Physical Activity Is Inversely Associated With Severe Intracranial Stenosis in Stroke-Free Participants of NOMAS.

BACKGROUND: Although protective in secondary stroke prevention of intracranial arterial stenosis (ICAS), it is uncertain if the benefits of leisure time physical activity (LTPA) extend to asymptomatic ICAS or extracranial carotid stenosis (ECAS). Therefore, we sought to determine LTPA's relationship with ECAS and ICAS in a stroke-free, race-ethnically diverse cohort. METHODS: This cross-sectional study included participants from the magnetic resonance imaging substudy of the Northern Manhattan Study, of whom 1274 had LTPA assessments at enrollment. LTPA was represented continuously as metabolic equivalent score (MET-score) and ordinally as model-based cluster analysis (LTPA-cluster), both based on the same LTPA assessments. We evaluated ECAS sonographically using carotid intima-media thickening and number of carotid plaques. ICAS was assessed with time-of-flight magnetic resonance angiograph and defined as ≥50% or ≥70% stenosis. We applied regression analyses to evaluate the association between LTPA with ECAS and ICAS, adjusting for confounders. RESULTS: Of 1274 included participants (mean age 71±9 years; 60% women; 65% Hispanic), the mean MET-score was 10±16 and 60% were in a LTPA-cluster with any activity. Among those with carotid ultrasound (n=1234), the mean carotid intima-media thickening was 0.97±0.09 mm, and 56% of participants had at least one carotid plaque identified. Among those with magnetic resonance angiograph (n=1211), 8% had ≥50% ICAS and 5% had ≥70% ICAS. For ICAS, MET-score was associated with ≥70% ICAS (adjusted odds ratio per unit increase in MET-score [95% CI, 0.97 [0.94-0.99]) but not with ECAS measures (carotid intima-media thickening, adjusted ß-estimate per unit increase in MET-score [95% CI], 0.002 [-0.003 to 0.006] or number of plaques, adjusted ß-estimate [95% CI], 0.0001 [-0.0001 to 0.0003]). Substituting MET-score with LTPA-clusters replicated the association between ≥70% ICAS and LTPA (adjusted odds ratio per each increased LTPA-cluster [95% CI], 0.83 [0.70-0.99]). CONCLUSIONS: In this diverse stroke-free population, we found LTPA most strongly associated with asymptomatic ≥70% ICAS. Given the high-risk nature of ≥70% ICAS, these findings may emphasize the role of LTPA in people at risk for ICAS.

Dietary Sodium to Potassium Ratio and Risk of Stroke in a Multiethnic Urban Population: The Northern Manhattan Study.

BACKGROUND AND PURPOSE: There is growing evidence that increased dietary sodium (Na) intake increases the risk of vascular diseases, including stroke, at least in part via an increase in blood pressure. Higher dietary potassium (K), seen with increased intake of fruits and vegetables, is associated with lower blood pressure. The goal of this study was to determine the association of a dietary Na:K with risk of stroke in a multiethnic urban population. METHODS: Stroke-free participants from the Northern Manhattan Study, a population-based cohort study of stroke incidence, were followed-up for incident stroke. Baseline food frequency questionnaires were analyzed for Na and K intake. We estimated the hazard ratios and 95% confidence intervals for the association of Na:K with incident total stroke using multivariable Cox proportional hazards models. RESULTS: Among 2570 participants with dietary data (mean age, 69±10 years; 64% women; 21% white; 55% Hispanic; 24% black), the mean Na:K ratio was 1.22±0.43. Over a mean follow-up of 12 years, there were 274 strokes. In adjusted models, a higher Na:K ratio was associated with increased risk for stroke (hazard ratio, 1.6; 95% confidence interval, 1.2-2.1) and specifically ischemic stroke (hazard ratio, 1.6; 95% confidence interval, 1.2-2.1). CONCLUSIONS: Na:K intake is an independent predictor of stroke risk. Further studies are required to understand the joint effect of Na and K intake on risk of cardiovascular disease.

Trajectories in Leisure-Time Physical Activity and Risk of Stroke in Women in the California Teachers Study.

