SURVEILLANCE of  RISK FACTORS

From surveillance of disease to surveillance of risk factors

Classical surveillance systems focus on monitoring mortality and to a lesser extent morbidity. These systems are adequate for assessing the effectiveness of public health intervention when the elimination of the cause has immediate impact on incidence or mortality rates. They are, however, insufficient when decades separate exposure to preventable factors from the clinical manifestations of a chronic disease. In this context, monitoring distributions of risk factors in populations provides short term indicators to identify preventive strategies, assess their effectiveness and predict emerging epidemics.

Since the 1960's, much methodological progress has been made following the implementation of national surveys and surveillance systems that repeatedly collect over time information about diets and other determinants of diseases.

Examples of national surveys and surveillance systems

In the United States		The National Health and Examination Survey, including NHANES I started in 1971, NHANES II  and NHANES 3 The Behavioral Risk Factors Surveillance System
In Europe		EURALIM
In Switzerland		The Geneva Bus Santé project
Multinational studies such as...		MONICA

These programs have allowed us to observe mass changes in environmental exposure (e.g., smoking, diet, exercise ) or biological measures (e.g., cholesterolemia, blood pressure).

Surveillance of risk factors is the object of the Geneva Bus Santé project.
Each year, about 1000 subjects are identified from the list of all residents published each year using a standardized procedure. Random sampling in age-sex-specific strata is proportional to the corresponding frequencies in the population. The participants answered a Food Frequency Questionnaire, a Physical Activity Frequency Questionnaire and additional questions about health in general. They also have their blood presssure, lipid profile and BMI measured.

Surveillance of risk factors has also become part of the US national health promotion and disease prevention objectives Healthy People 2000 . Timely collection of data on physical activity, nutrition, tobacco, alcohol, and biological function is required to evaluate whether the objectives of the program are met.

Less attention has been given to the coordination and harmonization of locally-run programs which are often population-based, decision and action oriented, relevant, timely, readily accessible and effectively communicated.

EURALIM (Europe Alimention, an European information campaign on diet and nutrition) is an example of how coordination of seven independent European locally-run surveys can bring together data but also authorities and experienced folks from various populations and countries to wrestle with prevention issues.

While the use of different protocols limits comparability, the perspective of a European surveillance system of risk factors derived from pooling locally-based survey data should not be rejected out of hand. Additional work is needed to practically determine the extent to which these data can be integrated into an international system of surveillance of risk factors.

References

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