Morning reduction of cerebral vasomotor reactivity

Ameriso, Sebastián F.; Mohler, John G.; Suárez, Manuel; Fisher, Mark

doi:10.1212/wnl.44.10.1907

Cited by 51 publications

(44 citation statements)

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“…In contrast, over the same time period, morning hypercapnic cerebral vascular reactivity is markedly reduced, a finding that is in agreement with others. 1,16 The similarity in the magnitude of the hypoxic cerebral vascular response between the evening and morning is noteworthy, because we have previously reported that this response is absent during NREM sleep 7 ; indeed, hypoxia is associated with a reduction in CBF during NREM sleep. 7 Although the mechanism responsible for the abolition of this response is unknown, the present data would suggest that, in the majority of individuals, the return of the hypoxic response on waking occurs rapidly.…”

Section: Discussionmentioning

confidence: 72%

“…1,18,28 Research suggests that the incidence of stroke is highest during the morning hours, especially on awakening, 30,31 a finding that has been attributed to a reduction in cerebral vascular reactivity. 1 An intact CBF response to IH, during this time period, could be interpreted as a protective mechanism, acting to maintain CBF during any hypoxic episode such as that reported in patients with OSA. It remains to be established if the present observations, in healthy young males, can be extrapolated to "at-risk" groups such as the elderly or those with OSA.…”

Section: Discussionmentioning

confidence: 99%

“…1 This reduction is suggested to be one cause for the increased risk of cerebral ischemia and stroke, [2][3][4] especially during the morning hours. 1 The mechanism responsible for this reduction is unknown. However, during nonrapid eye movement (NREM) sleep, cerebral metabolism, blood flow, and the cerebral vascular response to CO 2 are all reported to be reduced.…”

mentioning

confidence: 99%

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Overnight Changes in the Cerebral Vascular Response to Isocapnic Hypoxia and Hypercapnia in Healthy Humans

Meadows

Kotajima

Vazir

et al. 2005

Stroke

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Background and Purpose-The reduction in hypercapnic cerebral vascular reactivity that occurs in the morning after sleep is associated with an increased risk of cerebral ischemia and stroke. It is not known if the cerebral vascular response to hypoxia is similarly reduced in the morning, but such a reduction could be considered a further risk factor for cerebral vascular disease. Methods-To test if the cerebral vascular response to hypoxia is reduced in the morning, the overnight changes in the left middle cerebral artery velocity (MCAV) in response to isocapnic hypoxia (IH) and hypercapnia before and after a normal night sleep were determined in 18 individuals. Results-From evening to morning, hypercapnic cerebral vascular reactivity decreased significantly (evening 2.0Ϯ0.4, morning 1.3Ϯ0.2 cm/sec/mm Hg; PϽ0.05); in contrast, the increase in MCAV in response to IH (Ϫ10% SaO 2 ) was unchanged (evening 9.0Ϯ1.4, morning 8.7Ϯ2.2%; PϾ0.05). Conclusions-Our findings indicate that substantial differences exist in the regulation of the cerebral circulation in response to hypoxia and hypercapnia on waking from sleep. An intact cerebral vascular response to IH, during this time period, could be interpreted as a protective mechanism against cerebral ischemia and stroke; this is of particular relevance to patients with obstructive sleep apnea who arouse from sleep during hypoxia.

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Section: Discussionmentioning

confidence: 72%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

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Overnight Changes in the Cerebral Vascular Response to Isocapnic Hypoxia and Hypercapnia in Healthy Humans

Meadows

Kotajima

Vazir

et al. 2005

Stroke

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“…24 -28 It exhibits diurnal variations, reaching low points during morning hours when stroke events are most prevalent. 29 Both symptomatic and asymptomatic carotid artery stenosis are well-known contributors to impaired cVMR, 30 with vasomotor response to CO 2 lower on the stenotic side and improving after carotid endarterectomy. 27 Previous investigations report that impaired cVMR predicts higher stroke risk, 8,9,31 although one recent study suggests basal MCA-BFV is more important to stroke risk than cVMR.…”

Section: Discussionmentioning

confidence: 99%

Improved Cerebral Vasomotor Reactivity After Exercise Training in Hemiparetic Stroke Survivors

