Moderate-to-severe obstructive sleep apnea is associated with cerebral small vessel disease

Association of obstructive sleep apnea and cerebral small vessel disease: a systematic review and meta-analysis

Study Objectives

The objective of the present study was to investigate the association between obstructive sleep apnea (OSA) and the presence of various neuroimaging marker of cerebral small vessel disease (CSVD).

Methods

We systematically searched PubMed, Embase, Web of Science, Scopus, and Cochrane library (from inception to May 2019) for studies evaluating the association between OSA and CSVD, which included white matter hyperintensities (WMH), silent brain infarction (SBI), cerebral microbleeds (CMBs), and perivascular spaces (PVS). Pooled odds ratios (ORs) with 95% confidence interval (CIs) were estimated using random-effects meta-analysis.

Results

After screening 7290 publications, 20 studies were finally included involving 6036 subjects. The sample size ranged from 27 to 1763 (median 158, interquartile range: 67–393). The meta-analysis showed that moderate to severe OSA was positively associated with WMH (13 studies, n = 4412, OR = 2.23, 95% CI = 1.53 to 3.25, I2 = 80.3%) and SBI (12 studies, n = 3353, OR 1.54, 95% CI = 1.06 to 2.23, I2 = 52%). There was no association with CMBs (three studies, n = 342, OR = 2.17, 95% CI = 0.61 to 7.73, I2 = 60.2%) or PVS (two studies, n = 267, OR = 1.56, 95% CI = 0.28 to 8.57, I2 = 69.5%). There was no relationship between mild OSA and CSVD.

Conclusion

Current evidence suggests that moderate to severe sleep apnea is positively related to WMH and SBI, but not CMBs or PVS, which suggests that OSA may contribute to the pathogenesis of CSVD. Further large cohort studies should be prioritized to confirm the findings.

Practical Small Vessel Disease Score Relates to Stroke, Dementia, and Death

Background and Purpose- In the general population, we investigated the association of a recently developed cerebral small vessel disease (CSVD) sum score with stroke, dementia, and mortality. Methods- One thousand six hundred fifty-one stroke-free and nondemented participants (mean age, 73.3 years; 54.5% women) of the population-based Rotterdam Study underwent brain magnetic resonance imaging (1.5T) in 2005-2011 and were followed for stroke, dementia, and mortality until 2016-2017. The CSVD sum score was composed by counting the presence of 4 magnetic resonance imaging markers (white matter hyperintensities, lacunes, cerebral microbleeds, and perivascular spaces; range, 0-4). We determined the association of the CSVD score with risk of stroke, dementia, and mortality using Cox models, adjusting for age, sex, and other Framingham Stroke Risk Profile predictors. Additionally, we assessed mortality as a competing risk for stroke and dementia and calculated absolute risk estimates for all outcomes. Results- During a mean follow-up of 7.2 years, 66 participants developed stroke, 76 developed dementia, and 306 died. The Framingham Stroke Risk Profile-adjusted hazard ratios of 1 point higher sum score were 1.54 (95% CI, 1.16-2.03) for stroke, 1.25 (95% CI, 0.95-1.64) for dementia, and 1.15 (95% CI, 1.01-1.31) for mortality. No significant differences were seen for subdistribution hazard ratios for stroke and dementia. A higher CSVD score yielded higher absolute risk estimates for all outcomes, calculated during 10 years. Conclusions- The CSVD score is a practical measure of global vascular brain injury. A higher sum score on magnetic resonance imaging is associated with higher risk of suffering a stroke, developing dementia, and death.

Effect of Heart Rate Variability on the Association Between the Apnea-Hypopnea Index and Cerebral Small Vessel Disease

Background and Purpose- The apnea-hypopnea index (AHI) is associated with cerebral small vessel disease (cSVD), but pathogenesis of this association is elusive. We aimed to assess the effect of nighttime heart rate variability (HRV)-as a proxy of sympathetic upregulation-on the aforementioned association. Methods- Atahualpa residents aged ≥60 years undergoing brain magnetic resonance imaging, polysomnography, and 24-hour Holter monitoring (N=176) were included. The presence of moderate-to-severe white matter hyperintensities, deep cerebral microbleeds, lacunar infarcts, and >10 enlarged basal ganglia perivascular spaces were added for estimating the cSVD score. Interaction models were fitted to assess the effect modification of nighttime HRV in the association between the AHI and the cSVD score, and mediation analysis was utilized to assess the proportion of total effect by nighttime HRV on this association. Results- Generalized linear models showed a significant association between the AHI and the cSVD score (P=0.025), as well as a significant inverse association between nighttime HRV and the cSVD score (P=0.002), but no association between daytime HRV and the cSVD score (P=0.097). Interaction models showed a significant interaction of nighttime HRV on the association between AHI and the cSVD score (P=0.001), and mediation analysis found that the percent of total effect between AHI and cSVD score mediated by HRV was 30.8%. Predictive marginal means of the cSVD score were highly significant when the 10th percentile of nighttime HRV was compared across categories of 10th and 90th percentiles of the AHI (cSVD score margins, 0.61 [95% CI, 0.37-0.86] versus 1.67 [95% CI, 1.26-2.09]). Contour plots showed the effect of nighttime (but not daytime) HRV on the association between AHI and the cSVD score. Conclusions- This study shows an important effect of nighttime HRV on the association between the AHI and the cSVD score and provides further support for the role of sympathetic overactivity on this association.

