ASSESSING SEQUENTIAL IRREGULARITY OF BOTH ENDOCRINE AND HEART-RATE RHYTHMS

The quantification of subtle patterns in sequential data, and their ch anges, has considerable potential utility both in analysis of hormonal secretory dynamics, and of fetal heart rate rhythms. Approximate entr opy, a recently developed statistic quantifying serial irregularity, h as been applied in both these settings, and has yielded a number of ne w findings. Among endocrine applications, approximate entropy increase s with increasing age for luteinizing hormone and follicle stimulating hormone, for both women and men, indicating greater irregularity (mor e apparently random dynamics) in the older groups; for the luteinizing hormone-testosterone axis, both irregularity and asynchrony increases accompany advancing age for men. These findings produce a means to po tentially predict time until menopause onset, the efficacy of infertil ity drugs, and also provide firm quantitative support of a partial mal e menopause. In fetal monitoring, antepartum, and postnatal heart rate studies, approximate entropy consistently detected subtle shifts in h eart rate rhythmicity, with greater regularity clinically correspondin g to compromised physiology in all settings. Both the capability of ap proximate entropy to quantify rhythm changes undiscernible by ausculta tion, and a continuum interpretation linking per-individual antepartum , perinatal, and postnatal heart rate analyses provide considerable po tential enhancement to the present clinical utility of fetal monitorin g. (C) 1998 Lippincott-Raven Publishers.