The impact of disease characteristics on multiple sclerosis patients’ quality of life

OBJECTIVES The aim of this study was to assess the quality of life (QoL) of patients with multiple sclerosis (MS), and to investigate the effects of characteristics of MS such as disease course, severity, and relapses on patients’ QoL. METHODS This was a cross-sectional study, in which 171 patients were enrolled. Health-related QoL was assessed using the Persian version of the Multiple Sclerosis Quality of Life-54 questionnaire. To measure patients’ disability status, we used the Expanded Disability Status Scale. Other variables included in the study were disease course and relapses of the disease. RESULTS The average scores for patients’ physical and mental QoL were 60.9±22.3 and 59.5±21.4, respectively. In a bivariate analysis, disease course, severity of the disease, and relapses were significantly associated with the physical and mental health composite scores. In a hierarchal regression analysis, disease course, severity of the disease, and relapses were responsible for 38 and 16% of the variance in physical and mental QoL, respectively. It was also observed that relapses were a strong predictor of both physical and mental QoL. CONCLUSIONS Our results showed that disease characteristics significantly affected both dimensions of QoL. It is therefore suggested that health care providers should be aware of these characteristics of MS to more successfully improve MS patients’ QoL.


INTRODUCTION
HRQoL was assessed using the MSQoL54 questionnaire. This questionnaire is a psychological instrument consisting of 54 stan dard questions measuring the QoL in MS patients. The MSQoL54 questionnaire contains 36 questions in a short form for assessing overall health status and general QoL, and 18 questions designed especially for MS patients, with scales for healthrelated discom fort (4 items); sexual function and satisfaction (5 items); overall QoL (2 items); cognitive function (4 items); and energy, pain, and their social situation (3 items). The MSQoL54 questionnaire as sesses health status in two general scales: physical health (39 items) and mental health (15 items). The subscales of physical health in clude: physical function (assessing possible activities during a nor mal day), health perceptions, physical role limitations, pain, sexual function, social function, energy, and health distress. The five men tal health subscales are as follows: overall QoL, emotional wellbe ing, emotional role limitations (assessing any mental health relat ed problems in working or any other daily activities, such as de pression or anxiety), cognitive function (corresponding to prob lems related to focusing and thinking), and health distress (assess ing weight loss and discouragement due to health problems). To calculate the desirability scores for each scale, the weighted aver age score of the constituent subscales are calculated. These scores range from 0 to 100; in each scale, a higher score means a better QoL.
In this study, we used the Persian version of the MSQoL54 ques tionnaire, which was successfully validated by Ghaem & Haghighi [17], with a Cronbach alpha coefficient of 0.962 for measuring a patient's QoL.

Statistical analysis
Descriptive statistics such as mean, standard deviation (SD), number and percent were used to analyze all demographic and clinical variables, as well as the physical and mental dimensions of QoL. The Student ttest was used to compare mean differences in the physical and mental health composite scores by sex (male vs. female), marital status (single vs. married), education level (pri mary vs. secondary or higher), employment status (unemployed vs. employed), disease duration ( ≤ 5 years vs. > 5 years), age of onset ( ≤ 30 years vs. > 30 years), relapses in the past three months (yes vs. no), disease severity (mild vs. moderatesevere), disease course (relapsingremitting vs. progressive). The Pearson correla tion test was used to assess the relationship between the physical and mental health composite scores and continuous variables, such as disease duration, EDSS scores, and age of onset. To deter mine the predictors of the physical and mental health composite scores, hierarchical lineal regression was used. We entered two blocks of control variables and one block of predictors in the re gression model. The control variables consisted of demographic variables including sex, marital status, education level, and em ployment status (model 1) and disease duration and age of onset (model 2). The predictors included disease severity, disease course, and relapses in the past three months. The beta coefficient (β), p value, Rsquared, adjusted Rsquared, and Fvalue were reported the disability of patients increases, they become dependent on their family for carrying out their daily routines and activities, which leads to a reduction of their QoL [9].
The concept of QoL in the health field, which is based on pa tients' individual perspectives, appeared following the develop ment of technologies that increased longevity, and is used as a consideration in the assessment of social policymaking and health care outcomes [10]. Measuring QoL can be a good definition of treatment success, the improvement of a patient's health status af ter an invasive intervention, and the overall effect of treatment from a patient's perspective [11].
In the field of medicine, researchers often use the concept of healthrelated quality of life (HRQoL), which specifically assesses the impact of a disease or its treatment on an individual's selfcon ception of health status and life satisfaction. MS patients' QoL is often measured by the Multiple Sclerosis Quality of Life (MSQoL)54 questionnaire, which is considered to be the most common and standardized diseasespecific instrument for the assessment of QoL of MS patients [12,13].
Improvements can be made in the QoL of MS patients only through understanding effective, behavioral, mental, and social factors [14]. Therefore, studying the QoL of MS patients would help health authorities and policymakers in planning and imple menting interventions to increase MS patients' QoL [15]. This study aimed to assess the effect of disease characteristics such as severity, disease course, and relapses in the past three months on the QoL of MS patients.

