Research

Determinants of the daily rhythm of blood fluidity

Tatsushi Kimura¹ , Tsutomu Inamizu^2* , Kiyokazu Sekikawa^2* , Masayuki Kakehashi^2* and Kiyoshi Onari^3*

¹  Yasuda Women's College, Department of Kindergarten Education, Yasuhigashi 6-13-1, Asaminami-ku, Hiroshima 731-0153, Japan

²  Hiroshima University, Graduate School of Health Science, Institute of Health Sciences, Kasumi 1-2-3, Minami-ku, Hiroshima 734-0037, Japan

³  Fukuyama Heisei University, Department of Health and Sport Sciences, Miyuki Kamiiwanari 117-1, Fukuyama, Hiroshima 720-0001, Japan

author email corresponding author email* Contributed equally

Journal of Circadian Rhythms 2009, 7:7doi:10.1186/1740-3391-7-7

Published:	26 June 2009

Abstract

Background

Numerous processes in the living body exhibit daily rhythmicity. In this study, we characterized a daily rhythm of blood fluidity and identified its determinants.

Methods

The subjects were nine young males. We measured the physiological parameters and performed hematological and biochemical analyses. We repeated the measurements six times during the day at 7:30 (just after getting up and before breakfast), 10:00, 13:30 (after lunch), 16:30, 19:30 (after dinner), and 21:30. The subjects performed sedentary work all day, and the contents and time of the meals were uniform. Investigation of blood rheology was based on Kikuchi's microchannel method.

Results

Blood passage time varied significantly with time of day. Stepwise regression analysis was used to determine the significant factors affecting blood passage time. Body temperature, heartbeat, hematocrit, white blood cell and total cholesterol were significant determinants of blood passage time.

Conclusion

We confirmed that blood fluidity has a daily rhythm. In addition, we found that the determinants of blood fluidity included physiological parameters such as body temperature and heartbeat, hematological parameters such as hematocrit, and white blood cell and total cholesterol.