Role of automated measurements in understanding lifestyle effects on blood pressure

Heart rate variability rebound following exposure to persistent and repetitive sleep restriction

While it is well established that slow-wave sleep electroencephalography (EEG) rebounds following sleep deprivation, very little research has investigated autonomic nervous system recovery. We examined heart rate variability (HRV) and cardiovagal baroreflex sensitivity (BRS) during four blocks of repetitive sleep restriction and sequential nights of recovery sleep. Twenty-one healthy participants completed the 22-day in-hospital protocol. Following three nights of 8-hr sleep, they were assigned to a repetitive sleep restriction condition. Participants had two additional 8-hr recovery sleep periods at the end of the protocol. Sleep EEG, HRV, and BRS were compared for the baseline, the four blocks of sleep restriction, and the second (R2) and third (R3) nocturnal recovery sleep periods following the last sleep restriction block. Within the first hour of each sleep period, vagal activation, as indexed by increase in high frequency (HF; HRV spectrum analysis), showed a rapid increase, reaching its 24-hr peak. HF was more pronounced (rebound) in R2 than during baseline (p < 0.001). The BRS increased within the first hour of sleep and was higher across all sleep restriction blocks and recovery nights (p = 0.039). Rebound rapid eye movement sleep was observed during both R2 and R3 (p = 0.004), whereas slow-wave sleep did not differ between baseline and recovery nights (p > 0.05). Our results indicate that the restoration of autonomic homeostasis requires a time course that includes at least three nights, following an exposure to multiple nights of sleep curtailed to about half the normal nightly amount.

Dipping status and hostility in newly diagnosed essential hypertension

AIM

Personality traits, including hostility, play an important role in the development of cardiovascular disease. Moreover, abnormalities in blood pressure circadian pattern, such as a lack of nocturnal BP fall, are related with target organ damage and increased cardiovascular risk. The aim of this study was to investigate the impact of hostility and its dimensions on dipping status, in newly diagnosed hypertensive patients.

METHODS

The study population consisted of 114 newly diagnosed untreated essential hypertensives. All participants underwent 24-hour ambulatory blood pressure monitoring (ABPM) in order to assess dipping status. Hostility was assessed by Hostility and Direction of Hostility Questionnaire (HDHQ). The study population was divided in terms of dipping status in two groups, "dippers" and "non-dippers."

RESULTS

The statistical analysis revealed that dippers presented significantly higher score of extrapunitiveness (13.2 +/- 4.9 vs 11.4 +/- 3.9, p = 0.032), as well as significantly higher score of the dimension "urge to act out hostility (AH)" (4 +/- 3 vs 3 +/- 2, p = 0.025) compared to non-dippers. Multivariate regression analysis revealed extrapunitiveness as the only independent predictor of dipping status. The odds ratio (OR) for dipping status associated with each point increase in extrapunitiveness was 0.912 (95% CI: 0.832-0.992; p = 0.048).

CONCLUSION

The present findings may suggest that hostility and its features affect the circadian variation of blood pressure in hypertensive patients, providing a promising objective for future investigations linking psychological factors and dipping status in essential hypertension.

Sleep quality among relatively younger patients with initial diagnosis of hypertension: Dippers versus non‐dippers

BACKGROUND

Sleep is a basic physiological process. Normal sleep yields decrease in sympathetic activity, blood pressure (BP) and heart rate. Those, who do not have expected decrease in their BP are considered "non-dippers". We aimed to determine if there was any association between the non-dipping status and sleep quality, designed a cross-sectional study, and enrolled and evaluated the sleep quality of relatively young patients with an initial diagnosis of hypertension.

METHODS

Seventy-five consecutive patients, diagnosed to have stage 1 hypertension by their primary physicians, were referred to our study. Patients had newly diagnosed with stage 1 hypertension. Patients with a prior use of any anti-hypertensive medication were not included. Eligible patients underwent the Pittsburgh Sleep Quality Index (PSQI), which has an established role in evaluating sleep disturbances. All patients underwent ambulatory BP monitoring.

