Body mass index and response to a multidisciplinary treatment of fibromyalgia

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Rheumatol IntDOI 10.1007/s00296-014-3096-x

ORIgInal aRtIcle

Body mass index and response to a multidisciplinary treatment of fibromyalgia

Antoni Castel · Sonia Castro · Ramon Fontova · Maria José Poveda · Rosalia Cascón‑Pereira · Salvador Montull · Anna Padrol · Rami Qanneta · Maria Rull

Received: 2 april 2014 / accepted: 11 July 2014 © Springer-Verlag Berlin Heidelberg 2014

catastrophizing, psychological distress, health-related quality of life, and sleep disturbances. One hundred thirty patients participated in the study. no statistical significant differences regarding pre-treatment outcomes were found among the dif-ferent BMI subgroups, and between the two experimental conditions for each BMI category. general linear model anal-ysis showed a significant interaction group treatment × time in pain intensity (p < .01), functionality (p < .0001), cata-strophizing (p < .01), psychological distress (p < .0001), sleep index problems (p < .0001), and health-related quality of life (p < .05). no significant interactions were found in BMI × time, and in BMI × group treatment × time. there are not differences among normal weight, overweight and obese patients with FM regarding their response to a multi-disciplinary treatment programme for FM which combines pharmacological treatment, education, physical therapy and cognitive behavioural therapy.

Keywords Fibromyalgia · Body mass index · Multidisciplinary treatment · Physical therapy · Psychological therapy

Introduction

Fibromyalgia (FM) is a chronic syndrome characterised by generalised musculoskeletal pain and multiple symptoms that include fatigue, sleep alterations, cognitive dysfunction, and psychological distress [1, 2]. Various studies from the United States and Western europe have indicated that FM has an estimated prevalence between 2 % [3], and 2.9 % [4]. FM is more prevalent in female gender (5, 6), and among people with low educational level [3, 5, 7–9]. Other demo-graphic and social characteristics associated with FM are lower socio-economic status and being divorced [3, 5, 6].

Abstract the purpose of this study is to determine whether there are some differences in the treatment responses to a multidisciplinary fibromyalgia (FM) treatment related with the baseline body mass index (BMI) of the participants. Inclusion criteria consisted of female sex, a diagnosis of FM (american college of Rheumatology criteria), age between 18 and 60 years, and between 3 and 8 years of schooling. Baseline BMI was determined, and patients were randomly assigned to one of the two treatment conditions: conven-tional pharmacologic treatment or multidisciplinary treat-ment. Outcome measures were pain intensity, functionality,

a. castel (*) · a. Padrol · M. Rull Pain clinic, Hospital Universitari de tarragona Joan XXIII, c/Doctor Mallafré guasch, 4, 43007 tarragona, Spaine-mail: [email protected]

a. castel · R. Fontova · M. J. Poveda · R. cascón-Pereira · a. Padrol Multidisciplinary Pain Researh group, IISPV, tarragona, Spain

a. castel Department of Psychology, Universitat Rovira i Virgili, tarragona, Spain

S. castro · R. Fontova · M. J. Poveda Department of Rheumatology, Hospital Universitari de tarragona Joan XXIII, tarragona, Spain

R. cascón-Pereira Business Management Unit, Universitat Rovira i Virgili, Reus, Spain

S. Montull Physiotherapy Unit, Universitat Rovira i Virgili, Reus, Spain

R. Qanneta Fibromyalgia and chronic Fatigue Syndrome Unit, Hospital Universitari de tarragona, tarragona, Spain

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available evidence suggests that obesity and overweight are common in FM, with percentages ranging from 43 to 73 % [10–14]. Furthermore, obesity and overweight have been found to be associated with diverse pain syndromes as axial pain [15–17], migraine [18], or FM [12, 13, 19–22]. Moreover, there is evidence on the relationship between the severity of FM symptoms and the body mass index (BMI) [11, 14, 23, 24].

the guidelines of the american Pain Society (aPS) (2005), the association of the Scientific Medical Societies in germany (aWMF) (2008) and the european league against Rheumatism (eUlaR) (2007) assign a higher grade of evi-dence to a multidisciplinary treatment of FM composed by the combination of pharmacological treatment, education, physical exercise and cognitive behavioural therapy (cBt) [25, 26]. although there is some evidence about the influ-ence of previous patients characteristics such as age, educa-tional level or depression on the effects of multidisciplinary treatments of FM [27, 28], the understanding about the effect of overweight or obesity on treatment outcome in patients with FM remains unexplored [11].

therefore, the purpose of the present study is to deter-mine whether there are some differences in the treatment responses related with the baseline BMI of the participants.

