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Race and Restless Sleep Complaint in Older Chronic Dialysis Patients and Nondialysis Community Controls

^a Department of Rehabilitation Medicine, Department of Neurology, Emory University School of Medicine, Atlanta, Georgia
^b Sleep Disorders Center, Department of Neurology, Emory University School of Medicine, Atlanta, Georgia
^c Department of Biostatistics, Rollins School of Public Health, Emory University, Atlanta, Georgia

Nancy G. Kutner, Department of Rehabilitation Medicine, Emory University School of Medicine, 1441 Clifton Road, NE, Atlanta, GA 30322 E-mail: nkutner{at}emory.edu.

Decision Editor: Margie E. Lachman, PhD

	Abstract

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There is mixed evidence about the relation of race to risk of sleep disturbance. We explored the relation of race to restless sleep complaint in survey data from a cohort of 311 older patients undergoing chronic renal dialysis and a similarly aged cohort of 354 nondialysis controls. Older dialysis patients were significantly more likely to report restless sleep. Restless sleep complaint was related to comorbidity, depressed mood, use of sleep medications, and perceived health status in both groups. Black patients in the dialysis cohort had decreased odds of restless sleep, but Black and White controls did not differ significantly in reporting restless sleep. Compared with their more socially advantaged White counterparts, older Black dialysis patients may perceive the chronic dialysis care environment more favorably. The findings are consistent with the view that sleep quality in late life is likely to reflect a delicate balance between psychological as well as physical well-being.

SLEEP disturbance is reported by the majority of older persons. Among more than 9,000 community dwellers aged 65+ interviewed for the Established Populations for Epidemiologic Studies of the Elderly (EPESE), only 12% of the participants reported no sleep complaints ( Foley et al. 1995). Variables in addition to older age that are associated with an increased risk of sleep disturbance include female gender, lower educational level, presence of chronic health conditions, and presence of depressive symptoms. The relation of race to risk of sleep disturbance is less clear.

In the EPESE data Black participants had fewer sleep complaints relative to White participants, although models of interactions between various diseases and race and their association with disturbed sleep were not elucidated in detail. Black participants at the two EPESE sites that included large samples of elderly Blacks (New Haven, Connecticut, and the Duke EPESE Project in North Carolina) had lower sleep complaint scores on average than did Whites ( Blazer, Hays, and Foley 1995; Foley et al. 1995). In follow-up interviews conducted 3 years later with EPESE participants, however, Black women were found to have a significantly higher incidence of insomnia compared with Black men and with Whites ( Foley, Monjan, Izmirlian, Hays, and Blazer 1999).

Survey data from men studied in the Vietnam Era Twin Registry showed that Black (vs. White) race was associated with a lower risk of one or more sleep problems ( Fabsitz, Sholinsky, and Goldberg 1997). On the other hand, there appears to be a higher prevalence of sleep apnea in persons of African-American descent ( Redline, Tishler, Hans, Tosteson, Strohl, and Spry 1997). No differences between Whites and non-Whites in incidence or prevalence of insomnia or hypersomnia were found by Ford and Kamerow 1989.

To further explore the possibility of race differences in sleep disturbance, we investigated the complaint of restless sleep among older Black and older White participants in (a) a chronic illness cohort (persons with end-stage renal disease undergoing chronic hemodialysis) and (b) a "control" cohort of community dwellers who had similar sociodemographic and residence characteristics. Poor sleep is strongly associated with medical diseases ( Bliwise 1993; Foley et al. 1995). Sleep complaints are particularly prevalent in renal patients ( Parker 1997; Wadhwa and Akhtar 1998). We predicted that the prevalence of restless sleep complaint would be greater in an older dialysis cohort relative to community controls. We expected that race would impact minimally on these relationships, given the inconsistent conclusions from previous investigations of race and sleep disturbance.

	Methods

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We obtained our data during concurrent interviews with older chronic dialysis patients and older community dwellers. We purposely designed the samples from which these two cohorts were obtained to be similar on age, race, and gender distribution, as well as on urban and rural residence. In addition to restless sleep complaint and sociodemographic variables, we measured recent chronic health conditions, self-rated health, depressed mood, and use of sleep medications in both samples.

