Design and analysis of community trials: lessons from the Minnesota Heart Health Program.

Community trials remain the only design appropriate for the evaluation of lifestyle interventions that cannot be allocated to individuals. The Minnesota Heart Health Program, conducted in Minnesota and the Dakotas between 1980 and 1993, is one of the largest community trials ever conducted in the United States. That study suggests several lessons that should guide future community trials. Planners should 1) carefully assess the secular trends for their outcomes and be confident that they can demonstrate an intervention effect against those trends; 2) be confident that they have effective programs than can be delivered to a sufficiently large fraction of their target population; 3) avoid differences between study conditions in levels and trends for their outcomes through random allocation of a sufficient number of communities to each condition; 4) develop good estimates of community-level standard errors prior to launching future trials; and 5) take steps to ensure that power will be sufficient to test the hypotheses of interest.