Nocturia, Nocturnal Activity, and Nondipping

Abstract

Abstract-Patients with chronic kidney disease have less than expected decline in blood pressure during sleep (nondipping) and commonly experience the vexing symptom of nocturia. To better understand the relationship among nocturia, nighttime physical activity, and nondipping, we studied 98 patients with chronic kidney disease on 2 occasions, 1 month apart, with 24-hour ambulatory blood pressure monitoring and simultaneous activity monitoring with wrist actigraphy. Patients with nocturia had greater actigraphically recorded nighttime physical activity compared to those with no nocturia. The drop in activity from wake to sleep was reduced to a similar extent whether the patients had nocturia once or twice, but patients who had nocturia Ն3 times had the least reduction from wake to sleep activity (PϽ0.001 versus those with less degrees of nocturia). Those with nocturia had a lesser drop in systolic ambulatory blood pressure during sleep compared with those without nocturia. The average fall in sleep systolic blood pressure was 9.8 mm Hg (95% CI: 8.0 to 11.6 mm Hg) in those without nocturia compared with 3.4 mm Hg (95% CI: 2.7 to 4.1 mm Hg) in those with any severity of nocturia (PϽ0.001 for difference). Nondipping in patients with nocturia was mediated by nighttime physical activity. These differences were independent of estimated glomerular filtration rate, albuminuria, or use of diuretics. Thus, nocturia, which may reflect impaired renal tubular function, is associated with nondipping in patients with chronic kidney disease and appears to be mediated by increased nocturnal activity. Whether nocturia itself or the resulting nondipping associated with nocturia is of prognostic importance for cardiorenal events in patients with chronic kidney disease should be tested in future studies. Key Words: hypertension Ⅲ ambulatory blood pressure monitoring Ⅲ actigraphy Ⅲ CKD Ⅲ physical activity Ⅲ nocturia H ypertension, which is a widely prevalent and treatable cardiovascular risk factor in patients with chronic kidney disease (CKD), 1 is often difficult to assess accurately, because many patients with CKD have white-coat hypertension or masked hypertension. 2,3 Out-of-clinic measured blood pressure (BP) recordings are the preferred method of BP assessment, 4 and some studies have demonstrated that outof-clinic measured BP may be of greater prognostic importance for predicting cardiovascular and end-stage renal disease outcomes compared with clinic-measured BP recordings. 5,6 Home BP measurement and ambulatory BP monitoring are currently available tools to measure out-ofclinic BP, of which the latter has the advantage of measuring the fall in BP during sleep, a phenomenon termed "dipping." Although the exact cause for nondipping is unclear, nondipping is associated with CKD, sleep apnea, volume overload, sympathetic activation, and other factors. 4 Nocturia is defined as any waking at night to void and occurs when the rate of production of urine exceeds that of bladder volume. Many factors, eg, age, benign prostatic hyperp...

The Complex Relationship Between CKD and Ambulatory Blood Pressure Patterns

“…50 With the above in mind the high prevalence of nondipping in CKD should come as no surprise, in particular because CKD is well known to be associated with increased sympathetic activation. 51 Additionally, obstructive sleep apnea, 52 sedentary lifestyle, 53 and poor sleep quality 53 are all common in CKD, with the latter possibly driven by nocturia that is itself associated with nondipping in CKD 54 . However, an interesting of study of 14 highly selected hemodialysis patients and 14 matched controls suggests that comorbidities contribute significantly to the prevalence of nondipping in CKD.…”

“…In one study of paired 24 hour ABPM examinations 4 weeks apart in 65 CKD patients, 23% changed dipping status between studies and the κ statistic of reproducibility was only 0.415. 54 Similarly, when 24 hour ABPM was performed serially in 4 month intervals in 34 CKD patients the dipping status changed in 38% of paired examinations. 58 This may be on account of a combination of the poor sleep experienced by CKD patients 53 coupled with the ABPM procedure itself as it is associated with reduced daytime activity and poorer sleep, 59 both of which would be expected to reduce dipping.…”

The Effect of Measuring Ambulatory Blood Pressure on Nighttime Sleep and Daytime Activity—Implications for Dipping

“…Among patients with CKD, who have the highest prevalence of nondipping (13), the causes of nondipping include increased nocturnal physical activity (1), nocturia (14), increased sympathetic activation (15), and sodium sensitivity (16). ABPM-induced sleep disturbance should now be added to the list of causes of nondipping.…”

Physical Activity Is a Determinant of Circadian Blood Pressure Variation in Chronic Kidney Disease

“…The causes of non-dipping in these patients are not clear, but many factors have been proposed [24,25] such as sodium sensitivity [26], increased sleep activity [6], autonomic activation [27], endocrine dysfunction [28] and nocturia [29]. An advancing stage of CKD is associated with impaired dipping [5].…”