Читать книгу Discovering Precision Health - Lloyd Minor - Страница 41

The belief that genetics is the overwhelmingly dominant determinant of health is, in many respects, unfortunate. This is not to say that genetic determinants of disease are unimportant—quite to the contrary. But it is also incorrect for people to believe they are at the mercy of their genes and medical care, and thus their individual behaviors don’t have significant impact. The reality is dramatically different. As Cashell Jaquish, a genetic epidemiologist at the National Heart, Lung, and Blood Institute, has said, even a genetic predisposition to heart disease (the leading cause of death among Americans) “doesn’t mean you are fated to have [it]. Other factors, like not smoking, diet and exercise, can have a very large effect. Family history does increase your risk slightly, but not as much as [not doing] these other things” [5].

The nexus between genes and many chronic conditions can also be overcome with smart behavioral patterns. Consider obesity. “I like to say that obesity is 80 percent genetic and 100 percent environmental,” Philip F. Smith, codirector of the office of obesity research at the National Institute of Diabetes and Digestive and Kidney Diseases, told the Washington Post. “You won’t become obese unless you overeat.” He added, “For most people, I can say unequivocally that genes are not your destiny. They can predispose you to obesity, but only if you consume more calories than you burn off” [6].

Further proof of that comes from a 2007 study, published in the New England Journal of Medicine, based on people who were part of the landmark Framingham Heart Study. Although the study found that obesity was 40 percent more likely if one’s sibling had already become obese, it was 57 percent more likely if someone’s friend had become obese, and 171 percent more likely among close mutual friends [7]. One of the study’s coauthors pointed out, “What appears to be happening is that a person becoming obese most likely causes a change of norms about what counts as an appropriate body size. People come to think that it is okay to be bigger since those around them are bigger, and this sensibility spreads” [8]. A related issue is that close friends eat together and end up taking cues from each other about what’s customary when it comes to the types of foods to eat and how much.

Physical activity can help neutralize the impact of a genetic predisposition to obesity. A study published in 2011, involving more than 200,000 adults, found that although a certain gene variant (FTO) increased the risk of obesity by 23 percent, those with the variant who were physically active had a risk of obesity 27 percent lower than that of inactive adults [9].

While genes are not the exclusive drivers of health, the environment in which one lives—both the social and physical dimensions—is a critical influence. That influence takes several different forms, but it starts with something basic: social connections. “People who feel more connected to others have lower levels of anxiety and depression,” says Emma Seppälä, science director of the Stanford Center for Compassion and Altruism Research and Education and the author of The Happiness Track: How to Apply the Science of Happiness to Accelerate Your Success. She also points to studies showing that connected people have higher self‐esteem and greater empathy for others. They are also more trusting and cooperative, and as a consequence, she says, “others are more open to trusting and cooperating with them. … In other words, social connectedness generates a positive feedback loop of social, emotional and physical well‐being.”

A few years ago, trained interviewers met with 100 people from Santa Clara County (the county that encompasses most of Stanford) as part of a project launched by the Stanford Prevention Research Center. The questions during the one‐on‐one sessions revolved around wellness: what contributed to it, what detracted from it, etc. Following the interviews, researchers working on the project identified the 10 markers of wellness that were mentioned most often. The most important? The existence of a social network, which provided opportunities to receive support and companionship, to feel loved, and to have a sense of belonging [10].

As important as social networks and connections are, there are many other factors that influence health, and for many people—particularly children—there are multiple social determinants of health. This refers to the circumstances, outside of medical care and genetics, that influence health and well‐being. In challenging living conditions, for example, infants can be born with what’s known as a thrifty phenotype. It is supposed to help children adapt to the conditions in which they may be living. But the existence of this phenotype has also been linked to adverse health outcomes [11].

Health and life expectancy are often correlated with income, as I noted in the previous chapter. Consider that those with low incomes often live in so‐called food deserts, where there is little access to grocery stores selling a wide variety of healthy foods (particularly fresh fruits and vegetables). Similarly, those with low incomes may not have the time or resources to travel to neighborhoods offering healthy food options, and they may also lack access to quality health care services. For people living with those circumstances, and others like them, health outcomes are often much worse than those found in higher‐income communities.

Lisa Chamberlain, an associate professor of pediatrics at Stanford’s School of Medicine, has been active in highlighting health disparities and trying to remedy them. “So much of our health is generated by our environments and the choices that we have,” says Chamberlain.

It’s often thought that choices are simple. For example, do you choose to exercise or not exercise? Do you choose to eat healthy foods or unhealthy foods? People know they should be eating healthy and exercising regularly. But they are making logical choices based on their income level and where they live. That’s why health is often driven more by a person’s zip code than their genetic code. And that’s why you can see the health profile of entire neighborhoods decline. It’s not because they have the same genes—it’s because they all face the same choices.

She believes the most influential social determinant of health is education. For many children, that means they’ve already fallen behind in both categories by the time they enter kindergarten. “They’re set up to fail,” she says. “Many children from low‐income families don’t end up attending preschool because it costs $20 per hour, while the free federal program, Head Start, has huge waiting lists.”

Chamberlain also works as a physician at the Gardner Packard Children’s Health Center, a community‐based clinic serving primarily low‐income families. (Her work at Gardner followed 14 years of seeing patients at Ravenswood, a family health center in East Palo Alto.) When she sees children who are starting kindergarten, she ensures that they have the required immunizations and tests their vision and hearing. She also screens them developmentally to check their school readiness skills: Do they know their colors? Can they write their name? In one recent year, she and her colleagues evaluated five‐year‐old children in the clinic, and just 13 percent were ready for kindergarten. (The comparable figure for children attending Palo Alto schools, just a few miles away, is typically 85 to 90 percent.) “Not only are these children starting kindergarten behind,” says Chamberlain, “they’re being set up to fail.”

