ORIGINAL CONTRIBUTION Pain in Patients With Multiple Sclerosis A Population-Based Study Kristina Bacher Svendsen, MD; Troels Staehelin Jensen, MD; Kim Overvad, PhD; Hans Jacob Hansen, MD; Nils Koch-Henriksen, MD; Flemming W. Bach, MD Background: Pain is an important symptom in pa- Results: Response rates for MS patients and reference sub- tients with multiple sclerosis (MS). The estimated pain jects were 81.3% and 63.3%, respectively. Pain in the month prevalence varies between 30% and 90%. To our knowl- preceding assessment occurred in 79.4% of MS patients and edge, previous studies do not include a whole popula- in 74.7% of reference subjects (prevalence proportion ra- tion sample of patients with MS. tio, 1.06; 95% confidence interval, 0.99-1.13). Patients with MS had a higher pain intensity (“when pain is at its least” Objective: To assess pain prevalence and its clinical char- median visual analog scale score, 20.0 vs 11.0 mm [PϽ.01]; acteristics and impact on daily life in a population sample and “when pain is at its worst” median visual analog scale of MS patients and in a reference group. score, 68.0 vs 55.0 mm [PϽ.01]). Daily intake of analge- sics occurred in 24.4% of MS patients and 9.0% of refer- Design: Postal survey. ence subjects (prevalence proportion ratio, 2.7; 95% con- fidence interval, 2.0-3.6). Patients with MS more often Setting: Aarhus County, Denmark. reported that pain interfered with daily life “most of the time” or “all the time.” Participants: The population of patients with definite MS in Aarhus County (n=771) and a sex- and age-stratified ref- Conclusions: The frequency of reported pain in MS patients erence group from the general population (n=769). was not higher than in the background population. How- ever, pain intensity, the need for analgesic treatment, and Main Outcome Measures: Pain prevalence, inten- the impact of pain on daily life were higher in MS patients. sity, and treatment requirement; and the impact of pain on daily life. Arch Neurol. 2003;60:1089-1094 ULTIPLE SCLEROSIS found that pain affected the ability of a pa- (MS) is a chronic dis- tient with MS to perform as a worker, part- ease with no curative ner, parent, and friend. treatment. Accord- The present study (a) assesses the ingly, symptomatic pain prevalence in the preceding month Mtreatment is important. Pain has not pre- in a population sample of MS patients; (b) viously been considered an important el- assesses pain prevalence in a sex- and age- ement of MS, but in recent years, acute and stratified reference group from a back- chronic pain syndromes have been recog- ground population; and (c) compares pain nized as symptoms in patients with MS.1-11 prevalence, characteristics, treatment, and From the Danish Pain Research impact on daily life in the 2 groups. Center (Drs Svendsen, Jensen, The reported prevalence of pain in pa- and Bach) and the Department tients with MS differs considerably, with 1-3,5-14 of Neurology (Drs Jensen, figures ranging from 30% to 90%. Pre- METHODS Hansen, and Bach), Aarhus vious studies differ in design and type of University Hospital, Aarhus; pain registered. To our knowledge, no A postal survey concerning pain in the pre- the Department of study has been based on a representative ceding month was undertaken in the popula- Epidemiology and Social sample of the whole population of MS pa- tion of MS patients in Aarhus County, Den- Medicine, University of Aarhus, tients. mark, and in a sex- and age-stratified reference Aarhus (Dr Overvad); and the The presence of pain may influence group drawn from a general population. The Department of Neurology, population in Aarhus County includes 640000 quality of life and daily activities. In a pre- Aalborg Hospital, Aalborg, and 8 inhabitants. Invitations to participate, along the Danish Multiple Sclerosis vious study, one third of the MS patients with questionnaires, were mailed to potential Registry, Copenhagen indicated that pain was the worst symp- participants between January 18, and April 26, (Dr Koch-Henriksen), tom of MS. Archibald et al1 evaluated the 2001. Nonresponders received a reminder 1 Denmark. effect of pain on social performance, and month after the first mailing. (REPRINTED) ARCH NEUROL / VOL 60, AUG 2003 WWW.ARCHNEUROL.COM 1089 ©2003 American Medical Association. All rights reserved. Downloaded From: https://jamanetwork.com/ on 10/01/2021 dence intervals (CIs) were calculated. Bivariate analyses (Mantel- Danish Multiple Sclerosis Haenszel) were used to assess the impact of other pain treatment Registry Known in Not Known in on analgesic drug consumption. Differences in median visual the MS Clinic Patients With MS the MS Clinic analog scale scores were analyzed using the Mann-Whitney test. (n = 679) or Suspected MS (n = 180) in Aarhus County ␹2 Test statistics were used, comparing 2 or more frequencies (N = 860) (including pain treatment requirement and the