- Email: [email protected]
Health-related quality of life using the SF-36 in patients with bipolar disorder compared with patients with chronic back pain and the general population
Journal of Affective Disorders 57 (2000) 235–239 www.elsevier.com / locate / jad
Brief report
Health-related quality of life using the SF-36 in patients with bipolar disorder compared with patients with chronic back pain and the general population a, a b a Lesley M. Arnold *, Kathryn A. Witzeman , Michael L. Swank , Susan L. McElroy , a Paul E. Keck Jr. a
Biological Psychiatry Program, Department of Psychiatry, University of Cincinnati, College of Medicine, 231 Bethesda Avenue, ML 559, Cincinnati, OH 45267 -0559, USA b Freiberg Spine Institute and Department of Physical Medicine and Rehabilitation, University of Cincinnati, College of Medicine, 231 Bethesda Avenue, ML 559, Cincinnati, OH 45267 -0559, USA Received 30 September 1998; accepted 23 February 1999
Abstract Background: The purpose of this study was to assess and compare the health-related quality of life of patients with bipolar disorder and chronic back pain and, in turn, to compare these results with those previously generated for the general population. Methods: Subjects were patients with bipolar disorder (n 5 44), a comparison group of chronic back pain patients (n 5 30), and a population-based control sample (n 5 2,474). Health-related quality of life was assessed using the Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36), a self-administered questionnaire in which lower scores are indicative of greater impairment. Results: Patients with bipolar disorder had lower mean scores than the general population on all scales except Physical Functioning. Bipolar patients had significantly higher scores than chronic back pain patients in the categories of Physical Functioning, Role Limitations – Physical, Bodily Pain, and Social Function. There were no significant differences between bipolar disorder and chronic back pain groups in the Mental Health and Role Limitations – Emotional categories. Limitations: The results of the study are limited by the relatively small sample sizes of the bipolar and back pain patient groups. Conclusions: Patients with bipolar disorder had substantial impairment in health-related quality of life in comparison with the general population. Bipolar patients were less compromised in areas of physical and social functioning than chronic back pain patients but had similar impairment in mental health. 2000 Elsevier Science B.V. All rights reserved. Keywords: Bipolar disorder; Quality of life; Health status; Back pain
1. Introduction *Corresponding author. Tel.: 1 1-513-558-4622; fax: 1 1-513558-4280. E-mail address: [email protected] (L.M. Arnold)
A number of recent studies indicate that many patients with bipolar disorder who no longer meet
0165-0327 / 00 / $ – see front matter 2000 Elsevier Science B.V. All rights reserved. PII: S0165-0327( 99 )00042-7
236
L.M. Arnold et al. / Journal of Affective Disorders 57 (2000) 235 – 239
syndromal or symptomatic criteria following recovery from an acute affective episode nevertheless continue to display functional impairment (Dion et al., 1988; Tohen et al., 1990; Coryell et al., 1993; Cooke et al., 1996; MacQueen et al., 1997; Keck et al., 1998; Strakowski et al., 1998). Such residual and often prolonged deficits in psychosocial and vocational functioning exert substantial costs in human suffering and economic productivity (Lish et al., 1994; Wyatt and Henter, 1995). Recently, a growing societal awareness of the importance of quality of life, and not merely longevity, has led to an emphasis on methods of assessing patients’ perceptions of the impact of illness on health-related quality of life (HRQOL) (Tsevat et al., 1994, 1995). The development of instruments designed to assess the impact of illness on patients’ HRQOL is important for at least two reasons. First, they allow for comparisons of HRQOL among illnesses (Garratt et al., 1993; Thunedborg et al., 1995). Second, measurement of change in HRQOL provides an important index of outcome in studies of the effectiveness of specific clinical interventions (Garratt et al., 1993). Few studies to date have assessed the HRQOL in patients with bipolar disorder (Thunedborg et al., 1995; Cooke et al., 1996; MacQueen et al., 1997; Robb et al., 1997; Leidy et al., 1998). Cooke et al. used the 20-item Medical Outcomes Study (MOS) Short-Form General Health Survey (SF-20) in a study of clinically euthymic bipolar patients and found that the mean scores for the subscales of social functioning, mental health and overall health perception fell within or below the range of mean scores for MOS patient groups with eight chronic medical conditions. There has not been a study comparing the HRQOL between patients with bipolar disorder and patients with a chronic physical illness using the MOS 36-item Short-Form Health Survey (SF-36). Although it is possible to compare some of the results across studies using either the SF-20 or the SF-36, the SF-36 represents an improvement over the SF-20 (Ware and Sherbourne, 1992). The improvements include the addition of an item measuring energy level, distinguishing between physical and emotional causes of role limitations, increased measurement precision for physical, role, social, and bodily pain scales, and improved representation of
