Individual variation in sleeping metabolic rates in infants

Area of Science:

• Pediatrics
• Human Physiology
• Infant Metabolism

Background:

• Sleeping metabolic rate (SMR) is a key indicator of infant energy expenditure and thermal regulation.
• Understanding SMR variations in infants is crucial for optimizing their thermal environment and care.
• Previous research has not fully characterized the day-to-day and month-to-month variability of SMR in healthy infants during their first year.

Purpose of the Study:

• To quantify the variability in sleeping metabolic rate (SMR) among healthy infants throughout their first year of life.
• To assess the consistency of SMR measurements within individual infants over time.
• To determine the range of SMR values in infants aged 0-12 months.

Main Methods:

• SMR was measured in the homes of two groups of infants (0-12 months) at monthly intervals or over three consecutive days.
• Sixty-one infants participated, contributing to 181 SMR measurements.
• Environmental factors including room temperature, radiative temperature, humidity, and insulation were recorded.

Main Results:

• The mean SMR was 2.4 (0.4) W/kg (45 (10) W/m²), with no significant age-related changes observed between 0.25 and 1 year.
• A wide variation in SMR was found, with 98% of infants falling between 1.8 and 3.1 W/kg.
• Intra-infant variation in SMR ranged from 0.06 to 1.05 W/kg across different measurement frequencies.

Conclusions:

• Healthy infants exhibit substantial day-to-day and month-to-month variability in their sleeping metabolic rate.
• The wide range of SMR values observed suggests that individualized thermal comfort recommendations are challenging.
• Current guidance on infant clothing and bedding for thermal comfort must remain general due to this variability.