International Journal of Psychiatry in Clinical Practice, 2009; 13: 278284
ORIGINAL ARTICLE
Factor analysis of the Schizophrenia Quality of Life Scale Revision 4 (SQLS-R4) Chinese version and related factors
PO-JU KUO1, HUI-ING MA2, CHIEN-CHENG KUO3, WEI-CHE HUANG4 & MING-SHUN CHUNG3 1
Department of Occupational Therapy, Jianan Mental Hospital, Tainan, Taiwan, 2Department of Occupational Therapy & Institute of Allied Health Science, Medical College, National Cheng Kung University, Tainan, Taiwan, 3Department of Community Psychiatry, Jianan Mental Hospital, Tainan, Taiwan, and 4Department of Psychiatry, Sin Lau Hospital, Tainan, Taiwan
Abstract Objectives. To validate the Schizophrenia Quality of Life Scale Revision 4 (SQLS-R4) Chinese version with factor analysis. We also investigated factors influencing quality of life results. Method. One hundred patients with schizophrenia participated in this study. Experienced psychiatrists evaluated each patient’s current psychological condition to assure intact judgment. Participants then filled out the quality of life questionnaire, SQLS-R4. We used principal component analysis to analyze SQLS-R4 with oblique rotation. We also collected demographic data, another subjective and objective quality of life questionnaire, and information about the functional status of the participants at the same time. Multiple linear regression was used to analyze collected factors which may influence the quality of life of schizophrenic patients. Results. We extracted seven factors that explained a 68.1% variance in the patients’ quality of life. The factors were relationships with others, loneliness, exhaustion, depressed thinking, somatic concerns, vitality, and worry. Conclusion. We found that the SQLS-R4 factor analysis provided insights into the structure of the quality of life of patients with schizophrenia. We also found that subjective social participation, subjective health, and depression were quality-of-life-related factors. Whether other factors influence the quality of life in patients with schizophrenia requires further investigation.
Key Words: Quality of life, factor analysis, schizophrenia, SQLS-R4
Objective Schizophrenia, which includes positive and negative symptoms, is a chronic disease that affects multiple facets of life [1,2]. Patients with schizophrenia suffer not only from the symptoms, but also from life pressure, disability, unemployment, and reduced quality of life (QOL) [3,4]. The government as well as health providers use QOL data to determine resource distribution [57]. Because schizophrenia affects approximately 1% of the world’s population, it seems important to explore a useful, schizophrenia-specific QOL questionnaire that meets our needs in clinical practice. Wilkinson et al. developed a practical self-reported QOL questionnaire*the Schizophrenia Quality of Life Scale*the psychometric properties of which
have been rated ‘‘excellent’’ [8]. The reliability and validity of the Chinese version of the Schizophrenia Quality of Life Scale Revision 4 (SQLS-R4) have also been found acceptable [9]. However, there has been limited QOL research on persons with schizophrenia in Taiwan. Related factors that influence the QOL in patients with schizophrenia are unclear. According to the literature, these factors include sociodemographic data, using three or more psychoactive drugs, psychomotor agitation during interviews, anxiety, depressive symptoms or parkinsonism, unemployment, negative feelings and attitudes toward antipsychotics, emotional discomfort and extrapyramidal symptoms and so on [1013]. Determining and verifying the related factors of QOL in persons with schizophrenia in Taiwan still need further research.
Correspondence: Ming-shun Chung, MD. MA, Department of Community Psychiatry, Jianan Mental Hospital, Tainan, Taiwan, No. 80, Lane 870, ChungShan Road, Jen-Te Hsien, Tainan County, Taiwan 717. E-mail: [email protected]
(Received 3 December 2008; accepted 24 March 2009) ISSN 1365-1501 print/ISSN 1471-1788 online # 2009 Informa UK Ltd. DOI: 10.3109/13651500902919376
The Schizophrenia Quality of Life Scale Revision 4 Chinese version We aimed to validate the SQLS-R4 Chinese version questionnaire using factor analysis. In addition to clarifying the factor structure of the questionnaire, we tried to identify the demographic and psychopathological variables that influence QOL results.
Methods Patients One hundred patients were recruited from a public psychiatric center in Tainan, Taiwan. Inclusion criteria were (a) a diagnosis of schizophrenia according to DSM-IV, (b) 1865 years old, and (c) signed informed consent to participate in the study. Exclusion criteria were (a) diagnoses other than schizophrenia according to DSM IV or (b) a diagnosis of schizophrenia combined with other severe organic diseases, primary dementia, mental retardation, or a co-existing learning disability. Instruments Positive and Negative Symptom Scale (PANSS). PANSS is a rigorous and objective evaluative interview instrument [14]. It is used to check for seven positive and seven negative symptoms of schizophrenia, and 16 general pathological conditions [15]. Of the 16 items of general pathological conditions, three items comprised depression score [16]. The reliability of each of its domains, its internal consistency, and its inter-rater reliability are good. Its validity is also good according to factor analysis and validity testing comparisons with other symptom-evaluation instruments [14].
