Dear editor:

I have taken a great interest in the recently published article entitled “Reliability of heart period and systolic arterial pressure variabilities in women with fibromyalgia syndrome” by Andrade et al (1). However, I have a few remarks with respect to the methodology of the study.

First, obesity is one of the important factors for cardiovascular problems. The study reported a number 28 ± 2 for mean value of the body mass indexes for the study group which clearly demonstrated an obesity problem for the study group and this factor could change cardiac indices in the study (2, 3). Comparing study group according to patients BMI levels would be more effective for evaluating the outcomes of the study. Another limitation is sleeping problems in the FMS patients was not recorded, which can effect the cardiological indices such as blood pressure, heart rates (4). Patients with FMS could have a lot of comorbid symtoms (e.g., fatigue, depression, sleep disturbance) which is commonly seen in FMS patients and these symptoms are frequent problems which can effect cardiac problems and indices (5). It would be more effective if the study assessed the symptom severity and stress factors for FMS patients by using some specific tests (e.g, Fibromyalgia Impact Questionnaire, Perceived Stress Scale) and comparing the datas with these tests could be more effective for detecting the relationship of cardiac situations with FMS. On the other hand the fifteen day duration in the baseline and second evaluation is not clearly determined (e.g. new treatments, exercise programs, BMI changes). Finally, it seems that these suggestions come from the limited number of the patient group, Accordingly, additional high-quality studies with larger sample sizes (including male patients) and longer study duration are needed in order to further assess the relationship between cardiovascular situations in FMS.