Quality of Life in Black Hemodialysis Patients

Quality of Life in Black Hemodialysis Patients Janet L. Welch and Joan K. Austin The objectives of this study were to describe quality of life in a sample of black in-center hemodialysis patients, to identify relationships between quality of life (QOL) and selected demographic and illness variables, and to identify changes in quality of life over time. Data were collected at two points in time, 3 months apart. The data were obtained from 79 patients in two inner-city dialysis units and included persons new to dialysis. Structured interviews were conducted using the Quality of Life Index. On the average, these patients were satisfied with their QOL, although there was a large range of scores. Psychological/spiritual QOL (M = 4.27) was higher than health and functioning quality of life (M = 3.77) at both time periods. Younger age (M = 4.07) and more education (M = 4.00) were associated with poorer psychological/spiritual QOL at Time 1, whereas lower hematocrits (M = 3.55) and being new to dialysis (M = 3.41) were associated with poorer health and functioning QOL. The QOL of these black hemodialysis patients was fairly high and similar to the QOL previously reported for whites, suggesting that interventions to improve QOL in hemodialysis patients do not need to be tailored by race. In addition, findings suggest that nursing support may be the most needed during the early stages of dialysis. © 1999 by the National Kidney Foundation, Inc. Index Words: Quality of life; hemodialysis.

A

t the end of 1995, there were more than .1-\.257,000 persons in the United States being treated for end-stage renal disease (ESRD). Of this number, 31.9% were blacks. The incidence of ESRD is high for blacks, and they are disproportionately represented in the ESRD population. For example, in 1995 there was 1 in 313 blacks in the United States with ESRD compared to 1 in 1421 whites. 1 There is a growing trend to measure quality of life (QOL) as a treatment outcome for ESRD. QOL is generally considered to be a multidimensional construct2,3 composed of physical, emotional, social, and vocational dimensions. Studies have shown that QOL is lower for persons on center hemodialysis than for other ESRD treatment modalities,H and the majority of blacks ESRD patients use center hemodialysis as the treatment modality.l Despite the trend to measure QOL outcomes in ESRD, no reported studies have focused specifically on QOL associated with hemodialysis therapy among blacks. A few studies with small black subsamples have examined racial characteristics as related to QOL of hemodialysis patients. Blacks were reported to have better physical QOL than whites in one study,7 but poorer physical QOL in other studies.8-10 Economic QOL was poorer in blacks than in whites. 8,tO Blacks with advancing age had poorer physical functioning,tO-ll but more life satisfaction. ll

Some investigators have examined the relationships between QOL and demographic or illness characteristics of primarily white hemodialysis subjects. Consistent findings across studies indicate that persons treated with erythropoietin to raise hemoglobin levels have the highest QOL scores 12-15 and that women have higher emotional QOL than men. 8)6)7 Findings concerning other relationships have been equivocal. For example, some investigators have reported no relationship between length of time on dialysis and QOL,4.16.18 whereas others have reported poorer psychological QOL as time on dialysis increases. 19 These studies did not include subjects new to dialysis therapy. Several studies found that older patients had a better emotional and social QOL than younger patients,8.16 but that older patients had poorer physical QOL.7-8,1l,17 Another study, however, reported no age-related QOL differences. 2o Marital status and education have been found to be significantly related to the QOL of hemodialysis patients. 4,17,21 From the Adult Renal Services, Indiana University Medical Center; and the Dialysis Institute of Indiana, Indianapolis, IN. Supported by a grant from the National Kidney Foundation of Indiana (to J.L. W.). Address correspondence to Janet L. Welch, DNS, RN, Assistant Professor of Nursing, Indiana University School of Nursing, 1111 Middle Dr, NU 421, Indianapolis, IN 462025107, e-mail: [email protected]. © 1999 by the National Kidney Foundation, Inc. 1073-4449/99/0604-0009$3.00/0