SQLS-R4. The SQLS-R4 is a questionnaire for schizophrenia. There are 33 items divided into two dimensions: psychosocial (20 items) and vitality (13 items). Its reliability and validity are acceptable [9].
Global Assessment of Function (GAF). GAF yields a social functioning score that ranges from 0 to 100 [17]. The psychiatrist evaluates the client in terms of psychosocial, occupational, and educational performance. Researchers usually use GAF to monitor changes in their clients after the treatment in their studies. Therefore, GAF is widely used and has practical utility [14].
Lancashire Quality of Life Profile (LQOLP). The LQOLP is another widely used instrument. It is a
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structured interview that focuses on satisfaction with life in different life domains. The LQOLP Taiwanese version (T-LQOLP) has been developed and validated [18]. There are nine domains in this questionnaire: work, leisure, religion, finance, living situation, safety, family relations, social participation, and health. In each domain, there are objective and subjective items. Only the subjective items are rated using a Likert scale, and the mean of these items was adapted as a variable in this study. Its internal consistency is good (Cronbach’s a coefficient [0.87]) and has an intraclass correlation coefficients (ICC) testretest reliability score of 0.91. The construct validity is also acceptable [18]. Procedure After getting informed consent from all the patients, registered psychiatrists used PANSS to confirm that they were psychologically stable and not disturbed by psychotic symptoms during responding to questionnaires, and then used the GAF to evaluate their social functioning. The inter-rater agreement of the psychiatrists was above 0.75. The researchers then collected the patients’ demographic data, subjective items in the T-LQOLP, and self-reported SQLS-R4 results. The Institutional Review Board of Jianan Mental Hospital approved the study. Statistical analysis SPSS 13.0 was used to analyze data in this study. Patient characteristics were analyzed using descriptive statistics. ANOVA and t-tests were used to analyze SQLS-R4 subscale score differences in demographic categories. The Pearson correlation coefficient was used to test the association of the continuous demographic variables, and the PANSS, GAF, and T-LQOLP for the association of the subjective satisfaction items of psychosocial and vitality dimensions of SQLS-R4. We also used principal component analysis with oblique rotation to clarify factors of SQLS-R4. Finally, we examined educational level and T-LQOLP subjective satisfaction items using multiple linear regression to predict factors influencing quality of life. Results We recruited 100 patients (men/women: 75/25; mean age (SD): 36.9 (8.82) years old) for this study (Table I). Half were outpatients and half were inpatients. Their mean duration of illness was 12.5 years (SD: 7.47). A plurality (45%) were high school graduates, and a majority (74%) were unmarried. Only 20% were employed, 47% were unemployed,
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Table I. Characteristics of patients and SQLS-R4 scores in the psychosocial and vitality dimensions. Psychosocial Number (%) /mean9SD Total Resources Outpatients Inpatients Gender Male Female Education Did not graduate from high school Senior high school Post-graduate Occupation Employed Institutionalized Unemployed Age Duration of illness
12.5297.47
Mean9SD
Vitality
P value (R)
Mean9SD
P value (R)
100 (100%) 0.84 50 (50%) 50 (50%)
25.68917.85 24.93918.20
75 (75%) 25 (25%)
23.77917.08 29.90919.98
37 (37%) 45 (45%) 18 (18%)
19.80915.29 27.22918.64 31.81918.98
20 (20%) 33 (33%) 47 (47%) 36.9098.82
26.63914.86 24.24914.84 25.48921.14
0.98 28.96918.08 29.04917.25
0.14
0.16 27.56918.13 33.31915.35 0.57
0.04 26.66916.16 29.91918.64 31.52918.09 0.89
0.41 31.92914.00 25.82913.83 30.00920.96
0.06 (R0.19) 0.31 (R0.10)
0.70 (R0.04) 0.59 (R0.06)
However, most T-LQOLP subjective scores correlated significantly with SQLS-R4 (P B0.05, except for the correlation between subjective satisfaction with work and the vitality dimension of SQLS-R4). We used exploratory factor analysis in this study. The patients’ SQLS-R4 data were collected for use with the KaiserMeyerOlkin Measure of Sampling Adequacy (KMO) and with Bartlett’s Test of Sphericity. The KMO value was 0.87, and the Bartlett’s Test of Sphericity score was 1763.12 (P B0.001). These values indicated that the SQLS-R4 was
and 33% were institutionalized. There were no significant SQLS-R4 score differences between demographic items, except in education (P 0.04 in the psychosocial dimension). Age and duration of illness were not associated with the psychosocial and vitality dimensions of SQLS-R4 (age: r 0.19 and 0.04, respectively; illness duration: r 0.10 and 0.06, respectively). Neither GAF nor PANSS scores were significantly associated with SQLS-R4 scores in either dimension except for depression score of PANSS (Table II).
