Sumathy Rangarajan

RISK FACTORS FOR ISCHAEMIC AND INTRACEREBRAL HAEMORRHAGIC STROKE IN 22 COUNTRIES (THE INTERSTROKE STUDY): A CASE-CONTROL STUDY

BACKGROUND The contribution of various risk factors to the burden of stroke worldwide is unknown, particularly in countries of low and middle income. We aimed to establish the association of known and emerging risk factors with stroke and its primary subtypes, assess the contribution of these risk factors to the burden of stroke, and explore the differences between risk factors for stroke and myocardial infarction. METHODS We undertook a standardised case-control study in 22 countries worldwide between March 1, 2007, and April 23, 2010. Cases were patients with acute first stroke (within 5 days of symptoms onset and 72 h of hospital admission). Controls had no history of stroke, and were matched with cases for age and sex. All participants completed a structured questionnaire and a physical examination, and most provided blood and urine samples. We calculated odds ratios (ORs) and population-attributable risks (PARs) for the association of all stroke, ischaemic stroke, and intracerebral haemorrhagic stroke with selected risk factors. FINDINGS In the first 3000 cases (n=2337, 78%, with ischaemic stroke; n=663, 22%, with intracerebral haemorrhagic stroke) and 3000 controls, significant risk factors for all stroke were: history of hypertension (OR 2.64, 99% CI 2.26-3.08; PAR 34.6%, 99% CI 30.4-39.1); current smoking (2.09, 1.75-2.51; 18.9%, 15.3-23.1); waist-to-hip ratio (1.65, 1.36-1.99 for highest vs lowest tertile; 26.5%, 18.8-36.0); diet risk score (1.35, 1.11-1.64 for highest vs lowest tertile; 18.8%, 11.2-29.7); regular physical activity (0.69, 0.53-0.90; 28.5%, 14.5-48.5); diabetes mellitus (1.36, 1.10-1.68; 5.0%, 2.6-9.5); alcohol intake (1.51, 1.18-1.92 for more than 30 drinks per month or binge drinking; 3.8%, 0.9-14.4); psychosocial stress (1.30, 1.06-1.60; 4.6%, 2.1-9.6) and depression (1.35, 1.10-1.66; 5.2%, 2.7-9.8); cardiac causes (2.38, 1.77-3.20; 6.7%, 4.8-9.1); and ratio of apolipoproteins B to A1 (1.89, 1.49-2.40 for highest vs lowest tertile; 24.9%, 15.7-37.1). Collectively, these risk factors accounted for 88.1% (99% CI 82.3-92.2) of the PAR for all stroke. When an alternate definition of hypertension was used (history of hypertension or blood pressure >160/90 mm Hg), the combined PAR was 90.3% (85.3-93.7) for all stroke. These risk factors were all significant for ischaemic stroke, whereas hypertension, smoking, waist-to-hip ratio, diet, and alcohol intake were significant risk factors for intracerebral haemorrhagic stroke. INTERPRETATION Our findings suggest that ten risk factors are associated with 90% of the risk of stroke. Targeted interventions that reduce blood pressure and smoking, and promote physical activity and a healthy diet, could substantially reduce the burden of stroke. FUNDING Canadian Institutes of Health Research, Heart and Stroke Foundation of Canada, Canadian Stroke Network, Pfizer Cardiovascular Award, Merck, AstraZeneca, and Boehringer Ingelheim.