Materials and methods

Participants

this study was performed in accordance with the standards of the clinical Research ethics committee of our institu-tion, and all of the participants signed an informed consent document. Patients of the study were recruited from the rheumatology and pain clinic consultations. Inclusion cri-teria for study participation were as follows: female gender, FM diagnosed according to the american college of Rheu-matology (acR) criteria [29], age between 18 and 60 years old and having between 3 and 8 years of schooling. the exclusion criteria were as follows: one or more additional severe chronic medical pain conditions (e.g. sciatica, lum-bosciatica, patient who underwent arthrodesis), having been under psychiatric and/or psychological specialised treatment within the past 3 years for having severe psycho-pathology (e.g. psychosis, major depression, drug depend-ence), having been diagnosed with inflammatory rheumatic disease, having a cognitive, sensorial or physical important limitation to perform the treatments (e.g. dementia, blind-ness, open wound, skin disease) or a pending legal resolu-tion for disability.

Of the 460 patients initially screened, 199 were excluded for not meeting inclusion criteria, 87 refused to participate, 19 only participated in a pilot study, and 25

were excluded for failing to obtain their BMI. Finally, the study sample consisted of 130 participants with an average age of 49.2 years (range 29–60 years; SD 6.8 years), and an average length of their pain history of 11.8 years (range 0.5–49 years; SD 9.4 years). Of the sample, 77.7 % were married, 15.4 % were separated, 5.4 % were single, and the remaining 1.5 % widow. With regard to their occupa-tion, 53.8 % were currently employed, 33.1 % were house-wife, 6.9 % were unemployed and 6.2 % were receiving a working compensation. a total of 98 % of the sample were caucasian (Fig. 1). Respect to the presence of anxiety and depression assessed by the Hospital anxiety and Depres-sion Scale (HaDS), a cut-off ≥9 was considered [30]. the percentage of participants with a HaDS depression score ≥9 was 54.6 % (mean sample 9.2; SD 4.8), and the per-centage of participants with a HaDS anxiety score ≥9 was 66.9 % (mean sample 12.7; SD 4.4).

BMI determination

the World Health Organization (WHO) criteria for the clas-sification of weight status according BMI was considered. the determination of BMI was performed using objective measures of weight and height, and the participants were classified in the following subgroups: normal weight (BMI 18.5–24.9 kg/m2), overweight (BMI 25.0–29.9 kg/m2), and obesity (BMI ≥ 30 kg/m2). according with this classification, the 31.5 % of our sample was normal weight, the 37.7 % was overweight, and the remaining 30.8 % was obese.

Procedure

Participants who had met all of the inclusion criteria and had accepted to participate in the study were assigned to one of the two treatment conditions (a conventional phar-macological treatment or a multidisciplinary treatment). Patients were randomly assigned 1:1 ratio in blocks of 32 according to a computer-generated random-number table. By this procedure, the groups were composed of partici-pants with different BMI levels.

Before starting with any treatment, BMI was determined and the measurement instruments were applied. In the week immediately after the completion of the treatment, the same measurement instruments were reapplied, and the post-treatment score was obtained. the same instruments were reapplied after 3, 6 and 12 months follow-up. evalua-tors were masked to different treatment conditions.

treatment conditions

all the participants (control group and multidisciplinary group) received a conventional pharmacological treatment, which essentially included analgesics, antidepressants

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(tricyclics, selective serotonin reuptake inhibitors and dual reuptake inhibitors), benzodiazepine and nonbenzodiaze-pine hypnotics [2, 31]. Once baseline measures were taken, the pharmacological treatment started. Just after finish-ing treatment and at 3-, 6- and 12-month follow-up, both

groups of participants were individually attended again by the physician and the initial drug treatment was adjusted when necessary. Drug treatment was adjusted in both groups (control and multidisciplinary) as recommended by guidelines [2, 31].

PRE-TREATMENT (n = 61)

Normal weight: n = 18Overweight: n = 20Obesity: n = 23

PRE-TREATMENT (n = 69)

Normal weight: n = 23Overweight: n = 29Obesity: n = 17

POST-TREATMENT (n = 59)

Normal weight: n = 18Overweight: n = 19Obesity: n = 22

CONTROL GROUP

MULTIDISCIPLINARY GROUP

POST-TREATMENT (n = 69)

Normal weight: n = 23Overweight: n = 29Obesity: n = 17

ScreenedN = 460

Included (N = 130)Number who failed screening:No inclusion criteria: 199Refused to participate: 87Other reasons: 44