Table II. Correlation between PANSS, GAF, and T-LQOLP subjective scores with SQLS-R4. Psychosocial
Vitality
Correlation coefficient
P value
Correlation coefficient
P value
PANSS positive negative general supplement depression score GAF
0.04 0.01 0.07 0.11 0.09 0.30 0.03
0.73 0.93 0.47 0.30 0.39 0.00 0.79
0.12 0.05 0.03 0.18 0.06 0.30 0.11
0.25 0.60 0.81 0.07 0.53 0.00 0.30
TLQOLP work leisure finance living safety family social health
0.23 0.28 0.30 0.36 0.22 0.35 0.46 0.34
0.02 0.01 0.00 0.00 0.03 0.00 0.00 0.00
0.18 0.39 0.29 0.39 0.29 0.40 0.48 0.54
0.07 0.00 0.00 0.00 0.00 0.00 0.00 0.00
The Schizophrenia Quality of Life Scale Revision 4 Chinese version suitable to use with factor analysis. Therefore, using principal component analysis, we extracted factors and then used varimax rotation to adjust for them. We selected those factors for which the eigenvalue was greater than 1. In all, we determined and named seven factors for this study (Table III). We then conducted the step-wise selection to see which factors would relate to QOL in schizophrenia. Only the correlated factors, depression score, education level, and subjective T-LQOLP items, were considered in the multiple linear regression analysis. We found that ‘‘depression score’’, ‘‘subjective social participation’’ and ‘‘subjective health’’ were selected into the model in both SQLS-R4 dimensions (Table IV). These two sets of predictors accounted for 26% and 40% of the variance in the SQLS-R4 scores in the psychosocial and vitality dimensions, respectively.
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Discussion We extracted seven factors from the SQLS-R4 questionnaire: relationships with others, loneliness, exhaustion, depressed thinking, somatic concern, vitality, and worry. Together they explained 68.1% of the variance in SQLS-R4 scores. Kaneda et al. used principle component analysis to extract, from the Japanese version of the SQLS (JSQLS), three factors similar to the original dimensions of the JSQLS, that explained 55.8% of the variance in JSQLS scores [19]. Martin and Allen used confirmatory factor analysis on the SQLS-R4 to determine its psychometric properties. They reported two factors*comprising ‘‘cognition’’ and ‘‘vitality’’ for the first and ‘‘psychosocial feelings’’ for the second* that best fit the data, which was consistent with the original validation of the SQLS-R4 [8]. Our factor analysis results were not exactly the same as the
Table III. Factor analysis results and factor loadings. Factor 1 Psychosocial dimension worry about the future Lonely hopeless Panicky took things people said the wrong way difficult to mix with people Down mixed up and unsure have mood swings concerned wouldn’t get better Worry people avoid me upset about past cut off from world uncomfortable with people upsetting thoughts suicidal thoughts depressed restless Vitality Dimension lack energy couldn’t be bothered hard to concentrate slept well poor memory can’t think clearly Drowsy Tired physically weak wasn’t leading normal life Eigenvalues % variance
Factor 2
Factor 3
Factor 4
Factor 5
Factor 6
0.54 0.79 0.62 0.31 0.65 0.70 0.33
Factor 7
0.46 0.31 0.70 0.31
0.34 0.74 0.41 0.64
0.38 0.61 0.39 0.34
0.35 0.39
0.32 0.40 0.49 0.46
0.59 0.74 0.79 0.64 0.58
0.38 0.51 0.64
0.42
0.37
0.76 0.70 0.78 0.45
0.46
0.46 0.68 0.58 0.45
0.41 0.36 0.51 0.37
0.66 0.76 0.68
0.44 11.35 39.13
1.96 6.76
0.42 1.64 5.65
1.53 5.26
1.19 4.11
0.36 1.08 3.72
1.02 3.50
Factor 1: relationships with others; Factor 2: loneliness; Factor 3: exhaustion; Factor 4: depressed thinking; Factor 5: somatic concern; Factor 6: vitality; Factor 7: worry. Factor loading less than 0.30 is not listed in this table.
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Table IV. Multiple linear regression analysis to predict related factors influencing QOL. b
Partial R2
0.34 0.20 0.20
0.21 0.04 0.04
0.43 0.27 0.20
0.29 0.09 0.04
Independent variables and model’s properties Psychosocial dimension
Vitality dimension
Subjective social in T-LQOLP Subjective health in T-LQOLP PANSS depression score Adjusted R2 0.26 Subjective health in T-LQOLP Subjective social in T-LQOLP PANSS depression score Adjusted R2 0.40
Adjusted for subjective work, leisure, living situation, safety and law, and family relationships.
