Epidemiology of insomnia: what we know and what we still need to learn

Principles and Practice of Sleep Medicine

The Metabolic Consequences of Sleep Deprivation

Study objective Most but not all epidemiologic evidence suggests a female predisposition of insomnia. We applied meta-analytic methods to investigate sex differences in the risk of insomnia among the published epidemiologic studies. Design Meta-analysis with Comprehensive Meta-Analysis (Englewood, NJ); 9 different analyses were performed to investigate the sex difference of insomnia among different conditions. Setting A comprehensive search of the medical literature databases was performed to identify epidemiologic studies of insomnia. A rolling snowball method was also used. Participants General population. Interventions N/A. Result Thirty-one related papers were found, but 2 studies only reported the subtype prevalence of insomnia. All other studies (1,265,015 participants, female/male: 718,828/546,187) were included in the overall analysis of insomnia. A risk ratio of 1.41 [95% confidence interval: 1.28-1.55] for female versus male was found. The female excess in the risk of insomnia in large and quality studies was much higher than that of small and nonquality studies. The trend of female predisposition was consistent and progressive across age, with more significance in the elderly. The use of various criteria and frequency and duration of insomnia did not influence the predisposition of female in the risk of developing insomnia. Although obvious female excess in the risk of insomnia exists among different regions, there was a relatively lower female excess in East Asia. Conclusion This meta-analysis confirmed a female predisposition of insomnia. Further studies will be needed to examine the roles of different factors in leading to the sex difference of insomnia.

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Sex differences in insomnia: a meta-analysis.

Study objectives This study used empirically validated insomnia diagnostic criteria to compare depression and anxiety in people with insomnia and people not having insomnia. We also explored which specific sleep variables were significantly related to depression and anxiety. Finally, we compared depression and anxiety in (1) different insomnia types, (2) Caucasians and African Americans, and (3) genders. All analyses controlled for health variables, demographics, organic sleep disorders, and symptoms of organic sleep disorders. Design Cross-sectional and retrospective. Participants Community-based sample (N=772) of at least 50 men and 50 women in each 10-year age bracket from 20 to more than 89 years old. Measurements Self-report measures of health, sleep, depression, and anxiety. Results People with insomnia had greater depression and anxiety levels than people not having insomnia and were 9.82 and 17.35 times as likely to have clinically significant depression and anxiety, respectively. Increased insomnia frequency was related to increased depression and anxiety, and increased number of awakenings was also related to increased depression. These were the only 2 sleep variables significantly related to depression and anxiety. People with combined insomnia (ie, both onset and maintenance insomnia) had greater depression than did people with onset, maintenance, or mixed insomnia. There were no differences between other insomnia types. African Americans were 3.43 and 4.8 times more likely to have clinically significant depression and anxiety than Caucasians, respectively. Women had higher levels of depression than men. Conclusion These results reaffirm the close relationship of insomnia, depression, and anxiety, after rigorously controlling for other potential explanations for the relationship.

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Epidemiology of insomnia, depression, and anxiety

The study examined the prevalence and correlates of insomnia in a representative sample (n=3030) from the general population of Japan Using a structured questionnaire, we found that the overall prevalence of insomnia during the preceding month was 214%, including difficulty initiating sleep (DIS: 83%), difficulty maintaining sleep (DMS: 150%), and early morning awakening (EMA: 80%) Multiple logistic regression analysis showed that older age, being unemployed, lack of habitual exercise, poor perceived health, psychological stress, and being unable to cope with stress were associated with an increased prevalence of insomnia These findings indicate that the prevalence of insomnia in the general population of Japan is comparable to that reported in Western countries, and that insomnia is associated with multiple psychosocial factors

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An epidemiological study of insomnia among the Japanese general population

Study objective To examine the relationship between lifestyle, health status factors and sleep loss. Design A cross-sectional questionnaire survey conducted by the Ministry of Health and Welfare, Japan. Setting N/A. Patients or participants Approximately 30,000 subjects selected from the general population in Japan. Interventions N/A. Measurements and results This study indicated that approximately 28% of the general population sleep less than 6 hours nightly and approximately 65% sleep less than 7 hours. However, approximately 80% of the population reported getting sufficient sleep. Multiple logistic regression analysis showed that being females, being of younger age, living in an urban environment, being unemployed, and having an unhealthy lifestyle (i.e., lack of exercise, poor health status, and irregular eating habits) were associated with sleep loss. Conclusion In this study, sleep loss was found to be associated with having an unhealthy lifestyle and being in poor general health. These findings suggest that health education and promotion of a healthy lifestyle should be advocated.

The influence of lifestyle and health status factors on sleep loss among the Japanese general population.

Results: Stiff neck/shoulder (45.3%), backache (35.1%), and fatigue (31.4%) were the most common complaints in this population. In general, SPCs were more prevalent in younger persons and in women. Logistic regression analyses, controlling for other factors, showed that insomnia was significantly associated with a number of SPCs: backache (odds ratio [OR] 5 1.4, 95% confidence interval [CI] 5 1.1‐1.6), epigastric discomfort (OR 5 1.7, 95% CI 5 1.3‐2.2), weight loss (OR 5 2.0, 95% CI 5 1.2‐3.3), headache (OR 5 1.7, 95% CI 5 1.3‐2.2), fatigue (OR 5 1.7, 95% CI 5 1.4 ‐2.1), worrying (OR 5 1.6, 95% CI 5 1.1‐2.3), irritability (OR 5 1.4, 95% CI 5 1.1‐1.7), and loss of interest (OR 5 1.8, 95% CI 5 1.2‐2.7). Conclusions: SPCs were common and were largely associated with insomnia in the general adult population of Japan. Further study is needed to examine the causal links between SPCs and insomnia. Key words: somatic and psychological complaints, insomnia, cross-sectional study, general population.

Somatic and Psychological Complaints and Their Correlates With Insomnia in the Japanese General Population

The international classification of sleep disorders has proposed menstrual-associated sleep disorder. However, few studies have investigated its pathophysiological mechanism. A 34-year-old woman complaining of insomnia in the late luteal phase underwent continuous rectal temperature measurements and simultaneous actigraphic monitoring for 146 days. The acrophase of rectal temperature rhythm was delayed in the luteal phase, compared with that in the follicular phase. Her bedtime and risetime did not differ across the menstrual cycle. These results suggest that her insomnia in the luteal phase may have been a consequence of desynchronization between her temperature rhythm and sleep phase in the luteal phase.

Kyuja Kim

Papers

An epidemiological study of insomnia among the Japanese general population

The influence of lifestyle and health status factors on sleep loss among the Japanese general population.

Somatic and Psychological Complaints and Their Correlates With Insomnia in the Japanese General Population

Long-term rectal temperature measurements in a patient with menstrual-associated sleep disorder.

Circadian rhythms in humans' delta sleep electroencephalogram.