BMI but not age and sex negatively impact on the outcome of pharmacotherapy in fibromyalgia: a systematic review.

Introduction: The impact of sex, age, body mass index (BMI) in fibromyalgia is still unclear. A systematic review was conducted to investigate whether sex, age and BMI influence the clinical outcomes and rate of adverse events.

Methods: The present study was performed according to the PRISMA guidelines. The literature search was performed in February 2021. All the RCTs investigating pharmacological strategies for fibromyalgia were accessed.

Results: Data from 51 RCTs (17,311 patients) were collected. Short Form 36 emotional, Social function and physical role subscales showed evidence of a negative association with BMI (P = 0.02, P = 0.002 and P = 0.0001, respectively). Depression and anxiety subscales of the Hospital Anxiety and Depression score demonstrated evidence of a positive association with age (P = 0.04 and P = 0.001, respectively) and sex (P = 0.00005 and P = 0.0001, respectively). Visual analog scale evidenced a positive association with BMI (P = 0.04). Clinical Global Impression Severity scale demonstrated evidence of a negative association with BMI (P = 0.02).

Conclusion: Irrespective from the pharmacological approach, a higher BMI is negatively associated with a favorable outcome in patients with fibromyalgia. The association with sex and age remains controversial.

Level Of Evidence: I, systematic review of RCTs.