Use of secondary prevention drugs for cardiovascular disease in the community in high-income, middle-income, and low-income countries (the PURE Study): a prospective epidemiological survey

BACKGROUND Although most cardiovascular disease occurs in low-income and middle-income countries, little is known about the use of effective secondary prevention medications in these communities. We aimed to assess use of proven effective secondary preventive drugs (antiplatelet drugs, β blockers, angiotensin-converting-enzyme [ACE] inhibitors or angiotensin-receptor blockers [ARBs], and statins) in individuals with a history of coronary heart disease or stroke. METHODS In the Prospective Urban Rural Epidemiological (PURE) study, we recruited individuals aged 35-70 years from rural and urban communities in countries at various stages of economic development. We assessed rates of previous cardiovascular disease (coronary heart disease or stroke) and use of proven effective secondary preventive drugs and blood-pressure-lowering drugs with standardised questionnaires, which were completed by telephone interviews, household visits, or on patients presentation to clinics. We report estimates of drug use at national, community, and individual levels. FINDINGS We enrolled 153,996 adults from 628 urban and rural communities in countries with incomes classified as high (three countries), upper-middle (seven), lower-middle (three), or low (four) between January, 2003, and December, 2009. 5650 participants had a self-reported coronary heart disease event (median 5·0 years previously [IQR 2·0-10·0]) and 2292 had stroke (4·0 years previously [2·0-8·0]). Overall, few individuals with cardiovascular disease took antiplatelet drugs (25·3%), β blockers (17·4%), ACE inhibitors or ARBs (19·5%), or statins (14·6%). Use was highest in high-income countries (antiplatelet drugs 62·0%, β blockers 40·0%, ACE inhibitors or ARBs 49·8%, and statins 66·5%), lowest in low-income countries (8·8%, 9·7%, 5·2%, and 3·3%, respectively), and decreased in line with reduction of country economic status (p(trend)<0·0001 for every drug type). Fewest patients received no drugs in high-income countries (11·2%), compared with 45·1% in upper middle-income countries, 69·3% in lower middle-income countries, and 80·2% in low-income countries. Drug use was higher in urban than rural areas (antiplatelet drugs 28·7% urban vs 21·3% rural, β blockers 23·5%vs 15·6%, ACE inhibitors or ARBs 22·8%vs 15·5%, and statins 19·9%vs 11·6%; all p<0·0001), with greatest variation in poorest countries (p(interaction)<0·0001 for urban vs rural differences by country economic status). Country-level factors (eg, economic status) affected rates of drug use more than did individual-level factors (eg, age, sex, education, smoking status, body-mass index, and hypertension and diabetes statuses). INTERPRETATION Because use of secondary prevention medications is low worldwide-especially in low-income countries and rural areas-systematic approaches are needed to improve the long-term use of basic, inexpensive, and effective drugs. FUNDING Full funding sources listed at end of paper (see Acknowledgments).

Prevalence, Awareness, Treatment, and Control of Hypertension in Rural and Urban Communities in High-, Middle-, and Low-Income Countries