3 MONTH FOLLOW-UP (n = 50)

Normal weight: n = 13Overweight: n = 15Obesity: n = 22

3 MONTH FOLLOW-UP (n = 69)

Normal weight: n = 23Overweight: n = 29Obesity: n = 17

6 MONTH FOLLOW-UP (n = 48)

Normal weight: n = 13Overweight: n = 14Obesity: n = 21

6 MONTH FOLLOW-UP (n = 67)

Normal weight: n = 21Overweight: n = 29Obesity: n = 17

12 MONTH FOLLOW-UP (n = 36)

Normal weight: n = 12Overweight: n = 9Obesity: n = 15

12 MONTH FOLLOW-UP (n = 53)

Normal weight: n = 16Overweight: n = 23Obesity: n = 14

Fig. 1 trial profile

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In addition to the pharmacological treatment, the par-ticipants of the multidisciplinary group received cBt, and physical therapy, which were performed in a group for-mat (eight patients per group). the participants underwent a total of 24 sessions at a frequency of 2 days per week. When they attended the treatment sessions, the partici-pants underwent 1 h of cBt and 1 h of physical therapy. the cBt programme was delivered by a clinical psycholo-gist specifically trained for this programme. the physical therapy programme was delivered by a physiotherapist also specifically trained for this programme.

the cBt therapist sought to maximise patient rapport, patient adherence, group cohesion and group discussion related to the session topics. Participants were given a patient guide to follow or discuss during sessions, and read between sessions. also, home tasks were planned and revised every session. the cBt programme included: information about FM, theory of pain perception, cognitive restructuring skills training, cBt for primary insomnia, assertiveness training, goal setting, activity-pacing and pleasant activity-scheduling training, life values and relapse prevention. the physical therapy treatment emphasised aerobic capacity, muscular strengthening and flexibility and incorporated sessions of hydrokinesiotherapy and kinesiotherapy in a gymnasium. the sessions of hydrokinesiotherapy were conducted in a heated pool at 30 °c. each session started with global aerobic exer-cises combined with diaphragmatic breathing. afterwards, exercises to coordinate the upper and lower extremities fol-lowed. Finally, the session ended with relaxation exercises and gentle stretching of thorax muscle groups and limbs [32]. each session of kinesiotherapy in a gymnasium started with breath awareness and the work of pelvic floor muscles. after-wards, exercises that reinforce lumbar stabilization and lum-bar-pelvic dissociation followed. Finally, each session ended with training of the deep cervical muscles. all of the sessions included overall aerobic work, coordination exercises and flexibility exercises. Due to the variability of the physical con-dition of patients with FM, the difficulty of the exercises was individually tailored and progressively increased through the use of resistance media and a slow execution velocity [33]. Physical therapy was supplemented with an exercise routine between sessions and a scheduled daily March to facilitate the incorporation of the regular exercise into daily life. also, the participants practiced Schultz autogenic training [34] (for a more detailed description of the multidisciplinary treatment contents see castel et al. [28]).

Instruments of measure

Numerical Pain Intensity Rating Scale

the patient indicates the maximum, minimum and usual intensities of pain suffered in the last week using a

numerical scale with values ranging from 0 to 10. a value of 0 indicates “no pain”, while a value of 10 indicates “the maximum pain possible”. the average of these three scores was obtained and used as a measure of retrospective pain intensity. this procedure has demonstrated a high degree of reliability as a measure of the pain suffered during a par-ticular period of time [35, 36].

Hospital Anxiety and Depression Scale (HADS) [37]

this scale evaluates the presence of anxiety and depression in clinical settings, and it is widely used in chronic pain studies. the HaDS total score was used as an indicator of psychological distress [38].

Subscale of Catastrophizing from the Coping Strategies Questionnaire (CSQ) [39]

that measures catastrophizing related to pain. the ques-tionnaire is widely used and has shown adequate reliability and validity in different chronic pain pathologies including FM [40].

Fibromyalgia Impact Questionnaire (FIQ) [41]

the FIQ is a ten-item instrument that assesses FM’s impact on patient’s life. the test generates one global score. the higher the FIQ score, the higher the impact of FM on the patient’s life. the FIQ is widely used as an outcome meas-ure for patients with FM, and its reliability and validity have been demonstrated [42, 43].

Medical Outcomes Study (MOS) Sleep Scale [44]

the scale measures the duration and the quality of sleep. the scale has been found to be a reliable and valid assess-ment of sleep disturbances in patients with FM [45, 46]. although the complete scale was administered, only the domains “quantity of sleep” and “sleep problems index” has been considered for analysis.

Dartmouth COOP functional health assessment charts/Wonca [47]

the scale assesses quality of life related to health, in which the higher the score, the worse health-related quality of life. In this study, the global score was con-sidered as measure of quality of life [48]. a global score was obtained corresponding to the sum of all the draw-ings except for the charts of dimension five, correspond-ing to changes in health, which has a bipolar structure and is therefore rated in a different way from the rest [49].

