American Heart Association

epidemiology and genetics

Breath Well During Sleep; Have Less Risk for Recurrent Ischemic Strokes

Lina Palaiodimou, MD

Brown DL, Shafie-Khorassani F, Kim S, Chervin RD, Case E, Morgenstern LB, et al. Sleep-Disordered Breathing Is Associated With Recurrent Ischemic Stroke. Stroke. 2019;50:571–576.

The role of sleep-disordered breathing (SDB) is well established in the development of a first stroke or death from any cause. Previous studies have shown that SDB is associated with an increased incidence of stroke or death from any cause, and this association is independent of other cardiovascular and cerebrovascular risk factors. This condition appears both in prestroke patients and in poststroke patients, and is more often obstructive than central. An association between SDB and recurrent strokes is also being presumed, but there are no sufficient prospective data to demonstrate and support this association.

The study of Brown et al. is an attempt to enrich the scarce data regarding the interaction between SDB and recurrent strokes. More specifically, the primary endpoint of this study is to investigate the association between SDB and recurrent ischemic stroke and secondary endpoints are: possible association between SDB and all-cause poststroke mortality and possible influence of ethnicity on the interaction between SDB and outcome measures (recurrent stroke or mortality). For that purpose, the investigators designed a prospective study of 842 patients who suffered from an index ischemic stroke and underwent a sleep apnea study shortly after the event. Additionally, patients had to be above 45 years old and be a resident of Nueces County, as the study was limited in 7 acute care hospitals of this certain county. Demographics, stroke risk factors, clinical variables and the REI (which is the sum of apneas plus hypopneas per hour of sleep apnea study duration) were recorded. Patients were followed until the first recurrent stroke, death or the last follow-up date, whichever came first. Proportional hazard models were conducted, both unadjusted and adjusted, to assess the association between REI and recurrent stroke or death. Finally, the interaction of ethnicity, REI and each outcome was statistically analyzed.

Impact of Air Pollution on Stroke Mortality

Kristina Shkirkova, BSc

Chen G, Wang A, Li S, Zhao X, Wang Y, Li H, et al. Long-Term Exposure to Air Pollution and Survival After Ischemic Stroke. Stroke. 2019;50:563-570

The risk factors of stroke, a major contributor to the global burden of disability and mortality, include environmental exposure to air pollution. Pre-stroke long-term exposure to air pollution derived particulate matter is associated with higher mortality rates after ischemic stroke, the authors of the new study from China report.

The study by Chen et al. estimated the daily exposure of a cohort of 12291 ischemic stroke patients to air pollutants via a machine learning algorithm that accounted for temporal and spatial meteorological and satellite monitoring data for the geocoded location of patients’ home address. The authors looked at 3-year pre-stroke air levels of particulate matter with aerodynamic diameter ≤10 μm and nitrogen dioxide and the rates of mortality after ischemic stroke within 1 year follow up period between 2007 and 2008. Smaller coarse particles in the air mixture were the primary interest in this study, as they contain the most toxin and are able penetrate deeper through the respiratory system and cause an inflammatory response.

Rising Incidence of Stroke in Pregnancy: What’s to Blame?

Kara Jo Swafford, MD

Liu S, Chan W-S, Ray JG, Kramer MS, Joseph KS, and for the Canadian Perinatal Surveillance System (Public Health Agency of Canada). Stroke and Cerebrovascular Disease in Pregnancy: Incidence, Temporal Trends, and Risk Factors. Stroke. 2018;50:13–20.

Stroke is the most common cause of long-term disability in women after pregnancy. In Canada, the incidence of stroke at delivery was 4.8 per 100,000 deliveries between 2003-2007, with an associated case fatality of 9.4%. In the United States, the rate of stroke during the antepartum period increased from 15 to 22 per 100,000 deliveries between 1994-1995 and 2006-2007, with the rate during the postpartum period increasing from 12 to 22 per 100,000 deliveries over the same time period.

