Am J Cardiovasc Dis 2012;2(2):111-115

Original Article
Seasonal variation of endothelium-dependent flow-mediated vasodilation
measured in the same subjects

Masako Iwata, Yutaka Miyashita, Hiromichi Kumagai

Department of Clinical Nutrition, School of Food and Nutritional Sciences, University of Shizuoka, Shizuoka, Japan;
Miyashita Clinic, Shizuoka, Japan

Received March 1, 2012; accepted April 5, 2012; Epub May 15, 2012; Published June 15, 2012

Abstract: Background: Seasonal variation of flow-mediated vasodilation (FMD) remains controversial. A large cohort study
showing that FMD was highest in summer and lowest in winter has been performed in a cross-sectional manner on
different populations in different seasons, and the results for the same population were not compared. Methods: FMD was
compared between the cool season (14.4 ± 4.4°C) and warm season (28.8 ± 1.0°C) in the same 27 outpatients with
hypertension, diabetes mellitus and/or hyperlipidemia. Results: The mean resting brachial artery diameter was
significantly larger in the warm season than in the cool season. The maximal post-deflation brachial artery diameter was
also significantly larger in the warm season than in the cool season. FMD, which was calculated from the resting diameter
and the maximal diameter, was significantly higher in the warm season than in the cool season even when expressed as
the relative value (4.74 ± 2.15 vs. 5.71 ± 2.17%, p=0.03) or absolute value (0.18 ± 0.08 vs, 0.23 ± 0.07 mm, p=0.008).
Conclusions: FMD was significantly higher in the warm season than in the cool season when the measurements were
performed on the same subjects and a paired comparison was made. (AJCD1203001).

Keywords: Flow-mediated vasodilation, seasonal variation


Address all correspondence to:
Dr. Hiromichi Kumagai
Department of Clinical Nutrition
School of Food and Nutritional Sciences
University of Shizuoka, 52-1 Yada
Shizuoka 422-8526, Japan.
Tel: +81-54-264-5567; Fax: +81-54-264-5567
E-mail: kumagai@u-shizuoka-ken.ac.jp
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