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Surveillance of noncommunicable disease risk factors

Quality health information is essential for planning and implementing health policy in all countries. Risk factor data are especially important as predictors of future disease or injury. The World Health Report 2002: Reducing risks, promoting healthy life, identifies five important risk factors for non-communicable disease in the top ten leading risks to health. These are raised blood pressure, raised cholesterol, tobacco use, alcohol consumption, and overweight. The disease burden caused by these leading risk factors is global. In every region of the world, including the poorest, raised blood pressure, cholesterol, and tobacco use are causing serious disease and untimely deaths. The World Health Report estimates are regionally based but emphasize the need for better information on levels and trends of these major risk factors for all countries.

Country-level data is sparse for many of these major noncommunicable disease (NCD) risk factors. When data is available, it is not always complete or comparable, especially if it is based on self-reported health assessments or behaviours. A consistent approach to collecting and analysing NCD risk factor data is needed to promote the usefulness of this data both for country health policy development and also for comparisons across countries and regions. WHO is promoting the use of the STEPwise approach to enable countries to set up surveillance systems for NCD risk factors.

Identifying risk factors

Risk factors are defined as any attribute, characteristic or exposure of an individual, which increase the likelihood of developing a disease or injury. Measuring risk factors of noncommunicable disease is an attempt to predict the future distribution of NCDs in a population. This type of information is vital to promoting disease prevention and control programmes.

The World Health Report 2002 has identified the risk factors that are most important for predicting future disease burden. These risk factors share common characteristics that include having: the greatest impact on death and illness from a disease/or injury; the ability to be modified through effective primary prevention; measurement protocols which have been validated; and a method of taking measurements that does not violate ethical principles.

In addition to these requirements, it is useful to know the exposure level at which the risk factor leads to disease/or injury and the availability of data on population distribution of risk. The risk factors that cause NCDs have been extensively researched in a number of settings, mostly in developed countries. However, as developing countries now face a 'double burden' of disease, lingering communicable diseases with an increase in chronic conditions, it is important to have good quality data for on NCD risk factors in these countries as well. Research on the impact of risk factors in developing countries has shown similar effects on health outcomes as for populations in developed countries. As highlighted in the World Health Report 2002, just a few NCD risk factors account for the majority of noncommunicable disease burden. These risk factors, tobacco use, alcohol consumption, raised blood pressure, raised lipid levels, overweight, low fruit/vegetable intake, physical inactivity, and diabetes, are the focus of the STEPs approach to NCD risk factor surveillance.

The STEPwise approach to NCD risk factor surveillance

STEPs is a sequential process of gathering comparable and sustainable NCD risk factor information at the country-level. By using the same standardised questions and protocols, all countries can develop surveillance systems containing quality information about NCD risk factors in their unique settings. This information can, in turn, be used to plan for and implement currently available interventions to address the disease patterns caused by these risk factors.

The STEPS approach is based on the concept that NCD surveillance systems need to be simple, focussing on a minimum number of risk factors that predict disease - before placing too much emphasis on costly disease registers which are difficult to sustain long-term.

A tool for surveillance of risk factors, WHO STEPS, has been developed to help low and middle income countries get started. It is based on collection of standardized data from representative populations of specified sample size to ensure comparability over time and across locations. Step 1 gathers information on risk factors that can be obtained from the general population by questionnaire. This includes information on socio-demographic features, tobacco use, alcohol consumption, physical inactivity, and fruit/vegetable intake. Step 2 includes objective data by simple physical measurements needed to examine risk factors that are physiologic attributes of the human body. These are height, weight, and waist circumference (for obesity) and blood pressure. Step 3 carries the objective measurements of physiologic attributes one step further with the inclusion of blood samples for measuring lipid and glucose levels.

Measuring NCD risk factors in this manner provides a flexible system that can be useful in a variety of country settings. Questionnaire-based measurements (Step 1) may be all that is feasible in low resource settings, while physiological measurements (Steps 2 and 3) may provide the impetus for health programme modification in higher resource settings or countries with specific surveillance needs (i.e. high prevalence of diabetes type 2). Countries can determine which additional set of questions are appropriate to their needs and what can be accomplished in the context of an on-going surveillance system.

STEPS is now being planned or implemented in 33 countries in WHO's south east Asian region, western pacific region, African region and eastern Mediterranean region. WHO/HQ is offering technical support in order to ensure quality control and enhance the comparability of data collection. More countries will be added in consultation with regional and country offices of WHO. Some 40 countries will be in some phase of STEPS implementation by the end of 2003.

Sources: US Department of Health; The World Health Organization

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