original psychosocial and vitality dimensions. We divided the seven factors into three dimensions: psychosocial (relationships with others, loneliness, depressed thinking, and worry), physical condition (exhaustion status and somatic concern), and vitality (vitality). The dimensions of SQLS-R4 Chinese version emphasize the impact of physical condition on the QOL of patients with schizophrenia. This concept was verified in a report on health-related quality of life measures [3]. Age, gender, duration of illness, marital status, and employment status were not significantly associated with the two dimensions of the SQLS-R4. However, education level was significantly related with its psychosocial dimension. One study of 200 persons diagnosed with schizophrenia also reported that their demographic data were not significantly associated with QOL scores [20]. However, other studies reported that the factors associated with a poor QOL were: (1) male gender, unmarried, low income, low education level, and psychomotor agitation when interviewing were associated with poor QOL [10]; (2) female gender, unemployment, a higher level of mental health problems, and multiple previous hospitalizations [21]; and (3) age and the duration of illness [22]. Therefore, whether demographic data influence the QOL in patients with schizophrenia requires further investigation. We found that the GAF score were not significantly associated with QOL. Kusel et al. [23] and Kim et al. [24] both found that QOL results correlated with functioning scores, a finding inconsistent with a previous report on the GAF factor. Therefore, whether function status affects the QOL of persons with schizophrenia needs reconfirmation. On the other hand, we found that PANSS was not associated with QOL in either the psychological or vitality dimension. According to previous surveys, the QOL of patients with schizophrenia did relate to their mental health and symptoms [20,2228]. In sum, our findings were inconsistent with those in previous reports about the association between psychotic symptoms and QOL. This might have
been because of our inclusion criterion requiring that our study participants be in stable psychological condition, which might have affected the analyses and subsequent inferences based on them because the patients’ symptom scores were not normally distributed. We need more studies and more databases to confirm the results. Whether symptoms or PANSS scores influence QOL in patients with schizophrenia still requires further investigation. Because the eight subjective items of the T-LQOLP (subjective work, leisure, finance, living situation, safety, family relations, social participation, and health) correlated with the SQLS-R4, we put them and educational level, depression score of PANSS into the multiple regression analysis to test the factors that influence QOL. We found that subjective assessments of one’s social participation, subjective self-assessments of one’s health and depression score predict QOL scores. Studies have shown that more social participation, social interaction, or social networking promotes a better QOL [21,29,30]. The influence of social participation was evident. Other research has shown that ‘‘perceptions of health status’’, similar to our ‘‘subjective health’’ item, is one of the primary health-related quality of life (HRQL) dimensions [3]; however, there was limited report focus on the association between perceptions of health status and QOL in psychiatric patients. The association needs further studies for verification. In another aspect, the finding of depression score in PANSS correlated with SQLS-R4 is compatible with previous study [13]. In the process of analyzing QOL-related factors, we proved that depression is a factor apparently influencing subjective QOL in schizophrenic patients. There is an important facet of QOL, the limited agreement between self- and expert-rated QOL. We assumed that the QOL was a subjective issue in this study and therefore adopted the self-rated SQLS-R4 as index of QOL. However, Wehmeier et al. found different degrees of concordance of QOL between subjective and objective scales [31]. In Doyle’s research of subjective and external assessments of
The Schizophrenia Quality of Life Scale Revision 4 Chinese version QOL in schizophrenia, the results revealed that the correlation between subjective and objective QOL was limited in those individuals who had poor insight [32]. Therefore, there were complicated factors influencing correlation between self- and expertrated QOL. Future investigation should take account of this aspect.
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Acknowledgement This study was supported by a grant from Jianan Mental Hospital for Scientific Research. Statement of Interest The authors have no conflict of interest with any commercial or other associations in connection with the submitted article.
Conclusion After our factor analysis of a health-related QOL questionnaire (SQLS-R4), we extracted seven factors that may influence QOL of persons diagnosed with schizophrenia: ‘‘Relationships with Others’’, ‘‘Loneliness’’, ‘‘Depressed Thinking’’, and ‘‘Worry’’ are part of the psychosocial dimension, and ‘‘Exhaustion Status’’ and ‘‘Somatic Concern’’ are part of the physical condition dimension. These factors have much in common, however, and overlap. Had we named the factors differently, they may have been more adaptable. We found that subjective social participation, subjective health perceptions and depression were significantly related to the QOL of persons with schizophrenia, which supports the findings of other studies. Other demographic factors and psychological evaluation items were not clearly related to SQLS-R4 scores in this study. Other studies report that there are no definitive conclusions about factors that affect the QOL for persons with schizophrenia. Therefore, our findings were similar to those in other studies. More large-scale investigations are required to definitively determine what factors affect the QOL for persons with schizophrenia.
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Key points . Factor analysis of SQLS-R4 provided insights into the structure of the quality of life in patients with schizophrenia. . We extracted seven factors from the SQLS-R4: relationships with others, loneliness, exhaustion, depressed thinking, somatic concern, vitality, and worry. . The factor analysis results of SQLS-R4 Chinese version reflected the impact of physical condition on the quality of life in patients with schizophrenia in Taiwan. . Clinician could emphasize improvement of subjective social participation, subjective health perceptions and depression status in patients with schizophrenia.