Liu et al. investigated the incidence, trends and risk factors associated with stroke in pregnancy in Canada by performing a retrospective population-based cohort study including antenatal, delivery and postpartum admissions within 42 days between 2003-2016. Stroke incidence was 13.4 cases per 100,000 deliveries between 2003-2016; 60% hemorrhagic and 30% ischemic stroke, with a 7.4% case fatality rate. Over half (51.7%) of cases occurred during the postpartum period. The rate of stroke increased from 10.8 to 16.6 cases per 100,000 deliveries between 2003-2004 and 2015-2016. Risk increased with increasing gestational duration, advanced maternal age, gestational hypertension, preeclampsia, eclampsia, connective tissue disorders, sepsis, postpartum hemorrhage requiring blood transfusion, congenital heart disease, HIV infection and thrombophilia. Several potential confounders, such as smoking, body mass index, ethnicity and socio-economic status, were not available.

Article Commentary: “Long-Term Exposure to Particulate Matter Air Pollution Is a Risk Factor for Stroke”

Burton J. Tabaac, MD

Scheers H, Jacobs L, Casas L, Nemery B, Nawrot TS. Long-Term Exposure to Particulate Matter Air Pollution Is a Risk Factor for Stroke: Meta-Analytical Evidence. Stroke. 2018

A study in 2010, published in INTERSTROKE, detailed the risk factors for stroke in 22 countries. It was shown that 90% of all ischemic and hemorrhagic strokes can be attributed to 10 major risk factors, hypertension and current smoking being the most prominent.1 This current meta-analytical article, written by Scheers et al, analyzed the Pubmed citation database to quantify the pooled association between stroke incidence and mortality with long-term exposure to particulate matter. This meta-analysis suggests a statistically significant effect of recent particulate matter exposure and the risk of stroke.

The article incorporates 20 publications, including more than 10 million people, and more than 200,000 stroke events to reveal that the association between long-term particulate matter exposure and stroke event was positive in North America and Europe (but not statistically significant for the latter) and null in Asia. The authors are keen to differentiate recent and long-term exposure to particulate matter, as they are different pathophysiological concepts. The study focus regarding short-term exposure asks when strokes are most likely to occur, whereas the consideration pertaining to long-term exposure focuses on where people are at risk.

Article Commentary: “Smoking and Risk of Ischemic Stroke in Young Men”

Burton J. Tabaac, MD

Markidan J, Cole JW, Cronin CA, Merino JG, Phipps MS, Wozniak MA, et al. Smoking and Risk of Ischemic Stroke in Young Men. Stroke. 2018

For nearly 30 years, the dose-response relationship between tobacco consumption and stroke risk has been well established. First published in Stroke, in September 2008, this Maryland group of researchers demonstrated a strong dose-response relationship between current cigarette smoking and ischemic stroke (IS) risk among young women. This latest report demonstrates a similar dose-response effect among young men. Because of potential interactions between smoking and hormonal milieu, a separate examination of this issue in men is important. The authors are keen to note that cigarette smoking, a modifiable risk factor for ischemic stroke, has been on the rise among young adults. The team devised a population-based, case-control study of risk factors for IS in men ages 15 to 49 years, with a study population of 1145 subjects. Demographic characteristics of participants were adjusted for potential confounding factors, including age, race, education, hypertension, myocardial infarction, angina, diabetes mellitus, and body mass index.

Demographic Characteristics of Participants

Statins and Intracerebral Hemorrhage — Causation or Coincidence?

Kevin S. Attenhofer, MD

Gaist D, Goldstein LB, Cea Soriano L, García Rodríguez LA. Statins and the Risk of Intracerebral Hemorrhage in Patients With Previous Ischemic Stroke or Transient Ischemic Attack. Stroke. 2017

Statins are some of the most commonly prescribed drugs in the fields of cardio- and cerebrovascular disease. In the last two decades, randomized controlled trials have shown that statin therapy reduces the risk of major vascular events in high-risk populations. Definitions of these populations have changed over the years, but currently the AHA/ASA stroke guidelines recommend statins in all patients for secondary stroke prevention.

Despite the ubiquitous usage of statins, it has been noted that some data (from the Heart Protection Study (HPS) and the Stroke Prevention with Aggressive Reductions of Cholesterol Levels (SPARCL)) suggests that the benefits of high-dose atorvastatin treatment was partially offset by an increase in hemorrhagic stroke. The association of statins and intracerebral hemorrhage (ICH) has remained controversial ever since. Subsequent meta-analyses and case control studies — some of which included data from SPARCL — found no associated increase in the risk of ICH in patients on statin therapy.

Eating Healthy: Tips for Stroke Prevention

Rohan Arora, MD

Larsson SC. Dietary Approaches for Stroke Prevention. Stroke. 2017

This review by Susanna Larsson focuses on the current evidence from randomized controlled trials and prospective studies on dietary modifications that could help with stroke prevention.

