Correlation between nocturnal heart rate variability parameters and circulating neuropeptides in patients suffering from fibromyalgiaPor M.C. Navarro-Gonzalez, Claudia Lerma, F.I. López-Trejo, E. Aranda-Cano, A. Salgado-Aguayo, D. Paz-Gómez, M.I. Barrera-Villalpando, L.H. Silveira, V. Higuera-Ortiz, Manuel Martínez-Lavin, A. Vargas-Guerrero and Laura A. Martínez-Martínez