The protective role of oestradiol against silent myocardial ischemia and hypertension risk in South African men: The SABPA study.

BACKGROUND: Oestradiol has a protective effect on coronary artery health in women but the effect it has on men, is controversial. A translational approach was followed to assess whether sex hormone levels are associated with silent myocardial ischemia (SMI) and hypertension risk over a 3year period.

METHODS: Participants included 89 Black and 91 White men (aged 21-63years) participating in both phases of the Sympathetic activity and Ambulatory Blood Pressure in Africans prospective study. Fasting blood samples, ambulatory blood pressure and 2-lead ECG recordings were obtained.

RESULTS: No difference in the levels of the various baseline serum T fractions between the two ethnic groups occurred. Oestradiol of the Black men increased by 54.2% compared to a decrease of 24.1% in the White men. Changes in total oestradiol (adjusted R2 =0.33, β=-0.31, p=0.023) and free oestradiol (adjusted R2 =0.34, β=-0.33, p=0.019) were inversely associated with changes in SMI in the Black men but not in White men. Baseline serum nitric oxide metabolites were inversely associated with ΔSMI in the Blacks only (adjusted R2 =0.33, β=-0.28, p=0.047). Chronic SMI was associated with 24h hypertension in Blacks [cut point 1.5 events: Area under the curve 0.71 (95% CI: 0.60, 0.82); p=0.006; with sensitivity/specificity 44%/94%].

CONCLUSIONS: Chronic SMI events facilitated future ischemic heart disease in Black men. Up-regulated free oestradiol seems to be involved in the protection of the heart against SMI and hypertension risk in Black but not in White men. A similar protective role for testosterone could however not be shown.