Is Chronic Disease Burden a Population Health Outcome?

Originally posted 2/8/2011

Responding to last week’s post on which outcomes we should improve, Matt Stiefel from Kaiser Permanente asked about using the incidence or prevalence of chronic illness as a population health outcome measure. Matt’s important question prompts me to continue the conversation this week.

The Institute of Medicine’s 2008 State of the USA Health (SUSA) Indicators report (I served on this committee), called for an index of chronic disease prevalence among its seven other health outcome measures that “reflect the overall health of the nation and the efficiency and efficacy of U.S. health systems” such as life expectancy at birth, infant mortality, and  unhealthy days (physical and mental). To my knowledge, such an index has not yet been developed. As a member of the IOM SUSA committee, I am concerned with the classification of chronic disease prevalence (and other similar  factors) as outcomes per se, because improving these factors is the means, not the ultimate end that we seek (i.e., living longer healthier lives). This opens the door for the means to become the end.One strategy might be to add a third category of “intermediate outcomes” to our model of outcomes and determinants/factors. These “intermediate outcomes” could capture those factors (like smoking rates or primary medical care or burden of chronic disease) that, if improved, are likely to directly and significantly improve our ultimate outcomes over time. (Others call these “proximal determinants” in contrast to the more “distal determinants” such as income and education.) This category of “intermediate outcomes” could be very useful for guiding population health monitoring efforts and policy priorities, and indeed may be required when we want to track or reward short term improvement.

We don’t have to look far to see the potential value of this third category. The National Research Council’s recent report highlights diverging paths in longevity among high-income countries. The report points to smoking rates as one main reason why life expectancy in the U.S. is increasing at a slower rate than might be expected. Thirty years ago, smoking rates were much higher among U.S. adults than they are today (37% vs. 21%); what we’re seeing now is the time-delayed ripple of these “intermediate outcomes” or determinants affecting long-term health outcomes.  

Thinking about smoking rates as an “intermediate outcome” can be helpful from a policy perspective as well. Later this month, New York City’s Mayor Bloomberg is expected to sign a bill that will ban smoking in 1,700 city parks and along 14 miles of beaches. According to the New York Times, the new policy will represent the “most significant expansion of antismoking laws” since Mayor Bloomberg’s 2002 push to prohibit smoking in bars and restaurants. I hope the National Research Council will be able to credit these and similar policies to declining mortality in 2040. 

So, while I’d like to reserve the population health term “outcomes” for our ultimate goals of increasing the length and quality of lives, a third category of “intermediate outcomes” deserves greater attention by both policymakers and scholars. Developing consensus around which indicators would best fit into such a category – as well as what programs and policies could most cost-effectively improve these numbers – would be a great place to start.