Anatomy of a Disease: Type 2 Diabetes
Fueled by the growing obesity epidemic, type 2 diabetes afflicts an estimated 240 million people worldwide, many of them children and adolescents. That number is expected to double by 2030. In the U.S., approximately nine percent of the adult population suffers from the disease at any given time. Latinos, Native Americans, and African Americans are at especially high risk, with prevalence rates as high as 60 percent in some communities.
Type 2 diabetes can affect the heart, kidneys, blood vessels, nerves, eyes, and feet; it increases the risk of Alzheimer’s and other forms of dementia. Left uncontrolled, it can be life-threatening. Its economic cost to the U.S. is staggering—$174 billion a year, including $58 billion in reduced national productivity. There’s no easy fix. As shown below, researchers in the School of Public Health are tackling the problem on multiple fronts. Collectively, their efforts illustrate both the complexity of the disease and the complex, interdisciplinary nature of the approach needed to diminish its terrible toll.
Jump down to a description of a research project from any blue heading on the illustration below. Or scroll down to read them all.
- Diabetes and Dementia: Mexican-Americans have one of the highest rates of type 2 diabetes in the U.S. They also suffer high rates of metabolic syndrome, a set of conditions closely related to diabetes, which includes obesity, low HDL, high glucose levels, high blood pressure, and hyperinsulinemia. SPH epidemiologist Mary Haan is studying the effects of both diabetes and metabolic syndrome in older Mexican-Americans, with a focus on how these conditions affect the brain. It’s widely accepted that type 2 diabetes is directly related to Alzheimer’s and other forms of dementia, Haan says, so she’s hoping to decipher the precise nature of that link. Three pathways are candidates. The first is obesity—especially central-body obesity—which is associated with higher levels of hypertension, which can lead to stroke, which in turn is implicated in dementia. The second possible pathway is insulin. Visceral fat—the fat that surrounds organs—generates higher levels of insulin, which can affect the brain, so people with excess visceral fat are more susceptible to both diabetes and dementia. The third pathway is stroke itself, a common complication of type 2 diabetes, which can lead to physical and cognitive disabilities. “We’ve shown that people with type 2 diabetes have a threefold increased risk of dementia and Alzheimer’s,” Haan says. “We’ve also found that pepole who have a lot of central body fat have about a threefold increased risk of dementia.”
- REACH: It’s crucial that populations with high rates of type 2 diabetes, such as African Americans and Latinos, get access to health care. But there is ample evidence to suggest that even when they do have access to care, these populations are less likely to receive recommendations for the care they need and more apt to encounter barriers to diabetes self-management, says Michele Heisler, an associate professor of internal medicine with a joint appointment in health behavior and education. Through the REACH Detroit Partnership, a multilevel intervention, Heisler and other academic, health-system, and community partners, including the Community Health and Social Services Center (CHASS), are working in a variety of ways to prevent and manage diabetes in African-American and Latino residents of the city. REACH partners are collaborating with community centers and churches to establish and sustain free physical-fitness activities and to train community members to lead fitness classes. REACH partners are also working with the Henry Ford Health System and CHASS providers to improve cultural competence. In what Gloria Palmisano of CHASS says is “a very important component” of the intervention, they are training community health workers to work with people who have diabetes. They’re also addressing issues such as the lack of access to fresh vegetables and fruits in some neighborhoods. Future projects include helping residents secure certification as weight-management and healthy-lifestyle consultants, and a peer program that will train people with diabetes to lead diabetes support groups.
- Prescription Drugs: In 2006, as a result of a study conducted by the UM Center for Value-Based Research Design, under the direction of health management and policy faculty members Allison Rosen, A. Mark Fendrick, and Dean Smith, the UM implemented a program called MHealthy: Focus on Diabetes,. The program allows faculty, staff, and dependents enrolled in the UM Prescription Drug Plan who have any form of diabetes to receive some of their medications with no co-pays or reduced co-pays. More than 3,500 members participated in the pilot phase of the program, which ended in 2008. Because of its initial success, and to allow time for further study, the university has decided to continue the program for another three years. It’s the first program in the nation designed specifically to evaluate the impact of targeted co-pay reductions for preventive medications for a select high-risk group. The original V-BID concept was proposed by Fendrick and his colleagues in 2001. A subsequent study, led by Rosen, suggested that waiving co-pays for a specific type of medication that prevents heart attacks and strokes in individuals with diabetes could save lives and money. in the long run because costly medical complications are prevented or delayed.
