Heart rate control in normal and aborted-SIDS infants

S. M. Pincus, T. R. Cummins, G. G. Haddad

Research output: Contribution to journalArticle

199 Scopus citations


Approximate entropy (ApEn), a mathematical formula quantifying regularity in data, was applied to heart rate data from normal and aborted-sudden infant death syndrome (SIDS) infants. We distinguished quiet from rapid-eye-movement (REM) sleep via the following three criteria, refining the notion of REM as more 'variable': 1) REM sleep has greater overall variability (0.0374 ± 0.0138 vs. 0.0205 ± 0.0090 s, P < 0.005); 2) REM sleep is less stationary (StatAv = 0.742 ± 0.110) than quiet sleep (StatAv = 0.599 ± 0.159, P < 0.03); 3) after normalization to overall variability, REM sleep is more regular (ApEn(sub) = 1.224 ± 0.092) than quiet sleep (ApEn(sub) = 1.448 ± 0.071, P < 0.0001). Fifty percent of aborted-SIDS infants showed greater ApEn instability across quiet sleep than any normal infant exhibited, suggesting that autonomic regulation of heart rate occasionally becomes abnormal in a high-risk subject. There was an association between low ApEn values and aborted-SIDS events; 5 of 14 aborted-SIDS infants had at least one quiet sleep epoch with an ApEn value below the minimum of 45 normal-infant ApEn values.

Original languageEnglish (US)
Pages (from-to)R638-R646
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Issue number3 33-3
StatePublished - 1993


  • approximate entropy
  • nonstationary
  • probabilistic phenomenon
  • quiet sleep
  • rapid eye movement
  • variability

ASJC Scopus subject areas

  • Physiology

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