general health perceptions (Ware and Sherbourne, 1992; McHorney et al., 1993). Two studies specifically assessed the psychometric properties of the SF-36 in patients with bipolar disorder (Thunedborg et al., 1995; Leidy et al., 1998). Overall, SF-36 social function, vitality, role limitations-emotional, and mental health scales had good reliability and validity, and were responsive to changes in clinical status in patients with bipolar disorder. This study is the first to compare the HRQOL between patients with bipolar disorder and patients with a chronic physical illness using the SF-36. The objective of this study was to compare the impact of illness on HRQOL in patients with bipolar disorder, a general population control group, and a disease comparison group of patients with a chronic and sometimes disabling physical illness using the SF-36. Patients with chronic back pain were chosen as a comparison group for two reasons. First, patients with chronic back pain have high rates of disability and psychological disturbance (Waddell et al., 1986; Main et al., 1992). Patients with bipolar disorder also have high rates of disability and psychological disturbance (Dion et al., 1988; Coryell et al., 1993; Keck et al., 1998; Strakowski et al., 1998). Second, the validity and reliability of the SF-36 has been previously established in patients with chronic back pain (Grevitt et al., 1997).
2. Methods
2.1. Patient sample Forty-four outpatients with a DSM-IV diagnosis of bipolar disorder (type I, n 5 38; type II, n 5 5; and NOS, n 5 1), confirmed by administration of the Structured Clinical Interview for DSM-IV (SCID) (First et al., 1996), were consecutively recruited from the University of Cincinnati Medical Center site of the multicenter Stanley Foundation Bipolar Network (SFBN) Naturalistic Follow-Up Study (Leverich et al., 1999). The bipolar subjects completed the SF-36, the clinician-rated form of the Inventory of Depressive Symptoms (IDS-C) (Rush et al., 1986) and the Young Mania Rating Scale (YMRS) (Young et al., 1978). The IDS-C is a 30-item inventory of depressive symptomatology
L.M. Arnold et al. / Journal of Affective Disorders 57 (2000) 235 – 239
over the previous 7 days, scored from 0 (no depression) to 78 (severe depression). The YMRS is an 11-item measure that measures severity of manic symptoms over the past 48 h; it is scored from 0 (no mania) to 60 (severe mania). Thirty patients with chronic ( . 6 months) mechanical low back pain who later underwent surgery (discectomy, n 5 15; lumbar fusion, n 5 15) were administered the SF-36 as part of their initial consultation with an orthopedic surgeon (MLS). This consecutive series of patients presented to the same orthopedic surgeon from February 1996–February 1997. At the time of initial presentation, these patients did not yet know that their condition would require surgery. Demographic information from both patient groups was obtained from medical records. The general population subjects were a population-based group of noninstitutionalized men and women (n 5 2474) (McHorney et al., 1994). They were chosen from a sample of 3251 individuals from 2909 US households, 18 years of age or older, who completed the survey either by mail (80%) or telephone (20%).
2.2. Health-related quality of life measure The Short Form 36 (SF-36) health survey questionnaire is an abbreviated version of a battery of 149 health status questions developed and tested on a population of over 22 000 patients as part of the medical outcomes study (Tarlov et al., 1989; Stewart and Ware, 1992). The SF-36 contains eight scales for assessing Physical Function, Role Limitations – Physical, Bodily Pain, General Health, Vitality, Social Function, Role Limitations – Emotional, and Mental Health (McHorney et al., 1993; Ware et al., 1993). The 0–100 rating scale asks the respondent to rate their current state of health on a scale of 0 (worst possible health) to 100 (best health). Additional
237
information about the nature of the SF-36 subscales is described elsewhere (Ware and Sherbourne, 1992).
