Sex-based differences in apnoea of prematurity: A retrospective cohort study.

This retrospective cohort study assessed whether sex influences the occurrence of apnoea of prematurity (AOP) in preterm infants. The analysis included a cohort of 24,387 preterm infants born between the gestational ages (GA) of 240/7 and 336/7  weeks that were admitted to tertiary neonatal care units participating in the Canadian Neonatal Network from January 2011 to December 2015. Of those, 13,983 (57%) were diagnosed with AOP. More females were diagnosed with AOP than males, but the difference in the male/female ratio was marginal (P = 0.058). The majority (89%) of infants diagnosed with AOP received caffeine (89% of males; 89% of females). By using the discontinuation of caffeine therapy as a proxy for the resolution of significant AOP, data analysis showed that females born before 336/7 weeks of GA stopped caffeine treatment earlier than males whether the caffeine was discontinued before 34 or 37 weeks of GA. Consequently, females had fewer days of caffeine therapy than males, especially infants born between 260/7 and 276/7  weeks (P < 0.004), 280/7 and 296/7  weeks (P < 0.03), and 320/7 and 336/7  weeks of GA (P < 0.04). Similar trends were observed when the corrected GA at discontinuation of caffeine was used. Given that AOP is indicative of an immature respiratory system, our data suggest that the maturation of the respiratory system might occur more rapidly in females than males. We conclude that sex needs to be considered in future studies on AOP.