The WHO Noncommunicable Diseases Global Surveillance Strategy: Experience in the African Region Burden of noncommunicable diseases The growing burden of noncommunicable diseases (NCDs) represents a major challenge to health development. Chronic diseases like heart diseases, stroke, cancers, chronic respiratory diseases and diabetes are by far the leading causes of death in the world. In 2002, these major chronic, noncommunicable diseases accounted for 60% of all deaths and 47% of the global burden of disease. By 2020 these figures are expected to rise to 73% and 60%, respectively. 1 Contrary to common perception, the largely invisible epidemic of noncommunicable diseases is worst in low- and middle-income countries where 80% of all chronic diseases occur. The number of people dying from these NCDs is estimated to be twice the number of deaths from all infectious diseases (including HIV/AIDS, tuberculosis and malaria), maternal and prenatal conditions, and nutritional deficiencies combined. 1 NCDs and injuries in Africa accounted for 30% of mortality and 35% of illnesses in 2005; these figures will rise to 60% and 65%, respectively, by 2020, adding to the already high burden of communicable diseases. Complications of NCDs such as kidney failure, stroke, heart failure and blindness are very costly. Because of limited resources for health and the numerous priorities, the management of NCDs based only on the hospital-curative model cannot work. The major causes of chronic diseases are known. Elimination of these preventable risk factors would prevent 80% of heart * Dr Allel S. Louazani diseases, 80% of strokes, 80% of type 2 diabetes and 40% of cancer. A small set of common risk factors is responsible for most of the main chronic diseases, and these risk factors are the same in men and women. Global surveillance strategy WHO has responded to this growing burden by giving higher priority to NCD prevention, control and surveillance in its programme of work. Surveillance involves ongoing collection of data for better decision-making. It underpins public health action and health promotion activities. The WHO STEPwise approach to surveillance2 (STEPS) is the WHO-recommended NCD surveillance tool. Surveillance provides evidence for advocacy and action based on local needs for better impact and evaluation. 15
The guiding principles of the surveillance are: Identification and description of the key NCD risk factors, using recommended WHO definitions; Standardized approach for conducting surveillance of risk factors to allow international comparisons within and between countries; Continuous risk factor surveillance; Providing data for policy. The STEPs approach is based on the concept that surveillance systems require standardized data collection to ensure comparability over time and across locations. It is also sufficiently flexible to be appropriate in a variety of country situations and settings. The STEPwise approach, therefore, allows for the development of an increasingly comprehensive surveillance system, depending on local needs and resources. Core risk factors Risk factor refers to any attribute, characteristic or exposure of an individual which increases the likelihood of developing a noncommunicable disease (Figure 1). In the context of public health, population measurements of risk factors are used to describe the distribution of future disease in a population, rather than predicting the health of a specific individual. Knowledge of risk factors can be applied to shift population distributions of these factors. Because many factors associated with disease cannot be modified, emphasis in any surveillance system should be given to those risk factors that are amenable to intervention. Surveillance of just eight selected risk factors which reflect a large part of future NCD burden can provide a measure of the success of interventions. For example, inappropriate diet and physical inactivity resulting in high body mass index, raised blood pressure and raised blood lipids together with tobacco use explain at least 75% of cardiovascular disease. 1 Core risk factors have the greatest impact on NCD mortality and morbidity. Modification of risk factors is possible through effective primary prevention, and measurement is valid and can be obtained using appropriate ethical standards. Figure 1: Risk factors common to major chronic diseases conditions Risk factor Cardiovascular diseases Diabetes Cancer Respiratory conditions Smoking * * * * Alcohol * * * * Nutrition * * * * Physical inactivity * * * * Obesity * * * * Raised blood pressure * * * * Raised blood glucose * * * * Abnormal blood lipids * * * * 16