2.3. Data analysis Differences in the mean score for each category of the SF-36 among the three groups were tested by an analysis of variance (ANOVA) and paired t-tests. The level of significance (P value) for each analysis was set at 0.017 a priori, to adjust for multiple tests performed (according to Bonferroni recommendations). Analyses of covariance (ANCOVA) were used to control for differences in the demographic characteristics, including age, among the groups.
3. Results The demographic data are summarized in Table 1. The back pain group of patients was significantly older than the bipolar disorder group (P 5 0.01), but there was no significant difference in the sex distribution. The mean (6SD) IDS-C score for the bipolar group was 24.5615.5 and the mean YMRS score was 4.666.6. The bipolar disorder group had significantly lower SF-36 subscale scores than the general population group in every category except Physical Function. Similarly, the back pain group had significantly lower scores than the general population group in all categories except General Health (Table 2). In comparing the two patient groups, the back pain patients had significantly lower scores in four of eight categories; Physical Function, Role Limitations – Physical, Bodily Pain, and Social Function. Interestingly, there were no significant differences between the bipolar disorder and chronic back pain groups in the Mental Health and Role Limitation – Emotional categories, although both groups were
Table 1 Demographics of the groups
Back pain Bipolar General population
Total sample N
Males N (%)
Females N (%)
Mean age N6SD
30 44 2474
16 (53) 15 (34) 1055 (43)
14 (47) 29 (66) 1412 (57)
49.5614.2 41.869.8 43.6617.4
L.M. Arnold et al. / Journal of Affective Disorders 57 (2000) 235 – 239
238
Table 2 Mean and standard deviation SF-36 scores for bipolar patients, back pain patients, and general population SF-36 variable
Bipolar disorder
Back pain
General population
Physical function Role limitation – physical Bodily pain General health Vitality Social function Role limitation – emotional Mental health
78.8622.4 b 63.1641.6 a b 64.9625.7 a b 61.9625.4 a 43.6624.3 a 57.9627.7 a b 38.6643.1 a 55.3623.8 a
32.5625.3 a 10.0623.7 a 21.2619.4 a 68.1621.1 38.7620.1 a 42.3626.6 a 57.2645.4 a 65.9618.5 a
84.2623.3 80.9634.0 75.2623.7 71.9620.3 60.9620.9 83.3622.7 81.3633.0 74.7618.1
a b
P # 0.01 vs. general population. P # 0.01 vs. back pain.
significantly below normative scores in these areas. The age difference between the two patient groups did not significantly affect these findings.
4. Discussion HRQOL as assessed by the SF-36 was compromised in nearly all categories for patients with bipolar disorder compared with the general population group. For these patients, only Physical Function remained relatively unimpaired. Patients with bipolar disorder fared better in direct comparison with patients with chronic back pain in physical realms (Physical Function, Role Limitation – Physical, and Bodily Pain). It also appeared that physical compromise in these areas may have explained the poorer Social Function scores in the back pain patients compared with bipolar disorder patients. It is likely that the physical limitations associated with chronic back pain substantially impede and restrict social activities for these individuals. Both patient groups displayed significant impairment in Mental Health and Role Limitation – Emotional categories, although scores in the bipolar disorder group were numerically (but not significantly) lower than in the back pain group. These findings suggest that both bipolar disorder and chronic back pain are associated with substantial compromises in mental health. The results of this study should be interpreted with limitations in mind. First, the total sample size was relatively small, allowing for the possibility that significant differences (e.g. in Mental Health and / or
Role Limitations – Emotional) between the patient groups may have emerged with a larger group of patients. Second, since patients were recruited from a single treatment center, the degree to which the results of this study can be generalized to other cohorts of patients with bipolar disorder is uncertain. Third, the group of bipolar patients had moderate degrees of depression as measured by the mean IDS-C score. It is possible that HRQOL as measured by the SF-36 may have been diminished in patients with depression because of depressive distortions in patients’ self-reported functioning (Cooke et al., 1996). Future studies should examine HRQOL using the SF-36 in bipolar patients with different levels of symptom severity ranging from euthymia to frequent affective episodes. The findings of this study suggest that the HRQOL in outpatients with bipolar disorder is markedly diminished. Although the pharmacologic treatment for this illness has advanced significantly in the past decade, other therapeutic strategies are needed to improve HRQOL. Future research into specific psychosocial interventions targeting aspects of HRQOL is needed. Finally, the inclusion of measures of HRQOL should be considered in future clinical trials of pharmacologic agents for patients with bipolar disorder.