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ORIGINAL ARTICLE
Factor analysis of the Schizophrenia Quality of Life Scale Revision 4 (SQLS-R4) Chinese version and related factors
PO-JU KUO1, HUI-ING MA2, CHIEN-CHENG KUO3, WEI-CHE HUANG4 & MING-SHUN CHUNG3 1
Department of Occupational Therapy, Jianan Mental Hospital, Tainan, Taiwan, 2Department of Occupational Therapy & Institute of Allied Health Science, Medical College, National Cheng Kung University, Tainan, Taiwan, 3Department of Community Psychiatry, Jianan Mental Hospital, Tainan, Taiwan, and 4Department of Psychiatry, Sin Lau Hospital, Tainan, Taiwan
Abstract Objectives. To validate the Schizophrenia Quality of Life Scale Revision 4 (SQLS-R4) Chinese version with factor analysis. We also investigated factors influencing quality of life results. Method. One hundred patients with schizophrenia participated in this study. Experienced psychiatrists evaluated each patient’s current psychological condition to assure intact judgment. Participants then filled out the quality of life questionnaire, SQLS-R4. We used principal component analysis to analyze SQLS-R4 with oblique rotation. We also collected demographic data, another subjective and objective quality of life questionnaire, and information about the functional status of the participants at the same time. Multiple linear regression was used to analyze collected factors which may influence the quality of life of schizophrenic patients. Results. We extracted seven factors that explained a 68.1% variance in the patients’ quality of life. The factors were relationships with others, loneliness, exhaustion, depressed thinking, somatic concerns, vitality, and worry. Conclusion. We found that the SQLS-R4 factor analysis provided insights into the structure of the quality of life of patients with schizophrenia. We also found that subjective social participation, subjective health, and depression were quality-of-life-related factors. Whether other factors influence the quality of life in patients with schizophrenia requires further investigation.
Key Words: Quality of life, factor analysis, schizophrenia, SQLS-R4
Objective Schizophrenia, which includes positive and negative symptoms, is a chronic disease that affects multiple facets of life [1,2]. Patients with schizophrenia suffer not only from the symptoms, but also from life pressure, disability, unemployment, and reduced quality of life (QOL) [3,4]. The government as well as health providers use QOL data to determine resource distribution [57]. Because schizophrenia affects approximately 1% of the world’s population, it seems important to explore a useful, schizophrenia-specific QOL questionnaire that meets our needs in clinical practice. Wilkinson et al. developed a practical self-reported QOL questionnaire*the Schizophrenia Quality of Life Scale*the psychometric properties of which
have been rated ‘‘excellent’’ [8]. The reliability and validity of the Chinese version of the Schizophrenia Quality of Life Scale Revision 4 (SQLS-R4) have also been found acceptable [9]. However, there has been limited QOL research on persons with schizophrenia in Taiwan. Related factors that influence the QOL in patients with schizophrenia are unclear. According to the literature, these factors include sociodemographic data, using three or more psychoactive drugs, psychomotor agitation during interviews, anxiety, depressive symptoms or parkinsonism, unemployment, negative feelings and attitudes toward antipsychotics, emotional discomfort and extrapyramidal symptoms and so on [1013]. Determining and verifying the related factors of QOL in persons with schizophrenia in Taiwan still need further research.
Correspondence: Ming-shun Chung, MD. MA, Department of Community Psychiatry, Jianan Mental Hospital, Tainan, Taiwan, No. 80, Lane 870, ChungShan Road, Jen-Te Hsien, Tainan County, Taiwan 717. E-mail: [email protected]
(Received 3 December 2008; accepted 24 March 2009) ISSN 1365-1501 print/ISSN 1471-1788 online # 2009 Informa UK Ltd. DOI: 10.3109/13651500902919376
The Schizophrenia Quality of Life Scale Revision 4 Chinese version We aimed to validate the SQLS-R4 Chinese version questionnaire using factor analysis. In addition to clarifying the factor structure of the questionnaire, we tried to identify the demographic and psychopathological variables that influence QOL results.
Methods Patients One hundred patients were recruited from a public psychiatric center in Tainan, Taiwan. Inclusion criteria were (a) a diagnosis of schizophrenia according to DSM-IV, (b) 1865 years old, and (c) signed informed consent to participate in the study. Exclusion criteria were (a) diagnoses other than schizophrenia according to DSM IV or (b) a diagnosis of schizophrenia combined with other severe organic diseases, primary dementia, mental retardation, or a co-existing learning disability. Instruments Positive and Negative Symptom Scale (PANSS). PANSS is a rigorous and objective evaluative interview instrument [14]. It is used to check for seven positive and seven negative symptoms of schizophrenia, and 16 general pathological conditions [15]. Of the 16 items of general pathological conditions, three items comprised depression score [16]. The reliability of each of its domains, its internal consistency, and its inter-rater reliability are good. Its validity is also good according to factor analysis and validity testing comparisons with other symptom-evaluation instruments [14].