The article is very important since diet is one of the modifiable factors that can help with reducing the risk of stroke and promote cardiovascular health. The stroke survivors or their family members are of utmost curiosity to change their diet after seeing a family member suffer from stroke.

Physical Activity and Stroke Risk: A Role for Moderate Physical Activity

Mark R. Etherton, MD, PhD

Willey JZ, Voutsina J, Sherzai A, Ma H, Bernstein L, Elkind MSV, et al. Trajectories in Leisure-Time Physical Activity and Risk of Stroke in Women in the California Teachers Study. Stroke. 2017

In this entry, I discuss a recent publication by Joshua Willey and colleagues regarding the protective effects of physical activity on stroke risk.

A beneficial role of physical activity in the prevention of cardiovascular disease and ischemic stroke has been consistently demonstrated. An outstanding question, however, is how changes in physical activity impact incident stroke risk. The authors of this manuscript, therefore, set out to investigate the association between changes in self-reported physical activity at two time points and incident stroke risk.

The authors used the California Teachers Study cohort, which is a large prospective cohort of female teachers in the state of California, and examined self-reported physical activity at two time points (1995 and 2005-6). In total, 61,256 participants were included in the analysis with notable exclusion criteria, including history of stroke or age less than 26 years old. Exercise was reported as moderate (e.g. brisk walking) or strenuous (e.g. swimming, running) and quantified as hours per week and months per year in the past 3 years. The authors used this data to then establish average minutes/week and dichotomized the measures by the AHA recommendations for moderate (150 minutes/week) or strenuous (75 minutes/week) activity. Using these metrics of physical activity, the authors assessed incident stroke risk.

Location of Brain Infarct and Gender is Associated with Risk of Dementia: A Review of AGES-Reykjavik Study

Shashank Shekhar, MD, MS

Sigurdsson S, Aspelund T, Kjartansson O, Gudmundsson EF, Jonsdottir MK, Eiriksdottir G, et al. Incidence of Brain Infarcts, Cognitive Change, and Risk of Dementia in the General Population: The AGES-Reykjavik Study (Age Gene/Environment Susceptibility-Reykjavik Study). Stroke. 2017

The recent published longitudinal study by Sigurdsson and colleagues highlights the types of infarction that are associated with cognitive decline, as well as the sex factor that can contribute to dementia after ischemic strokes.

This study is based on the longitudinal data gathered from an Icelandic population-based cohort of men and women from 2002 to 2006, in which 5764 participants were examined. A total of 3316 patients were followed up from 2007 to 2011. The study utilized the MRI to get the baseline and follow-up imaging to define the location of the stroke. All types of infarcts were included and categorized into Cortical infarcts, subcortical infarcts, and cerebellar infarction. Of 3316 participants from the follow-up, 2612 participants (1070 male and 1542 female) were included. Rejection of the rest was based on exclusion criteria. Cognition was assessed regarding memory, processing speed, and executive function. The cognitive screening was done with mini-mental and digital symbol substitution test and later confirmed using a diagnostic battery of neuropsychological tests. For each infarction type, the sample was categorized into four groups based on a combination of incidence and prevalence to find gender-based differences.

Reducing Recurrent Strokes with Secondary Risk-Factor Modification — Reflections from Temporal Trends in a Population-Based Study

Gurmeen Kaur, MBBS

Bergström L, Irewall AL, Söderström L, Ögren J, Laurell K, Mooe T. One-Year Incidence, Time Trends, and Predictors of Recurrent Ischemic Stroke in Sweden From 1998 to 2010: An Observational Study. Stroke. 2017

The risk of recurrent stroke has been on a decline as per estimates from different countries, including Italy, Taiwan and the “Western world.” Rikstroke is the Swedish Stroke Register where all Swedish hospital admissions because of stroke are recorded. The authors describe an excellent longitudinal study design where patients with ischemic strokes were followed up from 1998 to 2009. From the year 1998, all Swedish hospitals and rehab centers report their admissions to the Rikstroke registry, which had an astounding 85% coverage in the year 2009.

The recurrence of ischemic stroke events was calculated by amalgamating the Rikstroke registry with the Swedish National Inpatient Register (IPR), which contains data about diagnoses and dates of discharge from hospitalizations in Sweden.