Acknowledgements Supported in part by a grant from the Theodure and Vada Stanley Foundation Scholars Program (Ms. Witzeman).
L.M. Arnold et al. / Journal of Affective Disorders 57 (2000) 235 – 239
References Cooke, R.G., Robb, J.C., Young, L.T., Joffe, R.T., 1996. Wellbeing and functioning in patients with bipolar disorder assessed using the MOS 20-item short form (SF-20). J. Affect. Disord. 139, 93–97. Coryell, W., Scheftner, W., Keller, M., Endicott, J., Mase, J., Klerman, G.L., 1993. The enduring psychosocial consequences of mania and depression. Am. J. Psychiatry 150, 720–727. Dion, G.L., Tohen, M., Anthony, W.A., Waternaux, C.S., 1988. Symptoms and functioning of patients with bipolar disorder six months after hospitalization. Hosp. Community Psychiatry 139, 652–657. First M.B., Spitzer R.L., Gibbon M., Williams, J.B.W., 1996. Structured Clinical Interview for the DSM-IV Axis I Disorders – Patient Edition (SCID-I / P), Version 2.0. Biometrics Research Department, New York State Psychiatric Institute, New York, NY. Garratt, A.M., Ruta, D.A., Abdalla, M.I., Buckingham, J.K., Russell, I.T., 1993. The SF-36 health survey questionnaire: an outcome measure suitable for routine use within the NHS? Br. Med. J. 306, 1440–1444. Grevitt, M., Khazim, R., Mulholland, R., Sheppard, J., 1997. The short form-36 health survey questionnaire in spine surgery. J. Bone Joint Surg. 79–B, 48–52. Keck, Jr. P.E., McElroy, S.L., Strakowski, S.M., West, S.A., Sax, K.W., Hawkins, J.M., Bourne, M.L., Haggard, P., 1998. Twelve-month outcome of bipolar patients following hospitalization for a manic or mixed episode. Am. J. Psychiatry 155, 646–652. Leidy, N.K., Palmer, C., Murray, M., Robb, J., Revicki, D., 1998. Health-related quality of life assessment in euthymic and depressed patients with bipolar disorder. Psychometric performance of four self-report measures. J. Affect. Disord. 48, 207–214. Leverich, G.S., Nolen W., Rush, A.J., McElroy, S.L., Keck, P.E., Denicoff, K.D., Suppes, T., Altshuler, L.L., Kupka, R., Frye, M.A., Kramlinger, K.G., Post, R.M., 1999. The Stanley Foundation Bipolar Network: I. The longitudinal methods of the Stanley Foundation Bipolar Treatment Outcome Network. J. Affect. Disord. In press. Lish, J.D., Dime-Meenan, S., Whybrow, P.C., Price, R.A., Hirschfeld, R.M.A., 1994. The National Depressive and ManicDepressive Association (DMDA) survey of bipolar members. J. Affect. Disord. 31, 281–294. MacQueen, G.M., Young, L.T., Robb, J.C., Cooke, R.G., Joffe, R.T., 1997. Levels of functioning and well-being in recovered psychotic versus nonpsychotic mania. J. Affect. Disord. 46, 69–72. Main, C.J., Wood, P.L.R., Hollis, S., Spanswick, C.C., Waddell, G., 1992. The distress and risk assessment method. A simple patient classification to identify distress and evaluate the risk of poor outcome. Spine 17, 42–52. McHorney, C.A., Ware, J.E., Raczek, A.E., 1993. The MOS 36-item short-form health survey: II. Psychometric and clinical tests of validity in measuring physical and mental health constructs. Med. Care 31, 247–263.
