title: Impaired sweating responses to a passive whole body heat stress in individuals with multiple sclerosis.
abstract: Multiple sclerosis (MS) is an autoimmune disease that affects the central nervous system (CNS), disrupting autonomic function. The aim of this study was to test the hypothesis that individuals with MS have blunted control of thermoregulatory reflex increases in sweat rate (SR) and cutaneous vasodilation compared with controls during a passive whole body heat stress (WBH). Eighteen individuals with relapsing-remitting MS and 18 healthy controls (Con) participated in the study. Core temperature (Tcore), skin temperature, heart rate, arterial blood pressure (10-min intervals), skin blood flow (laser-Doppler flux, LDF), and SR were continuously measured during normothermic baseline (34°C water perfusing a tube-lined suit) and WBH (increased Tcore0.8°C via 48°C water perfusing the suit). Following WBH, local heaters were warmed to 42°C, inducing peak cutaneous vasodilation at the site of LDF collection. Cutaneous vascular conductance (CVC) was calculated as the ratio of LDF to mean arterial pressure and expressed as a percentage of peak achieved during local heating. Individuals with MS had attenuated SR responses to WBH (ΔSR from baseline: Con, 0.65 ± 0.27; MS, 0.42 ± 0.17 mg·cm-2·min-1,P= 0.003), whereas Δ%CVC42Cfrom baseline was similar between groups (Con, 42 ± 16%; MS, 38 ± 12%,P= 0.39). SR responses were blunted as a function of Tcorein MS (interaction: group × Tcore,P= 0.03), of which differences were evident at ΔTcore0.7°C and 0.8°C (P< 0.05). No interaction was observed in Δ%CVC42CTaken together, the findings show MS blunts sweating responses, whereas control of the cutaneous vasculature is preserved, in response to WBH.NEW & NOTEWORTHYThis study is the first to assess the reflex control of the thermoregulatory system in individuals living with multiple sclerosis (MS). The novel findings are twofold. First, attenuated increases in sweat rate in subjects with MS compared with healthy controls were observed in response to a moderate increase (0.8°C) in core temperature via passive whole body heat stress. Second, it appears the reflex control of the cutaneous vasculature is preserved in MS.
authors.affiliation: Department of Applied Physiology & Wellness, Southern Methodist University, Dallas, Texas; and.
authors.forename: Dustin R
authors.initials: DR
authors.lastname: Allen
authors.affiliation: Department of Applied Physiology & Wellness, Southern Methodist University, Dallas, Texas; and.
authors.forename: Mu
authors.initials: M
authors.lastname: Huang
authors.affiliation: Department of Applied Physiology & Wellness, Southern Methodist University, Dallas, Texas; and.
authors.forename: Iqra M
authors.initials: IM
authors.lastname: Parupia
authors.affiliation: Department of Applied Physiology & Wellness, Southern Methodist University, Dallas, Texas; and.
authors.forename: Ariana R
authors.initials: AR
authors.lastname: Dubelko
authors.affiliation: Department of Neurology & Neurotherapeutics, University of Texas Southwestern Medical Center, Dallas, Texas.
authors.forename: Elliot M
authors.initials: EM
authors.lastname: Frohman
authors.affiliation: Department of Applied Physiology & Wellness, Southern Methodist University, Dallas, Texas; and sldavis@smu.edu.|Department of Neurology & Neurotherapeutics, University of Texas Southwestern Medical Center, Dallas, Texas.
authors.forename: Scott L
authors.initials: SL
authors.lastname: Davis
mesh_terms: D000328:Adult; D001794:Blood Pressure; D016022:Case-Control Studies; D005260:Female; D006339:Heart Rate; D018869:Heat-Shock Response; D006801:Humans; D008297:Male; D008875:Middle Aged; D020529:Multiple Sclerosis, Relapsing-Remitting / Q000503:physiopathology*; D012867:Skin / Q000098:blood supply; D012881:Skin Temperature; D013546:Sweating; D014664:Vasodilation
keywords: autonomic dysfunction; cutaneous vascular conductance; skin blood flow; sweat rate; thermoregulation