Components of the WHO STEPwise approach For surveillance to be useful, the STEPwise approach advocates that small amounts of good quality data are more valuable than large amounts of poor quality data. The key feature is the distinction between the three levels (3 Steps) of risk-factor assessment: Step 1 information by questionnaire, Step 2 physical measurements, Step 3 blood samples for biochemical analyses. There are three modules involved in describing each risk factor with the amount of information collected described as: core, expanded core and optional. For both core and expanded modules, assessment guidelines and standard questionnaires are provided. The core module is constituted by a set of basic or minimum information data to describe each risk factor. The expanded module is an expansion of the basic core questions to allow a more comprehensive assessment of key risk factors. The optional module includes more data on risk and protective behaviours such as seat-belt use, sexual behaviour, attitudes, beliefs, practices and use of health services. Step 1: Questionnaire-based assessment A Step 1 study is based on self-reported information. The core module of Step 1 contains as markers of current and future health status socio-economic data, data on tobacco and alcohol use, some measurements of nutritional status and physical inactivity. Standard WHO definitions for measuring the prevalence of tobacco use and alcohol consumption and internationally devised measures of physical activity are recommended. All countries should be able to undertake the core items of Step 1. Step 2: Questionnaires and physical measurements A Step 2 study includes as a minimum the Step 1 core module and adds simple physical measurements such as blood pressure, height, weight and waist circumference. Step 1 and Step 2 are desirable and appropriate for most countries. Step 3: Questionnaires, physical measurements and biochemical assessment A Step 3 study incorporates as a minimum the core modules from Steps 1 and 2 and adds measurements obtained from blood samples. The additional information at Step 3 is of a biochemical nature and is therefore not recommended by WHO in lessresourced settings unless low-cost technology is used. STEPS for local needs One of the greatest challenges in developing STEPS has been to achieve a balance between ensuring standardized tools and methods, and flexibility for use in a variety of country situations and settings. STEPS allows all countries to contribute to improving global information about trends in key measures of health. Expansion of the basic core questions is possible in settings where resources and local surveillance needs allow a more comprehensive assessment of these key risk factors. For both core and expanded core modules, assessment guidelines and standard questionnaires are provided. Optional modules can also be added to include more data on risk and protective factors in mental health, intentional and unintentional injury, and oral health, for example. The African Region is the first WHO region to complete STEPS training methodology. Twelve countries have completed and published their survey 17
results on risk factors. An additional five countries are in the process of publishing their results; in 12 countries the survey process is ongoing. Training in the STEPS methodology has been undertaken in 17 countries (see Figure 2). STEPS results The data from the 12 countries that have completed and published their survey results on risk factors indicate a high prevalence of risk factors for noncommunicable diseases in the Region. The prevalence of elevated blood pressure is 33.1% in Mozambique, 32.5% in the Republic of Congo, 29.1% in Algeria and 27.6% in Zimbabwe (Figure 3). Zimbabwe also has 10% elevated blood Figure 2: STEP surveys in the WHO African Region, 2007 Figure 3: STEPS data showing prevalence of risk factors in African countries (%) Risk factor Algeria Congo Eritrea Cameroon Madagascar Mozambique Côte d Ivoire Zimbabwe Tobacco use 12.8 14.4 8 4 20 18.7 9.5 12.1 Alcohol use 5.1 62.5 39.6 11 42.5 77.2 71 74.7 Obesity 16.4 8.6 3.3 18 2.42 7.1 9.1 14.1 Elevated blood pressure 29.1 32.5 16 25 17.6 33.1 21.7 27.6 Elevated blood sugar 6 6 1.4 10 18
sugar prevalence. Preventable blindness prevalence is currently between 0.4% and 4%. Other surveys using STEPS methodology such as the Global School-based student Health Survey show that these risk factors occur at early ages (Figure 4). The consequence of these levels of prevalence is a high mortality rate due to cardiovascular disease, diabetes, strokes and cancers. Figure 4: Percentage of students who spent three or more hours per day watching television, playing computer games, talking with friends, or doing other sedentary activities References 1 WHO, Preventing chronic diseases: a vital investment, Geneva, World Health Organization, 2005. 2 WHO, STEPwise approach to risk factor surveillance, available at: http://www.who.int.chp/steps/en/ 45 40 35 30 25 20 15 10 5 0 34.5 Botswana 40.9 Kenya 31 Namibia 27.5 Uganda 32.6 Zambia 43.8 Zimbabwe GSHS (aged 13-15 years) Conclusion As shown above, NCD risk factors are very high among youth in the African Region. Knowing that the risk factors of today are the NCDs of tomorrow, prevention interventions aimed at reducing these risk factors must start immediately. * Dr Louazani is the Regional Adviser for Noncommunicable Diseases Surveillance at the WHO Regional Office for Africa. 19