Sleeping like a baby--does gender influence infant arousability?

Abstract

Introduction: Victims of the sudden infant death syndrome (SIDS) may have preexisting abnormalities in their arousal pathways, inhibiting the progression of subcortical activation (SCA) to full cortical arousal (CA). Approximately 60% of SIDS victims are male, and it has been suggested that male infants have delayed cortical maturation compared to females. We hypothesized that CA frequency would be lower and CA threshold would be higher in male infants during both active (AS) and quiet (QS) sleep.

Methods: 50 healthy term infants (21 male, 29 female) were studied with daytime polysomnography at 2-4 weeks and 2-3 months after birth. Arousal from sleep was induced using a pulsatile air-jet to the nostrils at increasing pressures.

Results: At 2-4 weeks, arousability from AS was similar in males and females, however during QS, male infants required a lower stimulus to induce SCA and CA. This gender difference in arousal threshold was not observed at 2-3 months. CA frequencies were similar between genders during both sleep states at both ages, though overall, CA was more frequent in AS than in QS.

Conclusions: This study demonstrated that at 2-4 weeks, male infants were easier to arouse than female infants during QS. There were no significant effects of gender on total arousability or SCA and CA frequencies at 2-3 months, the age of peak SIDS incidence. Thus, although male infants are at greater risk of SIDS than female infants, this difference is unlikely to be associated with gender differences in CA threshold or frequency.

Figure 1

Mean driving pressures of air-jet stimuli which induced subcortical activation (SCA) and cortical arousals (CA) at (A) 2–4 weeks and (B) 2–3 months, in AS (solid bars) and QS (striped bars), for male (black bars) and female (grey bars) infants. *P < 0.05, male vs. female, ^#P < 0.05, AS vs. QS.

Figure 2

(A) Baseline HR data and (B) % HR change during arousal from sleep at 2–4 weeks and (C) at 2–3 months. Data are shown for male (black bars) and female (grey bars) infants, during both AS (solid bars) and QS (striped bars). *P < 0.05, male vs. female, ^#P < 0.05, AS vs. QS.