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McHorney, C.A., Kosinski, M., Ware, J.E., 1994. Comparisons of the costs and quality of norms for the SF-36 Health Survey collected by mail versus telephone interview: results from a national survey. Med. Care 32, 551–567. Robb, J.C., Cooke, R.G., Devins, G.M., Young, L.T., Joffe, R.T., 1997. Quality of life and lifestyle disruption in euthymic bipolar disorder. J. Psychiat. Res. 31, 509–517. Rush, A.J., Giles, D.E., Schlesser, M.A., Fulton, C.L., Weissenburger, J., Burns, C., 1986. The Inventory for Depressive Symptomatology (IDS): preliminary findings. Psychiatry Res. 18, 65–87. Strakowski, S.M., Keck, Jr. P.E., McElroy, S.L., West, S.A., Sax, K.W., Hawkins, J.M., Upadhyaya, V., Tugrul, K.C., Bourne, M.L., 1998. Twelve-month outcome following first hospitalization for affective psychosis. Arch. Gen. Psychiatry 55, 49–55. Stewart, A.L., Ware, J.E. (Eds.), 1992. Measuring Functioning and Well-Being: The Medical Outcome Study Approach, Duke University Press, Durham, NC. Tarlov, A.R., Ware, J.E., Greenfield, S., Nelson, E.C., Perrin, E., Zubkoff, M., 1989. The medical outcomes study: an application of methods for monitoring the results of medical care. J. Am. Med. Assoc. 262, 925–930. Thunedborg, K., Black, C.H., Bech, P., 1995. Beyond the Hamilton Depression Scores in long-term treatment of manic-melancholic patients: prediction of recurrence of depression by quality of life measurements. Psychother. Psychosom. 64, 131– 140. Tohen, M., Waternaux, C.S., Tsuang, M.T., 1990. Outcomes in mania: A 4-year prospective follow-up of 75 patients utilizing survival analysis. Arch. Gen. Psychiatry 47, 1101–1106. Tsevat, J., Weeks, J.C., Guadagnoli, E., Tosteson, A.N.A., Mangione, C.M., Pliskin, J.S., Weinstein, M.C., Cleary, P.D., 1994. Using health-related quality of life information: clinical encounters, clinical trials, and health policy. J. Gen. Int. Med. 9, 576–582. Tsevat, J., Cook, E.F., Green, M.L., Matchar, D.B., Dawson, N.V., Broste, S.K., Wu, A.W., Phillips, R.S., Oye, R.K., Goldman, L., 1995. Health values of the seriously ill. Ann. Int. Med. 122, 514–520. Waddell, G., Morris, E.W., DiPaola, M.P., bircher, M., Finlayson, D., 1986. A concept of illness tested as an improved basis for surgical decisions in low-back disorders. Spine 11, 712–719. Ware, J.E., Sherbourne, C.D., 1992. The MOS 36-Item ShortForm Health Survey (SF-36): I. Conceptual framework and item selection. Med. Care 30, 473–483. Ware, J.E., Snow, K.K., Kosinski, M., Gandek, B., 1993. SF-36 Health Survey: Manual and Interpretation Guide, The Health Institute, New England Medical Center, Boston, MA. Wyatt, R.J., Henter, I., 1995. An economic evaluation of manicdepressive illness – 1991. Soc. Psychiatry Psychiatr. Epidemiol. 30, 213–219. Young, R.C., Biggs, J.T., Ziegler, V.W., Meyer, D.A., 1978. A rating scale for mania: reliability, validity, and sensitivity. Br. J. Psychiatry 133, 429–435.