Ivey

Ryan

Hafer‐Macko

et al. 2011

Stroke

114

115

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Background and Purpose-Animal studies provide strong evidence that aerobic exercise training positively influences cerebral blood flow, but no human studies support the use of exercise for improving cerebral hemodynamics. This randomized study in stroke survivors assessed the effects of treadmill aerobic exercise training (TM) on cerebral blood flow parameters compared to a control intervention of nonaerobic stretching. Methods-Thirty-eight participants (19 in TM group and 19 in control group) with remote stroke (Ͼ6 months) and mild to moderate gait deficits completed middle cerebral artery blood flow velocity measurements by transcranial Doppler ultrasonography before and after a 6-month intervention period. Middle cerebral artery blood flow velocity was assessed bilaterally during normocapnia and hypercapnia (6% CO 2 ). Cerebral vasomotor reactivity (cVMR) was calculated as percent change in middle cerebral artery blood flow velocity from normocapnia to hypercapnia (cVMR percent) and as an index correcting percent change for absolute increase in end tidal CO 2 (cVMR index). Results-The TM group had significantly larger improvements than did controls for both ipsilesional and contralesional cVMR index (PՅ0.05) and contralesional cVMR percent (PՅ0.01). Statin users in the TM group (nϭ10) had higher baseline cVMR and lower training-induced cVMR change, indicating that cVMR change among those not using statins (nϭ9) primarily accounted for the between-group effects. There was a 19% increase in VO 2 peak for the TM group compared to a 4% decrease in the control group (PϽ0.01), and peak fitness change correlated with cVMR change (rϭ0.55; PϽ0.05). Conclusions-Our data provide the first evidence to our knowledge of exercise-induced cVMR improvements in stroke survivors, implying a protective mechanism against recurrent stroke and other brain-related disorders. Statin use appears to regulate cVMR and the cVMR training response. (Stroke.

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“…[1][2][3] A large number of publications have focused on identifying the underlying pathophysiological mechanisms and have reported rhythmic variation in blood pressure, vascular tone, platelet function, blood viscosity, fibrinolysis, cerebral vasomotor activity, and concentrations of hormones and coagulation factors to be of relevance in this context. [3][4][5][6][7][8][9][10][11][12][13] Furthermore, time-of-day-dependent variations in neuronal vulnerability to cerebral ischemia may also provide an explanation for temporal differences in stroke onset. 14,15 Most of these rhythms are governed by the circadian clock, which generates an endogenous rhythm via clock genes that interact in transcriptional/translational feedback loops.…”

mentioning

confidence: 99%

Abrupt Shift of the Pattern of Diurnal Variation in Stroke Onset With Daylight Saving Time Transitions

et al. 2008

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Background-Stroke onset shows a pattern of diurnal variation, with a peak in morning hours. Rhythmic changes in blood pressure, hormones, and other parameters have been suggested as underlying mechanisms, but exogenous factors such as increasing physical activity after awakening may also be of relevance. To characterize the impact of external clock changes on the rhythmic variation in stroke onset, this parameter was recorded in patients during transition periods into and out of Daylight Saving Time (DST). Methods and Results-The present study was based on a prospective stroke registry in Germany that contains time points of stroke onset from 44 251 patients admitted between 2000 and 2005. To achieve a uniform timeline, time points of stroke onset were set back from Central European Summer Time (CEST) to Central European Time (CET) for patients admitted during DST periods. Compared with the last week before the clock change, transition to or from DST resulted in an immediate shift of stroke onset time points within the first week after the clock change in reference to the uniform timeline (transition from CET to CEST Ϫ60 minutes for the time points in both the 25th and 50th percentiles of the diurnal pattern, PϽ0.001; transition from CEST to CET ϩ60 minutes for the time points in both the 25th and 50th percentiles, PϽ0.001; patients pooled on a weekly basis). A significant shift was already present the first and second day after the transitions (ie, Monday and Tuesday). Conclusions-Transition to or from DST is coupled with an immediate shift in the time pattern of stroke onset. This strengthens the idea that exogenous factors associated with awakening are important determinants of the pattern of diurnal variation of stroke onset, because entrainment of the human circadian clock within hours is unlikely.

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Morning reduction of cerebral vasomotor reactivity

Cited by 51 publications

References 0 publications

Overnight Changes in the Cerebral Vascular Response to Isocapnic Hypoxia and Hypercapnia in Healthy Humans

Overnight Changes in the Cerebral Vascular Response to Isocapnic Hypoxia and Hypercapnia in Healthy Humans

Improved Cerebral Vasomotor Reactivity After Exercise Training in Hemiparetic Stroke Survivors

Abrupt Shift of the Pattern of Diurnal Variation in Stroke Onset With Daylight Saving Time Transitions

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