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Abstract

African Americans are 6 times more likely to develop end-stage renal disease (ESRD) than whites. While observational studies show a direct relationship between the level of casual (office) BP and renal disease progression, level of casual BP can not account for the excess ESRD in African Americans. The primary objective of the AASK (African American Study of Kidney Disease and Hypertension) Cohort Study is to determine prospectively the course of kidney function and risk factors for kidney disease progression in African Americans with hypertensive kidney disease who receive recommended antihypertensive therapy that includes ramipril (JAMA, 2002;288:2421–2431). We hypothesize that abnormal diurnal patterns of BP, specifically, lack of a nocturnal decline in BP, may contribute to kidney disease progression in African Americans. In year 1 of the cohort phase of AASK, we performed ambulatory BP monitoring in 438 subjects. We defined daytime BP as the mean BP between 06:01–24:00 hours and nighttime BP as the mean BP between 00:01–06:00. Nocturnal fall of SBP was calculated as (daytime SBP-nighttime SBP)/daytime SBP. Based on the nocturnal fall in SBP we classified subjects into 5 categories: extreme dippers (>20%), dippers (>=10% to 20%), non-dippers (<10%), reverse dippers as 0 to −10% and extreme reverse dippers as > −10%. Mean daytime BP was 136/81 mm Hg and nighttime BP was 133/76 mm Hg. The distribution of nocturnal BP patterns is shown below: (See Table).

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Distribution of Nocturnal BP Patterns in AASK Cohort Study (n=438)

Nocturnal BP Category# Subjects% Subjects
Extreme Dippers61.4
Dippers7817.8
Non-Dippers18241.6
Reverse Dippers13530.8
Extreme Reverse Dippers378.4
Nocturnal BP Category# Subjects% Subjects
Extreme Dippers61.4
Dippers7817.8
Non-Dippers18241.6
Reverse Dippers13530.8
Extreme Reverse Dippers378.4
Open in new tab

Distribution of Nocturnal BP Patterns in AASK Cohort Study (n=438)

Nocturnal BP Category# Subjects% Subjects
Extreme Dippers61.4
Dippers7817.8
Non-Dippers18241.6
Reverse Dippers13530.8
Extreme Reverse Dippers378.4
Nocturnal BP Category# Subjects% Subjects
Extreme Dippers61.4
Dippers7817.8
Non-Dippers18241.6
Reverse Dippers13530.8
Extreme Reverse Dippers378.4

These results are remarkable for a preponderance of abnormal nocturnal BP patterns. Normal dippers accounted for only 17.8% of subjects while non or reverse dippers constituted 81% of participants. Whether a sustained elevation of nighttime BP, i.e. a lack of nocturnal decline in BP, is associated with rapid progression of kidney disease will be evaluated over the next 5 years. If present, such a relationship might eventually lead to new anti-hypertensive strategies that target nighttime BP.

Ambulatory blood pressure, nocturnal blood pressure, African Americans Table
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© American Journal of Hypertension, Ltd. 2003
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