Brief report
Health-related quality of life using the SF-36 in patients with bipolar disorder compared with patients with chronic back pain and the general population a, a b a Lesley M. Arnold *, Kathryn A. Witzeman , Michael L. Swank , Susan L. McElroy , a Paul E. Keck Jr. a
Biological Psychiatry Program, Department of Psychiatry, University of Cincinnati, College of Medicine, 231 Bethesda Avenue, ML 559, Cincinnati, OH 45267 -0559, USA b Freiberg Spine Institute and Department of Physical Medicine and Rehabilitation, University of Cincinnati, College of Medicine, 231 Bethesda Avenue, ML 559, Cincinnati, OH 45267 -0559, USA Received 30 September 1998; accepted 23 February 1999
Abstract Background: The purpose of this study was to assess and compare the health-related quality of life of patients with bipolar disorder and chronic back pain and, in turn, to compare these results with those previously generated for the general population. Methods: Subjects were patients with bipolar disorder (n 5 44), a comparison group of chronic back pain patients (n 5 30), and a population-based control sample (n 5 2,474). Health-related quality of life was assessed using the Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36), a self-administered questionnaire in which lower scores are indicative of greater impairment. Results: Patients with bipolar disorder had lower mean scores than the general population on all scales except Physical Functioning. Bipolar patients had significantly higher scores than chronic back pain patients in the categories of Physical Functioning, Role Limitations – Physical, Bodily Pain, and Social Function. There were no significant differences between bipolar disorder and chronic back pain groups in the Mental Health and Role Limitations – Emotional categories. Limitations: The results of the study are limited by the relatively small sample sizes of the bipolar and back pain patient groups. Conclusions: Patients with bipolar disorder had substantial impairment in health-related quality of life in comparison with the general population. Bipolar patients were less compromised in areas of physical and social functioning than chronic back pain patients but had similar impairment in mental health. 2000 Elsevier Science B.V. All rights reserved. Keywords: Bipolar disorder; Quality of life; Health status; Back pain
1. Introduction *Corresponding author. Tel.: 1 1-513-558-4622; fax: 1 1-513558-4280. E-mail address: [email protected] (L.M. Arnold)
A number of recent studies indicate that many patients with bipolar disorder who no longer meet
0165-0327 / 00 / $ – see front matter 2000 Elsevier Science B.V. All rights reserved. PII: S0165-0327( 99 )00042-7
236
L.M. Arnold et al. / Journal of Affective Disorders 57 (2000) 235 – 239
syndromal or symptomatic criteria following recovery from an acute affective episode nevertheless continue to display functional impairment (Dion et al., 1988; Tohen et al., 1990; Coryell et al., 1993; Cooke et al., 1996; MacQueen et al., 1997; Keck et al., 1998; Strakowski et al., 1998). Such residual and often prolonged deficits in psychosocial and vocational functioning exert substantial costs in human suffering and economic productivity (Lish et al., 1994; Wyatt and Henter, 1995). Recently, a growing societal awareness of the importance of quality of life, and not merely longevity, has led to an emphasis on methods of assessing patients’ perceptions of the impact of illness on health-related quality of life (HRQOL) (Tsevat et al., 1994, 1995). The development of instruments designed to assess the impact of illness on patients’ HRQOL is important for at least two reasons. First, they allow for comparisons of HRQOL among illnesses (Garratt et al., 1993; Thunedborg et al., 1995). Second, measurement of change in HRQOL provides an important index of outcome in studies of the effectiveness of specific clinical interventions (Garratt et al., 1993). Few studies to date have assessed the HRQOL in patients with bipolar disorder (Thunedborg et al., 1995; Cooke et al., 1996; MacQueen et al., 1997; Robb et al., 1997; Leidy et al., 1998). Cooke et al. used the 20-item Medical Outcomes Study (MOS) Short-Form General Health Survey (SF-20) in a study of clinically euthymic bipolar patients and found that the mean scores for the subscales of social functioning, mental health and overall health perception fell within or below the range of mean scores for MOS patient groups with eight chronic medical conditions. There has not been a study comparing the HRQOL between patients with bipolar disorder and patients with a chronic physical illness using the MOS 36-item Short-Form Health Survey (SF-36). Although it is possible to compare some of the results across studies using either the SF-20 or the SF-36, the SF-36 represents an improvement over the SF-20 (Ware and Sherbourne, 1992). The improvements include the addition of an item measuring energy level, distinguishing between physical and emotional causes of role limitations, increased measurement precision for physical, role, social, and bodily pain scales, and improved representation of
general health perceptions (Ware and Sherbourne, 1992; McHorney et al., 1993). Two studies specifically assessed the psychometric properties of the SF-36 in patients with bipolar disorder (Thunedborg et al., 1995; Leidy et al., 1998). Overall, SF-36 social function, vitality, role limitations-emotional, and mental health scales had good reliability and validity, and were responsive to changes in clinical status in patients with bipolar disorder. This study is the first to compare the HRQOL between patients with bipolar disorder and patients with a chronic physical illness using the SF-36. The objective of this study was to compare the impact of illness on HRQOL in patients with bipolar disorder, a general population control group, and a disease comparison group of patients with a chronic and sometimes disabling physical illness using the SF-36. Patients with chronic back pain were chosen as a comparison group for two reasons. First, patients with chronic back pain have high rates of disability and psychological disturbance (Waddell et al., 1986; Main et al., 1992). Patients with bipolar disorder also have high rates of disability and psychological disturbance (Dion et al., 1988; Coryell et al., 1993; Keck et al., 1998; Strakowski et al., 1998). Second, the validity and reliability of the SF-36 has been previously established in patients with chronic back pain (Grevitt et al., 1997).
