Increased platelet counts are associated with female sex and asthma severity

Significant sex differences occur in asthma phenotypes across the lifespan. Platelet activation is associated with a steroid-refractory asthma phenotype.

We sought to test the hypothesis that higher platelet counts in females are associated with increased prevalence and severity of asthma compared with males.

We conducted a cross-sectional analysis using data from participants' baseline visit in the UK Biobank. Binomial multivariable logistic regression was used to adjust for age, body mass index, sex, race, smoking status, serum C-reactive protein, absolute eosinophil count, and absolute neutrophil count.

Of the 351,203 patients included in the analysis, 5.7% had asthma, 2% met the British Thoracic Society criteria for moderate to severe asthma, and 57.4% were female. Female sex was associated with higher platelet counts among participants with or without asthma (P < .001). Median platelet counts were higher by 30 × 10³/μL in females with asthma when compared with males with asthma (median [interquartile range], 271.1 [235.0-312.0] vs 241.0 [209.0-279.4] × 10³/μL, P < .001, respectively). Among participants with asthma, higher platelet counts were also associated with increased asthma severity (P < .001). Platelet counts correlated positively with the blood absolute eosinophil count (r = 0.104, P < .001), blood neutrophil count (r = 0.254, P < .001), and C-reactive protein (r = 0.183, P < .001).

These findings suggest that platelet counts are associated with asthma and inflammation in both sexes and can serve as a potential biomarker for asthma severity with differential effects across the sexes. Future studies including mechanistic studies should characterize the interaction between sex hormones, platelet activation, and asthma severity.