Hypertension Does Not Alter the Increase in Cardiac Baroreflex Sensitivity Caused by Moderate Cold Exposure.
Exposure to cold increases blood pressure and may contribute to higher wintertime cardiovascular morbidity and mortality in hypertensive people, but the mechanisms are not well-established. While hypertension does not alter responses of vagally-mediated heart rate variability to cold, it is not known how hypertension modifies baroreflex sensitivity (BRS) and blood pressure variability during cold exposure. Our study assessed this among untreated hypertensive men during short-term exposure comparable to habitual winter time circumstances in subarctic areas. We conducted a population-based recruitment of 24 untreated hypertensive and 17 men without hypertension (age 55-65 years) who underwent a whole-body cold exposure (-10°C, wind 3 m/s, winter clothes, 15 min, standing). Electrocardiogram and continuous blood pressure were measured to compute spectral powers of systolic blood pressure and heart rate variability at low (0.04-0.15 Hz) and high frequency (0.15-0.4 Hz) and spontaneous BRS at low frequency (LF). Comparable increases in BRS were detected in hypertensive men, from 2.6 (2.0, 4.2) to 3.8 (2.5, 5.1) ms/mmHg [median (interquartile range)], and in control group, from 4.3 (2.7, 5.0) to 4.4 (3.1, 7.1) ms/mmHg. Instead, larger increase (p < 0.05) in LF blood pressure variability was observed in control group; response as median (interquartile range): 8 (2, 14) mmHg(2), compared with hypertensive group [0 (-13, 20) mmHg(2)]. Untreated hypertension does not disturb cardiovascular protective mechanisms during moderate cold exposure commonly occurring in everyday life. Blunted response of the estimate of peripheral sympathetic modulation may indicate higher tonic sympathetic activity and decreased sympathetic responsiveness to cold in hypertension.
Center for Environmental and Respiratory Health Research (CERH), University of OuluOulu, Finland; Medical Research Center Oulu (MRC Oulu), Oulu University Hospital and University of OuluOulu, Finland.
Heidi E
HE
Hintsala
Medical Research Center Oulu (MRC Oulu), Oulu University Hospital and University of OuluOulu, Finland; Research Unit of Internal Medicine, University of OuluOulu, Finland.
Antti M
AM
Kiviniemi
Medical Research Center Oulu (MRC Oulu), Oulu University Hospital and University of OuluOulu, Finland; Research Unit of Internal Medicine, University of OuluOulu, Finland.
Mikko P
MP
Tulppo
Research Unit of Medical Imaging, Physics and Technology, University of Oulu Oulu, Finland.
Heta
H
Helakari
Finnish Institute of Occupational HealthOulu, Finland; Research Unit of Biomedicine, University of OuluOulu, Finland.
Hannu
H
Rintamäki
Center for Environmental and Respiratory Health Research (CERH), University of Oulu Oulu, Finland.
Matti
M
Mäntysaari
Medical Research Center Oulu (MRC Oulu), Oulu University Hospital and University of OuluOulu, Finland; Research Unit of Biomedicine, University of OuluOulu, Finland; Biocenter of Oulu, University of OuluOulu, Finland; Department of Gastroenterology and Metabolism, Poznan University of Medical SciencesPoznan, Poland.
Karl-Heinz
KH
Herzig
Medical Research Center Oulu (MRC Oulu), Oulu University Hospital and University of OuluOulu, Finland; Center for Life Course Health Research, University of OuluOulu, Finland; Unit of Primary Health Care, Oulu University HospitalOulu, Finland.
Sirkka
S
Keinänen-Kiukaanniemi
Center for Environmental and Respiratory Health Research (CERH), University of OuluOulu, Finland; Medical Research Center Oulu (MRC Oulu), Oulu University Hospital and University of OuluOulu, Finland; Internal Medicine, Oulu University HospitalOulu, Finland.
Jouni J K
JJ
Jaakkola
Center for Environmental and Respiratory Health Research (CERH), University of OuluOulu, Finland; Medical Research Center Oulu (MRC Oulu), Oulu University Hospital and University of OuluOulu, Finland.
Tiina M
TM
Ikäheimo
baroreflex; blood pressure; cold temperature; hypertension; variability