Objectives: Defensive coping (AC) responses in urban African males have been associated with vascular responsiveness, partly explaining autonomic nervous system dysfunction. We therefore aimed to assess whether AC responses facilitate higher blood pressure and early sub-clinical structural vascular disease via alterations in frequency- and time-domain heart rate variability (HRV) responses.
Methods: We included 355 African and Caucasian men and women without pre-existing atrial fibrillation, aged 45 ± 9 years. Significant interaction on main effects (coping × ethnicity × gender) for left carotid intima media thickness far wall (L-CIMTf) and cross sectional wall area values necessitated selection of AC responders above mean via the Coping Strategy Indicator. We collected B-mode ultrasound L-CIMTf, ambulatory BP and-HRV data. Overnight fasting blood was obtained.
Results: Overall, Africans and AC Africans, mostly men, revealed a poorer lifestyle profile, higher prevalence of hypertensive status, disturbed sympathovagal balance and depressed HRV temporal and geometric patterns compared to the Caucasians (P ≤ 0.05). Moderately depressed non-linear and time-domain HRV (SDNN <100 ms) was prevalent in 28% of Africans compared to 11% of Caucasians. A similar trend was shown for the AC African participants (32%) compared to Caucasians (16%). Only depressed HRV time-domain (SDNN: adj. R(2) = 0.34; β = -0.24; p = 0.08) and vagal-impaired heart rate responses (RMSSD: adj. R(2) = 0.28; β = -0.28; p < 0.05) were associated with higher blood pressure and early structural vascular changes in AC African men.
Conclusion: Defensive coping facilitated autonomic nervous system dysfunction, which was associated with higher blood pressure and sub-clinical structural vascular disease in an African male cohort.
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