Provocation of efferent sympathetic outflow was undertaken in each subject by immersion of one hand in ice water (at 0°C) for one minute, with continuous blood pressure monitoring. Results are shown for final (post-cold) SBP, and analyzed by generalized estimating equations, establishing an exchangeable correlation matrix to take into account intra-twin-pair correlations.
Panel A: CHGA C+87T genotype effect on post-stress SBP; data are shown in all persons, as well as men and women separately. Genotype affected the trait (p=0.042), and there was no gene-by-sex interaction (p=0.159) on trait.
Panel B: Sex effect on post-stress SBP (p=0.009).