Advances in Population-Based Studies
In 2009, population-based studies have continued to generate many new results about stroke occurrence and interesting hypotheses about the relation between risk factors and stroke occurrence.
High levels of C-reactive protein have been associated with the risk of myocardial infarction, whereas the association with stroke remains controversial.1 The association between high-sensitivity C-reactive protein (hsCRP)and stroke was examined in the multiethnic, stroke-free, community-based cohort study in Northern Manhattan.2 hsCRP measurements were available for 2240 subjects age 40 years and older. Compared with subjects whose hsCRP values were <1 mg/L, those whose hsCRP levels were >3 mg/L were at increased risk for ischemic stroke (hazard ratio [HR]=1.20; 95% CI, 0.78 to 1.86), myocardial infarction (HR=1.70; 95% CI, 1.04 to 2.77), and death (HR=1.55; 95% CI, 1.23 to 1.96) after adjustment for demographic characteristics and risk factors. Different results among studies may depend on population characteristics such as age and other risk factors.
Glococorticoid Use and Atrial Fibrillation
Glucocorticoid (GCT) use is common for the treatment of many different diseases. However, treatment with high-dose GCT is associated with atherosclerosis, diabetes mellitus, and hypertension, and such treatment may increase the risk of cardiovascular disease, including stroke.3 A population-based, case-control study examined whether treatment with GCT was associated with atrial fibrillation,4 which is a well-established risk factor for stroke. All patients with a first hospital diagnosis of atrial fibrillation among a total population of 1.7 million were included, totalling 20 211 patients. Information about GCT treatment was based on linkage to national medical databases. For each case, 10 population controls were selected and matched by age and sex. Current GCT use was associated with an increased risk of atrial fibrillation compared with never use (adjusted odds ratio=1.92; 95% CI, 1.79 to 2.06); in new GCT users, the adjusted odds ratio was 3.62 (95% CI, 3.11 to 4.22), whereas former GCT use was not associated with increased risk. These results suggest that atrial fibrillation may act as an intermediary factor between GCT use and risk of ischemic stroke.
Thirty-Year Stroke Risk Prediction
Multiple risk scores have been developed for identifying subjects with an increased risk of stroke. The Framingham Study was 1 of the first to provide data on risk factor exposure and risk of stroke within a 10-year follow-up period. With increasing life expectancy, understanding the longer-term risk associated with risk factor exposure would improve projections of stroke burden and identify areas for intervention. Based on data from 4506 subjects of Framingham study offspring, a modified Cox model that allowed for adjustment for the competing risk of noncardiovascular death was used to construct a prediction algorithm for 30-year risk of coronary death, myocardial infarction, and stroke.5 Well-established risk factors such as male sex, level of systolic blood pressure, antihypertensive treatment, total and HDL cholesterol, tobacco smoking, and diabetes mellitus were significantly related to the incidence of cardiovascular events, including stroke. Current efforts to reduce exposure to well-established stroke risk factors may remain the focus of interventions to reduce future stroke burden.
Stroke Mortality in Subgroups
Current knowledge about trends in stroke mortality is limited to only a few populations living mostly in high-income countries or relies on nonvalidated routine mortality statistics.6 Despite the methodologic limitations, using routine data is often a first step in generating a platform for future studies. Populations undergoing rapid changes in lifestyle may be especially vulnerable for developing cardiovascular diseases, including stroke. A study among Alaska native people showed that, compared with US whites, their stroke mortality rates were significantly higher from 1994 to 2003.7 Alaska native women and men younger than 45 years had the highest risk. Differences in mortality rates were a result of stable rates in Alaska natives, whereas rates declined in US whites. Alaska native people have had a marked change in lifestyle in recent decades, with a shift to a Westernized diet, increasing body mass index, glucose intolerance, and hypertension. The study also suggests that in high-income regions, subgroups in the population may be at different stages in the stroke epidemic and deserve focused stroke prevention and intervention.
Explaining Stroke Prevalence in the US ‘Stroke Belt’
The US stroke belt consists of 11 states that have the highest age-adjusted stroke mortality compared with that of the remaining 39 states. Identification of factors associated with stroke prevalence is essential for developing interventions that can reduce stroke burden. Self-reported data sets from the 2005 and 2007 Behavioral Risk Factor Surveillance System were used, and the analysis included 153 106 respondents from the stroke belt region with 6615 cases of stroke and 612 262 respondents with 21 347 cases of stroke from the non–stroke belt region.8 Age, sex, ethnicity, socioeconomic status, risk factors (overweight, obesity, and smoking), and chronic diseases (hypertension, diabetes, and coronary heart disease) accounted for 72% of the excess stroke prevalence. Limitations include cross-sectional telephone survey, self-reported data, and that it was nonfatal stroke prevalence that was examined and not stroke mortality or incidence. However, the consistency with other studies strongly suggests that known risk factors and socioeconomic status account for most of the difference in stroke prevalence.