MATERIALS AND METHODS
This was a crosssectional study carried out among MS patients referred to the Center for Special Diseases and Multiple Sclerosis Society of Shiraz between February and October 2013. The inclu sion criteria were age greater than 18 years and having at least a 1year history of MS. Patients who were not willing to participate in the study or those who had a concomitant chronic disease that would impact their QoL were excluded. Ultimately, 171 patients enrolled in the study and were asked to fill out a questionnaire containing demographic (age, sex, marital status, educational lev el, and employment status) and clinical (disease duration, relapses during in last three months, and age of onset) questions. Disease course and neurologic disabilities for each patient were measured by a neurologist and recorded by an interviewer. All patients were classified as relapsingremitting, primary progressive, or second ary progressive based on their disease course. To measure patients' disability status, we used the Expanded Disability Status Scale (EDSS). The Kurtzke EDSS [16] is a quantitative method for as sessing MS disability that provides a total score on a scale ranging from 0, indicating a normal neurological examination, to 10, indi cating death due to MS. Based on their score, patients were cate gorized in three groups: mild disability (EDSS, 0.0 to 3.5), moder ate disability (EDSS, 4.0 to 6.5), and severe disability (EDSS, 7.0 to 9.5).
for the hierarchical regression models. Data were processed and analyzed using Excel 2007 (Microsoft, Redmond, WA, USA) and Stata version 14.1 (StataCorp., College Station, TX, USA).

Ethics
This study was approved by the Ethics Committee of the Shiraz University of Medical Sciences and written informed consent was obtained from all patients enrolled in the study. Table 1 presents descriptive statistics for the demographic and clinical characteristics of patients. The number (%) for dichoto mous variables and mean (SD) for continuous variables were re ported. A total of 171 patients (76.6% female) participated in this study, with a mean age of 35.7 (8.1) years. Statistically, there was no significant difference between males and females in terms of age (t 169 = 0.24, p = 0.8, ttest). Only 34.0% of patients were work ing; the rest were either unemployed or had to quit their job due to MS. The pluralities of participants had a primary education and were married. Approximately 83.6% of patients suffered from re lapsingremitting disease, while the remaining patients were cate gorized as having primary or secondary progressive disease.

RESULTS
The mean EDSS score was 2.1 ± 2.2, and 80.1% of patients had a mild disability (EDSS, 0.0 to 3.5), while 11.7 and 8.1% were cat egorized as having a moderate disability (EDSS, 4.0 to 6.5) and a severe disability (EDSS, 7.0 to 9.5), respectively. The distribution of patients by EDSS score is presented in Figure 1.
The average scores for patients' physical and mental QoL were 60.9 ± 22.3 and 59.5 ± 21.4, respectively. According to the QoL subscale scores, social function and energy had the highest scores (74.1 ± 24.6) and the lowest scores (51.8 ± 21.2), respectively. Fig  ure 2 presents the mean scores of the physical and mental sub scales in our study. Table 2 illustrates the relationships of the physical and mental dimensions of QoL with the demographic and clinical character istics of patients. Females reported higher scores in the physical  dimension than males (p < 0.05), while there was no significant difference in the mean mental composite score between males and females. Both physical and mental scores did not show statis tically significant differences according to marital status, educa tion level, or employment status. Individuals suffering from relapsingremitting disease had a significantly higher level of QoL in both the physical and mental dimensions. The relationship between QoL and disease relapse in the past three months was significant, such that patients who had experienced relapse had lower levels of physical and mental QoL than those who had not. Additionally, patients with an EDSS > 3.5, a disease duration of > 5 years, and an age of onset of > 30 years had the poorest QoL. These findings were also statistically signifi cant. Table 3 indicates that linear relationships were present between the dimensions of QoL and EDSS scores, disease duration, and age of onset. Based on the Pearson correlation test, EDSS scores showed a strong negative correlation with the physical health com posite scores and a moderate negative correlation with the mental health composite scores. We observed a weak negative relation ship between the physical dimension of QoL and disease dura tion, whereas the mental score did not show any association with the duration of disease. The correlation between age of onset and both composite QoL scores did not have statistical significance.
Hierarchical regression was used to assess the effects of demo graphic and clinical characteristics on the physical and mental health composite scores. As shown in Table 4, the total variance of the physical and mental dimensions that was explained by all vari ables was 0.382 and 0.166, respectively. After controlling for de mographic variables (model 1), other variables, such as disease duration, age of onset, disease course, disease severity, and relaps es in the past three months, were responsible for 35% of the vari ance in the physical composite score and 15% of the variance in the mental composite score. Disease severity and relapses in the past three months were the most significant determinants of physical status (p < 0.001), and relapses were the most significant predictor variable for the mental dimension.

