PROCEEDINGS of the23rd International Congress on Acoustics
9 to 13 September 2019 in Aachen, Germany

Influence of nocturnal noise on non-restorative sleep: Gendereffects
Daniel Y.T. FONG1; Sha LI1; Janet Y.H. WONG1; Bradley MCPHERSON1; Esther Y.Y. LAU2; Lixi
HUANG1; Mary S.M. IP1
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The University of Hong Kong, Hong Kong

The Education University of Hong Kong, Hong Kong

ABSTRACT
Nocturnal noise exposure may affect the sleep of men and women differently. However, evidence remains
limited, especially for non-restorative sleep (NRS). Therefore, this study aimed to assess the moderating
effect of gender on the effect of nocturnal noise exposure on NRS. This was a household survey of Chinese
adults. Participants completed the Chinese Non-restorative Sleep Scale (NRSS), standardized on a 0-100
scale, with a higher score indicating less NRS. Nocturnal noise level was measured by a dosimeter for oneweek. We recruited 90 subjects (58% female) with average age 37.0 years (range: 18-65). The mean nocturnal
noise level was 55.5dBA (SD: 5.5dBA). The mean NRSS domain scores were 57.3 (SD: 17.6) forRefreshment from sleep, 67.0 (SD: 16.7) for Physical/Mental symptoms, 60.5 (SD: 15.4) for Daytime
function, and 62.6 (SD: 21.6) for Affective symptoms. The gender-by-nocturnal noise exposure interaction
was significant (p=0.043) for the Refreshment from sleep domain. The influence of nocturnal noise exposure
on Refreshment from sleep was more profound in women (-1.00, 95% CI: -1.87 to -0.13) than in men (0.22,95% CI: -0.57 to 1.01). Women may be more vulnerable than men to the adverse impact of nocturnal noise
exposure on NRS.
Keywords: Gender, Noise, Non-restorative sleep

1. INTRODUCTION
Noise is often referred to as unwanted sound. The World Health Organization (WHO) has reported
that at least one million healthy years of life are lost in Europe each year due to excess exposure tonoise (1). The hypothesized pathways of the non-auditory impact of excess noise exposure on healthcan be both direct and indirect (2). Noise may directly affect our autonomic nervous system (ANS),
the reticular nervous system, as well as the cortical and subcortical brain centers. Alternatively, noise
may also make influences via annoyance that causes stress hormones resulting in pathophysiologicalchanges. Hence, excess noise exposure may result in various health problems including sleep.
Nonrestorative sleep (NRS) refers to the degree one feels unrefreshed upon waking up even after
adequate sleep. It is a defining symptom of insomnia, but it may not be co-morbid with other sleeprelated disturbances. Prolonged NRS may lead to the feeling of fatigue during day-time, chronic
illnesses, impaired psychological well-being, and even suicidal thought (3). Hence, it has gained muchattention as a treatment target. NRS was most previously assessed by a single item, but it can now beassessed using the standardized 12-item Nonrestorative Sleep Scale (NRSS) that is available in both
English and Traditional Chinese versions (4, 5).
The effect of environmental noise exposure on NRS has not been well studied. The literature has
so far reported people who have lower tolerance to noise have more NRS (3). Efforts have been madeto determine moderating factors on the health impacts of environmental noise, including gender. For
cardiovascular diseases, there is some evidence showing men are more affected by noise than women
but more evidence is needed (6, 7). For sleep or NRS, there is less work as yet on the potential roleof gender on the impact of noise. In view of this, the European Network of Noise and Health (ENNAH)
recommended more studies on identifying vulnerable groups, e.g. gender, to the effects of noise on
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dytfong@hku.hk

health (6).
Despite gender being considered as an important confounder when assessing noise effects on sleepproblems (8), its moderating role on NRS has not been examined. Therefore, this study aimed to assess
the moderating role of gender on the association between nocturnal noise exposure and NRS inChinese adults.

2. METHODS
2.1

DesignThis was a household survey of Chinese adults in Hong Kong. The study protocol and consent
form were approved by the Institutional Review Board of the University of Hong Kong/Hospital
Authority Hong Kong West Cluster (Reference Number: UW 17-011).
2.2 Subjects
Individuals aged 18 or above who could read and understand Chinese were recruited. Those whowere deaf, needed hearing aids, took sleeping pills or other medications for sleep disorders, werepregnant, had psychiatric illness, or had children under 2 years of age were excluded.
We used a representative sampling frame in Hong Kong to randomly identify residential addresses
for conducting the household visits. In each household visit, at most one eligible subject was identified.
Each eligible subject was explained of study details and written consent was obtained before study
participation.
2.3 Measurements
The participants self-completed a battery of questionnaires that included demographics, the 12item Chinese Non-restorative Sleep Scale (NRSS), the Hospital Anxiety and Depression Scale(HADS) - Depression, and the 10-item Chinese Perceived Stress Scale (PSS). The Chinese NRSS wasshown to be reliable and valid for assessing NRS in the Chinese population (5). It comprises a global
scale and the four domains: refreshment from sleep, the physical/medical symptoms of NRS, daytime
functioning, and affective symptoms of NRS. They were scored on the 0-100 scale, and a high scoreindicated less NRS. The Chinese PSS has been shown to have good validity and reliability inindividuals aged 10 or above (9).
Nocturnal noise level was also measured by asking each participant to place a dosimeter (Spark706RC, Larson Davis Inc, US) near their bed for one week.
2.4

Statistical Analysis
We conducted multiple linear regression analysis of the domains of the NRSS on nocturnal noise,age, gender, depression and stress, as well as the noise by gender interaction. The interaction term
was used to assess the moderating effects of gender on the influence of nocturnal noise on NRS. Whenan interaction term was insignificant, the interaction term was removed from the regression model
before the effect of nocturnal noise was reported. Adequacy of all models was assessed by examining
the normal probability plot of residuals and the scatter plot of residuals against predicted values. All
estimates were accompanied by 95% confidence intervals (CIs) and 5% nominal level of significancewas used in all significance tests. The R package was used for the statistical analysis.

