Abstract
Dr. Diette is Professor of Medicine, Epidemiology, and Environmental Health Sciences at the Johns Hopkins University. He is a pulmonologist with a practice devoted to the care of patients with obstructive lung diseases, including asthma and chronic obstructive pulmonary disease (COPD). Dr. Diette's current research focuses on identifying environmental causes of obstructive lung diseases, the role of diet in the development of asthma, as well as understanding and reducing disparities in the health of racial and ethnic minorities. Dr. Diette received his undergraduate degree in economics from the Wharton School of the University of Pennsylvania, his Doctor of Medicine degree from Temple University, and his Master's degree in epidemiology from the Bloomberg School of Public Health at Johns Hopkins University. He completed a residency in internal medicine at the Hospital of the University of Pennsylvania and fellowship training in pulmonary and critical care medicine at the Johns Hopkins Hospital.
Dr. Diette, you are primarily an adult pulmonologist, and your research focuses on identifying factors that cause or provoke asthma, particularly with regard to indoor air pollutants such as particulate matter, NO2, and secondhand smoke. However, I believe that much of your research has focused on asthma in children. Which factors contributed to your interest in studying this disease in a younger population?
One of the ways I became involved in pediatric asthma was through health services-oriented research projects I participated in, in which we were looking to identify where the biggest burdens lie for populations. Asthma is the number one chronic illness in children and the main cause for missed school days and visits to the emergency department. This led to the scientific question of what was it about the indoor home environments in which very young children, including preschool age children, spend a lot of their time that could be contributing to asthma risk.
There was no one moment during which I decided to start studying children. It depended on the research opportunities that were available. It also made sense to study these diseases in children because asthma and certain other respiratory illnesses do not start and stop in childhood. The adults we see in the clinic have the origins of their illnesses in childhood in many cases. I don't think it makes sense to partition asthma, for example, into being a childhood or adult illness. It is important to recognize it as an illness across the lifespan.
What are the main similarities and differences between asthma in children or young adults and in adults, and how are these important in diagnosis and treatment?
From a clinical perspective in particular, in adults there are more illnesses that could explain the symptoms we typically associate with asthma in children, such as shortness of breath, wheezing, or coughing. For example, lung cancer or heart failure might be the cause of these symptoms in adults, whereas they are much less likely in children. In children, there may be other explanations for these types of symptoms, but asthma is so common that it is by and large the predominant illness when these symptoms are present.
Although it appears that children can outgrow asthma, and a phenomenon has been described in which the symptoms go away and seem not to come back or become clinically apparent again, other studies have looked at lung tissue from people who had childhood asthma and seem to have outgrown it, and there is evidence of structural abnormalities. Biopsies of this tissue suggest that the disease may persist, but it may not be clinically apparent. Asthma may also appear to go away for a while when a person is a young adult and then return again later on in their 30s, 40s, or 50s for example.
How is children's lung disease relevant to adult pulmonology?
From the standpoint of lung development, you want the lungs to grow and develop as fully as they can, and once they have achieved that growth you want to protect them from losing function over time, which is a natural part of aging. Many of the same exposures, such as pollutants, can impact lung development and lung function from childhood through the adult years. Pollutants, for example, can limit lung growth in children and can accelerate lung decline in adults.
It is also relevant because there are a number of illnesses in which there is an issue of transition from childhood to adulthood, such as in cystic fibrosis (CF). CF used to be almost exclusively a childhood illness, but with better treatment it has become an adult illness. Groups such as the CF Foundation have made it clear that a different clinical approach is needed for adults with the disease compared to the traditional model for managing children.
In asthma, I think we recognize it as both a childhood and an adult illness, but there has not been a lot of attention paid to the transition between the two and what happens when a patient leaves the pediatric fold and becomes an adult patient with asthma. Other respiratory diseases of childhood, such as bronchopulmonary dysplasia, in which the lungs are either injured or for some other reason do not develop fully around the time of birth, have also become adult diseases, for the same reason as has CF—therapies have improved sufficiently to allow for longer survival. These patients all need to transition at some point to adult care, and people do not become adults at one particular point in time.
