Respiration during the first six months of life in normal infants: IV. Gender differences.

Respiratory rates and breathing pauses of various durations were examined in 19 normal infants, 12 male and 7 female, during the first 6 months of life. Twelve-hour all-night polygraphic recordings were obtained during the first week of life and at 1, 2, 3, 4 and 6 months. A computer program and visual analysis were used to score sleep state and calculate respiratory rates and apnea densities. In the newborn period there were no gender differences. Males breathed faster and exhibited fewer breathing pauses between 2 and 5 sec from one month of age on. The close correlation between respiratory rate and short breathing pauses suggests that the latter are an integral part of normal respiratory regulation. These findings can be explained by gender-related differences in metabolic rate or maturation of the central nervous system.