3. RESULTS
3.1 Sample Characteristics
A total of 90 eligible Chinese adults were recruited and completed the assessments. Theirdemographics are summarized in Table 1. There were 52 (58%) female subjects, and the average age
was 37.0 years (range: 18-65). Table 2 summarizes the nocturnal noise level and NRS experienced by
the participants.
3.2 Moderating Effects of Gender
Table 3 assesses the moderating effect of gender on the influences of nocturnal noise on NRS. The
gender-by-nocturnal noise exposure interaction was significant (p=0.043) for the Refreshment fromsleep domain of NRSS. The influence of nocturnal noise exposure on Refreshment from sleep was
more profound in women (-1.00, 95% CI: -1.87 to -0.13) than in men (0.22, 95% CI: -0.57 to 1.01).

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There was no significant gender by noise interaction and nocturnal noise effects on other domains ofNRSS.
Table 1 – Demographic characteristics
Female

Male

Total

(n = 52)(n = 38)(n = 90)39.5 (SD=13.6)

33.6 (SD=12.4)

37.0 (SD = 13.3)

Single24 (46.2%)

27 (71.1%)

51 (56.7%)

Married/Cohabitation

22 (42.3%)

11 (28.9%)33 (36.6%)

Separated/Divorced/Widowed

6 (11.5%)

0 (0%)

6 (6.7%)

Primary or below

2 (3.8%)0 (0%)

2 (2.2%)

Secondary/Diploma/Associate

28 (53.8%)

12 (31.6%)

40 (44.4%)

22 (42.3%)

26 (68.4%)

48 (53.3%)

Characteristics
Age (years), mean
Marital status

Education level

degreeTertiary or above

Table 2 – Nocturnal noise and nonrestorative sleep
Female

Male

Total

(n = 52)(n = 38)(n = 90)56.0 (SD = 4.8)

54.7 (SD = 6.2)

55.5 (SD = 5.5)

Refreshment from sleep

58.3 (SD = 18.5)

55.9 (SD = 16.4)

57.3 (SD = 17.6)

Physical/medical symptoms of NRS

67.4 (SD = 17.1)

66.4 (SD = 16.4)

67.0 (SD = 16.7)

Daytime functioning

61.4 (SD = 14.7)

59.4 (SD = 16.4)

60.5 (SD = 15.4)

Affective symptoms of NRS

64.9 (SD = 22.6)

59.3 (SD = 20.1)

62.6 (SD = 21.6)

Global scale

62.9 (SD = 12.7)

60.6 (SD = 11.3)

62.0 (SD = 12.1)

HADS-Depression (0-21)

5.1 (SD = 3.1)

5.7 (SD = 3.2)

5.4 (SD = 3.2)

Perceived Stress Scale (0-40)

15.9 (SD = 5.0)

17.9 (SD = 5.0)

16.8 (SD = 5.0)

Characteristics
Nocturnal noise (dBA)
Nonrestorative sleep (0-100)

Table 3 – Impact of nocturnal noise on nonrestorative sleep

Nonrestorative sleep (0-100)
Refreshment from sleep

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Estimated effects for 1dBA increase inModerating effectnocturnal noise (95% CI)

of gender

FemaleMalep-value-1.00 (-1.87, -0.13)

0.22 (-0.57, 1.01)

0.043

Physical/medical symptoms of NRS-0.03 (-0.65, 0.59)

0.304

Daytime functioning

0.01 (-0.52, 0.54)

0.450

Affective symptoms of NRS

0.32 (-0.42, 1.07)

0.785

Global scale

0.07 (-0.43, 0.56)

0.471

4. DISCUSSIONThis was the first study to assess the moderating effect of gender on NRS. Women reacted more tonocturnal noise than men in their feeling of refreshment from sleep. More specifically, increased
exposure to nocturnal noise reduced the degree of feeling refreshment from sleep in women but noeffect was found in men. There are also epidemiological studies that show women have a longer sleep
latency, report more sleepiness, sleep less, and have less non-rapid eye movement (NREM) stages 1and 2 sleep than men (10). However, there is some evidence showing women have more slow wave
sleep than men (11). Slow wave sleep allows our body to restore energy and strengthen the immunesystem. Yet, women had more complaints of sleep disorders than men (10). Moreover, thevulnerability of women towards noise is consistent to the hypothesized pathway of the influence ofnoise on ANS. There has been evidence showing that the ANS stress response system in women was
more sensitive (12), and thus would make women more vulnerable to the impact of noise.
Several study limitations are worth noting. First, the sample size may preferably be larger to ensure
adequate power for assessing the interaction effects. Moreover, the nocturnal noise effect on affective
symptoms of NRS may be potentially significant should the sample size be larger. Second, we only
assessed nocturnal noise exposure for at most one week. Longer-term assessment for better
representativeness of noise exposure and its associated longer-term effect on NRS is desirable.

5. CONCLUSIONSWomen were more vulnerable than men to the adverse impact of nocturnal noise exposure on NRS.
There has been research on the gender differences in sleep, but more epidemiological studies remain
necessary to develop improved care for both men and women.

ACKNOWLEDGEMENTS
Financial support from the Health and Medical Research Fund (Project No.: 14150801) of the Foodand Health Bureau of The Government of the Hong Kong Special Administrative Region is gratefully
acknowledged.

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