Davidson et al1 reported an excellent study correlating a blunted nocturnal fall in BP with the subsequent decline in renal function. I would like to mention that the loss or reversal of the physiologic nocturnal fall in BP was demonstrated many years ago in chronic kidney disease, independently from external interfering factors.2,3 Patients with chronic nephropathies and patients with essential hypertension were matched by age, sex, and mean 24-hour BP values. Ambulatory BP monitoring was performed in an open hospital ward for 48 hours at 15-minute sampling intervals after standardization of diet, meal times, sleep times, and activity schedules. In essential hypertension, the nocturnal fall in BP was preserved as in normal conditions, whereas patients with renal impairment displayed blunted or reversed nocturnal BP and heart rate patterns. Hence, it appeared that casual measurements of BP confined to daytime may underestimate a hypertensive condition associated with chronic kidney disease. Increased sympathetic tone related to renal impairment was proposed to play a role in such a finding.2,3