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Data analysis

Demographic and pre-treatment outcome variables were compared, separately for each BMI category of the two treatment groups, using chi-squared tests for categori-cal variables and T test analyses for continuous ones. an intent-to-treat analysis (Itt) was performed that included subjects who dropped out of the trial. Participants with missing data were included in the analysis, and missing final outcome variable values were replaced following last observation carried forward (lOcF) method [50] to diminish the different attrition rates between groups. lin-ear model analysis was performed to determine the effects of the reported treatments on changes in outcome meas-ures for each BMI subgroup. the analysis focused on the fixed effects considering whether there was an interaction between time and group treatment, between time and BMI group, and among time and the two independent variables, group treatment and BMI group. Significant interactions were broken down by exploring pairwise comparisons and corrected by Bonferroni method. Finally, the percentage of patients who experienced a clinically significant change was also calculated, and a cut-off of 30 % was accepted for pain intensity [51] and a cut-off of 14 % was accepted for the FIQ total score [52]. to compare the different BMI groups, pairwise chi-square tests were performed and odds ratios (ORs) were calculated.

Results

no statistical significant differences were found among the different BMI subgroups and between the two experimen-tal conditions for each BMI category, on age, pain dura-tion, number of tender points, marital status, as well as on work status (see table 1). also, when multidisciplinary and control groups were compared separately for each BMI category, no differences were found in any of the outcome baseline measures: pain intensity, catastrophizing, psycho-logical distress, functionality, sleep quantity, sleep index problems and health-related quality of life. Finally, when attendance to cBt sessions and to physiotherapy sessions were compared among the different BMI categories, no significant differences were found (see table 1).

general linear model analysis showed a significant interaction group treatment × time in pain intensity [F = 3.663; p < .01], catastrophizing [F = 4.757; p < .01], psychological distress [F = 10.230; p < .0001], FIQ total score [F = 10.445; p < .0001], sleep index problems [F = 22.532; p < .0001] and health-related quality of life [F = 3.175; p < .05]. no significant interactions were found in BMI × time, and in BMI × group treatment × time in none of the studied variables.

When baseline outcomes were compared with post-treat-ment, 3-month follow-up, 6-month follow-up and 12-month follow-up outcomes, in the normal weight group, post hoc

Table 1 Demographic and clinical data of the participants

continuous variables (mean and standard deviation); qualitative variables (number of subjects and percentage); BMI = body mass index; normal weight (BMI < 25 kg/m2 ), overweight (BMI: 25.0–29.9 kg/m2), obesity (BMI ≥ 30 kg/m2)

Variables control group Multidisciplinary group

normal weight (n = 18)

Over weight (n = 20)

Obesity (n = 23)

normal weight (n = 23)

Over weight (n = 29)

Obesity (n = 17)

age (years) 49.3 (SD 8) 47.7 (SD 7) 49.6 (SD 6.9) 47.8 (SD 7.5) 49.9 (SD 6.3) 51.2 (SD 5)

Marital status

Single 0 (0 %) 2 (10 %) 1 (4.3 %) 2 (8.7 %) 0 (0 %) 2 (11.8 %)

Married 15 (83.3 %) 14 (70 %) 16 (69.6 %) 15 (65.2 %) 26 (89.7 %) 15 (88.2 %)

Separated 3 (16.7 %) 4 (20 %) 6 (26.1 %) 5 (21.7 %) 2 (6.9 %) 0 (0 %)

Widow 0 (0 %) 0 (0 %) 0 (0 %) 1 (4.3 %) 1 (3.4 %) 0 (0 %)

Work status

currently employed 11 (61.1 %) 12 (60 %) 15 (65.2 %) 10 (43.5 %) 14 (48.3 %) 8 (47.1 %)

Housewife 5 (27.8 %) 8 (40 %) 4 (17.4 %) 9 (39.1 %) 10 (34.5 %) 7 (41.2 %)

Unemployed 2 (11.1 %) 0 (0 %) 4 (17.4 %) 2 (8.7 %) 1 (3.4 %) 1 (5.9 %)

Working compensation 0 (0 %) 0 (0 %) 0 (0 %) 2 (8.7 %) 4 (13.8 %) 1 (5.9 %)

Pain duration (years) 11.4 (SD 8.5) 10 (SD 8.3) 11.6 (SD 8.9) 14.1 (SD 12.2) 11.6 (SD 7.7) 13.1 (SD 10.2)

number of tender points 15.1 (SD 2.3) 15.8 (SD 2.1) 15.7 (SD 2.2) 15.4 (SD 2.7) 16.1 (SD 2.0) 15.6 (SD 2.5)

attendance cBt sessions – – – 22.6 (SD 1.3) 22.1 (SD 2.1) 22.4 (SD 1.9)

attendance physiotherapy sessions

– – – 21.7 (SD 2.1) 21.2 (SD 2.5) 21.9 (SD 2.3)

