Inter- and Intra-Individual Variations of Heart Rate Variability in Japanese Males

• Published in: Journal of PHYSIOLOGICAL ANTHROPOLOGY Vol. 26; no. 2; pp. 173 - 177
• Main Author: Kobayashi, Hiromitsu
• Format: Journal Article
• Language: English; Japanese
• Published: England Japan Society of Physiological Anthropology 2007; BioMed Central
• Subjects: Adult; Analysis of Variance; Heart Rate - physiology; heart rate variability; Humans; inter-individual; intra-individual; Japan; Male; Middle Aged; Posture - physiology; reproducibility; Japan
• ISSN: 1880-6791; 1880-6805
• DOI: 10.2114/jpa2.26.173

Spectral components of heart rate variability (HRV) were repeatedly measured (4–8 measurements; mean: 6 measurements) in 75 healthy Japanese male subjects (age range: 20–61) under two postural conditions (standing and supine). Low-frequency (LF) and high-frequency (HF) components and mean heart rate (HR) were analyzed with special reference to individual variations, which were classified into two types: inter- (interV) and intra-individual variations (intraV). The percent contributions and coefficients of variations were calculated for both interV and intraV. Percent contributions of intraV (intraV%) of HR with standing and supine postures were 15.8 and 12.9%, respectively. The intraV% of HF and LF on standing were 31.5 and 26.5%, while those in the supine posture were 27.8 and 35.5%, respectively. The coefficients of interV (interCV) and intraV (intraCV) were also calculated. The interCVs of HR, HF, and LF on standing were 14.9, 41.4, and 48.4%, while those in the supine posture registered 16.2, 42.9, and 44.2%, respectively. The intraCVs of HR, HF, and LF on standing were 5.0, 19.7, and 21.2%, while those in the supine posture indicated 4.7, 20.1, and 23.0%, respectively. We also calculated the interV and intraV of logarithmic-transformed HRV indexes. The log-transformation remarkably diminished both variables: interCV and intraCV registered 14–16 and 6–7%, respectively. Although interV variations were considerabley large, intraV variations of HRV were negligibley small. The HRV indexes decreased with age, although HR remained unchanged. The coefficients of determination (r2) were 14–34%. In the case of log-transformed HRV indexes, the coefficients of determination registered 9–15%, suggesting that 14–34% (raw) or 9–15% (log) of the observed interV may be due to variations in age.