Preventing chronic disease: a priority for global health

Misunderstandings about chronic diseases and their risk factors have contributed to their global neglect. Ebrahim and Smeeth1 revisit the debate about the usefulness of investing in chronic disease prevention and control. We respond here to the three main misunderstandings promulgated by Ebrahim and Smeeth in their editorial. We take this opportunity to bring attention to the widening gap that exists between the reality of the chronic disease burden worldwide and the response of national governments, civil society, and international agencies to this burden. Although misconceptions about chronic diseases, their risk factors, and prevention occur at different levels and throughout different sectors of society, the magnitude of the epidemic, its causes, costs, and options for control are now well documented.2 The main misunderstandings are that: The chronic disease ‘crisis’ has not materialized. Summary measures of population health, including the DALY, are a means to mobilize resources for non-fatal health outcomes at the expense of diseases that cause high mortality. Comparable country-level data on chronic disease risk factors are not available from the WHO Global InfoBase. The scope of the chronic disease epidemic is large and global. In 2005, an estimated 35 million people will die from heart disease, stroke, cancer, and other chronic diseases. Just under half of these deaths will be in people under the age of 70 years. An underappreciated fact is that 80% of these deaths will occur in low-income and middle-income countries and the death rates are often higher for middle-aged people in these countries than in high-income countries. Although the age-specific death rates from chronic diseases are declining in many high-income countries, the burden of the epidemic is increasing in low-income and middle-income countries, driven by both population ageing and rapid social and environmental changes that are leading to an increase in the prevalence of common, preventable risk factors.2,3 The causes of the major chronic diseases are the same regardless of socioeconomic status or gender. The main risk factors contributing to the rising number of deaths from chronic diseases are: Unfortunately, the availability of prevention, control, and treatment options does vary by ability to pay. Those who do not have the resources to pursue healthy choices suffer more. The costs of chronic diseases in low-income and middle-income countries are high and often borne by patients as out-of-pocket expenses, contributing directly to family poverty.4 The tragedy for people in low-income and middle-income countries is that the increase in chronic diseases and their risk factors is concurrent with unresolved communicable disease epidemics, particularly HIV/AIDS in Sub Saharan Africa. This is not a case of either–or but of directing resources to cost-effective interventions to address both communicable and chronic disease burdens. unhealthy diet; physical inactivity; and tobacco use. A small set of common, modifiable risk factors are responsible for the main chronic diseases. An estimated 80% of premature heart disease, stroke, and type 2 diabetes, and 40% of cancer, could be avoided through healthy diet, regular physical activity, and avoidance of tobacco use.2 Ebrahim and Smeeth1 suggest that specific health industries will benefit financially from raising the alarm about chronic diseases in the most world's populous countries. However, prevention of the major chronic diseases is achievable through simple, inexpensive prevention of these known, modifiable risk factors. Many countries are already actively engaged in these prevention activities.5–7 Some countries, mostly those with high incomes, have already made major reductions in chronic disease deaths through the implementation of these prevention activities including, salt reduction through voluntary agreements with the food industry and taxation of tobacco products. Summary measures, such as the disability adjusted life-year (DALY), are a tool for describing population health as accurately as possible in the absence of ‘perfect’ information about distribution of health states. The DALY incorporates two components: Clearly such a measure provides an opportunity to compare diseases with high case fatality with health conditions that do not necessarily lead to immediate death but still contribute to people living in a state of less than optimal health (such as visual and hearing impairment or depression). Because both YLLs and YLDs are included in the DALY, the results should not be biased in favour of one condition or another, or in favour of non-fatal conditions vs fatal conditions. In fact, the DALY attempts to provide an unbiased description of the global health situation as we find it, given the availability of health state information. Obviously, better information for one disease group over another will lead to a better description of the distribution and effect of that disease. However, the burden of disease approach makes every effort to use consistent and standard case definitions and to adjust for biases of under or over diagnosis of a condition in the final data product. years of life lost owing to premature mortality (YLL); and years of life lived in a state of less than perfect health, which some may term ‘disability’ (YLD). The DALY creates an opportunity for each disease/condition to be measured according to its merits and distributions in a population. Although reliable population-level information on both mortality and non-fatal conditions are limited for low-income countries, the Global Burden of Disease study's synthesis of data from thousands of piecemeal studies and data systems has provided the most comprehensive and objective picture to date of the disease and injury causes of loss of health in populations, and at the same time identified the need for better health information systems and descriptive statistics at the national level.8 There is a clear, global need for consistent, accessible, and transparent chronic disease information. The WHO Global InfoBase is working to meet this need by providing a single source for country-level chronic disease and risk factor data that meets minimum quality criteria. The current version of the InfoBase contains over 340 000 data points from more than 5000 sources and 9000 surveys. The success of the risk factor data collection is demonstrated by the increasing interest shown by a wide range of data users from many different countries. As chronic disease risk factor levels continue to rise in all countries, the need for a reliable source of transparent information to support evidence-based health policy is clear. However, identifying country-level data and assessing its validity is only the first step to developing better quality chronic disease data collections. One of our primary objectives has been to produce a standard way of describing and comparing risk factor data in all WHO member countries. This objective was met early in 2005 for three risk factors. We have adjusted country level data to provide comparable country-based estimates for overweight/obesity, mean systolic blood pressure, and mean total cholesterol. The country level estimations build on the methods published by WHO in the Comparative Quantification of Health Risks study.9 The comparisons of countries for obesity as presented by Ebrahim and Smeeth result in a misunderstanding of the data presented in the on-line tool of the WHO Global InfoBase. The comparable estimates presented in Figure 2 of Ebrahim and Smeeth are all based on country-level data, with the exception of Brunei Darussalam. Survey data do exist for measured height and weight for the Lao People's Democratic Republic and Myanmar and these are also held in the Global InfoBase, accessible through the on-line tool. This added transparency of the data used in the analysis process allows users to assess the quality of the data used, any assumptions made in adjusting it for comparisons and is what makes the Global InfoBase a unique tool. The Brunei estimates stand out and have been modelled using the one highly correlated covariate of BMI at the population-level, the gross domestic product per capita, measured in international dollars adjusted for purchasing power parity. We await data from a Brunei National Health Survey that includes measured height and weight information for what is one of the wealthiest populations in the region. The estimates presented in the comparable data section of the WHO Global InfoBase on-line tool are based on country studies, which are also available for all to use on the on-line InfoBase tool. The InfoBase provides the global health community with a benchmark for comparable estimates and also with the metadata that enable the quality of the both the country studies and the WHO estimates to be assessed and revised if appropriate. In summary, chronic diseases and their risk factors pose a serious threat to global health. At the same time, cost-effective interventions are available that have the potential to significantly improve healthy life expectancy in developing countries.5 Any single organization or group is unlikely to have the resources needed to address the complex public health issues related to chronic disease so new coalitions will need to be established between different sectors to ensure that the achievements in prevention, control, and treatment of chronic diseases benefit all. To proceed further, we need to have a common understanding of the use of health information and statistics to inform evidenced-based health policy. Now is the time to end the debate about the relative importance of chronic diseases in global health and to use the available data to take action against the rising global epidemic in a stepwise manner.