| Abstract: | The purpose of the present investigation was to examine possible genetic contributions to cardiovascular reactivity by contrasting patterns of association in 82 monozygotic (MZ) and 88 dizygotic (DZ) adult male twin pairs (age range = 21 to 61 years, M = 35 years). Systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate (HR) were recorded during baseline and during a mental arithmetic task (i.e., serial subtraction). The task produced significant elevations in all three cardiovascular measures (i.e., 10 mmHg SBP, 8 mmHg DBP, and 6 bpm HR, respectively). Levels of SBP and DBP reactivity were significantly correlated in MZ pairs but not in DZ pairs. Statistical tests suggest a heritability estimate of about 50% that was marginally significantly for SBP and DBP changes during the task. There was no indication of a genetic influence on HR reactivity. Resting level and static task period measures of SBP, DBP, and HR demonstrated statistically significant heritability estimates of 60% to 80%. |