Tobacco Cessation After Stroke
Tobacco smoking is a well-established risk factor for stroke, other cardiovascular diseases, and overall mortality.9 The risk of stroke rapidly declines in subjects who stop smoking, and epidemiologic studies suggest that tobacco cessation is effective in secondary stroke prevention.9 However, little is known about smoking cessation rates after stroke. A study of stroke patients living in Melbourne, Australia, aimed at estimating the proportion of stroke survivors at 5 years who had stopped tobacco smoking.10 Two of 3 who were smokers at the time of stroke symptom onset were still smoking 5 years later. Among ever-smokers, 40% could not recall receiving any advice about smoking cessation. The Australian study emphasizes the need for improving strategies for lifestyle modifications in patients after stroke, and there seems to be no safe way to use tobacco products: a systematic review and meta-analysis showed that consumers of smokeless tobacco had an increased risk of fatal stroke (1.40; 95% CI, 1.28 to 1.54).11
Differences in Stroke Between Blacks and Whites in South Africa
The majority of stroke events occur in low- and middle-income countries, and the number of events will increase with increasing life expectancy and changes in exposure to major stroke risk factors. With limited resources and capacity for “ideal” stroke studies, hospital-based stroke registries may provide important results that could identify possible areas for intervention. A hospital-based stroke register in Johannesburg, South Africa, included 524 patients with presumed stroke, of whom 432 (82%) were first-ever stroke patients and 308 (59%) were black.12 Significant differences were noted between black and white patients: the mean age of black patients was 51 years versus 61 years in whites, and cerebral hemorrhage was more common in black patients, 27%, versus 15% in whites. There were no significant differences in the prevalence of hypertension and diabetes, whereas cigarette smoking was more frequent in white patients, at 54% versus 23%. Differences in stroke subtype were linked to differences in risk factor exposure in black and white population groups.
Stroke in Europe
Stroke mortality rates have differed considerably among European countries, with relatively low rates in western European countries and high rates in eastern European countries.13 Comparisons of stroke incidence rates have been difficult owing to the low number of studies and different methodologies. Since the WHO MONICA project, the European Registers of Stroke is the first multinational study to report stroke incidence rates according to standardized criteria.14 First-ever stroke incidence rates were reported from populations in France (Dijon), Italy (Sesto Fiorentino), Lithuania (Kaunas), the United Kingdom (London), Spain (Menorca), and Poland (Warsaw), with a total source population of 1.l million inhabitants. Stroke incidence rates per 100 000 adjusted to the European population ranged from 101 in men and 63 in women in Sesto to 239 in men and 159 in women in Kaunas. Differences in exposure to major stroke risk factors were marked for hypertension, diabetes mellitus, and tobacco smoking. Stroke incidence rates remained highest in the eastern European populations.
Trends in Public Awareness 1995 to 2005
A high level of public awareness of stroke symptoms, risk factors, and treatment is important for fast referral of patients for thrombolytic therapy, rehabilitation, and sustained support for improving stroke prevention. Surveys in the Greater Cincinnati/Northern Kentucky region (United States) were previously done in 1995, 2000, and again in 2005.15 During the 10-year study period, 6209 interviews were completed. The proportion of the population who knew at least 1 risk factor increased from 59% in 1995% to 71% in 2000. Knowledge of at least 1 warning sign improved from 48% to 68%. The proportion of subjects with correct knowledge about 3 risk factors increased from 2.6% in 1995 to 4.8% in 2005, and correct mentioning of 3 warning signs increased from 5.4% in 1995 to 15.7% in 2005. Most of the increase in knowledge occurred between 1995 and 2000, with little improvement between 2000 and 2005. Public awareness about tissue plasminogen activator was low, with 19% who claimed to have heard about the treatment. Black race and <12th-grade education were independently associated with poorer knowledge about tissue plasminogen activator.
- Received November 9, 2009.
- Accepted November 12, 2009.
Elkind MS, Luna JM, Moon YP, Liu KM, Spitalnik SL, Paik MC, Sacco RL. High-sensitivity C-reactive protein predicts mortality but not stroke: the Northern Manhattan Study. Neurology. 2009; 20: 73: 1300–1307.
Pencina MJ, D'Agostino RB Sr, Larson MG, Massaro JM, Vasan RS. Predicting the 30-year risk of cardiovascular disease: the Framingham Heart Study. Circulation. 2009; 119: 3078–3084.
Truelsen T, Bonita R, Jamrozik K. Surveillance of stroke: a global perspective. Int J Epidemiol. 2001; 30 (suppl 1): S11–S16.
Liao Y, Greenlund KJ, Croft JB, Keenan NL, Giles WH. Factors explaining excess stroke prevalence in the US Stroke Belt. Stroke. 2009; 40: 3336–3341.
Boffetta P, Straif K. Use of smokeless tobacco and risk of myocardial infarction and stroke: systematic review with meta-analysis. BMJ. 2009; 339: b3060.
Connor MD, Modi G, Warlow CP. Differences in the nature of stroke in a multiethnic urban South African population: the Johannesburg Hospital Stroke Register. Stroke. 2009; 40: 355–362.
Incidence of stroke in Europe at the beginning of the 21st century. Stroke. 2009; 40: 1557–1563.
Kleindorfer D, Khoury J, Broderick JP, Rademacher E, Woo D, Flaherty ML, Alwell K, Moomaw CJ, Schneider A, Pancioli A, Miller R, Kissela BM. Temporal trends in public awareness of stroke: warning signs, risk factors, and treatment. Stroke. 2009; 40: 2502–2506.