Advances in Renal Replacement Therapy, Vol 6, No 4 (October), 1999: pp 351-357

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QOL studies to date have had severallimitations. First, because all studies have been cross-sectional, they have not looked for QOL changes over time. Second, the psychometric properties of the QOL instruments have not been reported. Third, patients new to dialysis therapy have not been included in studies and, therefore, little is known about this important period. Finally, no studies have specifically investigated black hemodialysis patients. With the escalating numbers of black patients receiving treatment for ESRD in the United States, it is essential that strategies be developed for improving QOL in this population. Before this can be done, however, the foregoing gaps in knowledge need to be corrected. The purpose of this study, which addresses several of the above limitations, was to describe QOL in a sample of black adults receiving in-center hemodialysis. The specific research questions were: 1. How does this sample of blacks describe their QOL in two domains (health/ functioning and psychological! spiritual) at two points in time 3 months apart? 2. What are the relationships between QOL (health/ functioning and psychological! spiritual) and, respectively, demographic (age, gender, marital status, and education) and illness variables (length of time on dialysis, hematocrit, and weight gain)? 3. What are the changes in QOL (health/ functioning and psychological! spiritual) over a 3-month period and are they associated with demographic (age, gender, marital status, and education) or illness variables (length of time on dialysis, hematocrit, and weight gain)?

Methods Sample and Setting Following institutional review board approval, a convenience sample of black adults currently undergoing in-center hemodialysis was interviewed twice, 3 months apart. To be included in the study the subjects had to be alert and oriented to time, place, and person; able to speak English; able to respond to questions; 18 years of age or older; have an absence of known psychiatric disorders, including major

depression; and have a score on a modified version of the Mini-Mental State22 of 16 or greater (range 0 to 24). The presence of other medical disease did not cause exclusion from the study. Subjects were recruited from one hospital-based and one free-standing dialysis clinic. A total of 97 persons were invited to participate, of whom 79 (80%) agreed, and chi-square analyses indicated no significant differences (P > .05) in length of time on dialysis, age, or sex between participants and those who declined to participate. Chi-square analyses also indicated no significant differences (P > .05) between subjects who continued the second interview compared with those who dropped out of the study in terms of length of time on dialysis, age, or sex. Table 1 lists demographic characteristics of the sample. Mean age was 54.5 years; there was an approximately even split of men and women and a wide range of education. Importantly, about one third of the sample had been on dialysis for less than 1 month. Instruments QOL. QOL was measured using a modified version of the Quality of Life Index (QLI)23,24 developed for use with dialysis patients. The original QLI contained 68 items with two sections: (1) 34 items assessing satisfaction with various life domains and (2) 34 items assessing the perceived importance of each domain. The original scale had four dimensions: health and functioning, psychological! spiritual, socioeconomic, and family. The scale has shown good internal consistency reliability,23,24 test-retest reliability,23 and construct validity.24 Higher numbers indicate higher QOL. In the present study, two changes were made in the QLI before data collection. The socioeconomic subscale was deleted to shorten the interview. Also, the response sets for the satisfaction and importance items on all subscales were changed to 5-point scales to gain a neutral point. Changes were also made after preliminary analysis. Adult in-center hemodialysis patients responded to the 27-item modified QLI for both the satisfaction and importance dimensions. The item "your relationship with your spouse/ significant other in general" was elimi-

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Table 1. Description of the Sample Time 1 Variable

Range

M

SD

n

%

Age (n = 79) 20-79 54.47 13.88 Gender 40 SO.6 Male 39 49.4 Female Education Less than high school 42 S3.2 Highschool 27 34.2 graduate Some college 6 7.6 3 3.8 College graduate Marital status Single, divorce, separated, 60 7S.9 widowed Married,living with someone 19 24.1 Length of time on dialysis Less than 1 month 25 31.6 21 26.6 6-18mo 2-Syr 33 41.8 Hematocrit 12 lS.2 20-24 25-29 25 31.6 26 32.9 30-34 7 9.0 3S-39 4 S.2 40-44 Interdialytic weight gain Less than 1 kg 10 12.8 1-1.9 kg 11 13.9 21 26.5 2-2.9 kg 24 30.4 3-3.9 kg 7 8.9 4-4.9 kg 6 7.7 Greater than S kg

nated from the analysis because almost half of the subjects reported a response option of "not applicable." Furthermore, the vast majority of respondents chose the "very important" response option for all QLI items, with mean scores ranging only from 4.08 to 4.97. Because of this lack of variability, the importance dimension also was eliminated from further analyses. All statistics pertaining to QOL were based on the satisfaction data alone. In this study, reliability was assessed using coefficient alpha. Reliabilities for the total QLI scale were .89 at both Time 1 and Time 2. Alpha coefficients for the health/ functioning subscale were .83 and .84 and for the psychological/ spiritual subscale were .83 and .90 at Time 1 and Time 2,

respectively. Alpha coefficients for the family subscale were less than .50, and these data were deleted from the analysis. Data Analysis All data were entered into a Statistical Package for the Social Sciences (SPSS-PC) program. Range, mean, and standard deviations were computed for the total scale and subscales. One-way analysis of variance was used to test differences between the QOL dimensions and the demographic and illness variables at Time 1 and Time 2. To determine if QOL changes were related to demographic and illness variables, simple change scores were calculated. Change scores were computed by subtracting Time 1 subscale scores from Time 2 sub scale scores. If the change score was positive, the QOL was greater at Time 2 than at Time 1. If the change score was negative, the QOL score was greater at Time 1 than at Time 2.

