Structural equation modeling of factors contributing to quality of life in Japanese patients with multiple sclerosis
- Hiromi Kikuchi†1,
- Nobuhiro Mifune†2,
- Masaaki Niino†3Email author,
- Jun-ichi Kira4,
- Tatsuo Kohriyama5,
- Kohei Ota6,
- Masami Tanaka7,
- Hirofumi Ochi8,
- Shunya Nakane9 and
- Seiji Kikuchi10
© Kikuchi et al.; licensee BioMed Central Ltd. 2013
Received: 25 September 2012
Accepted: 15 January 2013
Published: 22 January 2013
To improve quality of life (QOL) in patients with multiple sclerosis (MS), it is important to decrease disability and prevent relapse. The aim of this study was to examine the causal and mutual relationships contributing to QOL in Japanese patients with MS, develop path diagrams, and explore interventions with the potential to improve patient QOL.
Data of 163 Japanese MS patients were obtained using the Functional Assessment of MS (FAMS) and Nottingham Adjustment Scale-Japanese version (NAS-J) tests, as well as four additional factors that affect QOL (employment status, change of income, availability of disease information, and communication with medical staff). Data were then used in structural equation modeling to develop path diagrams for factors contributing to QOL.
The Expanded Disability Status Scale (EDSS) score had a significant effect on the total FAMS score. Although EDSS negatively affected the FAMS symptom score, NAS-J subscale scores of anxiety/depression and acceptance were positively related to the FAMS symptom score. Changes in employment status after MS onset negatively affected all NAS-J scores. Knowledge of disease information improved the total NAS-J score, which in turn improved many FAMS subscale scores. Communication with doctors and nurses directly and positively affected some FAMS subscale scores.
Disability and change in employment status decrease patient QOL. However, the present findings suggest that other factors, such as acquiring information on MS and communicating with medical staff, can compensate for the worsening of QOL.
KeywordsMultiple sclerosis Quality of life Structural equation modeling Severity Treatment and Intervention
Multiple sclerosis (MS) is a chronic disease of the central nervous system that manifests as inflammation, demyelination, axonal degeneration, and gliosis. To date, however, no known cure for the disease exists, and patients with MS may experience a number of neurological disabilities despite receiving adequate disease-modifying therapies. The disabling nature of the disease has multiple consequences which not only affect physical activity, psychological aspects, and social interplay, but also create burdens for family members . Role limitations and cognitive and emotional problems have a negative impact on the health-related quality of life (QOL) of patients that is just as significant as the impact of physical symptoms or disability status . A previous paper suggested that cognitive impairment and depression/anxiety decrease health-related QOL .
We previously reported the first evaluation of the entire QOL spectrum in Japanese MS patients by using the Functional Assessment of MS (FAMS), which consists of an MS-specific QOL scale with a self-reported questionnaire and the Nottingham Adjustment Scale-Japanese version (NAS-J), which is a self-reported questionnaire for determining psychological adaptation . Out investigation revealed that FAMS subscale scores for mobility, symptoms, emotional well-being, thinking and fatigue, and additional concerns correlated strongly and negatively with the Expanded Disability Status Scale (EDSS) score, which is a measure of physical disorder in MS patients . Moreover, additional factors affecting QOL (employment status, change of income, availability of disease information, and communication with medical staff)––as identified by MS patients in a focus group interview––were also investigated, and the first three factors were found to be important for maintaining the QOL of MS patients . Overall, environmental and social factors, as well as the disabilities directly due to MS, were found to affect the QOL of Japanese MS patients . Other studies have reported similar psychosocial and social effects on the QOL of MS patient. These factors include gender [5, 6], employment status [7, 8], income , education , and economic burden [11, 12].
To improve QOL in MS, it is important to decrease disability and prevent relapse. Therefore, in this study we used structural equation modeling for the following purposes: 1) to examine the causal and mutual relationships that contribute to QOL in Japanese MS patients; and 2) to develop path diagrams for determining the interventions that are useful for targeting the environmental factors with the potential to improve QOL.
Sample and data collection procedures
The study population of the present study is the same as that of our previous study . Briefly, subjects comprised 163 Japanese patients with MS (118 females, 45 males) at the following eight hospitals: Kyushu University, Tokushima University, Hiroshima University, Utano National Hospital, Nagoya University, Tokyo Women’s Medical University, Niigata University, and Hokkaido University. Mean age at onset of MS was 31.9 years, and mean duration of the disease was 10.4 years. Mean score on the Expanded Disability Status Scale (EDSS) was 3.99.
The study protocol was approved by the Ethics Committee of Hokkaido University, and written consent was obtained from all patients.
Questionnaire items for the 4 additional factors pointed out by MS patients in the focus group interview
What was your employment status before and after the onset of MS?
Did your income increase or decrease after the onset of MS?
How many sources do you have for obtaining information on MS?
(Number of sources of disease information)
Do you think that you have enough opportunities to obtain information on MS?
(Self-evaluation of sources of disease information)
1. Yes, a little
2. Yes, some
3. Yes, quite a bit
4. Yes, a lot
How much do you know about MS?
(Self-evaluation of knowledge of disease information)
1. A little
3. Quite a bit
4. A lot
Communication with medical staff
Are you satisfied with communication with your doctor/nurse?
1. Yes, a little
2. Yes, somewhat
3. Yes, quite a bit
4. Yes, very much
Using SPSS® Amos, structural equation modeling was performed to develop path diagrams of the factors that contribute to QOL. Models were constructed with the additional four factors as independent variables, FAMS subscales as dependent variables, and NAS-J subscales as mediator variables between the independent and dependent variables.
