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The Journals of Gerontology Series A: Biological Sciences and Medical Sciences 55:M406-M411 (2000)
© 2000 The Gerontological Society of America

Sleep Disturbances and Their Correlates in Elderly Japanese American Men Residing in Hawaii

Sardar Ijlal Babara, Paul L. Enrighta, Peter Boylea, Daniel Foleyb, Dan S. Sharpc, Helen Petrovitchc and Stuart F. Quana

a Sleep Disorders and Respiratory Sciences Centers, University of Arizona College of Medicine, Tucson
b National Institute on Aging, Bethesda, Maryland
c Honolulu Heart Program, Hawaii

Stuart F. Quan, Respiratory Sciences Center, 1501 N. Campbell Avenue, University of Arizona College of Medicine, Tucson, AZ 85724 E-mail: squan{at}resp-sci.arizona.edu.

Decision Editor: William B. Ershler, MD


   Abstract
Top
 Abstract
Methods
 Results
 Discussion
 References
 
Background.. Elderly people frequently report the presence of chronically disturbed sleep. However, most data are derived from predominantly Caucasian populations. The current study is an investigation of the prevalence and correlates of sleep disturbances in a cohort of elderly Japanese American men residing in Hawaii. The importance of this population lies in its representation of an ethnic group living in a culture different from their ancestry.

Methods. This study is a cross-sectional cohort analysis of data pertaining to sleep disturbances and their potential correlates from 3,845 elderly Japanese American men residing in Hawaii (mean age, 78 years; range, 71–93 years) who participated in the fourth survey of the Honolulu Heart Program (1991–1994), which is the baseline exam for the Honolulu-Asia Aging Study. Information collected included an extensive survey of medication use, medical history, and assessments of physical and mental function, quality of life, and sleep.

Results. The prevalence of insomnia (DIMS) was 32.6%, a rate similar to that reported in predominantly Caucasian populations. Depression, benzodiazepine use, and several chronic health problems were the most important factors associated with DIMS. In contrast, excessive daytime sleepiness (EDS) had a prevalence of 8.9%, a rate lower than that found in elderly Caucasian populations but close to that reported among native Japanese. Important factors related to EDS were symptoms of nocturnal respiratory disturbance, depression, perception of adverse quality of life, Parkinson's disease, and digitalis use.

Conclusions. Elderly Japanese men are less likely than elderly Caucasian men to report excessive daytime sleepiness. However, their insomnia rates are similar.

ELDERLY people frequently report the presence of chronically disturbed sleep (1). Sleep disturbances in the elderly population have multiple etiologies (2); the most important among these are chronic medical illnesses, psychological influences, and changes in sleep physiology (2)(3)(4).

Most epidemiologic studies of sleep disorders, including those studies with elderly participants, have focused on predominantly Caucasian populations (3)(5). Recently, however, an interest has developed in the role that ethnicity may play in influencing sleep disturbances. Blazer and colleagues (6) demonstrated a lower prevalence of reported sleep complaints among elderly African Americans compared with Caucasians. Redline and colleagues (7) showed that although sleep-disordered breathing had a similar prevalence among elderly Caucasians and African Americans, it was almost twice as prevalent among younger subjects in the latter group. Another study by Ancoli-Israel and colleagues showed that more African Americans than Caucasians had severe sleep-disordered breathing (8). Mechanisms discussed as possible explanations of these findings include differences in body mass indices and craniofacial morphology (7)(8).

A preliminary report from Japan suggests a lower prevalence of snoring and excessive daytime somnolence among the Japanese population compared with other ethnic groups (9). However, it is not clear whether these differences are a manifestation of hereditary or cultural distinctions between the Japanese and other populations. The Honolulu Heart Program is a longitudinal, epidemiologic cohort study of elderly Japanese men residing in Hawaii. It represents an ethnic group living in a culture different from their ancestry and provides an opportunity to determine the importance of cultural background on the prevalence of sleep disturbances.


   Methods
Top
 Abstract
 Methods
Results
 Discussion
 References
 
The Honolulu Heart Program and the Honolulu-Asia Aging Study were used as the database for the present study. Briefly, the Honolulu Heart Program is a prospective, epidemiologic investigation of coronary heart disease and stroke among men of Japanese ancestry who were born between the years 1900 and 1919 and were living on the island of Oahu in 1965. The initial survey was performed in a cohort of 8,006 men between 1965 and 1968. Eighty-eight percent of those enrolled were born in Hawaii, and 12% were born in Japan. A second survey was conducted two years later, and a third one between 1971 and 1975. The present study is based on questionnaire information obtained from the fourth survey conducted from 1991 to 1994 on 3,845 participants, although some were excluded from the analysis because of missing data (vide infra). This fourth examination of the Honolulu Heart Program focused on geriatric conditions such as physical functioning, quality of life, neurologic function, and the prevalence of dementia in the surviving cohort members. As a result of this change in emphasis, the survey became the baseline examination for the Honolulu-Asia Aging Study, renamed from the Honolulu Heart Program (10). Details of the initial recruitment of the Honolulu Heart Program and methods used in data collection have been previously published (11).