We indentified prevalent dialysis patients aged 60+ living in the state of Georgia from a census maintained by the local End-Stage Renal Disease (ESRD) Network. We drew a random sample after stratifying the census of older patients by race and gender. We obtained data during personal interviews conducted by trained interviewers with 349 patients ( Kutner and Brogan 1994). The sample of interviewed patients was similar to all patients aged 60+ years in the state with respect to primary cause of renal failure, number of months on dialysis, and dialysis treatment modality (hemodialysis, peritoneal dialysis). Analyses in this article focus on the 311 patients who were undergoing hemodialysis and were therefore homogeneous with respect to treatment modality. All of these dialysis patients were community residents.

We identified the cohort of nondialysis community dwellers from older persons who had participated in a prior household health survey in the state of Georgia ( Shulman, Martinez, Brogan, Carr, and Miles 1986). We stratified the sampling frame by race and gender, and sorted each stratum by geographic area of residence and by age within geographic area. We included a small number of community dwellers aged 56–59 to match the community cohort with the dialysis cohort on all the desired criteria. Within each area and age category, we conducted within-stratum sampling so that each race and gender sample of dialysis patients and nondialysis community dwellers had the same distribution on geographic area and age. We obtained data during personal interviews conducted by trained interviewers with 354 older community dwellers ( Kutner and Brogan 1994).

Measures
Restless sleep complaint.
We measured restless sleep complaint by an item from the Center for Epidemiologic Studies–Depression scale (or CES-D; Radloff 1977): "My sleep was restless." The item specifies a time frame of the week prior to the interview and is reported as "often," "sometimes," "rarely," or "never." For the analyses reported in this article, we dichotomized responses as often or sometimes vs. rarely or never.

Sociodemographic variables.
Race (Black or White) was the independent variable of primary interest. Additional sociodemographic variables were gender, age (continuous), and education (dichotomized as <high school vs. high school).

Sleep medications.
We asked participants during the interview if they had taken any medicines for sleep or nerves in the past week, prescription or nonprescription, and if so to name the medicine. We dichotomized responses to this item (reported sleep or nerve medication use vs. no reported sleep or nerve medication use).

Chronic conditions.
Non-ESRD health conditions reported by participants included: arthritis and/or rheumatism, lung or breathing problems, high blood pressure, cardiovascular comorbidity (heart disease or other heart problems, stroke, hardening of the arteries, circulation trouble), diabetes, malignancy, urinary or prostate problems and/or kidney stones, and gastrointestinal problems. We grouped all other health conditions reported by participants (e.g., skin disorders, bone fractures) into an additional "other" category. We treated the total number of health conditions as measured by the nine categories as a continuous variable (0-9).

Self-rated health.
We measured global self-rating of health with a single item that asked, "How would you rate your health at the present time—Would you say it is excellent, very good, good, fair, or poor?" ( House 1986).

Depressed mood.
We assessed depressive symptoms using the 20-item CES-D scale ( Radloff 1977). For this study, we determined a 14-item nonsomatic CES-D score, eliminating six items in the original CES-D instrument that measure somatic complaints ("I did not feel like eating; my appetite was poor"; "I had trouble keeping my mind on what I was doing"; "I felt like everything I did was an effort"; "My sleep was restless"; "I talked less than usual"; "I could not get going"). These six items reflect "retarded energy or enervation" ( Hays et al. 1998) and represent symptoms that are especially likely to be experienced by dialysis patients ( Hays, Kallich, Mapes, Coons, and Carter 1994). In addition, the item "My sleep was restless" was the dependent variable of interest in our study. Scores on the 14-item nonsomatic version of the CES-D range from 0–42; a higher score indicates greater depressed mood.

Statistical Analyses
We investigated the association of independent variables with restless sleep in each cohort in univariate analyses using chi-squared and t tests. We then used logistic regression in SAS ( SAS Institute, Inc 1990) to model the probability of restless sleep complaint. Categorical independent variables, each at two levels, were dialysis or control group membership (dialysis as reference), race (White as reference), gender (women as reference), educational level (less than high school as reference), sleep medication use (taking sleep or nerve medication as reference), and self-rated health (fair or poor rating as reference). Continuous independent variables were age, number of chronic conditions, and nonsomatic CES-D score.

A main effects model was fit first, followed by stepwise logistic regression to determine if interactions should be added to the model. We assessed goodness of fit of the models by the Hosmer-Lemeshow test ( Hosmer and Lemeshow 1989).

