Seasonal variation in muscle sympathetic nerve activity.
Epidemiologic data suggest there are seasonal variations in the incidence of severe cardiac events with peak levels being evident in the winter. Whether autonomic indices including muscle sympathetic nerve activity (MSNA) vary with season remains unclear. In this report, we tested the hypothesis that resting MSNA varies with the seasons of the year with peak levels evident in the winter. We analyzed the supine resting MSNA in 60 healthy subjects. Each subject was studied during two, three, or four seasons (total 237 visits). MSNA burst rate in the winter (21.0 ± 6.8 burst/min, mean ± SD) was significantly greater than in the summer (13.5 ± 5.8 burst/min, P < 0.001), the spring (17.1 ± 9.0 burst/min, P = 0.03), and the fall (17.9 ± 7.7 burst/min, P = 0.002). There was no significant difference in MSNA for other seasonal comparisons. The results suggest that resting sympathetic nerve activity varies along the seasons, with peak levels evident in the winter. We speculate that the seasonal changes in sympathetic activity may be a contribution to the previously observed seasonal variations in cardiovascular morbidity and mortality.
Penn State Hershey Heart and Vascular Institute, Pennsylvania State University College of Medicine Milton S. Hershey Medical Center, Hershey, Pennsylvania.
Jian
J
Cui
Penn State Hershey Heart and Vascular Institute, Pennsylvania State University College of Medicine Milton S. Hershey Medical Center, Hershey, Pennsylvania.
Matthew D
MD
Muller
Penn State Hershey Heart and Vascular Institute, Pennsylvania State University College of Medicine Milton S. Hershey Medical Center, Hershey, Pennsylvania.
Cheryl
C
Blaha
Division of Biostatistics and Bioinformatics, Department of Public Health Sciences, Pennsylvania State University College of Medicine Milton S. Hershey Medical Center, Hershey, Pennsylvania.
Allen R
AR
Kunselman
Penn State Hershey Heart and Vascular Institute, Pennsylvania State University College of Medicine Milton S. Hershey Medical Center, Hershey, Pennsylvania lsinoway@hmc.psu.edu.
Lawrence I
LI
Sinoway
Cardiovascular diseases; hemodynamic; nervous system; risk factors; sympathetic