When analyzing the total FAMS score as well as each FAMS subscale, the mean score of all FAMS subscales was taken to be the dependent variable, and the mean score of all NAS-J subscales was taken to be the mediator variable. Finally, the mediating effects of the NAS-J subscales were investigated by examining latent variables to determine whether any of the relationships among the measures had been incorrectly assumed during the modeling process.
Maximum likelihood estimation was used to estimate model parameters. During this process, we used the following three goodness-of-fit indices: results of a Chi-squared test (χ2, p), comparative fit index (CFI), and root mean square error of approximation (RMSEA). When parameters with a high goodness-of-fit were determined such that several models had high fitness indices, the most parsimonious model was selected based on the Akaike’s Information Criterion.
Causal and mutual relationships with FAMS total score (Figure 1)
Causal and mutual relationships with FAMS mobility score (Figure 2)
Causal and mutual relationships with FAMS symptom score (Figure 3)
Causal and mutual relationships with the FAMS emotional well-being score (Figure 4)
Causal and mutual relationships with FAMS general contentment score (Figure 5)
Causal and mutual relationships with FAMS thinking and fatigue score (Figure 6)
Causal and mutual relationships with FAMS family/social well-being score (Figure 7)
EDSS and QOL
The EDSS score had the most prominent affect on the NAS-J subscale scores as well as on all the FAMS subscale scores both directly and indirectly. Worsening of disability negatively affected psychological status, which was followed by worsening of FAMS scores. Furthermore, the EDSS score directly affected mobility, symptoms, emotional well-being, and thinking and fatigue. Taken together, the EDSS score is an important reflection of the QOL of MS patients, which means that, for example, prevention of relapse and improvement of disability through rehabilitation could improve patient QOL [14, 15]. Conversely, NAS-J subscales affected FAMS scores for symptoms, emotional well-being, general contentment, and thinking and fatigue to a greater extent than the EDSS score. It would appear then that improvement in these psychological factors can improve QOL, even if symptoms are deteriorating. Indeed, some studies have reported the success of cognitive behavior therapy for depression and fatigue in MS patients [16, 17], and some psychological interventions might compensate for the worsening of QOL in MS patients.
Changes in employment status and QOL
Changes in employment status after being diagnosed with MS reduced all NAS-J scores, and changes in employment status worsened patient anxiety, depression, acceptance of disability, and self-esteem scores. In contrast, obtaining more information on the disease compensated for worsening of the NAS-J scores in response to a change in employment status. We previously reported that 62% of patients experienced some kind of change in employment status, such as quitting a job or reducing their working hours, after the onset of MS . The age at onset for most MS patients is in their 20s or 30s, and thus it is important for patients to continue working, which may require the support of others. Support to preserve income and obtain sufficient information on the disease can compensate for the decrement in QOL caused by a change in employment status.
Information on MS and QOL
Obtaining information on MS improved the total NAS-J score, which was followed by improvement of many of the FAMS subscale scores. Increasing the number of sources of disease information also improved the scores for several NAS-J subscales. These findings indicate that acquiring information on MS is useful for psychological adjustment in MS patients and that awareness and coping may be associated with this improvement, as pointed out by Patti et al.. In contrast, the increased availability of sources and knowledge on disease information worsened the FAMS mobility, symptoms, and thinking and fatigue scores directly, not through the total NAS-J score. The reason for this discrepancy between the NAS-J and FAMS scores is not easy to discern, but one possibility is that the important thing for MS patients is the quality––not quantity––of information on the disease. Patients may consider the disease or their disease status to be more serious than it is when they have inadequate information on the disease. It is therefore vital that MS patients are provided with adequate and appropriate information on the disease.
Communication with medical staff and QOL
The effect of communication with medical staff differs between communication with doctors and that with nurses. Good communication with doctors improved the total FAMS score and FAMS symptom score directly, not through the total NAS-J score. Good communication with nurses also improved the FAMS family/social well-being score. The data suggest that good communication with medical staff can improve the QOL of MS patients while compensating for worsening disability. Moreover, it may be more effective for doctors to talk about symptoms and therapies with patients and for nurses to talk about daily life activities and self-care.
The findings of the present study, which are in agreement with those of previous studies, indicate that the progression of disability and changes in employment status are major factors that decrease QOL for MS patients. While progression of disability may not be avoidable even in patients receiving adequate treatment, our findings suggest that other factors such as acquiring adequate information on MS and communication with medical staff can compensate for the decrease in QOL. Interventions that target these factors have the potential to improve QOL in Japanese MS patients.
Quality of life
The functional assessment of multiple sclerosis
The Nottingham adjustment scale-Japanese version
The expanded disability status scale
The comparative fit index
The root mean square error of approximation.
The authors thank the following colleagues for enrolling patients in the study: Dr. Keiko Tanaka, Department of Neurology, Brain Research Institute, Niigata University; Drs. Takashi Ohashi and Yuko Shimizu, Department of Neurology, Tokyo Women’s Medical University School of Medicine; Dr. Masahiro Iijima, Department of Neurology, Nagoya University Graduate School of Medicine; Ms. Kyoko Tsunamoto, Clinical Research Center, Utano National Hospital; Ms. Hisami Hashida and Ms. Chie Masuda, Department of Clinical Neuroscience and Therapeutics, Graduate School of Biomedical Sciences, Hiroshima University; Drs. Ken Matsuoka and Yuji Kawano, Department of Neurology, Neurological Institute, Graduate School of Medical Sciences, Kyushu University; and Drs. Yusei Miyazaki, Ichiro Yabe, Jun Tashiro, Riichiro Kishimoto, Department of Neurology, Hokkaido University Graduate School of Medicine.
This work was supported in part by the Health and Labour Sciences Research Grant on Intractable Diseases (Neuroimmunological Diseases) from the Ministry of Health, Labour and Welfare of Japan.
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