Cancer is now responsible for twice as many deaths as cardiovascular disease (CVD) in high income countries, according to a new report from the PURE study published in The Lancet.
CVD, however, still remains the leading cause of mortality among middle aged adults globally, accounting for 40% of all deaths. It was estimated that 55 million deaths occurred in the world in 2017, of which approximately 17·7 million were due to CVD.
The PURE study is the only large prospective international cohort study that involves substantial data from a large number of high, middle and low income countries and employs standardised and concurrent methods of sampling, measurement and follow-up.
The first report, which followed 162,534 middle-aged adults (aged 35-70, 58% women) in four high income countries, 12 middle income countries and five low income countries over a median of 9.5 years (between 2005–2016), found that CVD related deaths were 2.5 times more common in middle-aged adults in low income countries compared with in high income countries, despite them experiencing a substantially lower burden of CVD risk factors compared with wealthier countries.
Authors suggested that higher CVD related mortality may be mainly due to lower quality of healthcare, given that the report found first hospitalisation rates and CVD medication use to be both substantially lower in low and middle income countries.
Common diseases in transition
“The world is witnessing a new epidemiologic transition among the different categories of non-communicable diseases (NCD), with CVD no longer the leading cause of death in high income countries,” said Dr. Gilles Dagenais, Emeritus Professor at Laval University, Quebec, Canada and lead author of the first report. “Our report found cancer to be the second most common cause of death globally in 2017, accounting for 26% of all deaths. But as CVD rates continue to fall, cancer could likely become the leading cause of death worldwide, within just a few decades.”
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A further report from the PURE study, also published in The Lancet and presented simultaneously at the ESC Congress 2019, explored the relative contribution (population attributable factor, or PAF) of 14 modifiable risk factors to CVD, among 155,722 community-dwelling, middle-aged people without a prior history of CVD, within the same 21 high, middle and low income countries.
Overall, modifiable risk factors, including metabolic, behavioural, socioeconomic and psychosocial factors, strength and environment, accounted for 70% of all CVD cases globally. Metabolic risk factors were the largest contributory risk factor globally (41.2%), with hypertension (22.3%) the leading factor within this group.
However, the relative importance of risk factors for CVD cases and death varied widely between countries at different stages of economic development. For deaths, the largest group of PAFs overall were for behavioural risk factors (26·3%), but in middle and low income countries, the importance of household air pollution, poor diet, low education, and low grip strength were substantially larger compared to their impact in high income countries. In line with the findings of the first report, metabolic risk factors including high cholesterol, abdominal obesity or diabetes, played a larger role in causing CVD in high income countries.
“We have reached a turning point in the development of CVD prevention and management strategies,” said Annika Rosengren, Professor of Medicine from Goteborg, Sweden. Sumathy Rangarajan, who coordinated the study said “While some risk factors certainly have large global impacts, such as hypertension, tobacco, and low education, the impact of others, such as poor diet, household air pollution, vary largely by the economic level of countries. There is an opportunity now to realign global health policies and adapt them to different groups of countries based on the risk factors of greatest impact in each setting.”
Authors of both studies acknowledged some limitations. Despite being the only studies involving as many as 21 countries in a cohort study, caution should be exercised in generalising results to all countries. In particular, PURE does not include data from west Africa, north Africa or Australia; the number of participants from the Middle East is modest; and data from low income countries are predominantly from south Asia with a few African countries.
Countries analysed in these two reports from the PURE Study include: Argentina, Bangladesh, Brazil, Canada, Chile, China, Colombia, India, Iran, Malaysia, Pakistan, Palestine, Philippines, Poland, Saudi Arabia, South Africa, Sweden, Tanzania, Turkey, United Arab Emirates, Zimbabwe.