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analyses adjusted with Bonferroni method showed a signif-icant effect of multidisciplinary treatment in catastrophiz-ing, psychological distress, FIQ, sleep quantity, sleep index problems and health-related quality of life. On the contrary, no significant differences were found among the respective levels in none of the studied variables of the control group (see table 2). Regarding the overweight group, the analyses showed a significant effect of multidisciplinary treatment in catastrophizing, psychological distress, FIQ, sleep quantity, sleep index problems and health-related quality of life. no significant effects were found in overweight patients of the control group (see table 3). Finally, in the obesity group, the analyses showed a significant effect of the multidisci-plinary treatment in all the studied variables. In the case of obese patients of the control group, significant changes were found in catastrophizing, and in psychological dis-tress at 3-month follow-up (see table 4).

last, the percentage of participants who met the stand-ard criteria for the minimum clinically significant differ-ence in FIQ total score and pain intensity were calculated (see table 5). In normal weight patients, significant dif-ferences were found between multidisciplinary treatment and control group in FIQ total scores at post-treatment [χ2 = 5.331; p < .05] [OR 4.571; 95 % cI 1.218–17.157], 3-month follow-up [χ2 = 6.740; p < .01] [OR 6.500; 95 % cI 1.467–28.804) and 12-month follow-up [χ2 = 5.487; p < .05] [OR 5.455; 95 % cI 1.235–24.087). Regarding to overweight patients, significant differences between multidisciplinary and control groups were found in FIQ total scores at post-treatment [χ2 = 7.209; p < .01] [OR 5.667; 95 % cI 1.511–21.246], and at 6-month follow-up [χ2 = 5.632; p < .05] [OR 1.909; 95 % cI 1.431–2.547]. Finally, in obesity patients, differences between multidisci-plinary and control groups were found in FIQ total score at post-treatment [χ2 = 16.667; p < .0001] [OR 22.167; 95 % cI 4.264–115.244], at 3-month follow-up [χ2 = 4.183; p < .05] [OR 4.050; 95 % cI 1.025–16.007], at 6-month follow-up [χ2 = 5.914; p < .05] [OR 7.350; 95 % cI 1.287–41.984], and at 12-month follow-up [χ2 = 8.286; p < .01] [OR 15.400; 95 % cI 1.665–142.541]. With regards to pain intensity, significant differences appeared between multi-disciplinary and control groups only with obesity patients at post-treatment [χ2 = 6.484; p < .05] [OR 12.000; 95 % cI 1.281–112.417]. Furthermore, no differences were found among the three BMI groups in the percentages of the standard criteria for the minimum clinically significant difference in FIQ total score and pain intensity.

Discussion

the main findings of this study have been: (1) the patients who underwent the multidisciplinary treatment for FM

improved more compared to the patients who followed the conventional pharmacological treatment, regardless of what was their BMI. (2) no significant differences in the treat-ment response to the multidisciplinary intervention were found among the different BMI groups.

Our results showed that multidisciplinary treatment was more effective than conventional pharmacological treat-ment to improve pain intensity, catastrophizing, psycho-logical distress, functionality, sleep problems and health-related quality of life regardless of whether the treated patient was normal weight, overweight or obese. also, our study indicated that subjects benefited similarly from the multidisciplinary treatment regardless what was their base-line BMI. according to these results, our work concludes that there is no effect of overweight or obesity on treatment outcomes in patients with FM.

In the long-term follow-up, improvements in some key symptoms of FM were maintained 1 year after the comple-tion of the multidisciplinary treatment. In particular, in nor-mal weight patients, data showed the maintenance of the improvements in psychological distress, sleep disturbances, number of hours slept, and health-related quality of life. In overweight patients, recovery was maintained not only in the latter reported measures but also in catastrophizing. Finally, in obese patients, improvements were maintained 1 year after the treatment completion in catastrophizing, number of hours slept, and sleep disturbances. thus, the maintenance of some symptom improvements refutes one of the most common criticisms of the efficacy of a multi-disciplinary treatment for FM, which refers that the thera-peutic benefits are only briefly maintained [26]. Our data also refute the absence of an effective reduction in the number of sleep disturbances in the short term, as this has been maintained [26]. Further and very importantly, our data also support the conclusion that the maintenance of changes does not depend of the patients BMI, as evidenced by the absence of statistically significant differences among the outcomes of the three BMI groups of patients.

the multidisciplinary programme has demonstrated to be effective in increasing functionality to the same extent in patients of all the BMI groups. thus, our results are in con-cordance with those of Kim et al. [11], who did not found discrepancy in the treatment response among the different BMI groups in FIQ total score, just exactly as we do. In our study, when baseline FIQ total score was compared with post-treatment and with 3, 6 and 12-months follow-up, ben-efits in functionality were not maintained over the 6 months. However, this does not mean that the changes were not main-tained beyond. Particularly, when improvements in FIQ total score were considered through the standard criteria for the minimum clinically significant difference, amelioration was maintained in all the BMI groups in about half of the patients 1 year after the multidisciplinary treatment was completed.