Results How does this sample of blacks describe their QOL in two domains (health/functioning and psychological/spiritual) at two points in time 3 months apart? Descriptive statistics for the QOL subscale scores at the first and second interviews are presented in Table 2. There were virtually no overall differences between scores at Time 1 and Time 2. Scores were higher on the psychological! spiritual dimension than on the health/ functioning dimension at both time periods. What are the relationships between QOL (health/ functioning and psychological/spiritual) and respectively, demographic (age, gender, marital status, and education) and illness variables (length of time on dialysis, hematocrit, and weight gain)? Table 3 presents a detailed view of these relationships. To analyze age-QOL associations, subjects were categorized into two groups: younger ages (18

Table 2. Descriptive Statistics for Sample on Instruments Health and Functioning Time 1

Time 2

Psychological/ Spiritual Time 1

Time 2

Range 1.5-5.0 1.29-S.0 1.00-S.00 1.00-S.00 Mean 3.77 3.72 4.27 4.28 Standard Deviation .86 .96 .93 .96

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Table 3. Health/Functioning and Psychological/Spiritual QOL by Demographic Variables at Time 1 and Time 2 With Change Scores

Demographic Variable Age <60yr 2':60 yr Total P Gender Male Female Total P Marital status No partner Partner Total P Education High school Total P

Time 1

Time 2

Change Score

n

Health

n

Psych

n

Health

n

Psych

n

Health

n

Psych

45 33 78

3.67 3.91 3.77

45 34 79

4.07 4.54 4.27

39 30 69

3.64 3.82 3.72

39 30 69

4.10 4.52 4.28

39 29 68

.13 .21 .16

39 30 69

.10 .02 .06

ns

40 38 78

3.70 3.84 3.77

40 39 79

3.73 3.89 3.77

60 18 78

ns

41 36 77

3.88 3.64 3.77 ns

4.20 4.34 4.27

ns

36 33 69

ns

ns

59 19 77

*

4.23 4.38 4.26 4.49 4.00 4.26

*

36 33 69

ns

52 16 68

ns

42 36 78

3.64 3.81 3.72

ns

3.70 3.75 3.71 3.95 3.45 3.72 ns

36 32 68

ns

52 16 68

ns

37 31 68

4.13 4.45 4.28

ns

4.25 4.34 4.27 4.42 4.11 4.28 ns

36 33 69

ns

51 16 67

.19 .06 .16

36 31 67

.29

.04 .18 ns

.06 .06 .06 ns

52 16 68

ns

ns

37 31 68

.06 .28 .16

ns

.08 .02 .06 ns

37 31 68

-.00 .17 .07 ns

Abbreviation: ns, not significant. *P < .05.

to 59 years) and older (60 years or over). At Time 1, older subjects reported significantly better psychological! spiritual QOL than their younger counterparts (M = 4.54 v 4.07). This difference was almost as great at Time 2 (M = 4.52 v 4.10, P = .07), but with a smaller n did not reach statistical significance. No other age-related differences were noted. To analyze education-related differences, subjects were separated into two groups: those with less than a high school education and those who had a high school education or more. Only one significant difference was found related to this variable. At Time 1, subjects with less education had better psychological! spiritual QOL than subjects who had more education (M = 4.49 v 4.00). To analyze relationships between QOL and length of time on dialysis, subjects were separated into three groups: those new to dialysis treatment, those on dialysis for 6 to 18 months, and those who had been on dialysis for 2 to 5 years. One important and significant difference was found related to this variable. A post hoc Scheffe' procedure set at a = .05 level revealed that at baseline subjects who were new to dialysis therapy had significantly and

