Community Intervention To Improve Health Does Just That Without Changing ObesityFriday, April 22, 2016
Population health strategies to prevent and reduce obesity have been the focus of much talk in the public health field, but hard evidence that this is in fact possible remain rather sparse (with a few notable exceptions).
Now, a paper by Ellina Lytvyak and colleagues from the University of Alberta, Edmonton, Canada, published in BMC Public Health, describes the 3 year results from a community intervention called the Healthy Alberta Communities Study (HACS).
The researchers looked at data from a multi-level intervention to create environments supportive of healthier dietary and physical activity behaviours within four diverse communities in Alberta (Bonnyville, St. Paul, Norwood and Medicine Hat), between 2006-2009.
Over the duration of the intervention, Community Coordinators built relationships with local stakeholders and worked with them to identify environmental determinants of chronic disease and obesity amenable to change at a community-level. Key accomplishments included the expansion of community gardens, improved access to recreation and sport facilities, development of a healthy choice restaurant program, a program to provide subsidized local produce to food insecure households, and a linked trail system for active transportation
Data was collected from 1554 and 1808 community residents at baseline (2006) and follow-up (2009), respectively and compared to a representative national survey.
Overall, there was no noticeable impact on any of the anthropometric variables measured (in fact, there was even a small but significant increase in waist circumference in 20-39 year olds in the intervention communities).
On the other hand, there was a small but significant reduction in blood pressure as well as a 4.5% reduction in individuals with stage 1 hypertension and a 5.9% increase in individuals with normal blood pressure measurements.
Shifting health indicators at a population level is clearly challenging (even more so if one hopes to demonstrate sustainable and durable changes resulting in relevant hard clinical endpoints – which, after all, is one of the key reasons to intervene in the first place). Thus, even the small left-ward shift of the blood pressure distribution curve is remarkable given the strong relationship between elevated blood pressure levels and cardiovascular disease (particularly stroke).
That body weight did not change (despite the focus of the intervention being to promote healthier nutrition and physical activity) may not be all that surprising and may well be reflective of the fat that interventions based on the simplistic notion of “energy-in-energy-out” or “eat-less-move-more”, which are largely ineffective in the long-term at the individual level, also tend to fail at the level of whole populations.
This does not mean that population interventions are not helpful – indeed they are and I have little doubt that the overall health in the intervention population did improve over the course of the intervention (the changes in blood pressure just being one indicator).
However, as the authors note,
“…while improvements in some clinical risk factors can be achieved through relatively diffuse and shorter-term community-level environmental changes, improvements in others may require interventions of greater intensity and duration.”
Obviously, the more intense and durable the intervention – the greater the cost of delivering such an intervention with a significant dilution of ROI when delivered at a whole-population level.
This is because high-intensity interventions are not only more feasible but also likely to pay off more when delivered to selected high-risk groups or individuals rather than entire populations.