2. Methods
2.1. Patient sample Forty-four outpatients with a DSM-IV diagnosis of bipolar disorder (type I, n 5 38; type II, n 5 5; and NOS, n 5 1), confirmed by administration of the Structured Clinical Interview for DSM-IV (SCID) (First et al., 1996), were consecutively recruited from the University of Cincinnati Medical Center site of the multicenter Stanley Foundation Bipolar Network (SFBN) Naturalistic Follow-Up Study (Leverich et al., 1999). The bipolar subjects completed the SF-36, the clinician-rated form of the Inventory of Depressive Symptoms (IDS-C) (Rush et al., 1986) and the Young Mania Rating Scale (YMRS) (Young et al., 1978). The IDS-C is a 30-item inventory of depressive symptomatology
L.M. Arnold et al. / Journal of Affective Disorders 57 (2000) 235 – 239
over the previous 7 days, scored from 0 (no depression) to 78 (severe depression). The YMRS is an 11-item measure that measures severity of manic symptoms over the past 48 h; it is scored from 0 (no mania) to 60 (severe mania). Thirty patients with chronic ( . 6 months) mechanical low back pain who later underwent surgery (discectomy, n 5 15; lumbar fusion, n 5 15) were administered the SF-36 as part of their initial consultation with an orthopedic surgeon (MLS). This consecutive series of patients presented to the same orthopedic surgeon from February 1996–February 1997. At the time of initial presentation, these patients did not yet know that their condition would require surgery. Demographic information from both patient groups was obtained from medical records. The general population subjects were a population-based group of noninstitutionalized men and women (n 5 2474) (McHorney et al., 1994). They were chosen from a sample of 3251 individuals from 2909 US households, 18 years of age or older, who completed the survey either by mail (80%) or telephone (20%).
2.2. Health-related quality of life measure The Short Form 36 (SF-36) health survey questionnaire is an abbreviated version of a battery of 149 health status questions developed and tested on a population of over 22 000 patients as part of the medical outcomes study (Tarlov et al., 1989; Stewart and Ware, 1992). The SF-36 contains eight scales for assessing Physical Function, Role Limitations – Physical, Bodily Pain, General Health, Vitality, Social Function, Role Limitations – Emotional, and Mental Health (McHorney et al., 1993; Ware et al., 1993). The 0–100 rating scale asks the respondent to rate their current state of health on a scale of 0 (worst possible health) to 100 (best health). Additional
237
information about the nature of the SF-36 subscales is described elsewhere (Ware and Sherbourne, 1992).
2.3. Data analysis Differences in the mean score for each category of the SF-36 among the three groups were tested by an analysis of variance (ANOVA) and paired t-tests. The level of significance (P value) for each analysis was set at 0.017 a priori, to adjust for multiple tests performed (according to Bonferroni recommendations). Analyses of covariance (ANCOVA) were used to control for differences in the demographic characteristics, including age, among the groups.
