Aim: 

Recently our group proposed the use of peripheral skin temperature (ST) rhythm as a marker rhythm for circadian system assessment in normal living humans. The aim of the present study was to describe the evolution from birth to adulthood of ST rhythm in subjects recorded under normal living conditions.

Methods: 

Wrist temperature was recorded by means of a data logger (Ibutton, Dallas) in four groups of subjects of different ages: newborns of 15 days (n=28), 30 days (n=28) and 60 days (n=28), scholars of 10-12 years old (n=25) and young adults of 22-24 years old (n=21). Temperature sensor was positioned in upper side of left foot in newborns and in the wrist of non dominand hand in scholars and young adults.

Results: 

In spite of a weak 24-h periodicity was already present in some infants at 15 days, a predominant ultradian ST rhythm (~3-h period) was observed in most newborns by Fourier analysis. The potency of the first Fourier harmonic (24-h) increased above the 8^th harmonic (3-h) and became statistically significant at 30 days after birth. A progressive increase in the 24-h rhythm amplitude and a phase delay was observed from childhood to adulthood. Scholars differed from the adult ST profile since they showed lower ST during the morning than the late afternoon and did not show the postprandial increase in ST nor the "wake maintenance zone" between 20:00-22:00 h which characterized the adult pattern.

Conclusions: 

The adult pattern of circadian rhythm of ST, characterized by high nocturnal and low diurnal values, appeared soon after birth but an adult like profile is not reached until puberty. The skin temperature rhythm can be used to assess the maturation of circadian system under normal living conditions.

This project was funded by Seneca Foundation (PI/05700/07), by Instituto de Salud Carlos III (RETICEF, RD06/0013/0019), and by the Ministry of Education and Science (BFU2007-60658/BFI).