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PURE: Contrasting associations between risk factor burden, CVD incidence and mortality in high, middle and low income countries


 Presenter abstract  Discussant report

All the Scientific resources on ESC Congress 365


By Salim Yusuf, on behalf of the PURE Investigators

Over 80% of the cardiovascular disease (CVD) mortality occurs in low and middle income countries (LIC, MIC); but it is not known whether this is due to higher risk factor levels, variations in CVD incidence, or differences in CVD mortality.

We enrolled 155,245 individuals from 628 urban and rural communities from 17 countries (3 high income countries, HIC: n=16,110, 10 MIC: n=104,260, 4 LIC: n=34,875) and assessed their CVD risk using the INTERHEART Risk Score (IHRS), and prevention practices (hypertension control, smoking cessation, use of lipid lowering drugs and secondary prevention). Participants were followed for mean of 3.5 years. Incident CVD events were documented.

Results (90% follow-up):
Mean IHRS was highest in HIC, intermediate in MIC and lowest in LIC (p<0.001). Hypertension control, smoking cessation and secondary prevention were highest in HIC compared to MIC or LIC. CVD hospitalizations or deaths were significantly higher in HIC (p<0.001) compared to MIC and LIC, with no differences between countries in the incidence of myocardial infarction, stroke or heart failure (p=0.25) but with markedly lower fatal CVD is HIC (0.5 per 1000 person years) compared to MIC (1.3) and LIC (2.7; p<0.001).

Although risk factor burden is highest in HIC, CVD mortality is lowest. While hospitalizations for major CVD showed little difference between HIC, MIC vs LIC, other less severe CVD hospitalizations were markedly higher in HIC. These data suggest that the high CVD risk factor burden in HIC is mitigated by better risk factor control, more aggressive management of less severe CVD, and better outcomes in those experiencing major CVD leading to much lower CVD mortality. Efforts at reducing the burden of risk factors in HIC, and avoiding rise in risk factors and better
management of those with CVD in MIC and LIC are both needed to reduce the global burden of health. 

Table: Mean IHRS, CVD incidence and mortality (per 1000 person years)

 HICMICLICp-value for
Mean IHRS (SD) 11.4 (6.1) 9.7 ( 5.6) 7.8 (5.0) <0.0001
CVD hosp./death 7.8 4.6 5.1 <0.0001
Major CVD* 3.7 3.6 4.2 0.254
Other CVD hosp. 4.0 1.0 0.9 <0.0001
Fatal CVD 0.5 1.3 2.7 <0.0001

Hosp. = hospitalization; *MI, stroke, HF hosp.

Discussant Report

Joep Perk

With 80 % of the global burden of cardiovascular disease lying in middle and low income countries (MIC, LIC) it is remarkable that so little yet is known about the state of preventive cardiology in these regions. So far, the epidemiological findings from the Western high income nations (HIC) have been directly applied to the global level. Prevention guidelines have mainly been derived from and directed to the practice in these high income countries not taking the significantly different conditions for providing health care in the less affluent nations into consideration. The PURE study has rightly questioned this extrapolation as the outcome of this landmark effort shows. The challenges are different!

Using the non-lab INTERHEART Risk Score (age, sex, smoking, diabetes, high BP, CVD heredity, waist-hip ratio, psychosocial stress, diet and physical activity) this score was significantly higher in HIC and lowest in LIC which is less surprising. However,  while the score predicts major, non-major and all CVD all participating countries, the absolute risk of major CVD is reported to be higher for a given risk score in poorer countries. The study shows that the incidence of major CVD is highest in LIC, intermediate in MIC and lowest in HIC (opposite to risk factor burden) and at the same time is the incidence of non-major CVD highest in HIC vs. MIC/LIC. What are the possible explanations, why this discrepancy? Lack of political decisions, lack of resources, insufficient training and failing engagement of health workers? Other explanations?

The contrast between risk level burden in the three regions and the CVD incidence and severity raises important questions both to the medical profession and to decision makers in middle and low income countries. Much can and should be improved in the practice of cardiovascular prevention. On all levels of CVD risk there is a challenge for preventive action, from early detection in populations at moderate risk (primary prevention) to active risk management in high risk individuals and in patients at very high risk (secondary prevention). Obviously there are significant differences in the quality of care as shown by the higher case-fatality rates in MIC and LIC which might even have relevance for the clinical cardiologist.

The PURE study should inspire to broad political action promoting cardiovascular health, such as tobacco legislation and public health campaigns combating adiposity and promoting physical activity. Clearly the study calls for more efficient health systems around the world, e.g. good access to health care facilities, cheaper drug treatment and post-CVD follow-up. Too often visiting a local doctor in a low income country takes the major part of a working day and the cost of drugs might equal as much as a 3-4 days income of the patient living a low income. Can preventive action be made affordable by engaging lower cost categories of health workers such as nurses or specially trained technicians? Can we learn from ongoing experiences in MIC and LIC around the globe?

With the statement of the WHO that 80% of all CVD can be prevented and with the United Nations’ call for action in the “25 by 25” campaign (reducing global CVD mortality with 25% by the year 2025) the PURE study will undoubtedly strengthen the rationale for improving CVD prevention, not merely in the middle and low income countries but even in the high income countries!


Session Title: PURE: Contrasting associations between risk factor burden, CVD incidence and mortality in high, middle and low income countries - 708

The content of this article reflects the personal opinion of the author/s and is not necessarily the official position of the European Society of Cardiology.