Human body morphology, prevalence of nasopharyngeal potential bacterial pathogens, and immunocompetence handicap principal.

Objective: Body height, body mass index (BMI) and waist-to-hip ratio (WHR) are the main traits characterizing human body morphology. Studies show that these traits are related to attractiveness and, therefore, according to an evolutionary point of view, are supposed to be honest signals of biological quality. If the immunocompetence handicap principal (IHP) is true, people with more attractive values of these traits should be more immunologically competent. To test this, we analyzed whether nasal and throat colonization with potentially pathogenic bacteria is related to body height and BMI in both sexes and to WHR in females.

Methods: 103 healthy females and 90 healthy males (with the mean age of 21.4 and 22.8, respectively) participated in the study. The heights and weights were self-reported and waist and hip circumferences measured. Six potentially pathogenic species (with the most common Staphylococcus aureus) isolated from nasal and throat swabs were identified by colony morphology, standard biochemical assays, and latex tests. To compare carrier and noncarrier individuals, Kruskal-Wallis test was used.

Results: Colonized males had higher BMI than non-colonized males (no difference for females) and colonized females had lower WHR's. Body height was not related to colonization in either sex.

Conclusions: We confirmed our hypothesis only for BMI in males. This result and a higher WHR in non-colonized females indicate higher immunocompetence of those who bear the costs of higher levels of testosterone, which according to previous studies is correlated negatively to BMI in males and positively to WHR in females.