Questionnaire Information
Among the information collected during the fourth survey of this cohort was an extensive survey of medication use, medical history, and assessments of physical and mental function, quality of life, and sleep. Questions used to ascertain information pertaining to sleep and other medical problems are listed in Table 1 .


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  		Table 1. Sleep and Medical Information Questionnaire Items

 
Difficulty initiating or maintaining sleep (DIMS), or insomnia, was defined as an affirmative answer to sleep questions 5, 6, or 7. Excessive daytime sleepiness (EDS) was defined as an affirmative answer to sleep question 3. However, data concerning DIMS and EDS were not available from 549 and 537 participants respectively, so these participants were excluded in the analysis. Because most of these subjects were older and had significant cognitive impairment, the examiners believed that responses from these individuals to the questions pertaining to sleep would be unreliable and so they were not queried. Possible responses to the question related to snoring were rarely, sometimes, often, always, or unknown. Participants were classified as snorers if they reported snoring at least "sometimes."

Occurrence of the various medical symptoms and conditions listed in Table 1 was defined as an affirmative response to each item. The prevalence of coronary heart disease was defined using an algorithm incorporating information obtained from the current and previous surveys of this population (electrocardiograms, questionnaires, and event surveillance), and these data have been used in previous analyses of this cohort (12)(13)(14). Nine categories of coronary heart disease as well as no disease were defined. Categories 1–4 were the following: (1) acute myocardial infarction; (2) silent myocardial infarction; (3) acute cardiac ischemia or angina pectoris with surgical intervention (including angioplasty or angiographic evidence of more than 70% stenosis of a coronary artery); and (4) reported angina pectoris or myocardial infarction, or hospitalization/surgery for coronary heart disease. Categories 5–9 represented classifications in which there was substantial doubt about the presence of coronary heart disease such as electrocardiographic evidence of a possible old myocardial infarction. After preliminary analysis, we dichotomized the data into definite coronary heart disease (includes definite myocardial infarction, interventions for treatment of coronary heart disease, and hospitalizations/surgery for coronary heart disease) representing categories 1–4 and doubtful/no coronary heart disease representing all other categories.

Height and weight (used to calculate body mass index [BMI]), spirometry (13), and use of diuretics, digitalis compounds, and benzodiazepines also were analyzed.

Psychosocial Indices
Assessment of depression was performed using a modified Center for Epidemiologic Studies Depression, or CES-D, instrument with a scale from 0 to 30 (15). General health and quality of life were assessed using the questions listed in Table 1 . After preliminary analysis, we dichotomized general health into fair/poor versus good/excellent, quality of life into dissatisfied/reasonably satisfied versus very satisfied/satisfied, and control over life into none/little versus a lot/some.

An index of physical activity was computed from questions related to the hours of daily physical activity performed by a participant (16). In addition, assessments were made of physical functioning derived from questions concerning the participant's ability to do certain tasks such as walk one-half mile, shop, and prepare meals. Annual income in $5,000–$10,000 increments, years of education, alcohol use, smoking, and marital status also were ascertained.

Data Analyses
Preliminary bivariate analyses of the relationship among DIMS and EDS, and categorical variables were performed using the chi-square test to identify factors that could have an independent association with either DIMS or EDS. For continuous variables, mean data were compared using Student's t test. Variables that were associated with DIMS or EDS on preliminary testing were then placed in multiple logistic regression models to determine whether they were independently associated with these sleep disturbances.


   Results
Top
 Abstract
 Methods
 Results
Discussion
 References
 
The average age of the 3,845 participants in this survey was 78 years (range, 71–93 years). The mean BMI was 23 (range, 12–39). The prevalence of the composite category of DIMS was 32.6%, whereas individual components ranged from 7.7% to 19.1%. Waking up several times a night was the least common DIMS symptom (7.7%) in comparison with trouble falling asleep (18.6%) and waking up too early (19.1%), which were more than twice as prevalent. In contrast, the prevalence of EDS was much lower (8.9%).

