Patients with Multiple Sclerosis Present more Chronic and Recurrent Pain than a Control Population

Abstract

Background and Objective: Multiple sclerosis (MS) is a chronic disease affecting the central nervous system. Although neuropathic pain may be a manifestation of MS, other types of pain can be present.

Method: Interviews were conducted individually with MS patients and matched controls (1:2). Participants were assessed for mood disorders (depression, anxiety) and pain, using validated instruments. In addition, their use of alcohol, tobacco and illicit drugs was assessed.

Results: Thirty-three patients with MS and 66 controls were enrolled in the study. Ninety percent of the patients with MS reported having one or more types of chronic pain, and headache was the most frequent type. Among the controls, the prevalence of chronic pain was 10.6%. Anxiety, depression and the use of tobacco, illicit drugs, depression or anxiety were similar between the two groups.

Conclusion: Patients with MS frequently presented chronic pain, which may be an additional burden of this disease.

Keywords: Multiple sclerosis; Pain; Alcohol; Illicit drugs

Introduction

Multiple sclerosis (MS) is a chronic inflammatory and degenerative disease of the central nervous system. Accumulated neurological disability is the main concern of doctors and patients alike, and all MS treatments aim at reducing the relapse rate of demyelination as well as postponing the moment when disability will become established.

MS lasts for decades and several symptoms are associated with the neurological manifestations of MS over this time. Fatigue [1], cognitive impairment [2], pain [3,4] and depression [5] are a few of the conditions that frequently accompany MS. Although depression and fatigue can be diagnosed in patients in the early stages of MS, pain does not follow a similar pattern [6]. Pain can originate from a large variety of situations in MS and there is no simple way of assessing this [4]. While some patients may suffer from neuropathic pain due to specific lesions in the central nervous system [7], others may suffer from pain due to treatment injections [8]. As expected, patients with MS who suffer from pain have worse outcomes in quality of life assessments [9].

Some studies have addressed the matter of pain in patients with MS in relation to control subjects. However, their results have not been uniform. Svendsen et al. showed that patients with MS had no more pain than the general population, although the former might have greater intensity of pain than the latter [10]. In other studies, a comparison between the prevalence and types of pain in patients with MS was assessed in relation to other chronic diseases [11]. Other evaluations have concentrated on the importance of pain as a condition that is not taken into consideration by the universally used expanded disability scale score (EDSS) in MS [12].

The aim of the present study was to assess the prevalence and types of pain in patients with MS in relation to controls, in a direct and comprehensive manner. Additionally, their use of alcohol, tobacco and illicit drugs was observed to see whether these habits were more frequent in patients with MS presenting pain.

Methods

This study was approved by the Ethics Committee of Universidade Metropolitana de Santos, under the number CAAE 25172713.2.0000.5509, in July 2014. All participants were aware of the characteristics of the study and signed a written consent form for enrollment.

This was a cross sectional study, assessing patients with MS and healthy controls from the general population by means of interviews with specific questionnaires and scales. Two controls for each patient were included, matched for gender, age and socioeconomic level. No financial compensation was given for participation in the study. Only patients who had not experienced a clinical relapse over the previous three months were included, since relapses may be accompanied by pain without reflecting a chronic condition.

All patients and controls were individually interviewed in an appropriate environment and data were collected on the demographic and socioeconomic aspects of each participant. The control group was selected from the general population in the same area, with the aim of adequate matching for gender, age and socioeconomic level. Patients and controls were defined as having pain if they presented daily or nearly daily pain for at last three months.

The interview consisted of simple questions about demographics and the presence of chronic or recurrent pain and its characteristics (duration, intensity, recurrence, etc). Once it had been established that painful conditions lasting for at least three months (continuously or recurrently) were present, the visual analogue scale and face scale were administered to the participant in order to grade that particular pain. Characteristics of the painful condition were also assessed as an attempt to classify the type of headache and the presence of fibromyalgia, for example. In addition, depression and anxiety were assessed by means of the Hospital Anxiety and Depression scale (HAD) and the AUDIT scale (alcohol use disorder identification test). One question regarding use of tobacco and any illicit drug (past or present) was also included in the interview.

Sample size was calculate and established to be 10. Statistical analysis on the results was performed using the Student t-test, oneway ANOVA, Fisher exact and chi-square tests, taking the cutoff for significance to be 5% (p = 0.05).

Results

The group of patients consisted of 33 individuals regularly attending the outpatient service at the Department of Neurology, Universidade Metropolitana de Santos. Patients were randomly chosen for participation: typically the first three or four cases coming for consultation on every outpatient day for six consecutive weeks. In total, 33 patients and 66 controls participated in the study. The study was sensitive enough to detect large (effect size d = 0.78) mean differences between groups at standard alpha and power levels (0.05 and 0.95 respectively) using t-tests.