IMPORTANCE Hypertension is the most important preventable cause of morbidity and mortality globally, yet there are relatively few data collected using standardized methods. OBJECTIVE To examine hypertension prevalence, awareness, treatment, and control in participants at baseline in the Prospective Urban Rural Epidemiology (PURE) study. DESIGN, SETTING, AND PARTICIPANTS A cross-sectional study of 153,996 adults (complete data for this analysis on 142,042) aged 35 to 70 years, recruited between January 2003 and December 2009. Participants were from 628 communities in 3 high-income countries (HIC), 10 upper-middle-income and low-middle-income countries (UMIC and LMIC), and 4 low-income countries (LIC). MAIN OUTCOMES AND MEASURES Hypertension was defined as individuals with self-reported treated hypertension or with an average of 2 blood pressure measurements of at least 140/90 mm Hg using an automated digital device. Awareness was based on self-reports, treatment was based on the regular use of blood pressure-lowering medications, and control was defined as individuals with blood pressure lower than 140/90 mm Hg. RESULTS Among the 142,042 participants, 57,840 (40.8%; 95% CI, 40.5%-41.0%) had hypertension and 26,877 (46.5%; 95% CI, 46.1%-46.9%) were aware of the diagnosis. Of those who were aware of the diagnosis, the majority (23,510 [87.5%; 95% CI, 87.1%-87.9%] of those who were aware) were receiving pharmacological treatments, but only a minority of those receiving treatment were controlled (7634 [32.5%; 95% CI, 31.9%-33.1%]). Overall, 30.8%, 95% CI, 30.2%-31.4% of treated patients were taking 2 or more types of blood pressure-lowering medications. The percentages aware (49.0% [95% CI, 47.8%-50.3%] in HICs, 52.5% [95% CI, 51.8%-53.2%] in UMICs, 43.6% [95% CI, 42.9%-44.2%] in LMICs, and 40.8% [95% CI, 39.9%-41.8%] in LICs) and treated (46.7% [95% CI, 45.5%-47.9%] in HICs, 48.3%, [95% CI, 47.6%-49.1%] in UMICs, 36.9%, [95% CI, 36.3%-37.6%] in LMICs, and 31.7% [95% CI, 30.8%-32.6%] in LICs) were lower in LICs compared with all other countries for awareness (P <.001) and treatment (P <.001). Awareness, treatment, and control of hypertension were higher in urban communities compared with rural ones in LICs (urban vs rural, P <.001) and LMICs (urban vs rural, P <.001), but similar for other countries. Low education was associated with lower rates of awareness, treatment, and control in LICs, but not in other countries. CONCLUSIONS AND RELEVANCE Among a multinational study population, 46.5% of participants with hypertension were aware of the diagnosis, with blood pressure control among 32.5% of those being treated. These findings suggest substantial room for improvement in hypertension diagnosis and treatment.

Risk factors for myocardial infarction in women and men: insights from the INTERHEART study

AIMS Coronary heart disease (CHD) is a leading cause of death among men and women globally. Women develop CHD about 10 years later than men, yet the reasons for this are unclear. The purpose of this report is to determine if differences in risk factor distributions exist between women and men across various age categories to help explain why women develop acute MI later than men. METHODS AND RESULTS We used the INTERHEART global case-control study including 27 098 participants from 52 countries, 6787 of whom were women. The median age of first acute MI was higher in women than men (65 vs. 56 years; P < 0.0001). Nine modifiable risk factors were associated with MI in women and men. Hypertension [2.95(2.66 -3.28) vs. 2.32(2.16-2.48)], diabetes [4.26(3.68-4.94) vs. 2.67(2.43-2.94), physical activity [0.48(0.41-0.57) vs. 0.77(0.71-0.83)], and moderate alcohol use [0.41(0.34-0.50) vs. 0.88(0.82-0.94)] were more strongly associated with MI among women than men. The association of abnormal lipids, current smoking, abdominal obesity, high risk diet, and psychosocial stress factors with MI was similar in women and men. Risk factors associations were generally stronger among younger individuals compared to older women and men. The population attributable risk (PAR) of all nine risk factors exceeded 94%, and was similar among women and men (96 vs. 93%). Men were significantly more likely to suffer a MI prior to 60 years of age than were women, however, after adjusting for levels of risk factors, the sex difference in the probability of MI cases occurring before the age of 60 years was reduced by more than 80%. CONCLUSION Women experience their first acute MI on average 9 years later than men. Nine modifiable risk factors are significantly associated with acute MI in both men and women and explain greater than 90% of the PAR. The difference in age of first MI is largely explained by the higher risk factor levels at younger ages in men compared to women.