	Results

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Restless Sleep in Dialysis Patients and Controls
Participants who reported restless sleep also reported sleeping fewer hours per day. Among dialysis participants who described their sleep as often or sometimes restless, 47.5% reported sleeping fewer than 7 hours in a typical 24-hour period, compared to 11.4% of dialysis participants who described their sleep as rarely or never restless. Among control participants who described their sleep as often or sometimes restless, 31.9% reported sleeping fewer than 7 hours in a typical 24-hour period, compared to 17.4% of controls who described their sleep as rarely or never restless.

Sociodemographic and health characteristics of the dialysis and nondialysis cohorts are reported in Table 1 . As predicted, the prevalence of restless sleep complaint was greater among older persons on chronic dialysis than among older community controls (p = .001). More than half of the dialysis patients reported experiencing restless sleep often or sometimes, compared to one third of the community control subjects.

Multivariate Regression Analysis
We included sociodemographic variables (race, gender, age, and education), number of chronic health conditions, nonsomatic CES-D score, use of sleep or nerve medications, perceived health status, and participants' cohort membership (dialysis or nondialysis) in a regression analysis predicting the probability of restless sleep complaint. Results of the final logistic regression model are shown in Table 3 . This model had adequate fit as measured by the Hosmer-Lemeshow test (p = .42).

A significant interaction was found between race and cohort membership in the prediction of restless sleep complaint. In the dialysis cohort, Black patients had decreased odds of restless sleep compared with White patients (p = .001). In the non-dialysis cohort, Blacks and Whites did not differ significantly in odds of reporting restless sleep.

	Discussion

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We used a single item to measure restless sleep complaint. A multi-item sleep complaint score such as the measure used by Foley and colleagues 1995 was not available in the dataset, but would be desirable for future analyses. As noted above, respondents who described their sleep as often or sometimes restless were less likely to report sleeping 7 or more hours a day than were respondents who described their sleep as rarely or never restless. Devins and colleagues 1993, who used the same restless sleep item in a study of 101 dialysis patients and renal transplant recipients, found that 40.8% reported experiencing restless sleep often or sometimes. The mean age of the study population in that research was 43.5 years and half of the sample had received transplants. In view of the older age of our study population and the fact that all were chronic dialysis patients, our finding of 53.6% reporting restless sleep often or sometimes seems quite reasonable in relation to the data reported by Devins and colleagues.

Univariate analyses showed that renal patients undergoing dialysis were more likely to report restless sleep than were community-based control subjects. This finding is consistent with data from epidemiologic studies in the elderly showing associations between poor sleep and chronic disease in general ( Bliwise 1993; Foley et al. 1995) and in renal patients in particular ( Suh, Wadhwa, and Mendelson 1997). Sleep disturbance in dialysis has been related to numerous physiologic alterations that accompany hemodialysis ( Parker, Bliwise, and Rye 1999, Parker, Bliwise, and Rye 2000). Alterations induced by dialysate temperature variability or changes in osmolality may have profound effects on the sleep–wake cycle of hemodialysis patients ( Parker et al. 1999). Renal patients have been shown to be at risk for restless legs syndrome, a neurologic condition with a typical nocturnal or early evening presentation known to disrupt sleep ( Winkleman, Chertow, and Lazarus 1996).

The odds of restless sleep complaint was greater among persons who were currently using sleep or nerve medications. A potential interpretation is that these medications were not effective in the two cohorts. Another potential interpretation is that the single item measure of "restless sleep" does not accurately reflect the degree of current sleep quality. Data from a cross-sectional study such as ours can certainly have varying interpretations, but it is clear that restless sleep complaint and sleep or nerve medication use were associated in the data we obtained from both the dialysis cohort and the control cohort. Older persons who reported restless sleep, compared with those who did not report restless sleep, were more likely to also report that they were currently taking medications for sleep or nerves.

A higher score on the 14-item CES-D was associated with restless sleep complaint in both the dialysis and the nondialysis cohorts. A relationship between depressed mood and sleep disturbance, as well as an association between comorbidity and sleep disturbance, is also seen in data from the general population ( Foley et al. 1995). Within dialysis patients, stress, anxiety, and depression negatively correlate with subjective sleep quality. For example, Holley, Nespor, and Rault 1992 found that worry was associated with increased sleep complaints in dialysis patients. Consistent with other researchers ( Walker, Fine, and Kryger 1995), we found no relationship between gender and restless sleep complaint in dialysis patients.