3. Results The demographic data are summarized in Table 1. The back pain group of patients was significantly older than the bipolar disorder group (P 5 0.01), but there was no significant difference in the sex distribution. The mean (6SD) IDS-C score for the bipolar group was 24.5615.5 and the mean YMRS score was 4.666.6. The bipolar disorder group had significantly lower SF-36 subscale scores than the general population group in every category except Physical Function. Similarly, the back pain group had significantly lower scores than the general population group in all categories except General Health (Table 2). In comparing the two patient groups, the back pain patients had significantly lower scores in four of eight categories; Physical Function, Role Limitations – Physical, Bodily Pain, and Social Function. Interestingly, there were no significant differences between the bipolar disorder and chronic back pain groups in the Mental Health and Role Limitation – Emotional categories, although both groups were
Table 1 Demographics of the groups
Back pain Bipolar General population
Total sample N
Males N (%)
Females N (%)
Mean age N6SD
30 44 2474
16 (53) 15 (34) 1055 (43)
14 (47) 29 (66) 1412 (57)
49.5614.2 41.869.8 43.6617.4
L.M. Arnold et al. / Journal of Affective Disorders 57 (2000) 235 – 239
238
Table 2 Mean and standard deviation SF-36 scores for bipolar patients, back pain patients, and general population SF-36 variable
Bipolar disorder
Back pain
General population
Physical function Role limitation – physical Bodily pain General health Vitality Social function Role limitation – emotional Mental health
78.8622.4 b 63.1641.6 a b 64.9625.7 a b 61.9625.4 a 43.6624.3 a 57.9627.7 a b 38.6643.1 a 55.3623.8 a
32.5625.3 a 10.0623.7 a 21.2619.4 a 68.1621.1 38.7620.1 a 42.3626.6 a 57.2645.4 a 65.9618.5 a
84.2623.3 80.9634.0 75.2623.7 71.9620.3 60.9620.9 83.3622.7 81.3633.0 74.7618.1
a b
P # 0.01 vs. general population. P # 0.01 vs. back pain.
significantly below normative scores in these areas. The age difference between the two patient groups did not significantly affect these findings.
4. Discussion HRQOL as assessed by the SF-36 was compromised in nearly all categories for patients with bipolar disorder compared with the general population group. For these patients, only Physical Function remained relatively unimpaired. Patients with bipolar disorder fared better in direct comparison with patients with chronic back pain in physical realms (Physical Function, Role Limitation – Physical, and Bodily Pain). It also appeared that physical compromise in these areas may have explained the poorer Social Function scores in the back pain patients compared with bipolar disorder patients. It is likely that the physical limitations associated with chronic back pain substantially impede and restrict social activities for these individuals. Both patient groups displayed significant impairment in Mental Health and Role Limitation – Emotional categories, although scores in the bipolar disorder group were numerically (but not significantly) lower than in the back pain group. These findings suggest that both bipolar disorder and chronic back pain are associated with substantial compromises in mental health. The results of this study should be interpreted with limitations in mind. First, the total sample size was relatively small, allowing for the possibility that significant differences (e.g. in Mental Health and / or
Role Limitations – Emotional) between the patient groups may have emerged with a larger group of patients. Second, since patients were recruited from a single treatment center, the degree to which the results of this study can be generalized to other cohorts of patients with bipolar disorder is uncertain. Third, the group of bipolar patients had moderate degrees of depression as measured by the mean IDS-C score. It is possible that HRQOL as measured by the SF-36 may have been diminished in patients with depression because of depressive distortions in patients’ self-reported functioning (Cooke et al., 1996). Future studies should examine HRQOL using the SF-36 in bipolar patients with different levels of symptom severity ranging from euthymia to frequent affective episodes. The findings of this study suggest that the HRQOL in outpatients with bipolar disorder is markedly diminished. Although the pharmacologic treatment for this illness has advanced significantly in the past decade, other therapeutic strategies are needed to improve HRQOL. Future research into specific psychosocial interventions targeting aspects of HRQOL is needed. Finally, the inclusion of measures of HRQOL should be considered in future clinical trials of pharmacologic agents for patients with bipolar disorder.
Acknowledgements Supported in part by a grant from the Theodure and Vada Stanley Foundation Scholars Program (Ms. Witzeman).
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