title: On the threshold - evaluation of variability in effects of acupuncture in a gender perspective.
abstract: Variable results of pain alleviation in response to acupuncture have been reported, complicating its interpretation. Sources of variability are probably multi-factorial, including the contribution of gender related effects. Gender related variation in perceived pain has been discussed frequently, but documented effects of acupuncture referring to gender are sparse. Furthermore, factors such as operationalisation of the outcome variable and the statistical method for evaluation could also be sources of variability. When pain is regarded as subjective, the produced data should be treated as ordinal. The rank-based method by Svensson, taking the non-metric qualities of the ordinal data into account as well as the variability at the group and the individual level, is therefore an alternative. The present commentary aims to (1) evaluate changes in electrical sensory thresholds and electrical pain thresholds after low frequency electro-acupuncture separately in healthy women and men; (2) introduce and exemplify the method by Svensson in a user-friendly approach. To analyze the systematic patterns of change in thresholds, indicating evidence of treatment on a group level, the relative position (RP) and relative concentration (RC), were measured. The variation related to the individual, the relative rank variation (RV) was also measured. The results were divergent between women (n = 23) and men (n = 22), i.e. unchanged sensory threshold after acupuncture at the group level in women while changed in men. The assessed pain threshold after acupuncture on the other hand was changed towards higher levels in women and unchanged in men. The individual variation was apparent in both women and men but larger in women. For statistical analysis of the variability for both group and individual related effects, the rank-based method by Svensson could be used. The present study indicates that evaluation of sensory and pain threshold response should be analysed separately in women and men.
authors.affiliation: Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden. Irene.Lund@ki.se.
authors.forename: Iréne
authors.initials: I
authors.lastname: Lund
authors.forename: Thomas
authors.initials: T
authors.lastname: Lundeberg
references.citation: J Postgrad Med. 2008 Jul-Sep;54(3):214-6
references.pmid: 18626172
references.citation: Stat Med. 1998 Dec 30;17(24):2923-36
references.pmid: 9921610
references.citation: Horm Behav. 2006 Jun;50(1):1-7
references.pmid: 16423353
references.citation: BMJ. 2004 Nov 20;329(7476):1216
references.pmid: 15494348
references.citation: BMC Complement Altern Med. 2006 May 23;6:20
references.pmid: 16719906
references.citation: Prog Neuropsychopharmacol Biol Psychiatry. 2000 Apr;24(3):385-95
references.pmid: 10836487
references.citation: Rheumatology (Oxford). 2008 Jun;47(6):887-93
references.pmid: 18403402
references.citation: Ann Neurol. 2008 Apr;63(4):507-12
references.pmid: 18300313
references.citation: Arch Phys Med Rehabil. 1989 Apr;70(4):308-12
references.pmid: 2535599
references.citation: Health Phys. 2007 Jun;92(6):591-5
references.pmid: 17495660
references.citation: Ann Intern Med. 2007 Jun 19;146(12):868-77
references.pmid: 17577006
references.citation: Acupunct Med. 2007 Jun;25(1-2):29-35
references.pmid: 17641565
references.citation: BMJ. 2005 Aug 13;331(7513):376-82
references.pmid: 16055451
references.citation: Med Hypotheses. 1995 Sep;45(3):271-81
references.pmid: 8569551
references.citation: Pain. 2007 Nov;132 Suppl 1:S1-S2
references.pmid: 17951005
references.citation: Lancet. 2005 Jul 9-15;366(9480):136-43
references.pmid: 16005336
references.citation: Acupunct Med. 2008 Jun;26(2):111-20
references.pmid: 18591910
references.citation: J Rehabil Med. 2001 Nov;33(6):279-83
references.pmid: 11766958
references.citation: Pain. 2006 May;122(1-2):81-9
references.pmid: 16527396
references.citation: Curr Rheumatol Rep. 2007 Dec;9(6):473-81
references.pmid: 18177601
references.citation: J Rehabil Med. 2002 Nov;34(6):251-9
references.pmid: 12440798
references.citation: Nat Neurosci. 2002 Nov;5 Suppl:1062-7
references.pmid: 12403987
references.citation: Acupunct Med. 2006 Sep;24(3):109-17
references.pmid: 17013357
references.citation: J Clin Epidemiol. 2007 Mar;60(3):280-7
references.pmid: 17292022
references.citation: Acupunct Med. 2008 Mar;26(1):33-45
references.pmid: 18356797
references.citation: Arch Intern Med. 2006 Feb 27;166(4):450-7
references.pmid: 16505266
references.citation: Physiother Theory Pract. 2005 Apr-Jun;21(2):81-92
references.pmid: 16392461
references.citation: J Rehabil Med. 2001 Jan;33(1):47-8
references.pmid: 11480471
references.citation: Headache. 2006 Nov-Dec;46(10):1492-502
references.pmid: 17115982
references.citation: BMC Complement Altern Med. 2008 May 01;8:18
references.pmid: 18452622
references.citation: Man Ther. 2009 Feb;14(1):3-12
references.pmid: 18511329
references.citation: Rheumatology (Oxford). 2007 Mar;46(3):384-90
references.pmid: 17215263
references.citation: Neurosci Lett. 2005 Feb 28;375(2):75-80
references.pmid: 15670645