Chronobiology international
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Randomized Controlled Trial
Ambulatory blood pressure monitoring: importance of sampling rate and duration--48 versus 24 hours--on the accurate assessment of cardiovascular risk.
Independent prospective studies have found that ambulatory blood pressure (BP) monitoring (ABPM) is more closely correlated with target organ damage and cardiovascular disease (CVD) risk than clinic BP measurement. This is based on studies in which BP was sampled every 15-30 min for ≤24 h, without taking into account that reproducibility of any estimated parameter from a time series to be potentially used for CVD risk assessment might depend more on monitoring duration than on sampling rate. Herein, we evaluated the influence of duration (48 vs. 24 h) and sampling rate of BP measurements (form every 20-30 min up to every 2 h) on the prognostic value of ABPM-derived parameters. ⋯ The HRs, however, were markedly overestimated for SBP and underestimated for DBP when the duration of ABPM was reduced from 48 to only 24 h. This study on subjects evaluated prospectively by 48-h ABPM documents that reproducibility in the estimates of prognostic ABPM-derived parameters depends markedly on duration of monitoring, and only to a lesser extent on sampling rate. The HR of CVD events associated with increased ambulatory BP is poorly estimated by relying on 24-h ABPM, indicating ABPM for only 24 h may be insufficient for proper diagnosis of hypertension, identification of dipping status, evaluation of treatment efficacy, and, most important, CVD risk stratification.
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Generally, hypertensive patients ingest all their blood pressure (BP)-lowering agents in the morning. However, many published prospective trials have reported clinically meaningful morning-evening, treatment-time differences in BP-lowering efficacy, duration of action, and safety of most classes of hypertension medications, and it was recently documented that routine ingestion of ≥1 hypertension medications at bedtime, compared with ingestion of all of them upon awakening, significantly reduces cardiovascular disease (CVD) events. Non-dipping (<10% decline in asleep relative to awake BP mean), as determined by ambulatory BP monitoring (ABPM), is frequent in diabetes and is associated with increased CVD risk. ⋯ The latter group also showed significantly higher prevalence of properly controlled ambulatory BP (p < .001) that was achieved by a significantly lower number of hypertension medications (p < .001) compared with patients treated upon awakening. Our findings demonstrate significantly lower asleep SBP mean and attenuated prevalence of a blunted nighttime BP decline, i.e., lower prevalence of markers of CVD risk, and improved metabolic profile in patients with type 2 diabetes ingesting hypertension medications at bedtime than in those ingesting all of them upon awakening. These collective findings indicate that bedtime hypertension treatment, in conjunction with proper patient evaluation by ABPM to corroborate the diagnosis of hypertension and avoid treatment-induced nocturnal hypotension, should be the preferred therapeutic scheme for type 2 diabetes.
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Some studies based on ambulatory blood pressure (BP) monitoring (ABPM) have reported a reduction in sleep-time relative BP decline towards a more non-dipping pattern in the elderly, but rarely have past studies included a proper comparison with younger subjects, and no previous report has evaluated the potential role of hypertension treatment time on nighttime BP regulation in the elderly. Accordingly, we evaluated the influence of age and time-of-day of hypertension treatment on the circadian BP pattern assessed by 48-h ABPM. This cross-sectional study involved 6147 hypertensive patients (3108 men/3039 women), 54.0 ± 13.7 (mean ± SD) yrs of age, with 2137 (978 men/1159 women) being ≥60 yrs of age. ⋯ The prevalence of a riser BP pattern, associated with highest cardiovascular risk among all possible BP patterns, was 4 times more prevalent in patients ≥60 yrs of age than those <60 yr of age. Most important, there was an attenuated prevalence of a blunted nighttime BP decline at all ages when ≥1 hypertension medications were ingested at bedtime as compared with when all of them were ingested upon awakening. These findings indicate that older age should be included among the conditions for which ABPM is recommended for proper cardiovascular risk assessment.
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The rhythmic recurrence of biological processes is driven by the functioning of cellular circadian clocks, operated by a set of genes and proteins that generate self-sustaining transcriptional-translational feedback loops with a free-running period of about 24 h. In the gastrointestinal apparatus, the functioning of the biological clocks shows distinct patterns in the different organs. The aim of this study was to evaluate the time-related variation of clock gene expression in mouse liver and stomach, two components of the digestive system sharing vascular and autonomic supply, but performing completely different functions. ⋯ The acrophase of the fractional variations of Bmal1, Per2, Per3, Rev-erbα, Rev-erbβ, and Dbp expression was delayed in the stomach, and the average delay expressed as mean ± SD was 19.10 ± 9.39 degrees (76.40 ± 37.59 minutes). A significantly greater fractional variation was found in the liver for Clock at 06:00 h (p = .034), Per1 at 02:00 h (p = .037), and Per3 at 02:00 h (p = .029), whereas the fractional variation was greater in the stomach for Clock at 10:00 h (p = .016), and for Npas2 at 02:00 h (p = .029) and at 06:00 h (p = .044). In conclusion, liver and stomach show different phasing and dynamics of clock gene expression, which are probably related to prevailing control by different driving cues, and allow them to keep going the various metabolic pathways and diverse functional processes that they manage.
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Randomized Controlled Trial Clinical Trial
Melatonin treatment effects on adolescent students' sleep timing and sleepiness in a placebo-controlled crossover study.
During the last few decades, the incidence of sleep-onset insomnia, due to delay of circadian phase, has increased substantially among adolescents all over the world. We wanted to investigate whether a small dose of melatonin given daily, administered in the afternoon, could advance the sleep timing in teenagers. Twenty-one students, aged 14-19 yrs, with sleep-onset difficulties during school weeks were recruited. ⋯ Morning melatonin values in saliva diminished compared with PL (p < .001) and evening values increased (p < .001), indicating a possible sleep phase advance. Compared with PL school weeks, the students reported less wake up (p < .05), less school daytime sleepiness (p < .05) and increased evening sleepiness (p < .005) during melatonin weeks. We conclude that a small dose of melatonin given daily, administered in the afternoon, could advance the sleep timing and make the students more alert during school days even if they continued their often irregular sleep habits during weekends.