Sleep and brain morphological changes in the eighth decade of life

OBJECTIVE

Sleep is important for brain health. We analysed associations between usual sleep habits and magnetic resonance imaging (MRI) markers of neurodegeneration (brain atrophy), vascular damage (white matter hyperintensities, WMH) and waste clearance (perivascular spaces, PVS) in older community-dwelling adults.

METHOD

We collected self-reported usual sleep duration, quality and medical histories from the Lothian Birth Cohort 1936 (LBC1936) age 76 years and performed brain MRI. We calculated sleep efficiency, measured WMH and brain volumes, quantified PVS, and assessed associations between sleep measures and brain markers in multivariate models adjusted for demographic and medical history variables.

RESULTS

In 457 subjects (53% males, mean age 76 ± 0.65 years), we found: brain and white matter loss with increased weekend daytime sleep (β = -0.114, P = 0.03; β = -0.122, P = 0.007 respectively), white matter loss with less efficient sleep (β = 0.132, P = 0.011) and PVS increased with interrupted sleep (OR 1.84 95% CI, P = 0.025).

CONCLUSION

Cross-sectional associations of sleep parameters with brain atrophy and more PVS suggest adverse relationships between usual sleep habits and brain health in older people that should be evaluated longitudinally.

Hypertension and Cognitive Decline: Implications of Obstructive Sleep Apnea

Hypertension and dementia are highly prevalent in the general population. Hypertension has been shown to be a risk factor for Alzheimer's dementia and vascular dementia. Sleep apnea, another common disorder, is strongly associated with hypertension and recent evidence suggests that it may also be linked with cognitive decline and dementia. It is possible that sleep apnea is the final common pathway linking hypertension to the development of dementia. This hypothesis merits further exploration as sleep apnea is readily treatable and such therapy could foreseeably delay or prevent the onset of dementia. At present, there is a paucity of therapeutic modalities that can prevent or arrest cognitive decline. In this review, we describe the associations between hypertension, dementia and sleep apnea, the pathophysiologic mechanisms underlying these associations, and the literature examining the impact of treatment of hypertension and sleep apnea on cognition. Potential areas of future investigation that may help advance our understanding of the magnitude and direction of the interaction between these conditions and the effects of treatment of high blood pressure and sleep apnea on cognition are highlighted.

Interarm Blood Pressure Difference has Various Associations with the Presence and Burden of Cerebral Small-Vessel Diseases in Noncardioembolic Stroke Patients

Background and Purpose

An interarm blood pressure difference (IABD) is independently related to the occurrence of cardiovascular disease and mortality. Cerebral small-vessel diseases (SVDs) are important risk factors for stroke, cognitive dysfunction, and mortality. We aimed to determine whether IABD is related to cerebral SVDs.

Methods

This study included 1,205 consecutive noncardioembolic ischemic stroke patients as confirmed by brain MRI and simultaneously measured the bilateral brachial blood pressures. We investigated cerebral SVDs based on high-grade white-matter hyperintensities (HWHs), presence of cerebral microbleeds (CMBs), high-grade perivascular spaces (HPVSs), and asymptomatic lacunar infarctions (ALIs) on brain MRI.

Results

In multivariate logistic regression, an interarm systolic blood pressure difference (IASBD) ≥10 mm Hg was independently related to the existence of HWHs [odds ratio (OR)=1.94, 95% CI=1.32–2.84, p=0.011] and had a tendency to be associated with the presence of HPVSs (OR=1.45, 95% CI=0.49–2.23, p=0.089) and ALIs (OR=1.42, 95% CI=0.96–2.11, p=0.052), but not with the presence of CMBs (OR=1.09, 95% CI=0.73–1.61, p=0.634). In multivariate linear regression adjusted for age, sex, and variables with p<0.1 in the univariate analysis, IASBD ≥10 mm Hg and interarm diastolic blood pressure difference ≥10 mm Hg were significantly correlated with an increased total burden of SVDs (β=0.080 and p=0.006, and β=0.065 and p=0.023, respectively).

