What social networks promote the spread of behavior change?

In the September 3 issue of Science Magazine a very interesting study by Demon Sentola provides supportive experimental evidence for why behavior change may be more likely in community-based approaches than in more linear health education settings. The paper reports on 6 experiments that show that  behavior change spreads more quickly, more thoroughly and is adopted more strongly in social networks with more clustering, i.e. with many interlinking ties between individuals, than in more random social networks with few casual ties between individuals. The latter social network is associated with quicker spread of infections and is regarded as more effective for spreading knowledge across societies. But these studies indicate that for behavior change, many interlinked direct social contacts may be needed to reinforce behavior changes.

The cost-effectiveness of health education and health promotion interventions

True evidence-based behavioral nutrition and physical activity interventions are hard to ac

complish. The health effects of such interventions are often only seen in the long run; increasing physical activity or healthful dietary changes will not immediately reduce the risks for heart disease or diabetes. It maye take years before such healthful behavior changes show in morbidity or mortality statistics. Evaluation of behavioral nutrition and physical activity is therefore mostly beased on analyses of changes in these behaviors, not on changes in actual health or disease. Economic evaluations, i.e. assessing the cost-effectiveness of behavior change interventions is therefore hardly ever done.

However, in recent years, evaluation of health effects and of the cost-effectiveness of behavior change interventions is more often attempted, by using epidemiological modelling. In such model-based evaluations the behavior change effects, e.g. the effects of the intervention in terms of minutes of extra physical activity per week, or extra servings of fruit and vegetables per day, is translated into expected health effects by means of epidemiological models that are based on the best available evidence on how such changes in behavior predict changes in health and disease in the (sometimes many) years to come.

In recent weeks two papers appeared that attempted to assess the cost-effectiveness of behavioral nutrition and physical activity interventions. The first study, by Dr. Saskia te Velde et al, published in Economics and Human Biology presents the assessements of long-term health effects and cost-effectivess of the Pro Children intervention. Pro Children was a European Commission funded project aiming to increase fruit and vegetable intakes among school children in Europe. Te Velde et al presented the positive effect on behavior change in an earlier paper in the British Journal of Nutrition, and now present clear indications of the cost-effectivenes of this fruit and vegetable promotion scheme based on an established epidemiological model. The second paper by Dr. Van der Keulen et al. (Hilde vander Keulen defended her doctoral thesis succesfully and thus got her PhD last Friday)

, published in the International Journal of Behavioral Nutrition and Physical Activity assessed the cost-effectiveness of the Vitalum interventions, a computer-tailored health education intervention, a motivational interviewing intervention, and a combination of both, to promote physical activity and fruit and vegetable intakes among older adults. This study also provides clear indications that these interventions are cost-effective, with the best economic evidence for the computer-tailored intervention.

These studies contribute to better evidence-based health education and health promotion and do indicate that such interventions can be cost-effective.