markedly poorer health/functioning QOL (M = 3.41) than subjects who had been on dialysis for 2 to 5 years (M = 4.16). In addition, subjects who had been on dialysis for 6 to 18 months had poorer health/ functioning QOL (M = 3.58) than subjects who had been on dialysis for 2 to 5 years (M = 4.16). To analyze relationships between QOL and hematocrit, subjects were separated into two groups: those with an hematocrit of less than 30 and those with an hematocrit of 30 or more. Subjects at Time 1 with a higher hematocrit had a better health/functioning QOL (M = 4.05) than those with a lower hematocrit (M = 3.55), but this difference disappeared at Time 2. No significant differences in health or psychological QOL were found based on gender, marital status, or interdialytic weight gain at either time period. In addition, no significant interaction effects were detected. What are the changes in QOL (health/functioning and psychological/spiritual) over a 3-month period and are they associated with demographic (age, gender, marital status, and education) or illness variables (length of time on dialysis, hematocrit, and weight gain)? Differences in change

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Quality of Life

in QOL by each of the demographic and illness variables were analyzed using analysis of variance (Tables 3 and 4). No significant change differences in QOL were found by age, sex, marital status, education, length of time on dialysis, or interdialytic weight gain. However, significant differences (P < .05) in QOL change were related to hematocrit. Persons with a baseline hematocrit less than 30 experienced better QOL at Time 2 compared with Time I, whereas persons with a baseline hematocrit of 30 more more experienced slightly poorer QOL at Time 2.

Discussion Past attempts to describe the QOL of patients with ESRD have focused on primarily white samples. Little is known, however, about the QOL of black in-center hemodialysis patients. Overall, the black subjects in this study rated their QOL as high in both domains at each time period, as has been reported for the primarily white samples in past research.7-11 All mean ratings were above the midpoint, indicating they were slightly to very satisfied with their QOL. The finding that subjects on the average were quite satisfied with their QOL also suggests that the Medicare program has facilitated a high QOL in these black patients. Similar findings have been reported

in other QOL studies using primarily white hemodialysis patients. 2s.28 This finding suggests that programs designed to improve QOL in ESRD patients do not need to be tailored based on race. Similar to the findings of Ferrans and Powers,26 subjects in this study were relatively less satisfied with the health/functioning domain, although their satisfaction scores were still above the midpoint. These results may reflect the admirable resilience of these individuals and their ability to live satisfying lives despite serious physical limitations. On the whole, these people seem to be doing well, and nurses probably do not need to do much empower them. The QOL scores, however, ranged from 1 to 5, indicating that some people are not doing quite as well, and these people certainly could use extra nursing support. A clinically useful strategy, as suggested by Rettig and Lohr,28 would be to assess the QOL of individual patients as part of regular therapy at consistent intervals. Identifying individual components using a standardized tool would facilitate the development of strategies to assist needy patients. Moreover, because psychological QOL has been found to be independent of medical condition,29 and because the psychological! spiritual subscale score was highest, it provides information for nurses to continue to

Table 4. Descriptive Statistics for the QOL Constructs Based on Illness Variables at Time I, Time 2, and by Simple Change Scores

Time 1

Time 2

Change Score

Illness Variable

n

Health

n

Psych

n

Health

n

Psych

n

Health

n

Psych

Length of time on dialysis New 6-18mo 2-5yr Total

24 21 33 78

3.41 3.58 4.16 3.77

25 21 33 79

3.99 4.33 4.45 4.27

22

3.41 3.72 3.94 3.72

22

4.00 4.37 4.44 4.28

21 16 31 68

.35 .38 -.08 .16

22

16 31 69

.11 .04 .04

32 32 64

.39 -.07 .16

P

Hematocrit <30 2::30 Total

P

Interdialytic weight gain :S3kg >3 kg Total

P

Abbreviation: ns, not significant. < .01.

