Unresolved Issues of the Morning Blood Pressure Surge: The Next Stage of Clinical Applicability for the Morning Surge

Wildfire-related smoke inhalation worsens cardiovascular risk in sleep disrupted rats

Introduction

As a lifestyle factor, poor sleep status is associated with increased cardiovascular morbidity and mortality and may be influenced by environmental stressors, including air pollution.

Methods

To determine whether exposure to air pollution modified cardiovascular effects of sleep disruption, we evaluated the effects of single or repeated (twice/wk for 4 wks) inhalation exposure to eucalyptus wood smoke (ES; 964 μg/m3 for 1 h), a key wildland fire air pollution source, on mild sleep loss in the form of gentle handling in rats. Blood pressure (BP) radiotelemetry and echocardiography were evaluated along with assessments of lung and systemic inflammation, cardiac and hypothalamic gene expression, and heart rate variability (HRV), a measure of cardiac autonomic tone.

Results and Discussion

GH alone disrupted sleep, as evidenced by active period-like locomotor activity, and increases in BP, heart rate (HR), and hypothalamic expression of the circadian gene Per2. A single bout of sleep disruption and ES, but neither alone, increased HR and BP as rats transitioned into their active period, a period aligned with a critical early morning window for stroke risk in humans. These responses were immediately preceded by reduced HRV, indicating increased cardiac sympathetic tone. In addition, only sleep disrupted rats exposed to ES had increased HR and BP during the final sleep disruption period. These rats also had increased cardiac output and cardiac expression of genes related to adrenergic function, and regulation of vasoconstriction and systemic blood pressure one day after final ES exposure. There was little evidence of lung or systemic inflammation, except for increases in serum LDL cholesterol and alanine aminotransferase. These results suggest that inhaled air pollution increases sleep perturbation-related cardiovascular risk, potentially in part by increased sympathetic activity.

Association between morning blood pressure surge and cardiovascular remodeling in treated elderly hypertensive subjects

BACKGROUND

It has remained unclear whether or not morning blood pressure (BP) surge (MS) is associated with cardiovascular remodeling in elderly (> or =60 years) hypertensive patients being treated by antihypertensive medications.

METHODS

In this cross-sectional study (n = 197; mean 74.6 years; 37% men), we evaluated the association between MS, defined as the highest quartile of morning BP increase from sleep (> or =48 mm Hg; n = 49), and extent of cardiac hypertrophy and carotid artery intima-media thickness (IMT).

RESULTS

Although there were no differences in 24-h BP levels and the number of prescribed antihypertensive medications between MS and non-MS group, the use of thiazide diuretics was more frequent in MS group than non-MS group (35% vs. 19%; P < 0.05). The MS group had significantly higher levels of left ventricular mass index (LVMI) and internal-carotid artery (ICA)-IMT than the non-MS group (both P < 0.01), independent of 24-h BP levels, daytime BP variability, the degree of nocturnal BP decline, the plasma low-density lipoprotein levels, and the use of diuretics. Even in subjects with a well-controlled 24-h BP level (<130/80 mm Hg; n = 75), these relationships were similar. A multiple logistic regression analysis showed that the presence of MS was an independent determinant of LV hypertrophy (LVH) (> or =125 g/m(2) in men and > or =110 g/m(2) in women) and assignment to the highest quartile of ICA-IMT (both P < 0.05).

CONCLUSIONS

The MS in subjects being treated with antihypertensive medications was significantly associated with cardiovascular remodeling, independently of 24-h BP level, daytime BP variability, and nocturnal BP decline.