- Intergenerational Transmission of Risk: Among Mexican Americans, as in many other populations, type 2 diabetes is being diagnosed at a younger and younger age, which leads SPH epidemiologist Mary Haan to wonder what impact lifecourse factors may have on the development of the disease and related metabolic markers. In an intergenerational study of a cohort of Mexican Americans, ages 16 to 80, Haan is examining how genetic and behavioral factors are transmitted from one generation to the next, and whether these accelerate the onset of diabetes and other diseases, such as atherosclerosis. She’s also studying the impact of cultural change. “One of things you hear about Mexican Americans is that as they become more adapted to U.S. culture, they may experience worse health,” she says. “In this context, cultural change seems to be related to a worsening risk of type 2 diabetes.” Although her focus is on Mexican Americans, Haan notes that her findings should be relevant to other immigrant populations as well.
- Health Literacy: One of public health’s biggest challenges is the growing number of children and adolescents being diagnosed with type 2 diabetes, both in the U.S. and abroad. It’s critical that new prevention strategies be identified to keep this population from developing the disease, says SPH Assistant Professor Melissa Valerio. Through a feasibility study involving at-risk African-American and Latino teens in Detroit, Valerio, in partnership with REACH Detroit and the Detroit Community-Academic Urban Research Center, is looking at the role health literacy plays in diabetes prevention. Valerio defines health literacy as “the understanding and use of information to make better health-related choices,” and she says that inadequate literacy affects people of all ages and can result in poor decisions related to disease prevention and daily disease management and difficulty navigating the health care system. The teens in Valerio’s study meet once a week for six weeks to learn about diabetes risk factors and how healthy eating and physical activity can help prevent diabetes. The program gives them weekly “challenges”—a concept drawn from reality TV—such as trying new foods and planning healthy menus for their families. Next steps: Valerio hopes to implement and test the study more broadly in Detroit and ultimately to translate findings to improve health literacy among young people nationwide.
- Chronic Infections: Several common persistent infections—including herples simplex virus, Helicobacter pylori, and hepatitis—have been linked to type 2 diabetes. It’s unclear whether these infections lead to higher levels of inflammatory response, which may contribute to the development of type 2 diabetes, or whether because diabetics are more susceptible to some infections, the disease itself predisposes individuals to infections. The situation could also be cyclical: infections could influence the progression of diabetes, and diabetes could lead to greater susceptibility to infections. SPH epidemiologist Allison Aiello is trying to untangle the mystery. One hypothesis, she says, is that the pathogen burden imposed by persistent infections, and their link to inflammation, may affect the risk for type 2 diabetes. “Our research shows that having a higher burden of common persistent infections leads to higher levels of chronic inflammatory response,” she says. “And given that inflammatory markers also cluster with diabetes, and are risk factors for the disease, this could be one pathway by which these infections influence diabetes.”
- Food and Fitness: The UM Center for Managing Chronic Disease, under the direction of SPH Professor Noreen Clark, provides technical assistance and serves as the evaluation team for the W.K. Kellogg Food and Fitness Environment Initiative. The Initiative is undertaking activities at the national, state, and local levels to bring about system and policy change—including changes in food systems, built environments, transportation systems, and public health systems that can lead to healthier environments and eventually reductions in type 2 diabetes and other chronic diseases. The Initiative includes intensive work with nine sites across the U.S., ranging from New York City to the Tohono O’odham Nation in south-central Arizona. Stakeholders in each of the intervention’s nine sites and across the U.S. are mobilizing to address and modify systems and policies so that people, especially in vulnerable communities, have greater access to healthy, affordable foods and to places where they can exercise and re-create. Specific targeted changes vary but can include modifications to school-lunch programs, efforts to get food stores to buy from local growers, and the creation of farmers markets. The UM Center is coordinating technical assistance for the Initiative and facilitating a national evaluation and cross-site evaluation of all nine community sites.
- Genes, Attitudes, and Behavior: As scientists explore new regions of the human genome that may be linked to type 2 diabetes, and as that research is publicized, there is a growing concern that people who believe they’re at risk for diabetes may think they can do nothing to protect themselves from developing the disease. “And yet we know, and studies show, that with exercise and diet, most cases of type 2 diabetes can be avoided,” says Toby Jayaratne, an SPH assistant research scientist who studies the psychology of health behaviors. In a recent pilot study, Jayaratne found that the more people believe type 2 diabetes is a genetic disease, the less they think it can be prevented or controlled. In collaboration with HBHE faculty members Melissa Valerio and Scott Roberts, Jayaratne hopes to undertake a nationwide study aimed at determining how people’s genetic explanations for diabetes, risk, and family history coalesce to predict key attitudes and behaviors related to diabetes prevention. Jayaratne is especially keen to know how cultural beliefs about disease affect the attitudes and behaviors of African Americans and Mexican Americans, who have higher-than-average rates of diabetes.