Urinary Sodium and Potassium Excretion, Mortality, and Cardiovascular Events

BACKGROUND The optimal range of sodium intake for cardiovascular health is controversial. METHODS We obtained morning fasting urine samples from 101,945 persons in 17 countries and estimated 24-hour sodium and potassium excretion (used as a surrogate for intake). We examined the association between estimated urinary sodium and potassium excretion and the composite outcome of death and major cardiovascular events. RESULTS The mean estimated sodium and potassium excretion was 4.93 g per day and 2.12 g per day, respectively. With a mean follow-up of 3.7 years, the composite outcome occurred in 3317 participants (3.3%). As compared with an estimated sodium excretion of 4.00 to 5.99 g per day (reference range), a higher estimated sodium excretion (≥ 7.00 g per day) was associated with an increased risk of the composite outcome (odds ratio, 1.15; 95% confidence interval [CI], 1.02 to 1.30), as well as increased risks of death and major cardiovascular events considered separately. The association between a high estimated sodium excretion and the composite outcome was strongest among participants with hypertension (P=0.02 for interaction), with an increased risk at an estimated sodium excretion of 6.00 g or more per day. As compared with the reference range, an estimated sodium excretion that was below 3.00 g per day was also associated with an increased risk of the composite outcome (odds ratio, 1.27; 95% CI, 1.12 to 1.44). As compared with an estimated potassium excretion that was less than 1.50 g per day, higher potassium excretion was associated with a reduced risk of the composite outcome. CONCLUSIONS In this study in which sodium intake was estimated on the basis of measured urinary excretion, an estimated sodium intake between 3 g per day and 6 g per day was associated with a lower risk of death and cardiovascular events than was either a higher or lower estimated level of intake. As compared with an estimated potassium excretion that was less than 1.50 g per day, higher potassium excretion was associated with a lower risk of death and cardiovascular events. (Funded by the Population Health Research Institute and others.).

Dietary Patterns and the Risk of Acute Myocardial Infarction in 52 Countries Results of the INTERHEART Study

Background— Diet is a major modifiable risk factor for cardiovascular disease, but it varies markedly in different regions of the world. The objectives of the present study were to assess the association between dietary patterns and acute myocardial infarction (AMI) globally. Methods and Results— INTERHEART is a standardized case-control study involving participants from 52 countries. The present analysis included 5761 cases and 10 646 control subjects. We identified 3 major dietary patterns using factor analysis: Oriental (high intake of tofu and soy and other sauces), Western (high in fried foods, salty snacks, eggs, and meat), and prudent (high in fruit and vegetables). We observed an inverse association between the prudent pattern and AMI, with higher levels being protective. Compared with the first quartile, the adjusted ORs were 0.78 (95% CI 0.69 to 0.88) for the second quartile, 0.66 (95% CI 0.59 to 0.75) for the third, and 0.70 (95% CI 0.61 to 0.80) for the fourth (P for trend <0.001). The Western pattern showed a U-shaped association with AMI (compared with the first quartile, the adjusted OR for the second quartile was 0.87 [95% CI 0.78 to 0.98], whereas it was 1.12 [95% CI 1.00 to 1.25] for the third quartile and 1.35 [95% CI 1.21 to 1.51] for the fourth quartile; P for trend <0.001), but the Oriental pattern demonstrated no relationship with AMI. Compared with the first quartile, the OR of a dietary risk score derived from meat, salty snacks, fried foods, fruits, green leafy vegetables, cooked vegetables, and other raw vegetables (higher score indicating a poorer diet) increased with each quartile: second quartile 1.29 (95% CI 1.17 to 1.42), third quartile 1.67 (95% CI 1.51 to 1.83), and fourth quartile 1.92 (95% CI 1.74 to 2.11; P for trend <0.001). The adjusted population-attributable risk of AMI for the top 3 quartiles compared with the bottom quartile of the dietary risk score was 30%. Conclusions— An unhealthy dietary intake, assessed by a simple dietary risk score, increases the risk of AMI globally and accounts for ≈30% of the population-attributable risk.