SQLS-R4. The SQLS-R4 is a questionnaire for schizophrenia. There are 33 items divided into two dimensions: psychosocial (20 items) and vitality (13 items). Its reliability and validity are acceptable [9].
Global Assessment of Function (GAF). GAF yields a social functioning score that ranges from 0 to 100 [17]. The psychiatrist evaluates the client in terms of psychosocial, occupational, and educational performance. Researchers usually use GAF to monitor changes in their clients after the treatment in their studies. Therefore, GAF is widely used and has practical utility [14].
Lancashire Quality of Life Profile (LQOLP). The LQOLP is another widely used instrument. It is a
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structured interview that focuses on satisfaction with life in different life domains. The LQOLP Taiwanese version (T-LQOLP) has been developed and validated [18]. There are nine domains in this questionnaire: work, leisure, religion, finance, living situation, safety, family relations, social participation, and health. In each domain, there are objective and subjective items. Only the subjective items are rated using a Likert scale, and the mean of these items was adapted as a variable in this study. Its internal consistency is good (Cronbach’s a coefficient [0.87]) and has an intraclass correlation coefficients (ICC) testretest reliability score of 0.91. The construct validity is also acceptable [18]. Procedure After getting informed consent from all the patients, registered psychiatrists used PANSS to confirm that they were psychologically stable and not disturbed by psychotic symptoms during responding to questionnaires, and then used the GAF to evaluate their social functioning. The inter-rater agreement of the psychiatrists was above 0.75. The researchers then collected the patients’ demographic data, subjective items in the T-LQOLP, and self-reported SQLS-R4 results. The Institutional Review Board of Jianan Mental Hospital approved the study. Statistical analysis SPSS 13.0 was used to analyze data in this study. Patient characteristics were analyzed using descriptive statistics. ANOVA and t-tests were used to analyze SQLS-R4 subscale score differences in demographic categories. The Pearson correlation coefficient was used to test the association of the continuous demographic variables, and the PANSS, GAF, and T-LQOLP for the association of the subjective satisfaction items of psychosocial and vitality dimensions of SQLS-R4. We also used principal component analysis with oblique rotation to clarify factors of SQLS-R4. Finally, we examined educational level and T-LQOLP subjective satisfaction items using multiple linear regression to predict factors influencing quality of life. Results We recruited 100 patients (men/women: 75/25; mean age (SD): 36.9 (8.82) years old) for this study (Table I). Half were outpatients and half were inpatients. Their mean duration of illness was 12.5 years (SD: 7.47). A plurality (45%) were high school graduates, and a majority (74%) were unmarried. Only 20% were employed, 47% were unemployed,
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Table I. Characteristics of patients and SQLS-R4 scores in the psychosocial and vitality dimensions. Psychosocial Number (%) /mean9SD Total Resources Outpatients Inpatients Gender Male Female Education Did not graduate from high school Senior high school Post-graduate Occupation Employed Institutionalized Unemployed Age Duration of illness
12.5297.47
Mean9SD
Vitality
P value (R)
Mean9SD
P value (R)
100 (100%) 0.84 50 (50%) 50 (50%)
25.68917.85 24.93918.20
75 (75%) 25 (25%)
23.77917.08 29.90919.98
37 (37%) 45 (45%) 18 (18%)
19.80915.29 27.22918.64 31.81918.98
20 (20%) 33 (33%) 47 (47%) 36.9098.82
26.63914.86 24.24914.84 25.48921.14
0.98 28.96918.08 29.04917.25
0.14
0.16 27.56918.13 33.31915.35 0.57
0.04 26.66916.16 29.91918.64 31.52918.09 0.89
0.41 31.92914.00 25.82913.83 30.00920.96
0.06 (R0.19) 0.31 (R0.10)
0.70 (R0.04) 0.59 (R0.06)
However, most T-LQOLP subjective scores correlated significantly with SQLS-R4 (P B0.05, except for the correlation between subjective satisfaction with work and the vitality dimension of SQLS-R4). We used exploratory factor analysis in this study. The patients’ SQLS-R4 data were collected for use with the KaiserMeyerOlkin Measure of Sampling Adequacy (KMO) and with Bartlett’s Test of Sphericity. The KMO value was 0.87, and the Bartlett’s Test of Sphericity score was 1763.12 (P B0.001). These values indicated that the SQLS-R4 was
and 33% were institutionalized. There were no significant SQLS-R4 score differences between demographic items, except in education (P 0.04 in the psychosocial dimension). Age and duration of illness were not associated with the psychosocial and vitality dimensions of SQLS-R4 (age: r 0.19 and 0.04, respectively; illness duration: r 0.10 and 0.06, respectively). Neither GAF nor PANSS scores were significantly associated with SQLS-R4 scores in either dimension except for depression score of PANSS (Table II).
