title: Nocturnal heart rate variability parameters as potential fibromyalgia biomarker: correlation with symptoms severity.
abstract: BACKGROUND
  At present, there is neither a laboratory test nor an imaging technique able to differentiate people with fibromyalgia (FM) from healthy controls. This lack of an objective biomarker has hampered FM recognition and research. Heart rate variability (HRV) analyses provide a quantitative marker of autonomic nervous system activity. Nighttime is a stable period in which most people are resting. Sleep is modulated by autonomic activity. Sleeping problems are prominent in FM. The objectives of this study are: 1) to explore different nocturnal HRV parameters as potential FM biomarkers and 2) to seek correlation between such HRV parameters and diverse FM symptoms.
  
  
  METHODS
  We studied 22 women suffering from FM and 22 age-matched controls. All participants filled out several questionnaires related to FM symptoms. All participants used a Holter monitor over 24 hours while undertaking their routine activities during the day and while sleeping at their homes at night. Time-domain HRV parameters analyzed from 0000 to 0600 hours included, among others: mean normal-normal interbeat intervals (mean NN), standard deviation of the NN intervals (SDNN), and standard deviation of the successive NN differences (SDSD).
  
  
  RESULTS
  Nocturnal SDNN of less than 114 ms had the greatest predictive value to set apart patients from controls with an odds ratio of 13.6 (95% confidence interval: 3.9 to 47.8). In patients, decreased nighttime HRV markers indicative of sympathetic predominance had significant correlations with several FM symptoms: SDSD was associated with pain intensity (r = -0.65, P = 0.001). SDNN correlated with constipation (r = -0.53, P = 0.001), and mean NN with depression (r = -0.53, P = 0.001). Controls displayed an opposite behavior. For them, increased nighttime SDNN correlated with Fibromyalgia Impact Questionnaire scores (r = 0.69, P = 0.001) and with other FM symptoms.
  
  
  CONCLUSIONS
  Nocturnal HRV indices indicative of sympathetic predominance are significantly different in FM women when compared to healthy individuals. In FM patients, these HRV parameters correlated with several symptoms including pain severity. Opposite associations were seen in controls. FM may not be just one end of a continuous spectrum of common symptoms. Nocturnal HRV analyses are potential FM biomarkers.
authors.affiliation: Electromechanical Instrumentation Department, National Institute of Cardiology Ignacio Chavez, Mexico, Juan Badiano 1, 14080. Mexico City, Mexico.
authors.forename: Claudia
authors.initials: C
authors.lastname: Lerma
authors.forename: Aline
authors.initials: A
authors.lastname: Martinez
authors.forename: Natllely
authors.initials: N
authors.lastname: Ruiz
authors.forename: Angelica
authors.initials: A
authors.lastname: Vargas
authors.forename: Oscar
authors.initials: O
authors.lastname: Infante
authors.forename: Manuel
authors.initials: M
authors.lastname: Martinez-Lavin
mesh_terms: D000328:Adult; D001341:Autonomic Nervous System / Q000503:physiopathology; D016022:Case-Control Studies; D002940:Circadian Rhythm / Q000502:physiology*; D003937:Diagnosis, Differential; D015716:Electrocardiography, Ambulatory; D005260:Female; D005356:Fibromyalgia / Q000175:diagnosis* / Q000503:physiopathology*; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D011379:Prognosis; D012372:ROC Curve; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires; D055815:Young Adult
references.citation: J Rheumatol. 2009 Sep;36(9):2009-16
references.pmid: 19684146
references.citation: Semin Arthritis Rheum. 2010 Jun;39(6):448-53
references.pmid: 19250656
references.citation: BMC Musculoskelet Disord. 2002;3:2
references.pmid: 11860612
references.citation: J Rheumatol. 2006 Nov;33(11):2291-9
references.pmid: 16960921
references.citation: Psychosom Med. 1975 Jul-Aug;37(4):341-51
references.pmid: 169541
references.citation: Neurology. 1999 Feb;52(3):523-8
references.pmid: 10025781
references.citation: Med Hypotheses. 2009 Jan;72(1):64-6
references.pmid: 18845401
references.citation: Med Care. 1992 Jun;30(6):473-83
references.pmid: 1593914
references.citation: J Appl Physiol (1985). 2006 Aug;101(2):676-8; discussion 681-2
references.pmid: 16645191
references.citation: Arthritis Res Ther. 2008;10(4):211
references.pmid: 18768089
references.citation: Biomed Sci Instrum. 2007;43:158-63
references.pmid: 17487074
references.citation: Eur Heart J. 2009 Mar;30(6):689-98
references.pmid: 19155249
references.citation: J Rheumatol. 1991 May;18(5):728-33
references.pmid: 1865419
references.citation: Fut Rheumatol. 2008 Oct 1;3(5):475-483
references.pmid: 19890437
references.citation: Arthritis Res Ther. 2007;9(5):R110
references.pmid: 17961261
references.citation: Rheumatol Int. 2012 Feb;32(2):427-30
references.pmid: 21120493
references.citation: Arthritis Rheum. 1998 Nov;41(11):1966-71
references.pmid: 9811051
references.citation: Clin Pharmacol Ther. 2001 Mar;69(3):89-95
references.pmid: 11240971
references.citation: Arthritis Res Ther. 2007;9(4):216
references.pmid: 17626613
references.citation: J Clin Rheumatol. 2009 Jun;15(4):172-6
references.pmid: 19342959
references.citation: Arthritis Rheum. 1990 Feb;33(2):160-72
references.pmid: 2306288
references.citation: Ann Rheum Dis. 1996 Jul;55(7):482-5
references.pmid: 8774169
references.citation: Acta Psychiatr Scand. 1983 Jun;67(6):361-70
references.pmid: 6880820
references.citation: Clin Physiol Funct Imaging. 2003 Mar;23(2):72-80
references.pmid: 12641600
references.citation: Arthritis Rheum. 2009 Jul;60(7):2169-73
references.pmid: 19565482