BACKGROUND AND PURPOSE: Whether changes in leisure-time physical activity (LTPA) over time are associated with lower risk of stroke is not well established. We examined the association between changes in self-reported LTPA 10 years apart, with risk of incident stroke in the CTS (California Teachers Study). We hypothesized that the risk of stroke would be lowest among those who remained active. METHODS: Sixty-one thousand two hundred and fifty-six CTS participants reported LTPA at 2 intensity levels (moderate and strenuous activity) at 2 time points (baseline 1995-96; 10-year follow-up 2005-2006). LTPA at each intensity level was categorized based on American Heart Association (AHA) recommendations (moderate, >150 minutes/week; strenuous, >75 minutes/week). Changes in LTPA were summarized as follows: (1) not meeting recommendations at both time points; (2) meeting recommendations only at follow-up; (3) meeting recommendations only at baseline; and (4) meeting recommendations at both time points. Incident strokes were identified through California state hospitalization records. Using multivariable Cox models, we examined the associations between changes in LTPA with incident stroke. RESULTS: Nine hundred and eighty-seven women were diagnosed with stroke who completed both questionnaires. Meeting AHA recommendations at both the time points was associated with a lower risk of all stroke (adjusted hazard ratio, 0.84; 95% confidence interval, 0.72-0.98). The protective effects for stroke were driven by meeting AHA recommendations for moderate activity and largely observed for ischemic strokes (adjusted hazard ratio, 0.70; 95% confidence interval, 0.55-0.88). CONCLUSIONS: Meeting AHA recommendations for moderate activity had a protective effect for reducing ischemic stroke risk. Participants who met AHA recommendations at baseline but not at follow-up, however, were not afforded reduced stroke risk.

Cox proportional hazards models with left truncation and time-varying coefficient: Application of age at event as outcome in cohort studies.

When analyzing time-to-event cohort data, two different ways of choosing a time scale have been discussed in the literature: time-on-study or age at onset of disease. One advantage of choosing the latter is interpretability of the hazard ratio as a function of age. To handle the analysis of age at onset in a principled manner, we present an analysis of the Cox Proportional Hazards model with time-varying coefficient for left-truncated and right-censored data. In the analysis of Northern Manhattan Study (NOMAS) with age at onset of stroke as outcome, we demonstrate that well-established risk factors may be important only around a certain age span and less established risk factors can have a strong effect in a certain age span.

Dissociation among hemodynamic measures in asymptomatic high grade carotid artery stenosis.

BACKGROUND: Cerebral blood flow (CBF) regulation is a critical element in cerebrovascular pathophysiology, particularly in large vessel disease, but the best method to use for hemodynamic assessment is not clear. We examined 4 different blood-flow related measures in patients with unilateral high-grade carotid artery disease, assessing asymmetry between the occluded vs non-occluded side, and the correlations among the measures. METHODS: Thirty-three patients (age 50-93, 19 M) with unilateral 80-100% ICA occlusion but no stroke underwent: 1) mean flow velocity (MFV) in both middle cerebral arteries by transcranial Doppler (TCD), 2) quantitative resting CBF using pseudo-continuous arterial spin labeling (pCASL) MRI, 3) vasomotor reactivity (VMR) in response to 5% CO2 inhalation, and 4) dynamic cerebral autoregulation (DCA) assessing the counter-regulation of blood flow to spontaneous changes in blood pressure using TCD monitoring and finger photoplethysmography. Paired t-tests and Pearson correlations assessed side-to-side differences within each measure, and correlations between measures. RESULTS: CBF (p=0.001), MFV (p<0.001), VMR (p=0.008), and DCA (p=0.047) all showed significantly lower values on the occluded side. The 4 measures were independent of each other on correlation analysis, even when controlling for age and anterior circle of Willis collateral (all partial correlations <0.233 and p-values >0.468). CONCLUSIONS: These 4 measures showed high sensitivity to the occluded carotid artery, but their dissociation suggests that any given measure only partially characterizes the hemodynamic state. Additional research is needed to explore the multifaceted biology of cerebral blood flow regulation.

Antenatal ultrasound assessment of placental/myometrial involvement in morbidly adherent placenta.

OBJECTIVES: To examine the usefulness of sonographic criteria in the assessment of the lateral extent and depth of myometrial involvement in morbidly adherent placenta. METHODS: From hospital records and a perinatal database, women with morbidly adherent placenta confirmed at delivery and antenatal ultrasound assessment in 2004-2007 were identified. The sonographic appearance at the time of antenatal assessment was compared with the clinical and histological findings at delivery. Following statistical analysis, useful sonographic features in the assessment of myometrial invasion were identified. RESULTS: Nine cases, including one case of placenta percreta, eight cases of accreta or increta of which one minor partial, were reviewed. The criteria useful for the assessment of the lateral placental/myometrial involvement were obliteration of retroplacental clear space, increased subplacental vascularity, placental-tissue interface disruption and vessels crossing the interface disruption site with the last 2 signs applicable for helpful for assessment of the parametrium; and for the assessment of the depth, bladder serosa-uterine wall interface hypervascularity, vessels extending from placenta to bladder, placental-tissue interface disruption and vessels crossing placental-tissue interface disruption. The myometrial vascular pattern was also helpful in assessing the extensiveness of myometrial involvement. There was bulging of the lower uterine wall in the case of placenta percreta. CONCLUSIONS: Assessment of the placental/myometrial involvement of morbidly adherent placenta is possible on antenatal ultrasound examination. Combinations of different criteria may be required in assessing the lateral extent and the depth of placental/myometrial involvement.