The relevance of public health research for practice: A 30-year perspective.

The Nordic context where public health responsibility is strongly devolved to municipalities raises specific demands on public health research. The demands for causal inference of disease aetiology and intervention efficacy is not different, but in addition there is a need for population health science that describes local prevalence, distribution and clustering of determinants. Knowledge of what interventions and policies work, for whom and under what conditions is essential, but instead of assuming context independence and demanding high external validity it is important to understand how contextual factors linked to groups and places modify both effects and implementation. More implementation studies are needed, but the infrastructure for that research in terms of theories and instruments for monitoring implementation is needed. Much of this was true also 30 years ago, but with increasing spending on both public health research and practice, the demands are increasing that major improvement of population health and health equity are actually achieved.