Demographic and clinical data are presented in Table 1. Briefly, the average age of both groups was circa 37 years, and the male-tofemale ratio was 1:2.5. The groups were comparable with regard to age, gender and socioeconomic level (Student t-test).

  

    
 
    
Gender
    
Average age ± SD (range)
      
in years
    
Average socioeconomic level
    
Average disease duration ± SD (range)  in years
    
Average EDSS
      
± SD (range)
  
  

    
Patients
      
(n=33)
    
Male= 12 (36.3%)
      
Female = 21
      
(63.7%)
    
37.7 ± 12.5
      
(18-59)
    
24.4 – class B2
      
(13-39)
      
(classes A2 to C)
    
6.6 ± 2.1
      
(1 to 16)
    
2.8 ± 1.1
      
(zero to 6.0)
  
  

    
Controls
      
(n=66)
    
Male= 24
      
(36.6%)
      
Female = 42 (63.7%)
    
38.2 ± 16.8
      
(18-61)
    
24.8 – class B2
      
(17-40)
      
(classes A2 to C)
    
 
  

Table 1:  Demographic data on patients with multiple sclerosis (MS) and healthy controls. Socioeconomic level was assessed using the IBGE scale (Instituto Brasileiro
de Geografia e Estatística) which classifies the individual as belonging to classes A1 to E, in decreasing levels of wealth. EDSS = expanded disability scale score,
which classifies the individual’s neurological disability between zero (normal) and 10 (death due to MS).

  

    
Types of pain
    
 
    
Headache 
    
Low back pain 
    
Fibromyalgia 
    
Joint pain 
    
Both hands 
  
  

    
Patients **
    
16
      
(48.5%)
    
5
      
(15.2%)
    
3
      
(9.1%)
    
7
      
(21.2%)
    
1
      
(3%)
  
  

    
Controls
    
4
      
(6.1%)
    
1
      
(1.5%)
    
0
    
1
      
(1.5%)
    
1
      
(1.5%)
  
  

    
 
    
Yes
    
No
    
Previous
    
 
  
  

    
Smoking 
    
Patients
    
6
      
(18.2%)
    
23
      
(69.7%)
    
4
      
(12.1%)
  
  

    
 
    
Controls
    
10
      
(15.2%)
    
51
      
(77.3%)
    
5
      
(7.5%)
  
  

    
 
    
Yes
    
No
    
Previous
    
Nearly daily drinking
  
  

    
Drinking 
    
Patients
    
13
      
(39.4%)
    
18
      
(54.5%)
    
2
      
(6.1%)
    
0
  
  

    
 
    
Controls*
    
42
      
(63.7%)
    
18
      
(27.3%)
    
4
      
(6%)
    
2
      
(3%)
  
  

    
 
    
 
    
Yes
    
No
    
Previous
    
 
    
 
  
  

    
Use of drugs 
    
Patients
    
2
      
(6.1%)
    
29
      
(87.8%)
    
2
      
(6.1%)
  
  

    
 
    
Controls
    
2
      
(3%)
    
64
      
(94%)
    
0
  
  

    
 
    
No
    
Mild
    
Moderate
    
Severe
  
  

    
Symptoms of Depression 
    
Patients
    
29
      
(87.9%)
    
2
      
(6.1%)
    
1
      
(3%)
    
1
      
(3%)
  
  

    
 
    
Controls
    
62
      
(97%)
    
1
      
(1.5%)
    
0
    
1
      
(1.5%)
  
  

    
 
    
No
    
Mild
    
Moderate
    
Severe
  
  

    
Symptoms of Anxiety 
    
Patients
    
31
      
(94%)
    
0
    
1
      
(3%)
    
1
      
(3%)
  
  

    
 
    
Controls
    
62
      
(94%)
    
1
      
(1.5%)
    
2
      
(3%)
    
1
      
(1.5%)
  

Table 2:  Number of patients with MS and controls in each of the above categories. Note that more than one type of pain was possible for the same individual.Pain
was significantly more frequent in patients with MS than in controls (** p=0.0001), while the use of alcohol was significantly higher among controls (* p=0.01). Other
parameters did not show statistical significance difference or correlation for either patients or controls.

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Citation: Olmo NRS, de Melo STL, de Brito LA and Fragoso YD. Patients with Multiple Sclerosis Present more Chronic and Recurrent Pain than a Control Population. Austin J Mult Scler & Neuroimmunol. 2014;1(1): 1005.

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