Genetic effects on cardiovascular responses to cold and mental activity in late adulthood.

The purpose of the present investigation was to examine the genetic contributions to cardiovascular reactivity in an adult cohort of male twins. A total of 47 monozygotic (MZ) twin pairs and 54 dizygotic (DZ) twin pairs, aged 59 to 69 years, were laboratory tested at four sites as part of the third examination of the National Heart, Lung, and Blood Institute Twin Study. Systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate (HR) were recorded during two tasks, a mental arithmetic task involving serial subtraction and the cold pressor test. Significant cardiovascular responsivity was observed during both tasks as measured by substantial elevations in SBP, DBP, and HR from resting periods to task periods. Heritability estimates were statistically significant for SBP and DBP but not HR levels during pretask baseline periods and during both tasks. Genetic variance was maintained for blood pressure reactivity to the mental arithmetic task after adjustments for baseline and performance. No genetic variance for SBP or DBP reactivity to the cold pressor test was evident.