Association of Urinary Sodium and Potassium Excretion with Blood Pressure

BACKGROUND Higher levels of sodium intake are reported to be associated with higher blood pressure. Whether this relationship varies according to levels of sodium or potassium intake and in different populations is unknown. METHODS We studied 102,216 adults from 18 countries. Estimates of 24-hour sodium and potassium excretion were made from a single fasting morning urine specimen and were used as surrogates for intake. We assessed the relationship between electrolyte excretion and blood pressure, as measured with an automated device. RESULTS Regression analyses showed increments of 2.11 mm Hg in systolic blood pressure and 0.78 mm Hg in diastolic blood pressure for each 1-g increment in estimated sodium excretion. The slope of this association was steeper with higher sodium intake (an increment of 2.58 mm Hg in systolic blood pressure per gram for sodium excretion >5 g per day, 1.74 mm Hg per gram for 3 to 5 g per day, and 0.74 mm Hg per gram for <3 g per day; P<0.001 for interaction). The slope of association was steeper for persons with hypertension (2.49 mm Hg per gram) than for those without hypertension (1.30 mm Hg per gram, P<0.001 for interaction) and was steeper with increased age (2.97 mm Hg per gram at >55 years of age, 2.43 mm Hg per gram at 45 to 55 years of age, and 1.96 mm Hg per gram at <45 years of age; P<0.001 for interaction). Potassium excretion was inversely associated with systolic blood pressure, with a steeper slope of association for persons with hypertension than for those without it (P<0.001) and a steeper slope with increased age (P<0.001). CONCLUSIONS In this study, the association of estimated intake of sodium and potassium, as determined from measurements of excretion of these cations, with blood pressure was nonlinear and was most pronounced in persons consuming high-sodium diets, persons with hypertension, and older persons. (Funded by the Heart and Stroke Foundation of Ontario and others.).

Prognostic value of grip strength: findings from the Prospective Urban Rural Epidemiology (PURE) study.

BACKGROUND Reduced muscular strength, as measured by grip strength, has been associated with an increased risk of all-cause and cardiovascular mortality. Grip strength is appealing as a simple, quick, and inexpensive means of stratifying an individuals risk of cardiovascular death. However, the prognostic value of grip strength with respect to the number and range of populations and confounders is unknown. The aim of this study was to assess the independent prognostic importance of grip strength measurement in socioculturally and economically diverse countries. METHODS The Prospective Urban-Rural Epidemiology (PURE) study is a large, longitudinal population study done in 17 countries of varying incomes and sociocultural settings. We enrolled an unbiased sample of households, which were eligible if at least one household member was aged 35-70 years and if household members intended to stay at that address for another 4 years. Participants were assessed for grip strength, measured using a Jamar dynamometer. During a median follow-up of 4.0 years (IQR 2.9-5.1), we assessed all-cause mortality, cardiovascular mortality, non-cardiovascular mortality, myocardial infarction, stroke, diabetes, cancer, pneumonia, hospital admission for pneumonia or chronic obstructive pulmonary disease (COPD), hospital admission for any respiratory disease (including COPD, asthma, tuberculosis, and pneumonia), injury due to fall, and fracture. Study outcomes were adjudicated using source documents by a local investigator, and a subset were adjudicated centrally. FINDINGS Between January, 2003, and December, 2009, a total of 142,861 participants were enrolled in the PURE study, of whom 139,691 with known vital status were included in the analysis. During a median follow-up of 4.0 years (IQR 2.9-5.1), 3379 (2%) of 139,691 participants died. After adjustment, the association between grip strength and each outcome, with the exceptions of cancer and hospital admission due to respiratory illness, was similar across country-income strata. Grip strength was inversely associated with all-cause mortality (hazard ratio per 5 kg reduction in grip strength 1.16, 95% CI 1.13-1.20; p<0.0001), cardiovascular mortality (1.17, 1.11-1.24; p<0.0001), non-cardiovascular mortality (1.17, 1.12-1.21; p<0.0001), myocardial infarction (1.07, 1.02-1.11; p=0.002), and stroke (1.09, 1.05-1.15; p<0.0001). Grip strength was a stronger predictor of all-cause and cardiovascular mortality than systolic blood pressure. We found no significant association between grip strength and incident diabetes, risk of hospital admission for pneumonia or COPD, injury from fall, or fracture. In high-income countries, the risk of cancer and grip strength were positively associated (0.916, 0.880-0.953; p<0.0001), but this association was not found in middle-income and low-income countries. INTERPRETATION This study suggests that measurement of grip strength is a simple, inexpensive risk-stratifying method for all-cause death, cardiovascular death, and cardiovascular disease. Further research is needed to identify determinants of muscular strength and to test whether improvement in strength reduces mortality and cardiovascular disease. FUNDING Full funding sources listed at end of paper (see Acknowledgments).