The multivariate logistic regression analysis showed that race was a predictor of restless sleep among dialysis patients, but not among community controls. Black renal patients reported less sleep disturbance relative to White renal patients, despite the presence of a similar chronic disease and treatment regimen. In addition, sleep apnea is common in renal patients ( Kimmel, Miller, and Mendelson 1989), and there is an apparent higher prevalence of sleep apnea in individuals of African American descent ( Redline et al. 1997). Although daytime hypersomnia rather than nighttime insomnia has been emphasized as occurring in conjunction with sleep apnea, disturbed nocturnal sleep among persons with sleep apnea has also been repported ( Hui et al. 2000; Rosenthal et al. 1997), and excessive daytime sleep may be associated with nocturnal sleep fragmentation ( Borbely and Achermann 2000).

Previously we have reported that among chronic renal patients race impacts on quality of life, with elderly Black patients reporting better perceived functioning and well-being than elderly White patients ( Kutner, Brogan, Fielding, and Hall 1991), although the basis of this finding remains unclear. We have speculated that an important contributor to the race difference in reported quality of life that we have observed may be receipt of psychosocial support in the dialysis care environment by a population that tends to have fewer health and social service resources readily available ( Kutner and Brogan 1994). Most patients receive dialysis treatment three times each week in an outpatient clinic. For aged Black persons living in the southeastern United States, chronic dialysis (a treatment funded by the federal government) provides not only a life-saving medical intervention but also a unique opportunity to interact with health care providers that may have been experienced only minimally throughout most of these participants' lives. The mean years of education of older Black dialysis patients (6.7 ± 3.9) was significantly less (p = .0001) than the mean years of education of older White dialysis patients (9.8 ± 3.5). White patients, with higher socioeconomic status and presumably greater lifetime exposure to health care resources, may relate to dialysis in a less favorable manner (e.g. construing maintenance dialysis as a burden that deprives them of freedom to enjoy their later years).

The racial difference in restless sleep that we observed in older dialysis patients fits well with the more comprehensive models of insomnia in old age proposed by Dew and associates 1994. These studies, which combine traditional polysomnographic measures of sleep with data on stressful life events, overall medical burden, social supports, and stability of daily routine, have portrayed disturbed sleep in late life as reflecting a delicate balance among such factors. In the model proposed by Dew and colleagues 1994, sleep disturbance is viewed not only in a biologic framework reflecting age-dependent changes in homeostatic and circadian state regulation ( Bliwise 2000) and perhaps genetic influences as well ( Rye, Dihenia, Weissman, Epstein, and Bliwise 1998), but also as a behavior highly susceptible to interpersonal contacts and daily routine, both of which are intrinsic to the dialysis treatment experience.

A final component of the model proposed by Dew and colleagues 1994 raises the possibility of reverse causality, which also must be considered. Better quality polysomnographic sleep may not only reflect better psychosocial adaptation but also could help buffer late life challenges to the integrity of psychological, and perhaps even physical, well-being. It is possible that better sleep experienced by Black renal patients in turn contributed to their higher life satisfaction and sense of well-being that we reported previously ( Kutner and Brogan 1994). It is also possible that there is a relationship between better sleep and longevity on dialysis, given that Black dialysis patients experience better survival than do White patients ( Bloembergen, Port, Mauger, and Wolfe 1994; Kutner, Lin, Fielding, Brogan, and Hall 1994). In view of the strong probability that sleep in old age reflects a delicate balance of both psychological and physical well-being ( Bliwise 2000), such hypotheses are quite plausible.

Subtle interactions among demographic variables, lifestyle characteristics, and morbid conditions may contribute to race differences in health behaviors and perceptions. Among cancer patients with similar stage of illness and self-reported health, Black patients have been found to be more reluctant to complete living wills and more accepting of life-sustaining therapy than are White patients ( McKinley, Garrett, Evans, Danis 1996). In a utility analysis, Cykert, Joines, Kissling, and Hansen 1999 found that patients with pulmonary problems, regardless of race, assigned very low quality-of-life ratings to states of limited physical function, but Black patients, compared with White patients, were willing to tolerate poorer functional status before downgrading their quality of life. In our data, older dialysis patients reported increased frequency of restless sleep compared to community controls, but Black dialysis patients were less likely to report restless sleep than were White patients. Our findings, consistent with those of McKinley and colleagues 1996 and Cykert and colleagues 1999, suggest that differential life experiences associated with race may critically affect the balance between psychological and physical well-being in later life and among persons with life-threatening disease.

	Acknowledgments

 
This study was supported by Grant AG05909 from the National Institute on Aging and Grant DK42949 from the National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health.

Received for publication May 16, 2000. Accepted for publication November 6, 2000.

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