If you had to pick a strategy to improve the health of a population, would you focus on reducing the number of high-risk individuals, or would you try to implement strategies to reduce the whole populations risk? In this module, we're going to compare high risk and population-based approaches. We're going to discuss something that's called the prevention paradox. Population health problems are like a leaky faucet. There are these upstream culprits that continuously give rise to higher risk of disease in a population. This is the issues of low income or not having enough, I will call, infrastructure for education or community support, or having toxic sites in our neighborhoods. This is creating this underlying risk that is just spreading more of our opportunities for disease than if we actually addressed them by turning them off. But the consequences of having that drip, drip, drip of risk and its consequences in terms of negative health outcomes, means that there is also all the spillage from that. A lot of health care is really designed exactly to tackle all of the health consequences of not having the adequate infrastructure that turns off the risk machine in a sense. Population health problems are going to manifest both because of the leak in the faucet, and we're going to see in our populations all those health consequences. We're going to need basically attention to turning off the faucet and mopping up the health difficulties that we see in our communities. The basic difference between a high risk targeted approach and a population, universal approach. In the high-risk approach, we're identifying individuals. Maybe small subgroups that are at high risk, and offering the very specific education, support, and treatment. This is the way our clinical services are set up. In the population or universal approach, we're really trying to take the entire population distribution and shift it down by five or 10 percent so that the risk of everybody is reduced. Let's compare those approaches. For the approach that is looking at just the high-risk individuals, the people at the tail of the distribution. The benefit is going to be really high for the individual. The effort is going to be significant by that individual. They're going to have to do the regimes that are prescribed by their physician. The communication about somebody's risk is at an individual level. We often have to screen many people to identify people that are at risk. For instance, the screening costs would be quite high in this scenario. But the benefit risk ratio is also quite good for the individual. The interventions are easy to understand. They're going to be the prescriptions that we take or the weight reduction programs that we participate in. Physicians are highly motivated to do this kind of high risk approach. The problem is, is that the depth of the solution is actually temporary. Many people that have the common chronic diseases that gave rise to some of the biggest burden on population health, they're moving towards, I'll call it better health outcomes, but often have a very difficult time holding it. If we look at the population approach where really the benefit is high for the whole population. The individual doesn't actually have a lot of, I'll call, heavy lifting to do. This is something that often is kind of done for them by policies or other kind of infrastructure. The communication is more of a mass variety. Many of us probably would never have thought that we would understand what cholesterol is. It's a kind of ILO-shaped molecule, but most of us know that term and know that high cholesterol is not good for us. The screening costs are nil because there's no need for screening. There's no need to identify high-risk individuals. We do have big questions about often the benefit risk ratio, because it's distributed across everybody. It's not focused really on any individual subgroup. This really challenges our norms about what interventions work. Doctors certainly don't have a lot of motivation to put forward their energy towards population health approaches that are at that universal level. The good thing is that it can create new norms. Many of us actually benefit from these new norms because like tobacco policies, our workplaces are now smoke-free. So are airplanes and other public places, as well as even within our families, because people really did start to see the benefits of stopping smoking. You can say this for many of the other population approaches that have been successful for reducing culprits within our foods, for instance. Population approach gives rise to a couple of different types of paradoxes that we just have to start to wrap our heads around. One is that a large number of people exposed to a small risk are likely to generate many more cases of disease than a small number that are exposed to a high-risk. How does this happen? Well, if you think about the normal distribution of risk, we know that one standard deviation above or below the mean, really is covering about 68 percent of a population. Another standard deviation out on either side of the mean, means that we're really talking about 95 percent of people in a population. High-risk individuals that are only on one tail, let's say that they are more than one standard deviation, is about 16 to 20 percent of the population. Whereas if we take an entire population and shift it, we're really talking about many more individuals than just a high-risk group. Often we're talking about 30 or 40 percent of the population has had a change in their risk in such a way that the number of cases that are actually prevented is much higher with a small shift on a population level than on addressing the risk of the high-risk individuals in a population. Another way to think about this is that the preventative measure that brings the largest benefit to the community offers little benefit to each participating individual. One of the reasons why this is so difficult is that most people think, well, why should I do this? Very little benefit for me to lower my cholesterol by two milligrams per deciliter. That's not much for me as an individual. However, if everybody does, then the number of people that it actually saves from having heart attacks is much bigger than the high risk alone. Of course, the best way to improve overall population health is to combine high risk and population approaches. Many public health agencies have focused on identifying what are the best buy interventions. Here I have represented the World Health Organization has put together a very nice compilation of the five areas that if we focused on those five areas, we really could actually bend the curve of risks for populations. There is tobacco use, harmful alcohol use, unhealthy diet and physical inactivity, cardiovascular disease and diabetes and cancer. The interventions that are suggested, things like tax increases, creating policies for smoke-free indoor workplaces or public places. Or for instance, restricting access to alcohol, replacing salt and trans fats, increasing public awareness and access to physical activity, and other things that actually combine this more high-risk and population-based approach, they really can have a major impact on the overall risk of a community. These are just a few ways that high-risk and population prevention approaches can go together. The big thing is to remember that population prevention often means nudging. It means nudging the mean of the population back so that everyone benefits.