Cardiovascular Risk and Events in 17 Low-, Middle-, and High-Income Countries

BACKGROUND More than 80% of deaths from cardiovascular disease are estimated to occur in low-income and middle-income countries, but the reasons are unknown. METHODS We enrolled 156,424 persons from 628 urban and rural communities in 17 countries (3 high-income, 10 middle-income, and 4 low-income countries) and assessed their cardiovascular risk using the INTERHEART Risk Score, a validated score for quantifying risk-factor burden without the use of laboratory testing (with higher scores indicating greater risk-factor burden). Participants were followed for incident cardiovascular disease and death for a mean of 4.1 years. RESULTS The mean INTERHEART Risk Score was highest in high-income countries, intermediate in middle-income countries, and lowest in low-income countries (P<0.001). However, the rates of major cardiovascular events (death from cardiovascular causes, myocardial infarction, stroke, or heart failure) were lower in high-income countries than in middle- and low-income countries (3.99 events per 1000 person-years vs. 5.38 and 6.43 events per 1000 person-years, respectively; P<0.001). Case fatality rates were also lowest in high-income countries (6.5%, 15.9%, and 17.3% in high-, middle-, and low-income countries, respectively; P=0.01). Urban communities had a higher risk-factor burden than rural communities but lower rates of cardiovascular events (4.83 vs. 6.25 events per 1000 person-years, P<0.001) and case fatality rates (13.52% vs. 17.25%, P<0.001). The use of preventive medications and revascularization procedures was significantly more common in high-income countries than in middle- or low-income countries (P<0.001). CONCLUSIONS Although the risk-factor burden was lowest in low-income countries, the rates of major cardiovascular disease and death were substantially higher in low-income countries than in high-income countries. The high burden of risk factors in high-income countries may have been mitigated by better control of risk factors and more frequent use of proven pharmacologic therapies and revascularization. (Funded by the Population Health Research Institute and others.).

The Prospective Urban Rural Epidemiology (PURE) study: Examining the impact of societal influences on chronic noncommunicable diseases in low-, middle-, and high-income countries

BACKGROUND Marked changes in the prevalence of noncommunicable diseases such as obesity, diabetes, and cardiovascular disease have occurred in developed and developing countries in recent decades. The overarching aim of the study is to examine the relationship of societal influences on human lifestyle behaviors, cardiovascular risk factors, and incidence of chronic noncommunicable diseases. METHODS The Prospective Urban Rural Epidemiology (PURE) study is a large-scale epidemiological study that plans to recruit approximately 140,000 individuals residing in >600 communities in 17 low-, middle-, and high-income countries around the world. Individual data collection includes medical history, lifestyle behaviors (physical activity and dietary profile), blood collection and storage for biochemistry and future genetic analysis, electrocardiogram, and anthropometric measures. In addition, detailed information is being collected with respect to 4 environmental domains of interest-the built environment, nutrition and associated food policy, psychosocial/socioeconomic factors, and tobacco environment. A minimum follow-up of 10 years is currently planned. RESULTS This report describes the design, justification, and methodology of the PURE study. The PURE study has been recruiting since 2002 and has enrolled 139,506 individuals by March 31, 2009. CONCLUSIONS The PURE study builds on the work and experience gained through conduct of the INTERHEART study. Its design and extensive data collection are geared toward addressing major questions on causation and development of the underlying determinants of cardiovascular disease in populations at varying stages of epidemiologic transition.