These types of issues are a good reason to broaden how we think about these illnesses. We should not just think about them as diseases of childhood or adulthood, and we should try to imagine how they will affect a patient over time.
You have incorporated a community-based participatory research model into your research program. What is this and why do you believe is it important, especially in this disease setting and patient population?
One of the studies I participated in required a community participatory model; it was built in by the funding agency. It has since become embedded in most of our field-based research. We have worked with our particular community advisory board for about 15 years, and I could give you a long list of reasons to use this model. One is that we get good ideas from the community. What we may think are the best things to study might not in fact be the best things to go after. The people who will be the study subjects often know things about themselves and their environment that can be incredibly valuable for fine-tuning the questions we want to ask. They have even helped us in thinking about how to ask certain questions. For example, in one study, we were interested in the area right outside the home, and we were going to ask about the “play area” where children play outside. We learned from community members that, in some neighborhoods, people called the sidewalk their yard. If we had asked people where they spent time, we would not have included the term “yard” because the property did not look like it had what we would traditionally think of as a yard. We had to change the language of the question to make sure we got the correct responses. This is an important factor for making sure you gather the information accurately.
Another advantage in working with a supportive community advisory board like ours is that they get the word out that our study is one in which community members can trust and enroll. This has been unbelievably important for initial recruitment and eventual retention, to have the stamp of approval from a community advisory board. It has helped us get beyond a lot of trust issues that may often be barriers between communities and big institutions.
In terms of dissemination of information, our traditional methods are to try to publish our data in journals or present them at a national meeting, but the community members do not read those journals or attend those meetings. They will not get the information unless we take a different approach. We have worked with the community advisory board to create brochures, and with a local art college to create posters that show different asthma triggers with a message that the advisory board wanted to get out warning people that asthma can kill. We have also developed a question-and-answer, game-show format that we have implemented in schools. We have worked with some very talented people to be sure the information has gotten back to the community in a form the people can understand.
What are the challenges of incorporating a community-based participatory research model into a research program?
It is definitely not easy, and it is not a linear process. Early on in the program, we had to spend a lot of time doing exercises to get to know each other. We had a retreat at which we brought together community members and our study team to try to agree on priorities for the research. The biomedical research goals were not necessarily the same as what the community members wanted to know, which was what in their homes might be hurting them. We had to create a list of priorities that reflected what we could all reach consensus on and what represented common ground. It is a lot of work and requires a lot of maintenance. We have to meet regularly and give each other updates. It is an ongoing process.
One of the first things we had to do was to define the community—the geographic boundaries and which people should be included. You need to work with the community members to create this definition. This is also very fluid, as the demographics change over time.
Much of your research has focused on how the inner-city environment contributes to asthma problems and asthma disparities. How did you become interested in these issues and what have been some of your key findings? What have been the most important challenges and missteps along the way?
I became interested in these problems and disparities because, by every measure of burden you can think of, inner-city asthmatics fare worse than non-inner-city asthmatics. It is a crucial place to study this disease simply to alleviate suffering and to understand scientifically why an illness is so concentrated in a particular area. For us, it was a matter of wanting to look at the homes in particular, and what about the insides of the homes especially might be influencing asthma. The obvious targets were allergens and pollutants and those that are common in indoor environments.
In terms of the key findings, one important finding was identifying mouse urine protein in 100% of the homes we studied, and airborne protein in more than 80% of the homes. This means it is a light enough allergen that it can float, making it possible for people to breathe it in. In preschool-aged children, we found that there was a striking risk among the kids who were sensitized to mouse allergen and who also had high exposure; they had an incredible burden of disease. Most of the children who were hospitalized were those who were both sensitized and highly exposed.