**P

37 37 74 41 37 78

**

3.55 4.05 3.80

**

3.75 3.79 3.77

ns

37 37 74 42 37 79

ns

4.15 4.41 4.28

ns

4.17 4.38 4.27

ns

16 31 69 32 32 64 36 33 69

ns

3.66 3.77 3.71

ns

3.77 4.09 3.92

ns

32 32 64 36 33 69

ns

4.23 4.34 4.28

ns

4.16 4.46 4.31

ns

36 33 69

ns

**

.03 .31 .16

ns

16 31 69

.06

ns

32 32 64

.16 -.05 .05

36 33 69

.07 .05 .06

ns

ns

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Welch and Austin

support components of psychological/ spiritual QOL to keep this aspect of QOL high. None of the selected demographic or illness variables consistently identified subjects at risk for poorer QOL, although persons who were younger and more educated had poorer psychological/spiritual QOL. The fact that older subjects perceived themselves to have a higher QOL than younger dialysis patients also supports the findings of Kimmel,11 Although age and education are not modifiable factors, knowledge of these relationships may help nurses identify who is most likely to need psychosocial interventions. Moreover, it has been suggested that many symptoms associated with normal aging are similar to the experience of chronic illness, such as fatigue, weakness, or changes in cognition. 3D They postulate that these changes are more distressing for the younger person because it is age inappropriate and that younger persons who are able to modify their goals will have better psychosocial outcomes. Perhaps the finding with the most clinical importance in this study was that persons who were new to dialysis had the poorest health/ functioning QOL, and those who had been on dialysis the longest had the best. This implies that nursing support may be particularly useful during the early stages of dialysis. The subjects in this study were purposively obtained to include those new to dialysis therapy. Patients new to dialysis have not been included in prior research, although length of time on dialysis has been investigated in previous research. 4,31 At Time 1, health/functioning QOL was significantly lower for patients new to treatment than for patients who had been on dialysis for 2 to 5 years; however, at Time 2, this difference disappeared because subjects new to dialysis therapy had made positive changes in their QOL scores. These findings suggest that new dialysis patients may be especially in need of support. Oldenburg and colleagues19 point out that initial psychological adjustment to dialysis may predict longterm psychological and illness adjustment. Thus, the beginning of dialysis therapy is a time to set the stage and help patients positively adapt, and developing programs and strategies to facilitate this adaptation for new patients will be important.

There was a strong trend for subjects with higher hematocrits to have better QOL in both domains, although these differences were not always significant. This finding, which has been reported in other research,12-14,32 is clinically important and may also be important to emphasize when nurses educate patients about the benefits of synthetic erythropoietin.

Recommendations for Future Work It may be beneficial in future studies to focus strictly on new dialysis patients and follow them over a longer period of time. Because QOL is thought to vary over time,4 QOL was measured at two points in time. A 3-month interval was selected because the Life Options Advisory Council recommended that clinical assessment occur every 3 months. Except for those new to dialysis, few significant changes occurred in that interval; however, because ESRD is a chronic condition, perhaps a 3-month interval was just not long enough to detect changes in these dialysis patients. Alternatively, perhaps the main observable changes occur early in dialysis treatments and plateau after that. Although periodic assessment of QOL is considered to be important with hemodialysis patients, perhaps a 6-month interval would be more useful clinically in detecting changes in this population while not being a burden to staff or patients. Because this sample was from one geographic region with primarily an inner-city convenience sample, it will be important to replicate these findings with other ESRD samples. The findings from this study suggest that we look more closely at subjects who are perceiving their QOL as being poor. What specifically is making them perceive worse QOL? Is this a changeable condition and, if so, how can it be improved?

Summary and Conclusion The blacks in this sample of in-center hemodialysis patients had QOL similar to that found for white in-center hemodialysis patients. This finding suggests that interventions to improve QOL in such patients do not need to be individually tailored by race. By continuing assessments over time, individual as well as

Quality of Life

group trends can be identified and appropriate strategies developed to intervene.

Acknowledgment The authors thank Barbara Hasbargen, Julie Bennett, Carmen Lowden, and Bob Sanford for help with data collection and Phyllis Dexter for her helpful comments and critique.

