Urinary albumin excretion among nondipper hypertensive patients is closely related with the pattern of nondipping

Abstract

The relationship between 24-hour urinary albumin excretion (UAE) rate and the pattern of nondipping (isolated systolic nondipping, isolated diastolic nondipping, and both systolic and diastolic nondipping) is not known. Medical history, physical examination, laboratory analysis, and office and ambulatory blood pressure measurements were performed. Twenty-four hour urine specimens were collected to determine creatinine clearance and UAE. In total, 158 essential hypertensive patients (104 dippers, 54 nondippers) were included. Fourteen patients were isolated systolic nondippers, 7 patients were isolated diastolic nondippers, and 33 patients were both systolic and diastolic nondippers. Among nondipper patients, 17 had microalbuminuria and, among dipper patients, 9 had microalbuminuria (P < .0001). The median UAE of dippers was lower when compared with nondippers (5.25 mg/day vs.23 mg/day, P < .0001). The median UAE of isolated systolic nondippers, isolated diastolic nondippers, and both systolic and diastolic nondippers were 8.45 mg/day, 7.7 mg/day, and 25.5 mg/day, respectively (P = .001). Subgroup comparison of patients revealed that UAE was higher in patients with both systolic and diastolic nondippers when compared with dippers (P < .0001), isolated systolic nondippers (P = .001), and isolated diastolic nondippers (P =  .017). Not only nondipping itself, but nondipping profile may be related with UAE in essential hypertensive patients.

Introduction

Microalbuminuria is a well-recognized marker for adverse cardiovascular outcomes in hypertensive subjects.1, 2 After the recognition of increased urinary albumin excretion (UAE) in essential hypertension, a large number of studies concerning different aspects of increased UAE in essential hypertension has been performed. These studies showed that microalbuminuric hypertensive patients had higher levels of blood pressure (BP) compared with normoalbuminuric subjects, and hypertensive patients manifest higher levels of UAE than do normotensive individuals.3, 4, 5, 6, 7, 8, 9, 10, 11 Additionally, it was shown that, among hypertensive patients, there was a positive correlation between UAE and office BP levels.4, 7, 9, 12, 13, 14, 15 The relationship between BP and UAE become even closer when BP levels are evaluated through ambulatory BP monitoring and a better relationship between the BP and UAE is observed when 24-hour ambulatory BP monitoring is used instead of office BP recordings. Positive correlations have been shown between 24-hour, daytime, nighttime systolic BP (SBP), and diastolic BP (DBP) measurements and UAE,5, 6, 9, 11, 15, 16, 17, 18, 19, 20 as well as altered circadian BP profile in microalbuminuric patients.6, 20, 21 Essential hypertensive subjects with enhanced UAE show a loss of nocturnal BP decline, and the magnitude of the blunted nighttime BP decrease is also closely related to the subclinical early phase of renal damage.4, 22, 23, 24

The exact mechanisms regarding the relationship between UAE and circadian BP are not known. Some authors suggested that correlation of albuminuria to nighttime BP dipping was less tight than to absolute BP. Although albuminuria, as a target organ damage, is found more frequently in nondippers then in dippers, there are no definite data whether the unfavorable outcome with respect to UAE in nondipper hypertensive subjects is caused by the absence of nocturnal BP decrease or by the accompanied greater hemodynamic load in this setting.25, 26 Thus, doubt is present whether the absolute levels or the dipping/nondipping status is more important in predicting UAE in hypertensive patients.

There are no data in the literature about whether UAE among nondippers is influenced by the pattern of nondipping (only systolic, only diastolic, or both systolic and diastolic nondipping). In the present study, we analyzed whether UAE differed according to nondipping pattern in essential hypertensive patients.