Factors that were significantly associated with DIMS on bivariate analyses are listed in Table 2 . In general, these factors were indicators of depression, chronic medical problems, quality of life, and use of alcohol or benzodiazepine medications. The most common conditions associated with a higher prevalence of DIMS were fair/poor general health, little or no control of life activities, alcohol use, and sleeping less than 6 hours a night. Of the medical problems related to DIMS, depression had the strongest association on bivariate analysis. On multivariate analysis (Table 3 ), DIMS was found to be most strongly associated with depression, less than 6 hours of sleep, and benzodiazepine usage. Other factors remaining in the model were chronic bronchitis, hayfever, nocturnal awakening related to coughing, alcohol use, perception of fair/poor health, and low income.


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  		Table 2. Bivariate Associations\|[dagger]\| with Insomnia (DIMS\|[Dagger]\|)

 

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  		Table 3. Logistic Regression Model for Insomnia (DIMS\|[dagger]\|)

 
Table 4 lists factors that were associated significantly with EDS on bivariate analyses. Similar to DIMS, these elements generally were indicators of chronic medical problems, poor quality of life, depression, and nocturnal awakenings. Low annual income, fair/poor general health, and little or no control over life activities were the most prevalent conditions related to EDS. Snoring was present in 33.2% of participants but was not related to EDS. Similar to DIMS, depression was the most common medical condition associated with EDS. However, both self-reported heart disease and definite coronary heart disease also had a relatively high occurrence of DIMS on bivariate analyses. Multivariate analysis (Table 5 ) showed depression to have the strongest association, followed by inability to walk one-half mile, Parkinson's disease, and digitalis use. Other factors independently associated with EDS were episodes of nocturnal apnea, fair/poor quality of life, nocturnal awakening related to coughing, and little or no control over activities.


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  		Table 4. Bivariate Associations\|[dagger]\| with Excessive Daytime Sleepiness (EDS)

 

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  		Table 5. Logistic Regression Model for Excessive Daytime Sleepiness (EDS)

 

   Discussion
Top
 Abstract
 Methods
 Results
 Discussion
References
 
Our study determined the prevalence and correlates of sleep disturbances in a population of elderly Japanese American men. This population is unique because it represents an ethnic group transposed into a cultural environment dissimilar to their ancestry. It thus allows the partitioning of some environmental influences from hereditary factors in comparisons of this particular ethnic population to others. We found the prevalence and major correlates of DIMS to be comparable to other age-matched, predominantly Caucasian populations. Although the factors associated with EDS were similar to those observed in other studies, the prevalence of EDS appears to be lower.

Relatively little information is available comparing the rates of sleep disturbances among ethnic groups. However, recently comparisons have been made between African Americans and Caucasians. Blazer and colleagues (6) found that elderly African Americans reported a lower frequency of all sleep complaints in comparison to similarly aged Caucasians. Ancoli-Israel and co-workers (8) observed a similar prevalence of sleep-disordered breathing in African Americans and Caucasians, but the severity was greater in African Americans. The prevalence of DIMS in our population of elderly Japanese American men (32.6%) is consistent with rates reported in predominantly Caucasian elderly male cohorts. In the Tucson Epidemiologic Study (5) and the National Institute on Aging's multicentered study, or EPESE (3), the prevalence rates of insomnia in elderly men ranged from 23.2% to 34.3%. In a more recent study by Newman and co-workers (1), a lower prevalence of 14% was found among elderly, predominantly Caucasian men. When adjusted for age, however, the prevalence of insomnia was seen to climb from 13% for those 66–69 years of age to 20% for those older than 85 years of age.

Not surprisingly, DIMS in this study correlated strongly with depression. The association between psychiatric complaints and sleep disturbances has been previously observed (17)(18). Insomnia was found to coexist with depression in 21% (18) and 14% (17) in these two series. Sleep disturbances may be an epiphenomenon or an integral part of the process leading to major depression (17). If the latter is true, treatment of sleep disorders may have implications in preventing the development of major depressive episodes.

The correlation of benzodiazepine use with DIMS is consistent with other studies and would be expected given the frequent use of this drug class both as a hypnotic and an anxiolytic (3)(18)(19). Similarly, alcohol also was associated with DIMS. Although alcohol is perceived by the general public to be an effective hypnotic, it actually fragments sleep and alters its architecture (20).

Individuals with insomnia frequently report sleeping a low number of hours during the night (21). Although total sleep time declines with increasing age, our finding that DIMS was more common in those sleeping less than 6 hours is consistent with the low total sleep time perceived by insomniacs.

We found DIMS to be associated with chronic bronchitis, hayfever, and nocturnal coughing, confirming observations in other studies that chronic medical conditions are a risk factor for insomnia (3)(4). Many chronic medical conditions are associated with symptoms that could be sleep disruptive and, if sufficiently severe, may result in insomnia. The correlation of DIMS with lower income also has been previously noted. Ohayon (22) recently demonstrated that women earning lower wages had significantly more insomnia than those in a higher income bracket.

