Race and diurnal blood pressure patterns. A review and meta-analysis

Investigators have reported variable findings regarding the role of race in diurnal blood pressure patterns. We performed a review and meta-analysis of this literature to identify the overall effect of race on circadian blood pressure patterns. Eighteen studies involving 2852 participants were reviewed. Meta-analyses were conducted using effect sizes calculated from the data provided directly in the study reports. Separate meta-analyses were conducted on effect sizes for differences between blacks and whites in daytime and nighttime systolic and diastolic blood pressure and nocturnal dip in systolic and diastolic blood pressure. To evaluate discrepancies in findings from studies involving American versus non-American blacks, overall meta-analyses as well as within-subset meta-analyses of black/white differences were conducted for comparisons involving American and non-American blacks. Results of overall meta-analyses indicate that blacks experience higher levels of systolic and diastolic blood pressure, both at night and during the day. These differences were significantly greater at night than during the day (P<0.05). Results of within-subset analyses involving American blacks mirrored those for all black/white comparisons, except that the effect of race on nocturnal dip, ie, that American blacks experienced less of a dip in both systolic and diastolic blood pressure at night, was significant (P<0.05). In contrast, the effect of race on nocturnal dip was not significant for comparisons involving non-American blacks. These results suggest a consistent difference in the chronobiology of blood pressure, particularly in American blacks.