Conclusions

This study found that IABD ≥10 mm Hg was associated with the presence and increased burden of cerebral SVDs in noncardioembolic stroke patients. This suggests that IABD ≥10 mm Hg could be a useful indicator of the presence and burden of cerebral SVDs in stroke patients.

Impact of Obstructive Sleep Apnea on Platelet Function Profiles in Patients With Acute Coronary Syndrome Taking Dual Antiplatelet Therapy

Background Obstructive sleep apnea ( OSA ) is a novel risk factor for acute coronary syndrome ( ACS ). Several studies have shown OSA to be associated with induced platelet reactivity. However, whether OSA have effects on platelet function profiles in ACS patients taking dual antiplatelet therapy remains unexplored. Methods and Results This was a cross-sectional observational study, in which ACS patients taking maintenance aspirin and clopidogrel therapy were included. OSA was defined as an apnea-hypopnea index ≥15 events/hour. The inhibitory rate of arachidonic acid or adenosine diphosphate pathway were assessed with thrombelastography and defined patients with high residual on-treatment platelet reactivity. Platelet indices were obtained from routine analysis of blood samples using an automated blood cell counter. A total of 127 ACS patients taking dual antiplatelet therapy were analyzed. Platelet volume indices, including mean platelet volume and platelet large cell ratio, were significantly increased in patients with OSA . Patients with OSA (n=68) had significantly lower inhibitory rate of adenosine diphosphate receptor pathway ( P=0.028) compared with those without (n=59). After adjustment for potential confounders, patients with OSA were more likely to have high residual on-treatment platelet reactivity after clopidogrel therapy (adjusted odds ratio: 3.25, 95% confidence interval: 1.19-8.87, P=0.021). Conclusions In ACS patients taking dual antiplatelet therapy, OSA is associated with an increased level of platelet volume indices, reduced clopidogrel-induced antiplatelet effects and a greater prevalence of high residual on-treatment platelet reactivity.

Neuroimaging and neuropathology indices of cerebrovascular disease burden

Objective

To systematically review the literature on the use of both neuroimaging and neuropathologic indices of cerebrovascular disease (CVD) burden, as estimation of this burden could have multiple benefits in the diagnosis and prognosis of cognitive impairment and dementia.

Methods

MEDLINE and EMBASE databases were searched (inception to June 2017) to obtain and then systematically review all pertinent neuroimaging and neuropathology studies, where an index of CVD was developed or tested.

Results

Twenty-five neuroimaging articles were obtained, which included 4 unique indices. These utilized a limited range of CVD markers from mainly structural MRI, most commonly white matter hyperintensities (WMH), cerebral microbleeds, and dilated perivascular spaces. Weighting of the constituent markers was often coarse. There were 7 unique neuropathology indices, which were heterogeneous in their regions sampled and lesions examined.

Conclusion

There is increasing interest in indices of total CVD burden that incorporate multiple lesions, as traditional individual markers of CVD such as WMH only provide limited information. Neuropathologic indices are needed to validate neuroimaging findings. The studies clearly demonstrated proof of concept that information from multiple imaging measures of CVD provide more information, including a stronger association with cognitive impairment and dementia, than that provided by a single measure. There has been limited exploration of the psychometric properties of published indices and no comparison between indices. Further development of indices is recommended, including the use of data from diffusion tensor and perfusion imaging.

Obstructive sleep apnea and cerebral white matter change: a systematic review and meta-analysis

Obstructive sleep apnea (OSA) can cause sleep fragmentation and intermittent hypoxemia, which are linked to oxidative stress. White matter changes (WMCs) representing cerebrovascular burden and are at risk factor for oxidative ischemic injury. The current study explores the mutual relationships between OSA and WMCs. We performed a systematic review of electronic databases for clinical studies investigating OSA and WMCs. Random-effects models were used for pooled estimates calculation. A total of 22 studies were included in the meta-analysis. The results revealed a significantly higher prevalence rate of WMCs [odds ratio (OR) 2.06, 95% confidence interval (CI) 1.52-2.80, p < 0.001] and significantly higher severity of WMCs (Hedges' g = 0.23, 95% CI 0.06-0.40, p = 0.009) in the patients with OSA than in controls. Furthermore, the results revealed a significantly higher apnea-hypopnea index (Hedges' g = 0.54, 95% CI 0.31-0.78, p < 0.001) and significantly higher prevalence rate of moderate-to-severe OSA (OR 2.86, 95% CI 1.44-5.66, p = 0.003) in the patients with WMCs than in controls, however there was no significant difference in the prevalence rate of mild OSA between the patients with WMCs and controls (OR 0.71, 95% CI 0.20-2.54, p = 0.603). OSA was associated with a higher prevalence and more severe WMCs, and the patients with WMCs had an increased association with moderate-to-severe OSA. Future large-scale randomized controlled trials with a longitudinal design are essential to further evaluate treatment in patients with OSA.

