Fibromyalgia and Obesity

The Association Between Body Mass Index and Disability, Depression, History of Abuse, Medications, and Comorbidities

Carmen E. Gota, MD; Sahar Kaouk; William S. Wilke, MD


J Clin Rheumatol. 2015;21(6):289-295. 

In This Article

Materials and Methods

Consecutive patients with FM who were new to the Rheumatology Department at the Cleveland Clinic (Cleveland, OH) diagnosed by 2 physicians (W.S.W. and C.E.G.) were enrolled in the Cleveland Clinic Fibromyalgia Cohort. The current study includes the first 305 consecutive patients seen between September 1, 2008, and January 31, 2011. Enrollment was based on the clinician's (W.S.W. or C.E.G.) clinical diagnosis of FM.

All patients evaluated met the American College of Rheumatology (ACR) 1990 FM criteria[1] and/or the survey criteria for FM.[18] The survey criteria include the regional pain score (RPS), the sum of 19 nonarticular painful sites, and the 0- to 10-point visual analog scale (VAS) fatigue scale (VAS fatigue). The survey criteria allow the calculation of the Symptom Intensity Scale (SIS) score, which is the result of (RPS/2 + VAS fatigue)/2; the SIS score ranges from 0 to 9.75; the cutoff point for FM diagnosis is 5.75.[18,19] An RPS score of 8 or greater together with VAS fatigue of 6 or greater constitutes sufficient criterion for the diagnosis of FM.[19] Clinical and survey criteria were found to be concordant in 74.8% of cases.[11,19] The Cleveland Clinic institutional review board approved this study.

As a measure of obesity, we used the BMI. The World Health Organization defines weight categories as follows: underweight, BMI less than 18.5 kg/m2; normal weight, BMI 18.5 to 24.9 kg/m2; overweight, BMI 25 to 29.9 kg/m2; and obese, BMI of 30 kg/m2 or greater. Obese patients can be further classified based on BMI as class I, BMI 30 to 34.9 kg/m2, class II, BMI 35 to 39.9 kg/m2, and class III, BMI of 40 kg/m2 or greater.[3]

Detailed demographic, socioeconomic, clinical data, medical, surgical, and psychiatric history and treatment data were collected. Patient-reported symptoms, such as pain, fatigue, and nonrefreshing sleep, were recorded as yes/no. Under medical comorbidities, we recorded medical conditions for which the patients had other doctor visits and/or were prescribed medications, such as, but not limited to, hypertension; coronary artery disease and its variants including angina pectoris, myocardial infarction, peripheral artery disease, heart failure, and valvular disease; diabetes mellitus; malignancies; asthma; chronic obstructive pulmonary disease; hypothyroidism; polycystic ovarian disease; autoimmune diseases such as rheumatoid arthritis, systemic lupus, and ulcerative colitis; peripheral neuropathy; stroke; and deep vein thrombosis. All of the enrolled patients with hypothyroidism were receiving thyroid hormone replacement and were assumed to be clinically euthyroid.

The following categories of medications were recorded (taking yes/no): selective serotonin reuptake inhibitor (SSRI) and serotonin norepinephrine reuptake inhibitor (SNRI), tricyclic and tetracyclic antidepressants, other antidepressants (bupropion, trazodone), antipsychotics/mood-stabilizing drugs, stimulants, barbiturates, benzodiazepines, nonnarcotic analgesics (paracetamol and tramadol), nonsteroidal anti-inflammatory drugs, narcotics, antiseizure analogs of γ-aminobutyric acid (gabapentinoids) (pregabalin or gabapentin), muscle relaxants, sleep medications, and other medications for FM. We summed all the medications taken in these categories to determine the total number of mediations taken for FM.

The Patient Health Questionnaire 9 (PHQ-9) can be used either as a diagnostic tool to make a probable diagnosis of major depressive disorder or as a continuous measure with scores ranging from 0 to 27.[20] Using a cutoff point of 10, PHQ-9 has sensitivity between 77% and 88% and specificity between 88% and 94% for the diagnosis of depression.[20–23]

The Brief PHQ anxiety module focused on anxiety and panic symptoms. We used the yes/no answer to the question, "In the last 4 weeks, have you had an anxiety attack, feeling fear or panic?" The Mood Disorder Questionnaire (MDQ) is a self-reported inventory that screens for lifetime history of manic or hypomanic syndrome; a modified MDQ, using a cutoff of 7 or more "yes" answers to the items included in question 1, without taking into account symptom clustering and severity in questions 2 and 3, was found to have a sensitivity of 68% to 81% and specificity of 63% to 95% for the diagnosis of bipolar disorder.[24,25]

The Epworth Sleepiness Scale (ESS) measures daytime sleepiness, by rating on a scale of 0 to 3 the chances of dozing in each of 8 different situations. An ESS score of 10 or higher is encountered in patients with various sleep problems, such as sleep apnea, narcolepsy, and restless leg syndrome.[26,27] In 1 study, 60% of FM patients who scored 10 or higher on ESS were found to have a positive study for sleep apnea.[28]

The FIQ has been extensively used as an outcome measure in FM-related studies. The FIQ is composed of 10 questions. The first question of FIQ disability index contains 11 items related to the ability to perform large muscle tasks, each rated on a 4-point Likert scale; questions 2 FIQ feel good and 3 FIQ missed work ask the patient to mark the number of days he/she felt well and the number of days he/she was unable to work because of FM symptoms. Items 4 to 10 are 0- to 10-point VAS to rate FIQ do job, FIQ pain, FIQ fatigue, FIQ morning tiredness, FIQ stiffness, FIQ anxiety, and FIQ depression. The maximum possible score is 100.[29]

The disability domain of the Health Assessment Questionnaire Disability Index (HAQ-DI) measures patients' abilities using their usual equipment through 8 categories: dressing and grooming, arising, eating, walking, hygiene, reach, grip, and common activities. There are 4 possible responses for each question: without any difficulty = 0, with some difficulty = 1, with much difficulty = 2, and unable to = 3. The sum of the computed categories scores is then divided by the number of questions answered. This gives a score in the 0- to 3-point range.[30]

Statistical Analysis

Continuous variables were presented as mean (SD). Variables recorded as yes/no are presented as percentage of yes cases. Comparisons across the BMI groups were performed using 1-way analysis of variance for continuous variables and χ2 tests for categorical variables. A Bonferroni correction for multiple comparisons was applied for post hoc pairwise tests. Bivariate relations between variables were examined with Pearson and Spearman correlation tests. A multivariable model of BMI was built from variables that demonstrated bivariate correlations with BMI. Variables demonstrating little importance for predicting BMI were excluded using a step-down procedure, and penalized estimation was used. The significance level was set at α = 0.05 for all analyses. Data analysis was conducted in SPSS version 21 (SPSS Inc, Chicago, IL).