RESULTS

There were 42 non-dipper patients (mean age = 47.5+/-11.9 years, 24 male/18 female), as a definition, 31 dipper hypertensive patients (mean age = 48.5+/-12.8 years, 21 male/10 female) and two with white coat hypertension. Daytime systolic and diastolic mean BPs were not significantly different between the two groups. Night-time mean systolic and diastolic BPs were significantly higher in non-dippers compared with dippers. PSQI scores, globally, were significantly higher in non-dippers compared with dippers. Total PSQI score was not correlated with body mass index. It was noticed that, individually, sleep quality, sleep efficiency and sleep disturbance scores were significantly higher in non-dippers. Being a poor sleeper in terms of high PSQI score (total score>5) was associated with 2.955-fold increased risk of being a non-dipper (95% confidence interval 1.127-7.747).

CONCLUSION

We showed that the risk of having non-dipping hypertension, a risk factor for poor cardiovascular outcomes among hypertensive individuals, was tripled (odds ratios) among poor sleepers. We think that evaluating sleeping status and sleep quality among the hypertensive population may help unmask non-dipper hypertension, enabling physicians to treat appropriately.

Brachial artery vasomotor function is inversely associated with 24-h ambulatory blood pressure

BACKGROUND

Impaired endothelial function has been reported in hypertensive individuals. The extent to which such changes reflect the co-existence of other cardiovascular disease risk factors rather than an independent association with blood pressure remains uncertain.

OBJECTIVE

To assess the relationship between brachial artery vasomotor function and ambulatory blood pressure in hypertensive individuals and normotensive controls.

METHODS

We assessed 24-h ambulatory blood pressure and brachial artery endothelial and smooth muscle function in 155 patients with hypertension and 40 normotensive controls. The vasomotor functions were determined by ultrasonographic assessment of vasodilator responses to flow and sublingual glyceryl trinitrate, respectively. Patients with hypertension were categorized as either treated (n = 85) or untreated (n = 70), and further subdivided on the basis of either no or at least one other cardiovascular risk factor. These included hyperlipidaemia, smoking, diabetes or a previous coronary or cerebrovascular event.

RESULTS

Age- and sex-adjusted flow-mediated and glyceryl trinitrate-mediated responses were not significantly different in hypertensive individuals with respect to treatment status or the presence of risk factors when compared with controls. However, when data from all 195 study participants were pooled, 24-h ambulatory systolic blood pressure was inversely related to flow-mediated response (P = 0.002), and both systolic and diastolic blood pressure were inversely related to glyceryl trinitrate response (P < 0.001 and P = 0.009, respectively). Observed relationships were largely unaltered after further adjustment for body mass index, antihypertensive treatment or the presence of other risk factors.

CONCLUSIONS

The finding of a direct and inverse relationship between the level of ambulatory blood pressure and flow-mediated and glyceryl trinitrate responses is consistent with a direct influence of blood pressure on conduit vessel vascular function.

Sleep disorders and the failure to lower nocturnal blood pressure

PURPOSE OF REVIEW

The failure to lower systolic blood pressure at night (called non-dipping) and sleep apnea are both associated with adverse cardiovascular outcomes. Sleep apnea is a common cause of non-dipping blood pressure.

RECENT FINDINGS

Sleep apnea increases night time blood pressure through enhanced cardiac pre-load, sleep disturbance and hypoxia. Hypoxia elicits increased levels of norepinephrine, endothelin and erythropoetin. Patients with sleep apnea tend to be elderly and obese, so they have poor endothelial nitric oxide release and blunted baroreflexes. They thus have several stimuli for high blood pressure and poor compensatory mechanisms to lower blood pressure.

SUMMARY

Non-dipping patients without sleep apnea have evidence of volume overload and correct their blood pressure pattern in response to diuretics. Individuals with sleep apnea have evidence of increased cardiac pre-load from episodes of negative intrathoracic pressure. Their daytime blood pressure responds poorly to many drugs, but beta blockers may be effective. Their night time blood pressure responds only slightly to therapy of their sleep apnea with continuous positive airway pressure, even though continuous positive airway pressure decreases their norepinephrine, erythropoetin and endothelin levels.