Gender differences in insomnia—a study in the Hong Kong Chinese population

https://doi.org/10.1016/S0022-3999(02)00437-3Get rights and content

Abstract

Objective: To study the epidemiology of insomnia in the adult Chinese population in Hong Kong and to examine the potential gender-related demographic and lifestyle factors in insomnia. Methods: A population study via random telephone survey with a structured questionnaire was carried out for noninstitutionalized Chinese adults aged 18–65 by trained lay interviewers. The questionnaire included demographic data, sleep habits and problems, insomnia symptoms and lifestyle questions. Results: A total of 9851 subjects (46.4% male; 53.6% female) were included in the final analysis. The overall prevalence of Hong Kong Chinese as suffering from insomnia during the preceding month (with a frequency of sleep disturbance of at least three times per week) was 11.9% (95% CI 11.2–12.6), including difficulty in initiating sleep (DIS) (4.5%; 95% CI 4.1–5.0), difficulty in maintaining sleep (DMS) (6.9%; 95% CI 6.4–7.5) and early morning awakening (EMA) (4.0%; 95% CI 3.6–4.4). Females were about 1.6 times at higher risk for insomnia than males. The prevalence of insomnia was also shown to increase with age. Multivariate analysis showed that unemployment, lower economic status, alcohol consumption, regular medication and psychiatric disturbance were all associated with higher risks of insomnia in both sexes. Furthermore, lower education level and being retired was associated with a higher risk of insomnia in males, but being a housewife, divorced/widowed, and complaining of a nocturnal noisy environment were associated with a higher risk of insomnia in females. Among all these factors, psychiatric disturbance was the most influential risk factor for insomnia in both sexes. The reasons for gender differences of insomnia may include their differences in the prevalence of psychiatric morbidities, symptom endorsement, gonadal steroids, sociocultural factors and coping strategies. Conclusions: Overall, 11.9% of the Hong Kong Chinese adult population complained of frequent insomnia in the preceding month. There was a higher prevalence of insomnia in females. Although there were common risk factors for insomnia in both sexes, there existed gender-specific risk factors.

Introduction

Gender differences have been reported across a number of medical, psychiatric and sleep disorders [1], [2], [3]. The search for any gender differences has a significant impact not only on the etiological and pathophysiological implications, but also on the health care utilization, treatment and prognosis of the disorders [1], [2].

Studies, in general, demonstrated that there were gender differences for insomnia with a higher prevalence in females [4], [5], [6], [7], [8]. However, the factors contributing to these differences were not clear. Lindberg et al. [9] investigated the relationship between gender differences of insomnia and their sex-related psychological status and reported a higher prevalence of anxiety among females. Another study on self-evaluations of factors disturbing sleep found that females perceived psychological factors as the most important causes of impeding sleep and males ranked work-related causes as the most important [10].

Insomnia is mostly a symptom and sometimes a syndrome [11]. It is one of the symptoms of a number of psychiatric (e.g., depression) and medical disorders. Patients with insomnia report difficulty in initiating sleep (DIS), i.e., not easily falling asleep, difficulty in maintaining sleep (DMS), i.e., having intermittent awakening during the night, or early morning awakening (EMA), i.e., awakening occurs in the early morning and unable to sleep again [12]. The duration of insomnia was also an important diagnostic implication. Insomnia lasting days is often a result of acute and transient stress but insomnia lasting longer than a few weeks is considered chronic and significant [13].

Insomnia is very common in the general population in most western and Japanese studies [14], [15], but there are relatively few studies about the epidemiology of insomnia in Chinese. Our recent study [16] investigated insomnia in 1034 noninstitutionalized elderly (age >70) in Hong Kong. We found that there was a high proportion of elderly suffering from insomnia (38.2%). The risk factors included being a female, older age, poorer physical and mental health. Our current study aimed to investigate whether demographic and psychosocial factors were associated with the sex differences for insomnia in the Chinese adult population in Hong Kong.

Section snippets

Study design

Wing et al. has described detailed methods related to the study [17]. Briefly, the study was conducted in the Hong Kong Chinese noninstitutionalized adult population aged 18–65 via random telephone interviews by trained interviewers in mid-1998. There were 6.5 million people in Hong Kong in the mid-1998 population estimation with the 18–65 age range constituting about 4.5 million (68.2%). Ninety-nine percent of the households in Hong Kong have telephones. An eligible household telephone number

Statistical analysis

Data were entered into Epi-Info ver 6 (Centres for Disease Control and Prevention, Atlanta, GA), and statistical analysis was performed using SPSS for Windows version 10.0 (SPSS, Chicago, IL). Descriptive results were presented as mean (S.D.) or percentage. The data were weighed to adjust for age and sex disparities between the sample and the mid-1998 population by direct standardization method. Statistical analysis was started with univariate analysis. Association of the potential risk factors

Results

A total of 43,921 telephone numbers were used in this study. After excluding the no-answer numbers, nonsubject rejection numbers (including those who hung up before/after introduction), fax numbers, commercial numbers and non-Chinese resident numbers, a total number of 13,738 telephone numbers were considered as eligible sample. In this targeted sample, 10,072 subjects were interviewed (72.9%) while 2354 targeted subjects were unable to contact at home after three attempts and 1312 subjects

Discussion

We observed the first large-scale cross-sectional study on insomnia among Chinese adults in Hong Kong. Overall, 11.9% of Hong Kong Chinese adults reported suffering from frequent insomnia (at least ≥3 times/week) for the preceding month with more female insomniacs than male (14.0% vs. 9.3%). People with insomnia were characterized with less nocturnal sleeping time and feeling inadequate rest in the morning. The most frequent sleep disturbance was DMS, followed by DIS and EMA. DMS being the most

Acknowledgements

This research was funded by Research Grants Council of Hong Kong, RGC CUHK 4282/97M.

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