Blood glucose and nocturnal blood pressure in African and Caucasian men: The SABPA study.

AIM To investigate the relationship between nocturnal blood pressure and chronically elevated blood glucose to determine if these elevated blood glucose concentrations contribute to a non-dipping blood pressure, especially in high-risk groups such as Africans. METHODS Nocturnal blood pressures and blood glucose levels of 41 non-dipping African and 28 non-dipping Caucasian men were investigated. Ambulatory systolic (SBP) and diastolic blood pressure (DBP) were measured and blood collected in sodium fluoride tubes from the antebrachial vein to determine serum glucose and glycosylated hemoglobin A1c (HbA1c) percentage. The estimated average glucose (eAG) was determined from HbA1c percentage with a regression formula. RESULTS The African non-dippers had higher blood pressures (p<0.001) and elevated HbA1c (p=0.037) and eAG (p=0.041) levels compared to the Caucasians. In single, partial and multiple regression analyses nighttime (00:00-04:00) SBP correlated positively with HbA1c (p=0.069) and eAG (p<0.001) in the African men. No correlations were found in the Caucasian men. Sensitivity analysis confirmed that the association between nighttime SBP (00:00-04:00) and eAG was independent of carotid intima-media thickness in the African men (R(2)=0.617; β=0.438; p=0.008). CONCLUSION The blunted nocturnal decline in SBP during the early morning hours is associated with chronically elevated blood glucose in non-dipper African men.