References 1. United States Renal Data System: 1997 annual data report. Am J Kidney Dis 30:540-553, 1997 (suppl1) 2. Ferrans CE: Quality of life: Conceptual issues. Semin Oncol Nurs 6:248-254, 1990 3. Katz S: The science of quality of life. J Chronic Dis 40:459-463,1987 4. Evans RW, Manninen DL, Garrison LP, et al: The quality of life of patients with end-stage renal disease. N Engl J Med 312:553-559, 1985 5. Simmons RG, Anderson C, Kamstra L: Comparison of quality of life of patients on continuous ambulatory peritoneal dialysis, hemodialysis, and after transplantation. Am J Kidney Dis 4:253-255,1984 6. Simmons RG, Abress 1: Quality of life and rehabilitation differences among alternate end-stage renal disease therapies. Transplant Proc 20:379-380, 1988 (suppl1) 7. Tell GS, Mittelmark MB, Hylander B, et al: Social support and health-related quality of life in black and white dialysis patients. ANNA J 22:301-308, 1995 8. Deniston OL, Carpentier-Alting P, Kneisley J, et al: Assessment of quality of life in end-stage renal disease. Health Serv Res 24:555-578, 1989 9. Julius M, Hawthorne VM, Carpentier-Alting P, et al: Independence in activities of daily living for end-stage renal disease patients: Biomedical and demographic correlates. Am J Kidney Dis 13:61-69, 1989 10. Kutner NG, Brogan D, Fielding B, et al: Older renal dialysis patients and quality of life. Dial Transplant 20:171-175,1991 11. Kimmel PL, Peterson RA, Weihs KL, et al: Aspects of quality of life in hemodialysis patients. J Am Soc NephroI6:1418-1426,1995 12. Barany P, Pettersson E, Konarski-Svensson J: Longterm effects on quality of life in haemodialysis patients of correction of anaemia with erythropoietin. Nephrol Dial Transplant 8:426-432,1993 13. Evans RW, Rader B, Manninen DL: The quality of life of hemodialysis recipients treated with recombinant human erythropoietin. JAMA263:825-830, 1990 14. McMahon LP, Dawborn JK: Subjective quality of life assessment in hemodialysis patients at different levels of hemoglobin following use of recombinant human erythropoietin. AmJ NephroI12:162-169, 1992 15. Moreno F, Aracil FJ, Perez R, et al: Controlled study on the improvement of QOL in elderly hemodialysis

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patients after correcting end-stage renal diseaserelated anemia with erythropoietin. Am J Kidney Dis 27:548-556,1996 16. Wolcott DL, Nissenson AR, Landsverk J: Quality of life in chronic dialysis patients: Factors unrelated to dialysis modality. Gen Hosp Psychiatry 10:267-277, 1988 17. Koch U, Muthny FA: Quality of life in patients with end-stage renal disease in relation to the method of treatment. Psychother Psychosom 54:161-171,1990 18. Molzahn AE, Horthcott HC, Hayduk L: Quality of life of patients with end stage renal disease: A structural equation model. Qual Life Res 5:426-432,1996 19. Oldenburg B, MacDonald GJ, Perkins RJ: Prediction of quality of life in a cohort of end-stage renal disease patients. J Clin EpidemioI41:555-564, 1988 20. Morgan BW: The relationship between chronological age and perceived quality of life of hemodialysis patients. Am Nephrol Nurs Assoc J 17:63-67, 1990 21. Rozenbaum EA, Chaimovitz C, Bearman JE: Quality of life of patients on chronic dialysis. Isr J Med Sci 20:104-108,1984 22. Folstein MF, Folstein SE, McHugh PR: "Mini-Mental State": A practical method for grading the cognitive state of patients for the clinician. J Psychiatr Res 12:189-198,1975 23. Ferrans CE, Powers MJ: Quality of life index: Development and psychometric properties. Adv Nurs Sci 8:15-21,1985 24. Ferrans CE, Powers MJ: Psychometric assessment of the Quality of Life Index. Res Nurs Health 15:29-38, 1992 25. Bihl M, Ferrans C, Powers M: Comparison of stressors and quality of life of CAPD and hemodialysis patients. Am Nephrol Nurs Assoc J 15:27-37, 1988 26. Ferrans CE, Powers MJ: Quality of life of hemodialysis patients. Am Nephrol Nurs Assoc J 20:575-581,1993 27. Johnson J, McCauley C, Copley J: The quality of life of hemodialysis and transplant patients. Kidney Int 22: 286-291,1982 28. Simmons RG, Abress L: Quality of life issues for end-stage renal disease patients. Am J Kidney Dis 15:201-208,1990 29. Rettig RA, Lohr KN: Measuring, managing, and improving quality in the end-stage renal disease treatment setting: Conference overview. Am J Kidney Dis 24:228-234,1994 30. Devins GM, Beanlands H, Mandin H, et al: Psychosocial impact of illness intrusiveness moderated by self-concept and age in end-stage renal disease. Health PsychoI16:529-538,1997 31. Wolcott DL, Nissenson AR: Quality of life in chronic dialysis patients: A critical comparison of continuous ambulatory peritoneal dialysis (CAPD) and hemodialysis. Am J Kidney Dis 11:402-412, 1988 32. Canadian Erythropoietin Study Group: Association between recombinant human erythropoietin and quality of life and exercise capacity of patients receiving haemodialysis. BMJ 300:573-578,1990