impact of pain or physical health on daily life). Individuals with missing in- formation from the questionnaire were excluded from the spe- Uncertain Dead Patients Diagnosis Diagnosis cific analysis. (n = 1) Letter Not Not or Patient to GP Registered Confirmed Not (n = 197) With a GP (n = 19) Informed? (n = 2) (n = 19) RESULTS At study start (December 12, 2000), 860 subjects in Diagnosis Confirmed Diagnosis GP Could Aarhus County who were 18 years or older were regis- and Patient Informed Confirmed Not Confirm (n = 641) and Diagnosis tered in the Danish Multiple Sclerosis Registry with defi- Patient (n = 36), 15 Informed Patient nite or probable MS (using the criteria of Poser et al ). (n = 130) Dead (n = 5), The inclusion and exclusion of patients is shown in Patient Unable to Figure 1. Questionnaires were mailed to 771 MS pa- Questionnaire Answer or tients and 769 reference subjects. After 1 written re- (n = 771) Not Aware About minder, 627 (81.3%) of the MS patients and 487 (63.3%) Diagnosis of the reference subjects had returned the question- (n = 23), Returning the GP Did Not naire. Nonresponders in the MS group were older than Questionnaire Know the responders; no difference was found in sex distribution. (n = 627) [81.3%]) Patient (n = 3) Nonresponders in the reference group did not deviate from (n = 67) responders regarding sex and age. Figure 1. Inclusion and exclusion of patients in the study. The Multiple DEMOGRAPHIC CHARACTERISTICS Sclerosis Clinic was affiliated with the Department of Neurology, Aarhus University Hospital, Aarhus, Denmark. GP indicates general practitioner; MS, multiple sclerosis. No differences in sex distribution and age were found between MS patients and reference subjects (Table 1). The distribution in 10-year age groups was also equal in Patients with MS living in Aarhus County were identified the 2 groups when splitting the groups according to through the Danish Multiple Sclerosis Registry. Inclusion crite- sex. Patients with MS had a lower prevalence of re- ria were as follows: (a) living in Aarhus County, (b) definite MS ported muscle joint disorders than the reference sub- (criteria of Poser et al15), (c) 18 years or older, and (d) patient aware of the diagnosis. To ensure the correctness of the diagno- jects, while the prevalence of other diseases was similar sis and the patient’s awareness of the diagnosis, one of us (H.J.H.), (Table 1). The distribution of educational levels dif- from The MS Clinic, Aarhus, covering all inhabitants of the county, fered between the groups, with a lower educational reviewed the medical records for all patients known in the clinic. level in the MS group (Table 1). In case the patient was unknown in the clinic, the diagnosis was uncertain, or the patient’s knowledge about the diagnosis could MS DISEASE not be documented, the general practitioner was contacted. The general practitioner was asked whether she or he could confirm Of the 627 MS patients who responded to the question- the diagnosis and the patient’s awareness about the diagnosis and naire, 73 (11.6%) reported attacks in the preceding month approve the contact to the individual patient. (ie, an episode [Ն24 hours’ duration] with new neuro- Reference subjects were randomly selected from the same general population as MS patients. They were identified through logical symptoms or aggravation of existing neurological the Central Office of Civil Registration, in which all inhabit- symptoms not associated with fever). Of these 73 pa- ants in each area of Denmark are registered. We obtained in- tients, 46 (63.0%) reported pain during the attack. Of the formation about birth date, name, and address from the regis- 627 responders, 356 (56.8%) reported muscle spasms. Of ter. Inclusion criteria were as follows: (a) sex and age stratified these 356 patients, 47.7% reported painful muscle spasms. to patients with MS and (b) living in Aarhus County. The only exclusion criterion was a diagnosis of MS. PAIN A questionnaire was developed (data available from the authors). Questions about pain focused on pain experienced Pain Prevalence in the month preceding the assessment. Acute and chronic pain syndromes were included. If needed, participants were con- No difference in pain prevalence in the month preced- tacted by telephone for clarifying responses. The local ethical ing the assessment was found (498 [79.4%] of 627 re- committee and the Danish Data Protection Agency approved sponders in the MS group vs 364 [74.7%] of 487 re- the study, which was performed according to the Declaration sponders in the reference group reported pain) (PPR, 1.06; of Helsinki. Comparisons regarding demographic characteristics were 95% CI, 0.99-1.13). In the reference group, 74.0% (304/ conducted using the ␹2 test for categorical data and the non- 411) of subjects answering the first request had pain vs parametric Mann-Whitney test comparing median age.