Defining the nocturnal period in 24-h ambulatory blood pressure monitoring: a comparison of three methods

Abstract

Objectives The purpose of our study was to compare three definitions of ambulatory blood pressure (BP) nocturnal period and to assess their agreement in determining nocturnal BP dipping patterns. Methods We investigated 69 subjects with metabolic syndrome, aged 50–55 years. In all subjects, we assessed 24-h BP monitoring, electrocardiogram and actigraphy profiles. The nocturnal period was defined in three ways: as a fixed narrow nighttime period from 01:00 to 06:00, as a self-reported sleeping period and as a disappearance and onset of physical activity recorded by the actigraph. Results Our study revealed a significant discrepancy between the self-reported and actigraphy-based nocturnal periods (P < 0.001). In addition, different definitions of the nighttime yielded significant differences in determining nondipping, extreme dipping and dipping BP patterns, the identification of the latter being affected the most. The actigraphy-based approach best aligned with the fixed-time determination of the nocturnal period: Cohen’s kappa coefficient for the nondipping pattern was 0.78 (0.58–1), for the dipping pattern 0.75 (0.59–0.91) and for the extreme dipping pattern 0.81 (0.65–0.97). In comparison to the self-reported determination of the nocturnal period, using the actigraphy-based approach resulted in reclassifying the nocturnal BP pattern in 20.3% of subjects. Conclusions The lack of agreement between fixed-time, self-reported and actigraphy-based determinations of the nighttime period affects the identification of the nocturnal BP patterns. In comparison to the self-reported nocturnal period estimation, the actigraphy-based approach results in the reclassification of BP dipping status in every fifth subject.

Comparing effect of definition of diurnal periods by diary, fixed periods, and actigraphy on ambulatory blood pressure parameters in a Chinese population

“…Furthermore, contrary to the findings of Booth et al [ 3 ], our findings show ABPM parameters defined by patient's diaries had highest reproducibility. Slusniene et al [ 7 ] conducted similar study in 69 patients with elevated BP (BP >135/85 mmHg) and found similar BP values regardless of the definition used (narrow fixed time, actigraphy and diary) but one-fifth of dipping status changed when defined by actigraphy. Finally, the Li et al [ 6 ] study was the only prior Chinese study that found similar SBP/DBP values from only diary and narrow fixed time methods but did not include comparison to actigraphy.…”

“…Currently, several methods are used to define these diurnal periods: patient's selfreported diary, wide-fixed predefined periods, narrow-fixed predefined periods and actigraphy [2]. However, there have been only five relevant studies that directly compared some of these diurnal definitions and found conflicting results [3][4][5][6][7]. Importantly, no previous studies have compared between all four commonly used definitions.…”

“…Ethnic differences are important as racial differences in sleep duration, amount of deep sleep and 24-h BP pattern are well described and can affect BP and dipping status on ABPM [8,9]. Furthermore, there have been no previous studies investigating the relationship between differences in diurnal definition and presence of end-organ damage [3][4][5][6][7]. Therefore, superiority of any diurnal definition used on ABPM cannot be confirmed and different diurnal definitions are still used by clinicians and in research [10,11].…”

Clinical and life style factors related to the nighttime blood pressure, nighttime dipping and their phenotypes in Korean hypertensive patients

“…One of the most important barriers to the research for nighttime BP pattern is the poor reproducibility [ 20 ]. How to define the sleep time is also an important issue in nighttime BP measurement, given its recognized influence on the dipping patterns of nighttime BP [ 21 ]. The aforementioned limitations regarding obtaining nighttime BP, especially during sleep-time BP, may be difficult to overcome in situations where the current "cuff-based" ABPM method is the only widely available method for assessing nighttime BP, even though it can easily disturb sleep [ 22 ].…”