Among the many health challenges faced by low‐income children are the meals they’re served at school. These meals—which include lunch and sometimes breakfast—often have little or no nutritional value, thus setting the children on a path to weight gain and, potentially, obesity. Low‐quality food is a longstanding problem at schools, but there are entities trying to make a difference. Revolution Foods, for example, works with more than 1,500 schools, spread across 16 states and Washington, DC, and it is focused on providing healthy foods, such as fruits and vegetables.

But bringing healthy food into schools often faces significant obstacles. Chamberlain, for example, tried to get a low‐income district to drop its existing food provider and switch to Revolution. But the existing provider—a national company that provides meals to schools throughout the country—was able to come in at a lower cost, as it provided something that Revolution did not: cafeteria workers. Dropping the national company would lead to the district incurring unsustainable fiscal deficits. The superintendent told Chamberlain, in so many words, “I know these kids need healthier food. But what am I supposed to do? I have enough trouble focusing on academics and everything else. I can’t take on food as well.”

That story is emblematic of the challenges we face in improving the diets of all people, and it’s a potent reminder of how the environment in which you live can have a major influence on your health. There’s considerable evidence that attention to and improvements in the environment and social and behavioral factors lead to better health. Consider Los Angeles in the 1990s. The air quality was poor; now, it’s much improved. A study by investigators at the University of Southern California showed gains in lung function in children that paralleled improvement in air quality in Los Angeles. In 1998, 7.9 percent of 15‐year‐olds had significant lung defects. In 2011, the percentage of 15‐year‐olds with these lung defects had fallen to 3.6 percent [12].

While health challenges are often more pronounced for those with lower incomes, the challenges are embedded in the way most Americans live their lives. We tend to drive much more than we walk. We eat processed food rather than cooking fresh food. We sit in chairs for much of the day, staring at a screen. Increasingly, we do our shopping and get our entertainment without even leaving our homes. While these conveniences certainly have benefits, there are also trade‐offs. One of them is that many researchers believe we now have a culture that is obesogenic (i.e., it contributes to obesity). “Our whole economy is driven toward convenience,” says Abby King, a professor of health research and policy and of medicine at the Stanford School of Medicine, “and convenience often goes hand‐in‐hand with poorer choices in terms of health.”

King is working to remedy this—not by eliminating the conveniences of modern life, but rather by spurring changes to local communities that can contribute to the health of people living in those communities. She and her team are doing this through empowering and activating residents themselves to be part of positive change in their local neighborhoods and communities. The global initiative that she leads, called Our Voice, has completed a range of projects, such as promoting better food and physical activity environments in low‐income sections of California’s San Mateo County [13], increasing the community’s understanding of the variety of foods being offered at farmers’ markets in Arizona [14], and investigating the walkability of higher‐ and lower‐income neighborhoods in Mexico [15]. “We focus on monitoring, nudging, and activating residents to not just change their own behaviors, but also to change the context in which they and their neighbors live,” says King [16].

They describe their efforts as “citizen science by the people,” and the community engagement process begins with a mobile app called the Stanford Healthy Neighborhood Discovery Tool [17]. Using this app, residents walk around their environments and narrate what helps or hinders their health. They then meet with other residents to talk about what they’ve seen and learned, and then learn how to communicate this information and advocate for healthier neighborhoods with local decision makers. “People love to be engaged in this way,” says King, “and see their neighborhood from a different perspective.” Harnessing technology, she says, can help advance the ultimate goal: for everyone to lead healthy, active lives.

King and others are helping us understand the social, environmental, and behavioral determinants of health. This is vitally important, but it is not enough. We must also understand health in its entirety. William Osler, whom I mentioned in the introduction, moved medicine forward with his studies of the natural histories of diseases. Today’s challenge is to understand the natural history of health. To begin to create such a history, researchers from Stanford Medicine and Verily are studying biological markers and recording health data from devices that will be worn by thousands of people. This data is enabling us to understand markers of health trajectories better than ever before.

We are also working to expand the understanding of wellness and well‐being in a larger sense, with a focus on identifying what factors help people maintain health and wellness, in order to develop techniques that will help people to change their lifestyles. The Stanford Prevention Research Center, which I mentioned earlier, is on the frontlines of this effort. John Ioannidis, a professor of medicine at Stanford, is forthright about what he wants to achieve. “This is an effort to change the world of medicine and health,” he says. “I see this as a way to refocus the key priorities of biomedical research.”

The vast majority of biomedical research has focused on treating diseases. A much smaller part has focused on maintaining health and maybe some prevention efforts. But there’s very, very little research that has tried to look at the big picture—what makes people happy, resilient, creative, fully exploring their potential and living not only healthy, but more‐than‐healthy lives [18].

The center’s research has involved enrolling 40,000 people—10,000 each in the United States, China, Taiwan, and Singapore, and possibly also other countries downstream—and asking them 76 questions that are connected to 10 different dimensions of well‐being. Blood samples, as well as other biological samples collected from participants in most sites, will be available to be studied. These analyses, says Ioannidis, may reveal biological markers for wellness and well‐being. “Just as we can monitor diabetes by looking at blood sugar levels, is there some biomarker that can tell us something about how one feels about one’s life? Are there biomarkers that indicate levels of wellness and well‐being and that change as people’s levels of well‐being increase or decrease?”