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With regards to the improvements in pain intensity, our results are not as satisfactory as Kim et al. [11] reported. In our study, only obese patients demonstrated a signifi-cant amelioration at post-treatment. a probable explanation for this divergence in results may be due to the different

assessment procedures, being this the pain subscale of the FIQ in the study of Kim et al. [11], and the average of three retrospective scores of pain intensity in our study. never-theless, despite these differences, our work it is in line with meta-analytic reviews that concluded the absence of

Table 2 Pre-treatment, post-treatment, 3-month follow-up, 6-month follow-up and 12-month follow-up outcome measures of participants with BMI < 25 kg/m2 (normal weight patients) in each treatment condition

Results are expressed in mean and standard deviation. T test p values were adjusted by Bonferroni Method. Intent-to-treat analysis (Itt) was performed, and missing final outcome variable values were replaced following the last observation carried forward (lOcF) method

Significance: * p < .05; ** p < .01; *** p < .001. Values of significance in the respective line correspond to: baseline post-treatment, baseline 3-month follow-up, baseline 6-month follow-up, and baseline 12-month follow-up

Outcome control group (n = 18) Multidisciplinary group (n = 23)

Pain intensity

Baseline 7.4 ± 1.3 6.8 ± 1.2

Post-treatment 6.8 ± 1.6 5.9 ± 2.4

3-month follow-up 7.1 ± 1.0 6.4 ± 1.9

6-month follow-up 6.7 ± 1.5 6.9 ± 1.6

12-month follow-up 7.0 ± 1.6 6.6 ± 1.6

Catastrophizing

Baseline 20.8 ± 9.1 20.3 ± 12.5

Post-treatment 18.4 ± 9.6 11.0 ± 10.4**

3-month follow-up 19.2 ± 9.6 11.5 ± 11.5*

6-month follow-up 17.4 ± 9.0 11.4 ± 13.2**

12-month follow-up 17.0 ± 9.0 12.9 ± 12.8

Psychological distress

Baseline 21.8 ± 7.8 22.9 ± 8.0

Post-treatment 21.1 ± 9.2 13.9 ± 8.7**

3-month follow-up 21.7 ± 9.0 14.6 ± 9.6**

6-month follow-up 22.1 ± 9.0 16.2 ± 10.1*

12-month follow-up 21.6 ± 9.7 14.4 ± 9.2**

FIQ

Baseline 66.9 ± 13.0 65.1 ± 13.3

Post-treatment 61.9 ± 13.4 45.3 ± 22.4**

3-month follow-up 66.8 ± 15.2 51.8 ± 20.4*

6-month follow-up 66.1 ± 17.2 56.5 ± 21.3

12-month follow-up 66.7 ± 15.4 52.0 ± 23.2

Sleep quantity

Baseline 4.6 ± 1,2 5.7 ± 1,4

Post-treatment 4.8 ± 1.0 6.8 ± 1.2**

3-month follow-up 5.5 ± 1.6 6.7 ± 1.1**

6-month follow-up 5.0 ± 2.0 6.3 ± 1.4

12-month follow-up 5.5 ± 1.6 6.7 ± 1.3*

Sleep index problems

Baseline 24.6 ± 6.1 28.3 ± 8.5

Post-treatment 28.2 ± 6.7 44.0 ± 6.8***

3-month follow-up 27.8 ± 7.2 42.3 ± 9.0***

6-month follow-up 27.9 ± 5.4 39.0 ± 10.1**

12-month follow-up 28.6 ± 6.4 42.1 ± 9.6***

Health-related quality of life

Baseline 27.9 ± 4.6 29.1 ± 4.3

Post-treatment 26.3 ± 5.3 23.4 ± 5.4**

3-month follow-up 27.6 ± 5.2 24.8 ± 6.0*

6-month follow-up 28.2 ± 6.0 25.8 ± 5.8

12-month follow-up 27.6 ± 5.6 25.4 ± 5.8*

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evidences about the efficacy of the multicomponent treat-ment in reducing pain at the long term [26].

