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Author Notes:

Address correspondence to: Michelle Lampl, PhD, MD, Department of Anthropology, Emory University, 1557 Dickey Drive, Atlanta, Georgia 30322(404) 727-2214(404) 727-2860mlampl@emory.edu


Research Funding:

Data collection was supported by the Developmental Psychobiology Research Group and the Wenner-Gren Foundation.


  • Sleep regulation
  • biological rhythms
  • saltatory growth
  • saltations

Infant Growth in Length Follows Prolonged Sleep and Increased Naps


Journal Title:



Volume 34, Number 5


, Pages 641-650

Type of Work:

Article | Post-print: After Peer Review


Study Objectives: The mechanisms underlying infant sleep irregularity are unknown. This study tests the hypothesis that sleep and episodic (saltatory) growth in infant length are temporally coupled processes. Study design: Daily parental diaries continuously recorded sleep onset and awakening for 23 infants (14 females) over 4-17 months (n = 5798 daily records). Multiple model-independent methods compared day-to-day sleep patterns and saltatory length growth. Measurements and Results: Approximate entropy (ApEn) quantified temporal irregularity in infant sleep patterns; breastfeeding and infant sex explained 44% of inter-individual variance (P = 0.001). Random effects mixed-model regression identified that saltatory length growth was associated with increased total daily sleep hours (P < 0.001) and number of sleep bouts (P = 0.001), with breastfeeding, infant sex, and age as covariates. Infant size and illness onset were non-contributory. CLUSTER analysis identified peaks in individual sleep of 4.5 more h and/or 3 more naps per day, compared to intervening intervals, that were non-randomly concordant with saltatory length growth for all individuals (P < 0.05), with a time lag of 0-4 days. Subject-specific probabilities of a growth saltation associated with sleep included a median odds ratio of 1.20 for each additional hour (n = 8, 95% CI 1.15 to 1.29) and 1.43 for each additional sleep bout (n = 12, 95% CI 1.21-2.03). Increased sleep bout duration predicted weight (P < 0.001) and abdominal skinfold accrual (P = 0.05) contingent on length growth, and truncal adiposity independent of growth (P < 0.001). Conclusions: Sleeping and length growth are temporally related biological processes, suggesting an integrated anabolic system. Infant behavioral state changes may reflect biological mechanisms underlying the timing and control of human growth. Citation: Lampl M; Johnson ML. Infant growth in length follows prolonged sleep and increased naps. SLEEP 2011;34(5):641-650.

Copyright information:

© 2011 Associated Professional Sleep Societies, LLC.

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