Effects of government policies on health behaviour must be studied

EDITOR—The Heartbeat Wales programme,1 in common with several other community health promotion projects that aim to reduce the risk of cardiovascular diseases,2 has reported no net changes in intervention compared with control regions. Tudor-Smith et al report these negative findings in an exemplary way, using a straightforward analysis.1 Their study concludes that more debate on the most appropriate methods of assessing the effectiveness of such programmes is needed.

The investigators suggest that lack of power and contamination of the control region explain their failure to detect effects of the programme. The study had sufficient power to detect a 5% difference in prevalence between intervention and control regions. If the other community based interventions that were previously reviewed2 were included in a meta-analysis, the power would increase, but the lack of effect would still be apparent as these other programmes also had essentially negative results.

Contamination of the control region is a possible explanation for the findings. Similar community health promotion programmes conducted from the 1970s to the 1990s have, however, reported consistent findings—no net difference in risk factors or clinical events attributable to the intervention. Moreover, the downward secular trends in mortality from cardiovascular disease in countries with diverging practices in health …