Response to Dipping Deeper Into the Ambulatory Arterial Stiffness Index

Although we regret that Adiyaman et al 1 misinterpreted some of our results, we are glad to see that they agree with the main findings of our study, 2 in which we described a strong and previously undetected inverse association between ambulatory arterial stiffness index (AASI) and day-night blood pressure (BP) fall. Indeed, they were able to replicate our findings in 2 different cohorts. diyaman et al 1 argue that the estimate of AASI may be influenced by the night:day ratio of the number of BP readings. However, to support their view, they rely on ambulatory BP recordings performed with a very low frequency of nocturnal BP readings. In fact, the night:day ratio of the number of BP readings in their study was only 0.30 with 26 to 30 measurements during the day and 8 to 9 measurements at night (see the figure in the letter by Adiyaman et al 1 ) because of a longer nocturnal interval between automated measurements. In our representative patients (Figure Such a distribution, rather than including a "disproportionally large" number of nocturnal readings, is the desirable result of having BP evenly measured every 15 minutes throughout the 24 hours. By avoiding an artificially lower BP sampling frequency at night than during the day, in our article the night:day ratio in the number of BP readings simply mirrors the physiologically different duration of the nighttime and daytime subperiods.