Table II. Correlation between PANSS, GAF, and T-LQOLP subjective scores with SQLS-R4. Psychosocial
Vitality
Correlation coefficient
P value
Correlation coefficient
P value
PANSS positive negative general supplement depression score GAF
0.04 0.01 0.07 0.11 0.09 0.30 0.03
0.73 0.93 0.47 0.30 0.39 0.00 0.79
0.12 0.05 0.03 0.18 0.06 0.30 0.11
0.25 0.60 0.81 0.07 0.53 0.00 0.30
TLQOLP work leisure finance living safety family social health
0.23 0.28 0.30 0.36 0.22 0.35 0.46 0.34
0.02 0.01 0.00 0.00 0.03 0.00 0.00 0.00
0.18 0.39 0.29 0.39 0.29 0.40 0.48 0.54
0.07 0.00 0.00 0.00 0.00 0.00 0.00 0.00
The Schizophrenia Quality of Life Scale Revision 4 Chinese version suitable to use with factor analysis. Therefore, using principal component analysis, we extracted factors and then used varimax rotation to adjust for them. We selected those factors for which the eigenvalue was greater than 1. In all, we determined and named seven factors for this study (Table III). We then conducted the step-wise selection to see which factors would relate to QOL in schizophrenia. Only the correlated factors, depression score, education level, and subjective T-LQOLP items, were considered in the multiple linear regression analysis. We found that ‘‘depression score’’, ‘‘subjective social participation’’ and ‘‘subjective health’’ were selected into the model in both SQLS-R4 dimensions (Table IV). These two sets of predictors accounted for 26% and 40% of the variance in the SQLS-R4 scores in the psychosocial and vitality dimensions, respectively.
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Discussion We extracted seven factors from the SQLS-R4 questionnaire: relationships with others, loneliness, exhaustion, depressed thinking, somatic concern, vitality, and worry. Together they explained 68.1% of the variance in SQLS-R4 scores. Kaneda et al. used principle component analysis to extract, from the Japanese version of the SQLS (JSQLS), three factors similar to the original dimensions of the JSQLS, that explained 55.8% of the variance in JSQLS scores [19]. Martin and Allen used confirmatory factor analysis on the SQLS-R4 to determine its psychometric properties. They reported two factors*comprising ‘‘cognition’’ and ‘‘vitality’’ for the first and ‘‘psychosocial feelings’’ for the second* that best fit the data, which was consistent with the original validation of the SQLS-R4 [8]. Our factor analysis results were not exactly the same as the
Table III. Factor analysis results and factor loadings. Factor 1 Psychosocial dimension worry about the future Lonely hopeless Panicky took things people said the wrong way difficult to mix with people Down mixed up and unsure have mood swings concerned wouldn’t get better Worry people avoid me upset about past cut off from world uncomfortable with people upsetting thoughts suicidal thoughts depressed restless Vitality Dimension lack energy couldn’t be bothered hard to concentrate slept well poor memory can’t think clearly Drowsy Tired physically weak wasn’t leading normal life Eigenvalues % variance
Factor 2
Factor 3
Factor 4
Factor 5
Factor 6
0.54 0.79 0.62 0.31 0.65 0.70 0.33
Factor 7
0.46 0.31 0.70 0.31
0.34 0.74 0.41 0.64
0.38 0.61 0.39 0.34
0.35 0.39
0.32 0.40 0.49 0.46
0.59 0.74 0.79 0.64 0.58
0.38 0.51 0.64
0.42
0.37
0.76 0.70 0.78 0.45
0.46
0.46 0.68 0.58 0.45
0.41 0.36 0.51 0.37
0.66 0.76 0.68
0.44 11.35 39.13
1.96 6.76
0.42 1.64 5.65
1.53 5.26
1.19 4.11
0.36 1.08 3.72
1.02 3.50
Factor 1: relationships with others; Factor 2: loneliness; Factor 3: exhaustion; Factor 4: depressed thinking; Factor 5: somatic concern; Factor 6: vitality; Factor 7: worry. Factor loading less than 0.30 is not listed in this table.
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Table IV. Multiple linear regression analysis to predict related factors influencing QOL. b
Partial R2
0.34 0.20 0.20
0.21 0.04 0.04
0.43 0.27 0.20
0.29 0.09 0.04
Independent variables and model’s properties Psychosocial dimension
Vitality dimension
Subjective social in T-LQOLP Subjective health in T-LQOLP PANSS depression score Adjusted R2 0.26 Subjective health in T-LQOLP Subjective social in T-LQOLP PANSS depression score Adjusted R2 0.40
Adjusted for subjective work, leisure, living situation, safety and law, and family relationships.
