If you work in public health, you’ve probably heard about the new era of practice — an era being dubbed Public Health 3.0. Among the components that define this new phase is an emphasis on building cross-sector collaborations to affect the social determinants of health. In other words, public and private sectors have a role — and a stake — in improving community health. And now there’s evidence that such collaborations can save people’s lives.

In a study published in November in the journal Health Affairs, researchers set out to see whether communities that convened multisector networks to implement health improvement activities actually reaped any measurable benefits. The short answer is a resounding yes. The study found that communities that undertook such networking efforts experienced a significant decline in deaths due to heart disease, diabetes and the flu. In fact, researchers found that mortality due to these preventable diseases were up to 20 percent lower in communities with “comprehensive system capital” — a phrase the researchers used to describe a broad spectrum of health improvement activities conducted via a dense network of collaborating organizations — than in communities that didn’t have such capital.

So, why is this a big deal? Because for years, public health workers and advocates have been saying that it’ll take much more than insurance cards to improve health, slow health care spending and close health disparity gaps — that in addition to affordable care access, we must also work collaboratively to address the community conditions that enable good health. Now, with a study like this, public health workers have even more evidence that public health partnerships save people’s lives.

When people ask “what’s the value of investing in public health and prevention,” you can add this study to the list.

Study co-author Glen Mays, the F. Douglas Scutchfield endowed professor in health services and systems research at the University of Kentucky College of Public Health, explained to me why he did this study: “There’s a growing interest and urgency for finding ways of improving health on a population basis. We’re falling further behind our peers around the world, and within our country, we still have large and persistent disparities in health status…we have large segments of the population now seeing declines in life expectancy, which we never expected to see. There’s a lot of signals that we need to find ways to improve health on a population basis.”

To conduct the study, Mays and colleagues examined 16 years worth of data from the Robert Wood Johnson Foundation’s National Longitudinal Survey of Public Health Systems, which follows a cohort of U.S. communities and measures the breadth of each community’s population health activities as well as the sectors and organizations involved. The survey collects info on 20 population health activities recommended by leaders in the field, such as periodic community health needs assessments, engaging residents in carrying out health interventions, and multisector priority setting and planning. The data set also reflects which organizations were involved in implementing community health interventions, such as public health departments, hospitals, employers, schools and faith-based groups.

“We wanted to look at the extent to which communities were forming these multisector networks, particularly because we know that social and economic factors are major determinants of health,” Mays told me. “So that suggests that if we can better connect social and medical sectors, it could create a better pathway for improving health.”

Mays said that he and colleagues used the “strongest possible research design” to test their hypothesis. In addition to the obvious benefits of having a data set covering a 16-year span, researchers also controlled for a wide range of variables that impact people’s health. And because the research design approximates what a randomized trial would do, Mays said the study provides some of the strongest evidence to date on the health impacts of multisector networks.

The main finding of the study: Communities that implemented a broad spectrum of population health activities and did so through a dense network of multisector players reaped a “dramatic” reduction in death rates from preventable causes. Mays described the reductions as “large in magnitude” — in particular, a 10 percent to 20 percent decline in death rates from the major causes of premature mortality, such as heart disease and diabetes. Those are “very compelling health gains,” Mays said.

Researchers also found that as of 2014, about 40 percent of U.S. metropolitan communities had levels of system capital associated with the drops in mortality found in this study. That percentage is up from 24 percent in 1998.

So, how exactly do these dense multisector networks improve health? The study doesn’t tease out the specific mechanism. But Mays has a hypothesis: crowdsourcing.

“These communities can make better-informed decisions about what to do in their communities and how to invest limited resources to achieve the highest impacts on health,” he said. “It’s basically a form of crowdsourcing. So when communities build these strong collaborative networks…they’re arriving at high-impact solutions faster than communities that don’t have these networks.”

For example, Mays said communities that had comprehensive system capital were much more likely to succeed at passing smoking bans and reduce their smoking rates, especially among low-income residents. Mays and study co-authors Cezar Mamaril and Lava Timsina write:

From a policy perspective, our findings suggest that multisector engagement in health planning, implementation, and evaluation activities can produce sizable communitywide benefits. Building strong and durable capabilities for carrying out these foundational activities may be at least as important to population health as are the downstream choices made by communities about which specific interventions and target populations to pursue at a given point in time. These results underscore the importance of building strong incentives and sustainable infrastructure at the community level to support multisector work in population health.

Mays said based on the size of the preventable death declines, it’s “very reasonable” to assume that the resources saved by reducing mortality should far outweigh the resources needed to make such multisector partnerships a reality.

“It’s fantastic news,” Mays said of the study results. “But on the flip side, the majority of communities in the U.S. have not progressed to building the kind of strong networks that generate these outcomes. We still see enormous inequities and we still need to focus on building strong capacity across the country. Every community deserves the ability to do this work, and it’s work we know how to do. But it does take resources and it does take support from policymakers.”

To request a full copy of the partnership study, visit Health Affairs.

Kim Krisberg is a freelance public health writer living in Austin, Texas, and has been writing about public health for 15 years.