Description:
<jats:title>Abstract</jats:title><jats:sec><jats:title>Background</jats:title><jats:p>The hormone leptin has been suggested to play a role in the respiratory and immune systems. Evidence on sex‐specific concentrations of leptin in human milk and sex‐specific associations with the development of asthma and wheeze has been put forward but is still scarce.</jats:p></jats:sec><jats:sec><jats:title>Objective</jats:title><jats:p>To investigate whether male and female infants receive different levels of leptin through human milk and whether leptin is implicated in the development of asthma and wheeze in a sex‐dependent manner using data from the two Ulm Birth Cohort studies.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>Leptin data were available from human milk samples collected at 6 weeks (Ulm Birth Cohort Study [UBCS, <jats:italic>n</jats:italic> = 678; Ulm SPATZ Health Study, <jats:italic>n</jats:italic> = 587]), and, in SPATZ only, at 6 months (<jats:italic>n</jats:italic> = 377) and 12 months (<jats:italic>n</jats:italic> = 66) of lactation. Sex‐specific associations with doctor‐diagnosed asthma and wheeze phenotypes were assessed in crude and adjusted models using logistic regression. Adjustments were made for maternal allergy, exclusive breastfeeding, infant age at the time of milk sampling, and child BMI z‐score.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>At 6 weeks, leptin levels (median [min, max], in ng/L) were higher in the milk for girls (197 [0.100, 4120]) than in milk for boys (159 [1.02, 3280], <jats:italic>p</jats:italic> = .045) in UBCS. No significant sex differences were observed in SPATZ (<jats:italic>p</jats:italic> = .152). There were no significant associations of leptin with asthma or wheeze in both studies, even in a sex‐dependent manner (<jats:italic>p</jats:italic> > .05).</jats:p></jats:sec><jats:sec><jats:title>Conclusion</jats:title><jats:p>It remains unclear whether male and female infants receive different levels of leptin through human milk. However, leptin in human milk may not be associated with history and development of asthma and wheeze in a sex‐specific manner.</jats:p></jats:sec>