title: Daytime variation in ambient temperature affects skin temperatures and blood pressure: Ambulatory winter/summer comparison in healthy young women.
abstract: It is widely accepted that cold exposure increases peripheral vascular resistance and arterial blood pressure (BP) and, hence, increases cardiovascular risk primarily in the elderly. However, there is a lack of concomitantly longitudinal recordings at personal level of environmental temperature (PET) and cardiophysiological variables together with skin temperatures (STs, the “interface-variable” between the body core and ambient temperature). To investigate the intra-individual temporal relationships between PET, STs and BP 60 healthy young women (52 completed the entire study) were prospectively studied in a winter/summer design for 26 h under real life conditions. The main hypothesis was tested whether distal ST (Tdist)mediates the effect of PET-changes on mean arterial BP (MAP). Diurnal profiles of cardiophysiological variables (including BP), STs and PET were ambulatory recorded. Daytime variations between 0930 and 2030 h were analyzed in detail by intra-individual longitudinal path analysis. Additionally, time segments before, during and after outdoor exposure were separately analyzed. In both seasons short-term variations in PET were positively associated with short-term changes in Tdist (not proximal ST, Tprox) and negatively with those in MAP. However, long-term seasonal differences in daytime mean levels were observed in STs but not in BP leading to non-significant inter-individual correlation between STs and BP. Additionally, higher individual body mass index (BMI) was significantly associated with lower daytime mean levels of Tprox and higher MAP suggesting Tprox as potential mediator variable for the association of BMI with MAP. In healthy young women the thermoregulatory and BP-regulatory systems are closely linked with respect to short-term, but not long-term changes in PET. One hypothetical explanation could serve recent findings that thermogenesis in brown adipose tissue is activated in a cool environment, which could be responsible for the counter-regulation of cold induced increase of BP in winter leading to no seasonal differences in MAP. Our findings suggest that the assessment of diurnal patterns of STs and PET, in addition to the conventional ambulatory BP monitoring, might improve individual cardiovascular risk prediction.
authors.affiliation: Chronobiology Laboratory, Department of Physiology, Faculty of Biology, University of Murcia, 30100 Murcia, Spain.
authors.forename: Antonio
authors.initials: A
authors.lastname: Martinez-Nicolas
authors.affiliation: Thermophysiological Chronobiology, Centre for Chronobiology, Psychiatric Hospital of the University of Basel, Switzerland.
authors.forename: Martin
authors.initials: M
authors.lastname: Meyer
authors.affiliation: Thermophysiological Chronobiology, Centre for Chronobiology, Psychiatric Hospital of the University of Basel, Switzerland.
authors.forename: Stefan
authors.initials: S
authors.lastname: Hunkler
authors.affiliation: Chronobiology Laboratory, Department of Physiology, Faculty of Biology, University of Murcia, 30100 Murcia, Spain.
authors.forename: Juan Antonio
authors.initials: JA
authors.lastname: Madrid
authors.affiliation: Chronobiology Laboratory, Department of Physiology, Faculty of Biology, University of Murcia, 30100 Murcia, Spain.
authors.forename: Maria Angeles
authors.initials: MA
authors.lastname: Rol
authors.affiliation: Department of Psychology, Division of Clinical Psychology and Epidemiology, University of Basel, Switzerland.
authors.forename: Andrea H
authors.initials: AH
authors.lastname: Meyer
authors.affiliation: Department of Ophthalmology, University of Basel, Switzerland.
authors.forename: Andy
authors.initials: A
authors.lastname: Schötzau
authors.affiliation: Department of Ophthalmology, University of Basel, Switzerland.
authors.forename: Selim
authors.initials: S
authors.lastname: Orgül
authors.affiliation: Thermophysiological Chronobiology, Centre for Chronobiology, Psychiatric Hospital of the University of Basel, Switzerland. Electronic address: kurt.kraeuchi@upkbs.ch.
authors.forename: Kurt
authors.initials: K
authors.lastname: Kräuchi
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001794:Blood Pressure / Q000502:physiology*; D018660:Blood Pressure Monitoring, Ambulatory; D015992:Body Mass Index; D002940:Circadian Rhythm / Q000502:physiology*; D004777:Environment; D005260:Female; D006801:Humans; D012621:Seasons; D012881:Skin Temperature / Q000502:physiology*; D013696:Temperature; D013997:Time Factors; D055815:Young Adult
keywords: Ambulatory blood pressure monitoring; Distal skin temperature; Outdoor exposure; Path analysis; Personal-level environmental temperature; Proximal skin temperature