Quality of Life in Patients With Bipolar Disorder: Defining and Measuring Goals

Bipolar disorder (BD) is a complex and heterogeneous condition characterized by a variety of symptoms and marked variability in disease course. A patient with BD can experience episodes of depression, hypomania, mania, or psychosis and, indeed, can experience a mixture of emotional states or cycle rapidly between them. In fact, recent research has highlighted the prevalence of marked subsyndromal features between episodes,¹ but despite currently available treatments, BD remains a chronic relapsing condition.²

Given the symptom profile of BD, it is not surprising that the diagnosis is typically associated with significant disability and impaired functioning. According to World Health Organization (WHO) estimates, BD was the 6th leading cause of disability worldwide among young adults at the turn of the century.³ For example, if BD develops in a woman at the age of 25, she may lose 9 years in life expectancy (because of cardiovascular and other medical problems), 14 years of productivity, and 12 years of good health.⁴ Disturbingly, the lifetime suicide rates of patients with BD (treated or not) may be as high as 15%.⁵

Beyond symptoms to quality of life
While outcomes in patients with BD have traditionally been assessed as objectively measured clinicalinformation (such as relapse rates, number of hospitalizations, or symptom reduction as rated by a clinician-rated scale), a number of arguments suggest the need for the addition of functional and quality-of-life (QOL) measures.^6-8 It has been observed clinically, for example, that some patients appear to function poorly despite relatively few symptoms, while others function well in the context of relatively severe symptoms.⁷ Likewise, there is evidence for a disjunction between symptom change and QOL change in response to treatment, with the latter typically lagging substantially behind the former.⁹ Finally, as discussed later in this article, patients themselves attend to more than symptoms when assessing the success of their treatment, and it would be reasonable to expect that the treatment alliance would benefit when clinicians share this more holistic viewpoint.⁶

The movement toward a broader set of outcome measures in BD is consistent with a change in the zeitgeist of BD research in the past decade. Mirroring the developments that occurred in schizophrenia research a decade earlier,¹⁰ biopsychosocial models of BD have recently been proposed,^11-13 and a number of adjunctive psychosocial treatments for BD have been found efficacious.^14,15 Researchers from this contemporary tradition have called for expanded targets for therapy⁷ and, hence, an expanded range of outcome mea-surements in BD. Indeed, it may be in the area of functional outcomes that psychosocial interventions make their strongest contribution.¹⁶ As asserted by Harvey,¹⁷ for example: "recovery should not be defined merely by symptomatic remission or even syndromal remission; rather, recovery should include symptomatic recovery, syndromal recovery, functional recovery, and a return to an acceptable quality of life for the patient."

Although the terms "QOL" and "functioning" are often used interchangeably, it may be useful to distinguish between them. Functioning is typically clinician-assessed and refers to objective function in a variety of behavioral domains. In contrast, QOL is commonly understood as a subjective indicator of patient well-being. The WHO has described QOL as the "individuals' perception of their position in life in the context of the culture and value systems in which they live and in relation to their goals, expectations, standards, and concerns."¹⁸ Although the domains encompassed by QOL and functioning may overlap (eg, social, occupational, and independent living), the former are characterized by an emphasis on subjective assessment of satisfaction. This article focuses on the subjective assessments of QOL in BD. Given the limited evidence base, our review will not distinguish between a broad conceptualization of QOL and health-related quality of life (HRQOL), with the latter referring specifically to those aspects of life that are impacted by health or ill health.

Quantitative studies
Compared with the study of QOL in unipolar depression, research into QOL in BD has been sparse.¹⁰ However, to date, the literature permits preliminary conclusions on 2 fundamental questions; namely, the degree of QOL impairment in BD patients compared with that in nonclinical and other patient populations, and the differential impact on QOL of the phases of BD.^19-22

Several studies have sought to determine the degree of QOL impairment experienced by patients with BD. Not surprisingly, QOL in populations with BD appears to fall far below that observed in general population samples. For example, one study using the medical outcome survey (MOS) SF-36²³-the most widely used HRQOL measure in the BD population to date-compared scores of patients with BD (N = 44) with previously reported norms for a general population sample (N = 2474).²⁴ The SF-36 contains 8 subscales that assess physical functioning, social functioning, role limitations (physical), role limitations (emotional), pain, mental health, general health, and vitality. The results of the study indicated that HRQOL was significantly compromised in patients with BD in all SF-36 domains except physical functioning as compared with the general population. While the study provided a useful initial comparison, its findings must be interpreted with caution because of the disparate sample sizes and the use of previously published norms for the HRQOL instrument.

More recent data are provided by Yatham and colleagues,²⁵ who reported on SF-36 scores in a large sample of patients with BD type I (BDI) (N = 920) who either were currently depressed or had experienced a recent episode of depression. Scores were significantly lower across all scale domains in the group of patients with BD than in the general population in the United States, with the patients with BD scoring markedly lower in the mental health, vitality, social functioning, and role emotional domains.