We also discovered important information about certain pollutants, such as particulate matter and small particles in the respirable range that come from tobacco smoke, cooking, and cleaning activities, as well as some that come from outside the home. These pollutants and nitrogen dioxide are the ones we focused on primarily. Nitrogen dioxide is produced by combustion, such as from smoking and cooking. We learned that the predominant cooking method was with a gas stove, and most of the stoves were not vented to the outside, so the particles become pollutants throughout the house, and when the pollutants are higher, the asthma is worse.
Were any of the findings especially surprising?
One surprise was how much smoking there was in the home. The national average is that a little more than 20% of adults in the United States smoke cigarettes, whereas in our study about 56% of the homes had an active smoker, and these were homes with an asthmatic child. We had a control population, and it was really remarkable that there was no difference in smoking rates or amounts of smoking between homes with or without asthmatic children, meaning there was no clear attempt not to smoke when there was a child with asthma in the house. We assumed that the caregivers of children who had worse asthma would be less likely to smoke, but that was not the case.
What would you identify as some of the most important research, clinical, and public policy implications of your work?
Our center conducts clinical trials and is also trying to influence public policy. We have had a couple of trials that have been successful at influencing the levels of indoor air pollutants and have been able to achieve reduced symptoms. The most recent trial had three treatment arms and included the use of air cleaners, which were shown to be able to reduce particles in the air by a substantial amount, resulting in reduced symptoms in homes where there was a smoker. The main goal of the study was to see if we could get parents to quit smoking or change their behavior, but we had very little success in making smoking go away. We were, however, able to show that an air cleaner could be a partial solution. We found that, even with an air cleaner, the amount of airborne nicotine was not affected, and the amount of cotinine, as a measure of exposure of the children to cigarette smoke, was not different. So some part of the cigarette smoke still makes it into the children.
From a policy standpoint, by working with city and state health departments and trying to make inroads nationally, our aim is to make the point that asthma is not a drug deficiency. It is not an illness in which people are missing inhaled corticosteroids or beta-agonists. It is a disease of the environment; it is brought on by and perpetuated by the environment. So our key focus should be on trying to mitigate the problems with the environment. We may not know the single best strategy to use in every circumstance, but we know the strategies that work to reduce the pollutants, and we are trying very hard to expand the evidence base for what we know does work and to make sure the information gets out there. We are talking to people about changing reimbursement policies, such as coverage for air cleaning devices by Medicaid and other private insurers. They are not that expensive; they cost hundreds of dollars, which is what medication might cost for just a couple of months. They don't have side effects and they don't harm people.
I also want people to think about the standards of evidence needed. Our guidelines are drafted in such a way that they acknowledge studies based on quality and quantity. Whereas we need large-scale studies to determine the safety and efficacy of drugs that people are going to put into their bodies, when we are evaluating something that we know is harmful, such as a pollutant, I think it is worthwhile to take a chance with something that might reduce that harm and not wait for multiple large-scale clinical trials to show an effect.
One of our ongoing studies, called the “Stove” study, involves going into homes and either replacing a gas stove with an electric stove, fitting the gas stove with a fan that sends the exhaust to the outside, or using air cleaners, and we are evaluating which of these strategies is more effective and more feasible for reducing nitrogen dioxide and improving asthma symptoms. This initial study is in preparation for a larger-scale trial.
Looking back to the early days of your medical education and training, what interests, experience, and events led you to pursue your current career path? What advice would you give to young physicians considering a specialty in pulmonology?
From a pulmonary standpoint, I enjoyed the study of lung physiology. Cardiology and pulmonology were my favorite topics, and it seemed like there was more work to be done in the pulmonary area. Collectively there had been less research done, and there were more opportunities to jump right in and hopefully make a difference. In terms of picking asthma, I was attracted to something that was burdensome on a massive scale, affected many people, was costly, and by almost every measure was an important illness affecting large segments of the population.
My advice would be to pick something that is fun and enjoyable—above all, to find colleagues who are great to work with and share your interests. Find a niche in which you are happy to go to work every day and enjoy the people you work with.