INDIVIDUAL VARIATION IN SLEEPING METABOLIC RATES IN INFANTS

Aim-To measure the variation in sleeping metabolic rate (SMR) of healt hy infants in the first year of life. Methods-Attempts were made to me asure SMR in the home of one group of infants at monthly intervals ove r the first year of life and of another group in the 1 to 12 age range , over three consecutive days. Sixty one infants were recruited and 18 1 measurements made. In 11 infants sin or more satisfactory measuremen ts were made a monthly intervals and in another 11 infants, three cons ecutive daily measurements were obtained. Parents chase the clothing a nd bedding that they judged their infant needed to fall asleep. The ro om air and radiative temperatures, humidity, and amount of insulation were recorded. Results-The mean (SD) SMR was 2.4 (0.4) watts (W)/kg or 45 (10) W/m(2). The rate was the same for infants in the age groups 0 .25, 0.5, 0.75, and 1 years; individual infants did not show a systema tic change with age. There was wide variation. Ninety eight per cent o f infants had a SMR between 1.8 and 3.1 W/kg. The mean SMR for the inf ants measured on three consecutive days varied from 1.7 to 3.1 W/kg, a nd SMR varied within infants, from 0.06 to 0.86 W/kg. The variation wi thin six to 11 measurements on infants over the first year of life ran ged from 0.38 to 1.05 W/kg. Conclusion-Infants in the first year of li fe exhibit wide variations in SMR from day to day and from month to mo nth. As the range is wide, guidance on clothing and bedding for therma l comfort can be given only in broad terms.