DISCUSSION
The aim of this study was to assess the effects of MS characteris tics such as disease severity, disease course, and relapses in the past three months on the physical and mental dimensions of QoL in patients with MS. Our findings highlight that disease character istics were especially important factors for the physical health composite score, more so than for the mental health composite score. Demographic and clinical characteristics explained 38% of the variance in the physical health dimension and 16% of the vari ance in the mental health composite score.
According to our results, there were no significant relationships between demographic factors and QoL in MS patients, except for sex and the physical health composite score. Some other studies conducted in Iran also reported that demographic characteristics were unrelated to HRQoL in MS patients [1821]. In contrast, some studies showed that being female [22], having a lower education level [23], and being older [24] were factors related to poorer QoL.
In this study, we found a statistically significant negative rela tionship between the duration of disease and the physical dimen sion of QoL (r= 0.25, p< 0.001) which shows that a longer dura tion of the disease was associated with a poorer QoL. A negative relationship, but not a significant one, was observed between the duration of the disease and the mental dimension of QoL (r= 0.08, p = 0.25). Some studies have also stated that the duration of the   [24,30]. It seems that along duration of MS, with corre sponding physical limitations, leads to a decrease in QoL in the physical dimension. In the present study, patients with relapsingremitting MS had better physical and mental QoL than patients with progressive MS. Mitchell et al. [15] showed that the disease course negatively affected patients' QoL. The more aggressive the disease course was, the poorer the QoL. Tadić et al. [25] reported that since the disease develops faster in MS patients with a progressive disease course, their QoL is negatively affected.
The results of our study showed a negative relationship between the QoL score and severity of the disease, such that pati ents with less severe disease had a better QoL. In previous studies, a strong negative correlation between disability status and QoL has been reported [2,3133]. Regression analysis show ed that the severity of the disease was the most relevant independent variable predicting variance in the physical dimension of patients' QoL. Szilasiova et al. [29] reported that disability was significantly related to both the physical and mental dimensions of QoL; but after adjusting the regression model to account for depression and anxiety, no significant relationship was observed between disability and the mental dimension of QoL. The contribution of disability level of MS to QoL variation has been reported to range from 2% in the US to 29% in Austria. This wide variation is due to the use of dif ferent questionnaires for assessing QoL [34]. Petersen et al. [35] argued that physicians mostly pay attention to the physical dimen sions of a disease, while from the patients' point of view; mental health is an important QoL determinant. Therefore, it should be noted that the EDSS is not able to provide information about the mental health dimension.
In the present study, it was also observed that relapse of the dis ease was a strong predictor of both physical and mental QoL. A study conducted by Miller et al. [36] showed that more relapses in the last two years were associated with poorer QoL. They also found that preventing disease relapse led to improvements in QoL. Jones et al. [37] also found that patients who experienced relapses had poorer HRQoL than those with no relapses. In another study, Mäu rer et al. [38] showed that patients who had experienced severe re lapses had significantly poorer HRQoL. Healy et al. [39] reported a relationship between relapses and HRQoL, in which patients with more severe relapses had a greater decline in HRQoL than those with mild relapses.
Our study has some limitations that should be considered.  First, caution should be used in interpreting our findings as indic ative of a causal relationship between QoL and disease character istics because of the crosssectional study design. Second, the sample size of participant was somewhat small. Third, we did not consider variables such as fatigue, depression, anxiety, and social support, which might also affect QoL. Briefly, our study showed that both the physical and mental di mensions of MS patients' QoL were significantly affected by dis ease characteristics, such as its severity and the occurrence of re lapses. It is therefore suggested that health care providers should be appropriately informed about these characteristics of MS, in order to more successfully improve MS patients' QoL.