoms related with air-conditioner use during sleep: a cohort study in Singapore. 2
About the conditions on elevated symptoms
During the past month:
0.1 Central Nervous System
18. Have you ever had headache?
2 Yes, time(s).
2 No
19. Have you ever got lethargy(feeling of slowness, sluggishness, tiredness, or lack of energy,
and including fatigue, drowsiness, lethargy, tiredness, malaise, listlessness
2 Yes, time(s).
2 No
0.2 Upper Respiratory/Mucus Membrane
20. Have you ever had any of these nose symptoms?
2 Blocked nose, time(s).
2 Runny nose, time(s).
2 Others, please specify and time(s).
2 None
21. Have you ever coughed?
2 Yes, time(s).
2 No
22. Did you usually bring up phlegm over the last month?
2 Yes, time(s).
2 No
23. Have you ever had any of these throat symptoms?
2 Dry throat time(s).
2Sore throat time(s).
2 None
24. Have you ever had any of these eye symptoms?
2 Itching eyes time(s).
2 Irritated eyes time(s).
2 Dry eyes time(s).
2 None
0.3 Lower Respiratory
25. Have you ever had tight chest?
2 Yes, time(s).
2 No
26. Have you ever wheezed?
2 Yes, time(s).
2 No
27. Have you ever felt short of breath?
2 Yes, time(s).
2 No
28. Have you ever had ﬂu-like symptoms?
2 Yes, time(s).
2 No
0.4 Skin
29. Have you ever had any of these skin symptoms?
2 Dry skin time(s).
2 Itching skin time(s).
2 Rash time(s).
2 None

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