Results
The population under study consisted of 178 women and 86 men. Men (mean age: 32.3, SD = 10.3) were about three years older than women (mean age: 29.1, SD = 10.3), t = -2.45, p = 0.015, Cohen d = 0.32. Among women, we detected 43 (24.2%) Rh-negative homozygotes, 52 (29.2%) Rh-positive homozygotes, and 83 (46.6%) Rh-positive heterozygotes. Among men, we detected 24 (27.9%) Rh-negative homozygotes, 23 (26.7%) Rh-positive homozygotes, and 39 (45.3%) Rh-positive heterozygotes (Rh genotype-sex: Chi2 = 0.466, df = 2, p = 0.792).
The ANCOVA test with physical health problems score ormental health problems score as the dependent variable, sex and Rh genotype as factors, and age as a covariate found a significant negative association of age with physical health problems score(beta = -0.172) and mental health problems score (beta = -0.235), as well as a significant association of Rh genotype-sex interaction with the physical health problems score, see the Table 1. Visual inspection of figure 1 showed that Rh-negative homozygotes had similar physical health as Rh-positive heterozygotes, however, male Rh-positive homozygotes have the best, and female Rh-positive homozygotes the worst physical health of all six groups. The shape of the distributions also suggested that subpopulations of heterozygotic women and Rh-positive homozygotic men might be heterogenic – they could contain two distinct populations. Also, the physical health problems score of heterozygotic men might be negatively affected by a small number of outliers with very bad health. Separate ANCOVA tests showed that the association between Rh genotype and physical health problems score was significant for 178 women (p = 0.039, eta2 = 0.035) but not for less numerous (86) men (p = 0.429, eta2 = 0.020). The association of Rh genotype with the mental health problems scorewas neither significant for women (p = 0.225, eta2 = 0.017), nor for men (p = 0.795, eta2 = 0.006).
Tab. 1 Effects of Rh genotype on physical and mental health measured with ANCOVA