Sympathetic Overactivity Based on Heart-Rate Variability in Patients with Obstructive Sleep Apnea and Cerebral Small-Vessel Disease

Background and Purpose

Obstructive sleep apnea (OSA) is associated with cerebral white-matter changes (WMC), but the underlying mechanisms are not completely understood. Our aim was to identify the cardiovascular autonomic characteristics during sleep that are associated with cerebral WMC in OSA patients.

Methods

We recruited subjects from our sleep-center database who underwent both polysomnography and brain MRI within a 1-year period. Sixty patients who had OSA with WMC (OSA+WMC), 44 patients who had OSA without WMC (OSA−WMC), and 31 control subjects who had neither OSA nor WMC were analyzed. Linear and nonlinear indices of heart-rate variability (HRV) were analyzed in each group according to different sleep stages and also over the entire sleeping period.

Results

Among the nonlinear HRV indices, the Poincaré ratio (SD12) during the entire sleep period was significantly increased in the OSA+WMC group, even after age adjustment. Meanwhile, detrended fluctuation analysis 1 during non-rapid-eye-movement sleep tended to be lowest in the OSA+WMC group. These indices were altered regardless of the presence of hypertension or diabetes. In the subgroup analysis of middle-aged OSA patients, approximate entropy during rapid-eye-movement sleep was significantly lower in OSA+WMC patients than in OSA−WMC patients. Overall, the nonlinear HRV indices suggest that sympathetic activity was higher in the OSA+WMC group than in the OSA−WMC and control groups.

Conclusions

Our findings suggest that dysregulation of HRV, especially overactivation of sympathetic tone, could be a pathophysiologic mechanism underlying the development of WMC in OSA patients.

Sleep Disturbances as a Risk Factor for Stroke

Sleep, a vital process of human being, is carefully orchestrated by the brain and consists of cyclic transitions between rapid eye movement (REM) and non-REM (NREM) sleep. Autonomic tranquility during NREM sleep is characterized by vagal dominance and stable breathing, providing an opportunity for the cardiovascular-neural axis to restore homeostasis, in response to use, distress or fatigue inflicted during wakefulness. Abrupt irregular swings in sympathovagal balance during REM sleep act as phasic loads on the resting cardiovascular system. Any causes of sleep curtailment or fragmentation such as sleep restriction, sleep apnea, insomnia, periodic limb movements during sleep, and shift work, not only impair cardiovascular restoration but also impose a stress on the cardiovascular system. Sleep disturbances have been reported to play a role in the development of stroke and other cardiovascular disorders. This review aims to provide updated information on the role of abnormal sleep in the development of stroke, to discuss the implications of recent research findings, and to help both stroke clinicians and researchers understand the importance of identification and management of sleep pathology for stroke prevention and care.

New Insight into the Role of Obstructive Sleep Apnea in Cardiometabolic Diseases

Humans spend almost one third of their life sleeping, thus sleep deprivation or poor sleep quality will have consequences upon the quality of life. Obstructive sleep apnea (OSA) is the most common sleep disorder that represents a respiratory cessation for at least ten seconds, which appears repeatable during sleep and it is accompanied by decreased oxygen saturation. The diagnosis of OSA is possible by filling in the STOP, STOP BANG, BERLIN questionnaires and performing the polysomnography, an accessible and more accurate method but yet very expensive. The prevalence of OSA is continuously increasing, but because of the nonspecific symptoms, the percentage of un-diagnosed cases is further increased. Data from 11 epidemiological studies published between 1993 and 2014 indicated an OSA prevalence of 22% in men and 17% in women. It has been suggested that there is a bidirectional causal relationship between OSA and obesity, and numerous studies have shown association of OSA with insulin resistance, diabetes mellitus, diabetic micro- and macrovascular complications and atrial fibrillation.

Perivascular spaces, glymphatic dysfunction, and small vessel disease

Cerebral small vessel diseases (SVDs) range broadly in etiology but share remarkably overlapping pathology. Features of SVD including enlarged perivascular spaces (EPVS) and formation of abluminal protein deposits cannot be completely explained by the putative pathophysiology. The recently discovered glymphatic system provides a new perspective to potentially address these gaps. This work provides a comprehensive review of the known factors that regulate glymphatic function and the disease mechanisms underlying glymphatic impairment emphasizing the role that aquaporin-4 (AQP4)-lined perivascular spaces (PVSs), cerebrovascular pulsatility, and metabolite clearance play in normal CNS physiology. This review also discusses the implications that glymphatic impairment may have on SVD inception and progression with the aim of exploring novel therapeutic targets and highlighting the key questions that remain to be answered.