Our work has other strengths that must be considered. One is its ecological validity, as evidenced by the similar-ity between the percentage of overweigh and obese patients

(37.7 and 30.8 %, respectively) of our sample, similar to those reported by other authors [10, 12–14]. Second is the length of follow-up, which extends 12 month and which determines the sustainability of the treatment effect. Finally, other strength of our study is related with its rationale, that is, to compare

Table 3 Pre-treatment, post-treatment, 3-month follow-up, 6-month follow-up and 12-month follow-up outcome measures of participants with BMI: 25.0–29.9 kg/m2 (overweight patients) in each treatment conditions

Results are expressed in mean and standard deviation. T test p values were adjusted by Bonferroni Method. Intent-to-treat analysis (Itt) was performed, and missing final outcome variable values were replaced following the last observation carried forward (lOcF) method. BMI: Body Mass Index

Significance: * p < .05; ** p < .01; *** p < .001. Values of significance in the respective line correspond to: baseline post-treatment, baseline 3-month follow-up, baseline 6-month follow-up, and baseline 12-month follow-up

Outcome control group (n = 20) Multidisciplinary group (n = 29)

Pain intensity

Baseline 6.1 ± 2.1 6.3 ± 1.3

Post-treatment 6.1 ± 2.2 5.6 ± 1.7

3-month follow-up 5.6 ± 2.4 6.2 ± 2.1

6-month follow-up 6.0 ± 2.2 6.0 ± 2.0

12-month follow-up 6.2 ± 2.3 6.2 ± 1.9

Catastrophizing

Baseline 20.1 ± 10.0 15.8 ± 11.7

Post-treatment 16.9 ± 11.4 7.9 ± 8.1***

3-month follow-up 16.1 ± 11.8 8.5 ± 8.6**

6-month follow-up 14.1 ± 10.8 7.1 ± 7.7***

12-month follow-up 14.9 ± 11.7 7.1 ± 8.7**

Psychological distress

Baseline 20.8 ± 8.7 20.9 ± 8.1

Post-treatment 20.0 ± 7.9 12.9 ± 8.7***

3-month follow-up 18.7 ± 8.7 12.9 ± 8.1***

6-month follow-up 18.3 ± 8.4 13.8 ± 8.7***

12-month follow-up 20.3 ± 9.9 14.2 ± 9.3***

FIQ

Baseline 57.7 ± 15.8 59.8 ± 17.2

Post-treatment 58.8 ± 17.5 46.4 ± 17.5***

3-month follow-up 57.4 ± 19.8 53.4 ± 18.8

6-month follow-up 58.7 ± 20.0 50.5 ± 19.1*

12-month follow-up 64.5 ± 19.6 56.1 ± 20.1

Sleep quantity

Baseline 5.8 ± 1.4 5.9 ± 1,5

Post-treatment 5.8 ± 1.0 6.6 ± 1.3

3-month follow-up 5.9 ± 1.5 6.5 ± 1.5

6-month follow-up 5.8 ± 1.1 6.6 ± 1.1*

12-month follow-up 5.7 ± 1.1 6.4 ± 1.4

Sleep index problems

Baseline 31.7. ± 9.1 32.4 ± 8.4

Post-treatment 30.7 ± 7.5 42.8 ± 7.4***

3-month follow-up 33.7 ± 9.9 42.5 ± 9.5***

6-month follow-up 32.9 ± 10.1 42.4 ± 8.5***

12-month follow-up 31.4 ± 11.0 40.5 ± 8.7***

Health-related quality of life

Baseline 26.3 ± 5.2 25.8 ± 4.6

Post-treatment 24.3 ± 5.2 22.9 ± 5.7

3-month follow-up 24.5 ± 5.6 23.9 ± 5.4

6-month follow-up 24.8 ± 5.4 23.6 ± 5.5

12-month follow-up 24.5 ± 6.3 23.0 ± 5.3*

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the efficacy of the multidisciplinary treatment with respect to the conventional treatment considering the differences in treatment response among three groups of BMI patients. this allows more accurately determine the response of patients of different BMI groups to multidisciplinary treatment.

nonetheless, our experimental study has some limita-tions that should be considered. Because we have lim-ited our study sample to women with low educational levels, the potential for generalising our results is par-tially restricted. However, this limitation is nuanced by

Table 4 Pre-treatment, post-treatment, 3-month follow-up, 6-month follow-up and 12-month follow-up outcome measures of participants with BMI: ≥ 30 kg/m2 (obesity patients) in each treatment conditions

Results are expressed in mean and standard deviation. T test p values were adjusted by Bonferroni Method. Intent-to-treat analysis (Itt) was performed, and missing final outcome variable values were replaced following the last observation carried forward (lOcF) method. BMI: Body Mass Index