A number of studies have investigated HRQOL in BD compared with other psychiatric conditions. One study from the Netherlands compared SF-36 scores in patients with BD (N = 136) with scores found in patients with a variety of other psychiatric disorders.²⁶ Participants with BD showed significantly more impairment in most SF-36 domains compared with other participants. For example, in the domain of mental health, participants with BDI experienced significantly lower scores (62.3) than people with mood (75.2), anxiety (74.0), substance use (80.2), or no psychiatric disorders (85.8).

In the study by Yatham and colleagues,²⁵ the SF-36 scores in their sample of patients with BD were compared with scores reported in 7 large studies of HRQOL in patients with unipolar depression. Scores on 4 domains (general health, social functioning, role-physical, and role-emotional) were consistently lower in the group with BDI than in the group with unipolar depression; however, the patients with unipolar depression tended to exhibit higher scores in the bodily pain domain.

Although hypomanic symptoms are used to distinguish BD from unipolar depression in the current DSM classification, much of the morbidity and mortality in BD appears to be a consequence of the depressive phase of the disorder, rather than the defining hypomanic or manic phases. Among a sample of 129 patients, those who experienced acute depressive or mixed depressive episodes were at significantly higher risk for suicide, panic disorder, and psychosis than those patients who experienced purely manic episodes.²⁷

There is growing evidence that the deleterious impact of depressive episodes and subsyndromal depressive symptoms in BD extends to QOL and functioning.^28-31 Altshuler and colleagues³² found that subthreshold depressive symptoms of BD were significantly predictive of impaired role functioning-specifically, impairment in work, home functioning, and relationships. Indeed, in this sample of 759 patients, odds of experiencing significant impairment in role functioning among patients with subthreshold depressive symptoms were 3 to 6 times greater than for those who were not depressed. Recent findings from the ongoing multicenter STEP-BD trial funded by the NIMH underscore the relationship between depressive symptoms and QOL in BD.³³ By comparing the baseline clinical states of the first 2000 participants enrolled in the STEP-BD, Zhang and colleagues⁸ demonstrated that depressive symptoms were strongly associated with poorer emotional QOL (as measured by the SF-36 mental health subscale), even after relevant confounding variables were controlled for.

Growing evidence for the marked association between depressive symptoms and lowered QOL in BDI is clinically significant, given that depressive symptoms predominate over manic symptoms in patients with BDI and particularly those with BDII.^1,34 A large proportion of the QOL challenge of BD may therefore be attributable to depression, consistent with some evidence that QOL scores may be lower in patients with BDII in comparison to patients with BDI.³⁵

The lack of a disorder-specific QOL scale is a limitation of the existing quantitative literature on QOL in BD. Although key aspects of QOL in BD are captured in generic QOL and HRQOL instruments, some of the disorder's unique features (eg, financial indiscretion and hypersexuality when hypomanic) demand specific measurements.³⁶ For this reason, our group has undertaken a program of research to develop a disorder-specific scale for BD (QOL.BD).^37,38

Qualitative data
As part of the development of the disorder-specific scale, QOL.BD, we conducted a series of in-depth qualitative interviews to identify themes in the QOL impacts of BD.³⁷ We sought the views of a representative sample of people in whom both BDI and BDII had been diagnosed. The sample included individuals with a range of illness severity, from those patients who had been clinically stable for several years to inpatients who were recovering from a severe episode of depression or mania. We also interviewed caregivers of people severely affected by BD, health care workers with expertise in BD, and international experts. In total, we conducted 35 interviews with persons who had BD, 5 with caregivers, and 12 with health care professionals or experts (identified by both convenience and purposive sampling).

Respondents described a wide variety of factors that influenced QOL, including the adverse effects of medications, occupation, level of education, physical functioning, environment, health care factors, leisure activities, routine, and sexuality. On the other hand, a number of patients were functioning exceptionally well despite their diagnosis, and a minority espoused the view that BD had opened new doors of opportunity (eg, improved career paths or social networks). On the whole, however, even these individuals described having undergone several years of hardship and adjustment before getting "back on track."

Some of the factors mentioned (eg, independence, stigma and disclosure, identity, and spirituality) are not frequently examined in relation to QOL, yet they appear to have a significant impact on people's ability to lead full lives in the context of BD. We are continuing to develop the QOL.BD in close consultation with patients and health care professionals with the aim of maximizing the validity of the resulting instrument.

There are currently no consensus guidelines for the clinical measurement of outcomes for QOL in BD. Drawing on our own research and related literature, however, we are able to make provisional recommendations for clinicians, as outlined in the Table.

Concluding remarks
There has been a recent upsurge of interest in measuring QOL in BD. Although research is at an early stage, there is no doubt that symptom measures alone constitute a limited assessment of BD outcomes, and more valid understandings (scientifically and clinically) are achieved with the addition of QOL measures. Existing research has revealed, for example, the marked negative impact of BD on QOL, a disjunction between symptom level and functional outcome in BD, and the apparent primacy of depressive over hypomanic symptoms in BD QOL outcomes.

In sum, the emerging body of research clearly suggests that it is both feasible and important to assess QOL in patients with this complex condition. For the practicing clinician, routinely adding a QOL measure to outcome monitoring will enrich understanding of patient progress, with consequent benefits for tailoring treatment regimens and for the therapeutic alliance.

References:

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