In contrast to our findings related to DIMS, the prevalence of EDS in elderly Japanese American men (8.9%) appears to be lower than in Caucasians, where the prevalence ranges from 28.6% to 39.0% in several studies (5)(23)(24). Nearly identical rates of occurrence were observed in a study of native Japanese, where the prevalence of EDS was found to be 8% to 9% (9). Thus, transposition into a different cultural environment does not seem to have altered the prevalence of EDS among those of Japanese ancestry.

It is unclear why EDS may be less prevalent in those of Japanese descent. Inherent cultural interpretation of EDS among ethnic Japanese may be a factor. Additonal information from second- and third-generation Japanese Americans, in whom any influence related to native Japanese culture should be less, may help resolve this question. However, EDS is a common symptom of obstructive sleep apnea (OSA), and obesity is a well known risk factor for OSA. Ohta and co-workers (25) have suggested that the lower BMI of Japanese may explain their lower prevalence of EDS. However, Japanese Americans living in Hawaii have a higher BMI than age-matched subjects living in Japan (26), thus rendering this hypothesis less tenable. Alternatively, the craniofacial structure of Japanese is different from that of Caucasians (27), and specific types of craniofacial morphology are associated with an increased risk of OSA (28). It is possible that the craniofacial structure of Japanese may be protective against the development of OSA, thus explaining the lower prevalence of EDS we observed. Confirmation of this theory will require studies correlating ethnic differences in craniofacial morphology with prevalence rates of OSA. Our failure to find a relationship between snoring and EDS does not appear to support the proposed linkage of EDS prevalence to OSA. However, snoring is a weak marker of OSA in the elderly population (29). Depression (18), sleep disruption from chronic medical problems (1), and periodic limb movement disorder (30) are other common causes of EDS in elderly people. Whether differences in any of these conditions contribute to the apparent lower EDS rate observed in this study is not known.

We also found EDS to independently correlate with digitalis use in our population. We believe this is most likely a result of sleep fragmentation produced by congestive heart failure and central sleep apnea (31) in those taking digitalis. However, experimental data suggest that digitalis preparations also may directly produce sleep-disordered breathing leading to sleep fragmentation and EDS (32).

The association of sleep complaints with respiratory symptoms has been extensively evaluated (5)(33)(34). The overall prevalence of both DIMS and EDS has been noted to increase in groups with diagnoses of obstructive airways disease. Particularly high prevalences for both have been found in those with coexistent asthma and chronic bronchitis (5). Our observation that hayfever and chronic bronchitis correlated with the presence of DIMS in elderly Japanese Americans is consistent with these previous studies and extends their findings to a non-Caucasian population. Interestingly, in a subsequent study, sleep disorders correlated more with respiratory symptoms than with degree of airway obstruction (34). This suggests that sleep fragmentation produced by respiratory symptoms is the likely cause for sleep disturbance rather than oxygen desaturation, as proposed by others (35)(36).

Our finding of a correlation between EDS and Parkinson's disease is well known (37). Although insomnia may be experienced, fragmentation of sleep with resultant EDS is the most common complaint (37). Both the disease itself, and the anti-Parkinsonian drug treatment are thought to contribute to sleep disruption (37).

We found an inability to walk one-half mile to correlate with EDS. Elderly individuals who are physically fit are found to have more continous sleep, less wake time, and deeper sleep than their more sedentary counterparts (38), which may explain our finding.

We acknowledge that it may be difficult to compare prevalence rates among epidemiologic studies unless the questions asked of participants are substantially equivalent. However, the questions in this survey relating to insomnia are similar to those used in other cohorts; thus comparisons should be valid (1)(3)(4). In contrast, assessments of sleepiness are less standardized among studies (1)(4)(23)(24). The questions regarding sleepiness used in this study may have restricted affirmative responses, thus resulting in a low prevalence of EDS. Nevertheless, the prevalence rate we observed is still lower than in other studies in which a relatively restrictive definition was used (1)(4).

In conclusion, we have demonstrated that the prevalence of insomnia is similar in elderly Japanese Americans when compared with aged Caucasian populations. However, the prevalence of excessive daytime somnolence is lower and is similar to that reported in the native Japanese population. Finally, we also found a correlation between EDS and digitalis use that may be related to concomitant presence of congestive heart failure, or the correlation may be a direct effect of the drug on central sleep apnea.


   Acknowledgments
 
This research was supported by Grants NIA NO1-AG-4-2149 and NHLBI NO1-HC-02901. These results were presented, in part, at the annual meeting of the Association of Professional Sleep Societies, May 30, 1996, Washington, DC.

Received May 12, 1999

Accepted November 24, 1999


   References
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 Abstract
 Methods
 Results
 Discussion
 References
 

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