Association between symptoms and quality of life in patients with schizophrenia: A pooled analysis of changes over time
Introduction
Quality of life is regarded as a relevant outcome criterion in the treatment of patients with schizophrenia (Priebe and Fakhoury, 2008). There are objective and subjective indicators of quality of life, and patients' rating of their own quality of life (referred to as subjective quality of life, SQOL) are widely used in research. The US Food and Drug Administration (US FDA, 2009) explicitly referred to it when underlining the importance of using patient reported outcomes in trials. Whilst there is no universal consensus on its precise definition, several scales are based on Lehman's (Lehman, 1996) approach of measuring SQOL as satisfaction with life in general and major life domains.
Many research studies and evaluations of routine care have found symptomatology to be associated with SQOL scores (Priebe and Fakhoury, 2008). Numerous cross-sectional studies, including meta- and pooled analyses (Eack and Newhill, 2007, Vatne and Bjorkly, 2008, Priebe et al., 2011), have reported that higher symptom levels are associated with less favourable SQOL ratings. These findings have led to suggestions that SQOL ratings in patients with schizophrenia might be too heavily influenced by symptoms and therefore not a valid independent outcome criterion (Atkinson et al., 1997, Katschnig, 1997).
However, treatment effects are commonly evaluated by investigating changes over time. For assessing whether SQOL can be used as an outcome criterion independent of symptoms, evidence is required on how changes in symptoms and changes in SQOL over time are associated. Cross-sectional associations can either overestimate or underestimate the extent of associations of changes over time. Only a few studies have investigated the association of symptom change and change in SQOL in a longitudinal design (Kaiser and Priebe, 1998, Fakhoury et al., 2002). These studies had small sample sizes and produced inconsistent findings. While Kaiser and Priebe (1998) reported an association between change in anxiety and depressive symptoms, symptoms of hostility, and change in SQOL, there was no evidence of such an association for general psychopathology and other types of symptoms. Further, Fakhoury et al. (2002) even found an absence of evidence of an association of changes in SQOL with changes in general psychopathology and depression/anxiety symptoms.
Using a pooled analysis of individual patient data from several studies, we aimed to study the association of changes in psychopathological symptoms and changes in SQOL in patients with schizophrenia. A pooled analysis considers both studies and individual patients as the unit of analysis and has several advantages compared to a conventional meta-analysis of aggregate data sets: it enables a more precise estimate of the effects of influential factors; allows for controlling of confounding factors including heterogeneity across studies at the patient level; and reduces effects of heterogeneity from aggregation of methodologically diverse studies by using the same statistical model (Blettner et al., 1999, Reininghaus and Priebe, 2007).
Section snippets
Methods
In a pooled analysis, linear mixed models were applied to individual patient data from samples of patients with schizophrenia, with SQOL change scores as the dependent variable.
Included studies and samples
Eight studies (Roder-Wanner and Priebe, 1998, Priebe et al., 2002, Priebe et al., 2007, Priebe et al., 2009, Ruggeri et al., 2002, Slade et al., 2006, Kallert et al., 2007), including one unpublished study (Junghan, 2009, unpublished data), were included (see Table 1). Five were prospective observational and three randomised controlled trials. From these 8 studies,BPRS and SQOL change scores were available for a total of 886 patients with schizophrenia, schizotypal, or delusional disorders. The
Discussion
After controlling for heterogeneity of findings across studies in linear mixed models, a reduction in symptoms was associated with improvements of SQOL scores. In univariate analyses, changes in each BPRS subscale were associated with changes in SQOL scores. Only associations of depression/anxiety and hostility subscales and SQOL change scores remained significant in a multivariate model. Whilst these associations were statistically significant in a large sample, the shared variance of symptom
Role of funding source
This work was supported by a Research Training Fellowship funded by the National Institute for Health Research (UK) to U.R. The report is an independent research and the views expressed in this publication are those of the authors and not necessarily those of the NHS, the National Institute for Health Research or the Department of Health.
Contributors
SP designed the study and had overall responsibility for completion. UR conducted the literature searches and managed the data. SP, RM, UJ, TK, MR, and MS took each responsibility for at least one of the data sets in the analysis. UR and SP analysed the data. All authors contributed to and have approved the manuscript.
Conflict of interest
None of the authors reported potential conflicts of interests.
Acknowledgements
None.
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2023, Psychiatry Research CommunicationsQuality of life after involuntary psychiatric admission
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