Circadian blood pressure classification scheme and the health of patients with chronic kidney disease

Abstract

Background: In health, a sinusoidal rhythm is observed in systolic blood pressure (BP) that peaks (acrophase) during the waking hours (in-phase), but in those with chronic kidney disease (CKD) the acrophase is often observed during sleeping hours (out-of-phase). Yet in others the amplitude of the variation may be so blunted that acrophase may not be definable (phase-less). Circadian rhythms in systolic BP are often described by the dichotomous dipper classification but may not be adequate to fully characterize derangements in cyclical variation in BP.

Methods: To compare classification of circadian BP variation by phase-based classification to dipper-status we examined the cross-sectional relationship of these classification patterns to several markers of health such as health-related quality of life (Kidney Disease Quality of Life Survey, KDQOL) and physical activity (actigraphy over 2 weeks). We also assessed the relationship of circadian BP variation with circadian variation in urine electrolyte and albumin excretion rates.

Results: Among 103 veterans with CKD (97% men, age 69, diabetes mellitus 30%, eGFR 38.8 ml/min/1.73 m(2)) no differences were seen between dippers and non-dippers (n = 77, 75%) in eGFR, urinary Na and Cl excretion rates, or KDQOL. However, non-dippers had lower levels of physical activity and greater albuminuria compared to dippers. The same patients were classified to be in-phase (n = 36, 35%), phase-less (n = 19, 18%) or out-of-phase (n = 48, 47%). Patients in-phase had a higher eGFR and somewhat surprisingly also had the highest Na and Cl excretion rates compared to others. Those with out-of-phase systolic BP had the lowest physical composite score on KDQOL, the lowest level of physical activity, and the greatest amount of albuminuria.

Conclusions: Among patients with CKD, circadian BP profile described by either dipper-based or phase-based classification is related to the level of physical activity and the severity of kidney damage. The circadian BP profile is related to overall health and nutritional intake only when using the phase-based classification. The value of these classification schemes to profile circadian BP will require longitudinal studies.