Association of ferritin levels with depression, anxiety, sleep quality, and physical functioning in patients with fibromyalgia syndrome: a cross-sectional study

AIM: To determine the frequency of ferritin deficiency in individuals with fibromyalgia syndrome (FMS) and to evaluate the association of ferritin level with depression, anxiety, sleep quality, and physical functioning. METHODS: This cross-sectional study, conducted from 2016 to 2017, compared the frequency of ferritin deficiency between 100 non-anemic fibromyalgia patients and 100 non-anemic individuals without FMS. Serum ferritin level of <30 ng/mL indicated iron deficiency. FMS patients filled out demographic questionnaire, Fibromyalgia Impact Questionnaire, Beck Anxiety Inventory, Beck Depression Inventory, and Pittsburg Sleep Quality Index. RESULTS: Median serum ferritin level was 20.95 ng/mL. A total of 64% of patients and 42% of controls had iron deficiency. Beck Anxiety Inventory, Beck Depression Inventory, and Pittsburgh Sleep Quality Index scores were not associated with ferritin levels. FMS patients with poor sleep quality had significantly higher Beck Depression Inventory, Beck Anxiety Inventory, and Fibromyalgia Impact Questionnaire scores (P < 0.05). In individuals with poor sleep quality, lower ferritin levels also correlated with higher Beck Depression Inventory scores (r = -0.277, P < 0.05). Sleep quality was not significantly associated with age, body mass index, duration of diagnosis, and serum ferritin levels. CONCLUSIONS: Patients with fibromyalgia syndrome have a rather high prevalence of non-anemic iron deficiency. No associations were found between serum ferritin level and anxiety, depression, sleep quality, and physical functioning. ClinicalTrials.gov identifier: NCT03825393.