Significance: * p < .05; ** p < .01; *** p < .001. Values of significance in the respective line correspond to: baseline post-treatment, baseline 3-month follow-up, baseline 6-month follow-up, and baseline 12-month follow-up

Outcome control group (n = 23) Multidisciplinary group (n = 17)

Pain intensity

Baseline 7.2 ± 1.2 7.3 ± 1.3

Post-treatment 7.2 ± 1.4 5.4 ± 1.8**

3-month follow-up 7.0 ± 1.9 6.5 ± 1.6

6-month follow-up 7.5 ± 2.1 6.5 ± 2.3

12-month follow-up 7.5 ± 2.0 6.8 ± 1.5

Catastrophizing

Baseline 22.0 ± 10.9 20.1 ± 10.7

Post-treatment 19.2 ± 12.0 8.2 ± 6.7**

3-month follow-up 15.5 ± 11.1* 11.7 ± 10.8

6-month follow-up 18.0 ± 12.3 10.9 ± 10.5**

12-month follow-up 18.6 ± 12.4 10.0 ± 11.0*

Psychological distress

Baseline 24.3 ± 8.5 20.2 ± 8.4

Post-treatment 21.8 ± 9.8 12.5 ± 7.4**

3-month follow-up 18.9 ± 9.2* 14.0 ± 8.6**

6-month follow-up 22.6 ± 9.6 15.3 ± 7.9*

12-month follow-up 23.6 ± 11.0 14.5 ± 10.8

FIQ

Baseline 67.2 ± 17.2 64.7 ± 14.4

Post-treatment 70.2 ± 14.1 42.3 ± 17.0***

3-month follow-up 64.0 ± 18.9 53.2 ± 17.7*

6-month follow-up 73.9 ± 19.0 56.5 ± 20.9

12-month follow-up 74.9 ± 13.9 56.8 ± 20.4

Sleep quantity

Baseline 5.2 ± 1.3 5.0 ± 1.7

Post-treatment 6.1 ± 1.5 6.0 ± 1.5

3-month follow-up 5.5 ± 1.6 6.3 ± 1.6*

6-month follow-up 5.5 ± 1.3 6.2 ± 1.7**

12-month follow-up 5.8 ± 1.3 6.2 ± 1.9*

Sleep index problems

Baseline 27.1. ± 7.8 28.9 ± 9.1

Post-treatment 29.3 ± 8.7 43.8 ± 6.9***

3-month follow-up 31.1 ± 9.4 42.3 ± 9.0***

6-month follow-up 27.3 ± 9.5 40.5 ± 9.2**

12-month follow-up 29.3 ± 8.3 40.0 ± 10.1**

Health-related quality of life

Baseline 27.4 ± 5.7 26.3 ± 5.7

Post-treatment 26.3 ± 6.1 22.2 ± 6.6

3-month follow-up 25.3 ± 5.7 24.2 ± 6.6

6-month follow-up 27.0 ± 7.3 23.3 ± 6.1

12-month follow-up 27.0 ± 6.4 23.3 ± 7.2

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the fact that the majority of the FM patients of the gen-eral population are women, and by the fact that a high percentage of them have a low educational level. also, our results could be criticised by other restrictive crite-ria followed in the selection of the sample, as was the absence of severe psychopathology. nevertheless, this limitation is tempered by the fact that over half of our sample has significant levels of depression and anxiety, in line with that found in similar studies [53]. the fact that this study relied on a relatively small sample is also an important limitation since it limits the power of the present analysis. thus, studies with larger samples are needed to draw more definitive conclusions about corre-lates of multidisciplinary treatment for FM considering the different BMI of the treated patients. another limita-tion of our work is related to the fact BMI was assessed only at baseline and not over follow-up. therefore, we can not determine whether the treatment effect was con-ditioned by changes in BMI. Finally, beliefs and expec-tancies about treatment were not assessed, and as have been demonstrated, are significant predictor variables of treatment outcomes in cBt of chronic pain patients, FM included [54].

In conclusion, there are not differences among normal weight, overweight and obese patients with FM regarding their response to a multidisciplinary treatment programme for FM which combines pharmacological treatment, educa-tion, physical therapy and cBt.

Acknowledgments We would like to thank Marta Salvat, Patricia Zaldívar and eva luque, scholarships holder in our unit, for their effi-cient collaboration in the project. We would also like to thank all the participants for their collaboration and patience, without whom we would not have been able to accomplish this study. Supported by the Foundation Marató tV3 grant number 070910.

Conflict of interest none of the authors have any conflict of interests.

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Results are expressed in number of subjects with clinically significant differences and percentage; BMI = Body mass index; normal weight (BMI < 25 kg/m2 ); overweight (BMI: 25.0–29.9 kg/m2); obesity (BMI > 30 kg/m2)

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