original psychosocial and vitality dimensions. We divided the seven factors into three dimensions: psychosocial (relationships with others, loneliness, depressed thinking, and worry), physical condition (exhaustion status and somatic concern), and vitality (vitality). The dimensions of SQLS-R4 Chinese version emphasize the impact of physical condition on the QOL of patients with schizophrenia. This concept was verified in a report on health-related quality of life measures [3]. Age, gender, duration of illness, marital status, and employment status were not significantly associated with the two dimensions of the SQLS-R4. However, education level was significantly related with its psychosocial dimension. One study of 200 persons diagnosed with schizophrenia also reported that their demographic data were not significantly associated with QOL scores [20]. However, other studies reported that the factors associated with a poor QOL were: (1) male gender, unmarried, low income, low education level, and psychomotor agitation when interviewing were associated with poor QOL [10]; (2) female gender, unemployment, a higher level of mental health problems, and multiple previous hospitalizations [21]; and (3) age and the duration of illness [22]. Therefore, whether demographic data influence the QOL in patients with schizophrenia requires further investigation. We found that the GAF score were not significantly associated with QOL. Kusel et al. [23] and Kim et al. [24] both found that QOL results correlated with functioning scores, a finding inconsistent with a previous report on the GAF factor. Therefore, whether function status affects the QOL of persons with schizophrenia needs reconfirmation. On the other hand, we found that PANSS was not associated with QOL in either the psychological or vitality dimension. According to previous surveys, the QOL of patients with schizophrenia did relate to their mental health and symptoms [20,2228]. In sum, our findings were inconsistent with those in previous reports about the association between psychotic symptoms and QOL. This might have
been because of our inclusion criterion requiring that our study participants be in stable psychological condition, which might have affected the analyses and subsequent inferences based on them because the patients’ symptom scores were not normally distributed. We need more studies and more databases to confirm the results. Whether symptoms or PANSS scores influence QOL in patients with schizophrenia still requires further investigation. Because the eight subjective items of the T-LQOLP (subjective work, leisure, finance, living situation, safety, family relations, social participation, and health) correlated with the SQLS-R4, we put them and educational level, depression score of PANSS into the multiple regression analysis to test the factors that influence QOL. We found that subjective assessments of one’s social participation, subjective self-assessments of one’s health and depression score predict QOL scores. Studies have shown that more social participation, social interaction, or social networking promotes a better QOL [21,29,30]. The influence of social participation was evident. Other research has shown that ‘‘perceptions of health status’’, similar to our ‘‘subjective health’’ item, is one of the primary health-related quality of life (HRQL) dimensions [3]; however, there was limited report focus on the association between perceptions of health status and QOL in psychiatric patients. The association needs further studies for verification. In another aspect, the finding of depression score in PANSS correlated with SQLS-R4 is compatible with previous study [13]. In the process of analyzing QOL-related factors, we proved that depression is a factor apparently influencing subjective QOL in schizophrenic patients. There is an important facet of QOL, the limited agreement between self- and expert-rated QOL. We assumed that the QOL was a subjective issue in this study and therefore adopted the self-rated SQLS-R4 as index of QOL. However, Wehmeier et al. found different degrees of concordance of QOL between subjective and objective scales [31]. In Doyle’s research of subjective and external assessments of
The Schizophrenia Quality of Life Scale Revision 4 Chinese version QOL in schizophrenia, the results revealed that the correlation between subjective and objective QOL was limited in those individuals who had poor insight [32]. Therefore, there were complicated factors influencing correlation between self- and expertrated QOL. Future investigation should take account of this aspect.
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Acknowledgement This study was supported by a grant from Jianan Mental Hospital for Scientific Research. Statement of Interest The authors have no conflict of interest with any commercial or other associations in connection with the submitted article.
Conclusion After our factor analysis of a health-related QOL questionnaire (SQLS-R4), we extracted seven factors that may influence QOL of persons diagnosed with schizophrenia: ‘‘Relationships with Others’’, ‘‘Loneliness’’, ‘‘Depressed Thinking’’, and ‘‘Worry’’ are part of the psychosocial dimension, and ‘‘Exhaustion Status’’ and ‘‘Somatic Concern’’ are part of the physical condition dimension. These factors have much in common, however, and overlap. Had we named the factors differently, they may have been more adaptable. We found that subjective social participation, subjective health perceptions and depression were significantly related to the QOL of persons with schizophrenia, which supports the findings of other studies. Other demographic factors and psychological evaluation items were not clearly related to SQLS-R4 scores in this study. Other studies report that there are no definitive conclusions about factors that affect the QOL for persons with schizophrenia. Therefore, our findings were similar to those in other studies. More large-scale investigations are required to definitively determine what factors affect the QOL for persons with schizophrenia.
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Key points . Factor analysis of SQLS-R4 provided insights into the structure of the quality of life in patients with schizophrenia. . We extracted seven factors from the SQLS-R4: relationships with others, loneliness, exhaustion, depressed thinking, somatic concern, vitality, and worry. . The factor analysis results of SQLS-R4 Chinese version reflected the impact of physical condition on the quality of life in patients with schizophrenia in Taiwan. . Clinician could emphasize improvement of subjective social participation, subjective health perceptions and depression status in patients with schizophrenia.
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