- Tailored Treatments: The complications from type 2 diabetes can vary immensely from one person to the next. Some people have an elevated risk of heart attack and stroke, for example, and a low risk of eye and kidney disease, while others have the opposite. But when it comes to treating diabetes, physicians tend to take a “one-size-fits-all approach,” says Rod Hayward, professor of health management and policy and internal medicine, and director of the Measurement Core of the Michigan Diabetes Research and Training Center. Working at the crossroads of epidemiology and health policy, Hayward is developing ways to tailor diabetes treatment based on individual risk. Key to his efforts are factors such as age and heart-disease risk. “We figure out a patient’s individual risk and make treatment decisions based on what will yield the greatest benefit,” Hayward says, “and we share those decisions with the patients.” It’s important not to overburden patients with unhelpful treatments, he adds, “and it’s equally important for us as a society to put our resources where they can do the greatest good.”
- Healthy Choices: SPH Assistant Professor Derek Griffith is working with African-American men to reorder their eating and exercise priorities so that they can help prevent chronic diseases like type 2 diabetes.
- 11. Teens and Soft Drinks: Countless American teens consume soft drinks and other sweetened beverages, but in some communities the habit may be especially harmful. This may be the case with a group of Native American teens in a New Mexico tribe where more than a third of the adult population suffers from type 2 diabetes. A recent study found that teens in the tribe consumed large amounts of sweetened beverages, including soft drinks. Suzanne Cole, a lecturer in EHS who worked on the study, says researchers found that the teens’ intake of micronutrients and fiber was also “quite low”—a matter for concern, because diets low in micronutrients and dietary fiber may contribute to the development of chronic diseases, including type 2 diabetes. Cole and her colleagues introduced an intervention to bring spring water and diet soft drinks into the schools for the teens to drink, and the researchers worked to improve the teens’ overall diet and physical activity. “If we target the younger population,” Cole says, “we might be able to modify their behaviors so their risk of type 2 diabetes is not as great.”
- Diabetes, Menopause and Metabolic Change: In the past two decades, the average age of onset for type 2 diabetes has dropped from 62 to 52 years of age. For women—who suffer higher rates of the disease than men—this means a confluence of two major hormone-related events: the menopause transition and a change in energy and carbohydrate metabolism. In an effort to understand how this confluence may contribute to the development of diabetes, SPH epidemiologist MaryFran Sowers is analyzing data from two groups of women in their late 50s and 60s, whose health she’s been characterizing for up to 15 years. She and her research team are looking at “the usual cast of characters,” she says, including obesity, but “in much greater detail.” They’re studying changes in muscle and fat tissue as well as changes in endocrine markers and other substances associated with these tissues, such as leptin, adiponectin, and resistin. They’re also looking at other dysfunctionalities that arise concurrently with type 2 diabetes, such as peripheral neuropathy—the deterioration of feeling in the extremities. Sowers hopes to determine how these pathological conditions develop in relation to diabetes and obesity status. She is also interested in assessing the degree to which obesity in combination with a metabolic abnormality, like diabetes, contributes to the development of osteoarthritis. Obesity has long been considered a significant risk factor for a range of diseases, she notes, but it may be that obesity in combination with metabolic dysfunctionality poses the greatest risk.
- Environments:SPH epidemiologist Ana Diez-Roux is studying the effects of neighborhood environments on health outcomes, including diabetes.
- Diabetes Control: As the program office for the national Alliance to Reduce Disparities in Diabetes, the UM Center for Managing Chronic Disease (under the direction of Noreen Clark, the Myron E. Wegman Distinguished University Professor of Public Health) is undertaking two tasks. First, the center is contributing to the efforts of stakeholders around the country to reduce diabetes disparities. Second, it is facilitating the work of five partnerships that are assisting adults with diabetes in low-income communities in the U.S. The partnerships are implementing community-wide, comprehensive approaches to disease control. These approaches, Clark says, offer a combination of proven interventions designed to enhance the activities of health care facilities and support systems. Interventions may include diabetes registries, improved referral systems, coordinated clinical care, and disease self-management programs. Each of the communities in the Alliance has a high prevalence of type 2 diabetes, which tends to be true for disadvantaged minority populations throughout the country, Clark says. The hope is that by encouraging a comprehensive approach to diabetes control at community through national levels, the Alliance can help reduce the adverse physical, economic, and social consequences of the disease.
- Genes: SPH biostatisticians Michael Boehnke, Goncalo Abecasis, and Laura Scott have played a leading role in identifying 18 regions of the human genome linked to type 2 diabetes. Common genetic variants in these regions, which are present in everyone, are each associated with 10–20 percent increases in diabetes risk, but Boehnke says he and his colleagues are now working to identify less common variants in those same regions, whose impact on disease risk in specific individuals may be greater. The researchers hope that by understanding the genetic underpinnings of the disease, they can “expand their understanding of its basic biology, contribute to the development of new and more targeted therapies for its treatment and control, and do a better job of predicting who is at greatest risk for type 2 diabetes,” says Boehnke. He points out that the driving force behind the increasing frequency of diabetes is not genetic, however, but behavioral. “Obesity is the epidemic that is preceding the diabetes epidemic.”