Population impact--definition, calculation and its use in prevention science in the example of tobacco smoking reduction.

INTRODUCTION: Population Impact is a criterion that can enhance prevention practices and provide a solid foundation for integrating policies and programs for prevention. However, to quantify the population impact of programs a statistical measure is needed. The objective of this article is to (a) deduct a formula to quantify population impact (PI), (b) define the formula for population impact of smoking prevention measures and (c) apply this formula on smoking prevention programs.
METHODS: Decision analytical approach.
RESULTS: The measurement of PI is defined with four parameters: recruitment, retention, efficacy and prevalence. A formula is mathematically deducted and the PI for different smoking prevention programs is calculated. DISCUSSION: The formula supports decision makers in deciding what prevention measure shows a higher impact on the population, gives hints where to improve the measure to increase the impact, whether recruitment, retention or efficacy needs to be improved and makes it easy to do analyses of costs on the population level.
CONCLUSIONS: To enhance prevention practice prevention measures need to provide all parameters to calculate the PI, research needs to focus on all parameters influencing the PI and costs of prevention measures need to be provided.