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Address correspondence to: Sarah Gehlert, PhD, E. Desmond Lee Professor of Racial and Ethnic Diversity, Box 1196, Washington University, One Brookings Drive, St. Louis MO 63130
The aging of the Baby Boomer population, the roughly 69 million adults who were born in the U.S. between 1946 and 1964, presents a number of important public health challenges. This cohort that now represents 26.4% of the total U.S. population is living longer than any cohort that came before it. Men aged 65 years are projected to live to age 83 years, and women aged 65 years are projected to live to 85 years, compared to about 46 years for men and 48 years for women in 1900.
This trend toward increased longevity is expected to continue, with the number of adults aged ≥65 years increasing from 35 million, or 13% of the U.S. population, in 2010 to 72 million, or 20% of the population, in 2030.
The growing number of the aging population in the U.S. has major implications for cancer prevention and control. That the cumulative risk of developing cancer continues to expand until about age 70 years suggests that the number of middle- and older-aged people who are at risk for developing some type of cancer during their lifetimes will continue to increase as the population grows.
Addressing modifiable risk factors for cancer in childhood through middle adulthood thus seems essential to improving the lives of this growing segment of the population. In fact, it has implications for the health of the nation as a whole.
Realizing the need to set an agenda for cancer prevention in midlife, the Division of Cancer Prevention and Control at the CDC brought together in 2012 an expert panel of investigators from a range of disciplines and approaches to acquiring knowledge. The purpose was to discuss cancer risk in middle adulthood, with a shared aim of preventing cancer.
This workshop was part of an innovative CDC-sponsored series entitled Cancer Prevention Across the Lifespan. The workshop on cancer prevention during midlife followed a 2011 CDC-sponsored workshop on preadolescent and adolescent exposures and risk for adult cancer.
Taken together, the two workshops represent an innovative approach to cancer prevention, one that takes into account the intersections of age, cancer risk, and cancer prevention, with consideration for how they might vary by race/ethnicity, SES, and considerable comorbidities such as serious mental illness.
Although taking such an integrated and holistic approach is admirable, it presents major challenges to advancing the expert panel’s agenda for cancer prevention during key periods of the life cycle. Not only would it require convening diverse groups of experts such as those who participated in the 2011 and 2012 CDC-sponsored workshops and expanding them to include scholars with newly identified areas of pertinent expertise, such as experts at the intersection of developmental biology and race, but its success also would depend on the ability to develop an infrastructure for fostering these kinds of collaborations. In order to inform such an approach, the argument is posited in this article for a means of capturing the complexity of age, cancer risk, and cancer prevention in the context of race/ethnicity, SES, and comorbidities, using findings from the 2012 CDC-sponsored expert panel on cancer prevention during midlife. In doing so, specific suggestions are offered for developing and sustaining such an approach.
Exploring a Case for a Developmental Approach to Primary Cancer Prevention
make a strong argument for the wisdom of taking a developmental approach to preventing cancer in midlife and older adulthood, noting that cancers develop over a period of many years and that many of the more than half of cancers diagnosed in 2009 were in adults aged ≥65 years. Colditz and colleagues
to support their contention that benefits are best achieved through prevention that is timed earlier in life.
Although chronologic aging cannot be linked directly to the development of diseases such as cancer (i.e., one’s chances of acquiring a disease do not increase with each additional year of life), aging involves a series of biological processes that may predispose a person to cancer and other diseases. One example is cumulative exposure to environmental pathogens such as pesticides that are known to contribute to the development of cancer and other diseases. Ory et al.
write about midlife as a watershed in which host immunity begins to decline and the effects of risks and exposures accumulate. Likewise, poor health habits like smoking, sun exposure, and inactivity, which have been linked to a number of chronic diseases including cancer, begin to take their toll during midlife and continue to accumulate into older adulthood. Recent evidence
that DNA methylation age of tissue measures the cumulative effect of an epigenetic maintenance system provides promise for helping to understand the relationships among age, developmental biology, and cancer.
make a strong case for midlife as a critical period of focus for primary cancer prevention, while at the same time acknowledging that a definition of midlife as ages 45–64 years may be somewhat arbitrary. Just as preadolescence and adolescence are times when positive health habits can be shaped and individuals and their families can begin to set a course for minimizing harmful exposures like radiation, midlife also represents a period when positive change is possible. Although harmful health behaviors may persist through young adulthood into middle adulthood, Ory et al.
note that the relative stability of middle adulthood allows more opportunities for health behavior change than do earlier phases of the life cycle.
For many adults in the U.S., midlife is a time when family life and work begin to stabilize. Workers achieve seniority, and their employment may provide health-enhancing benefits like insurance coverage and a platform for worksite wellness programs. Midlife also often brings a lightening of responsibilities within the nuclear family. Rolland
characterizes midlife as a centrifugal period in the family life cycle, in the sense that parents can focus outward, beyond the immediate activities of childrearing. Child care duties decrease as children leave home to begin their own lives, allowing parents to focus on their own lives. At the same time, individuals are exposed to the aging of their friends, colleagues, and parents, which may sensitize them to their own health. Thus, midlife can be seen as a period when adults are able to focus their behavior change efforts to reduce their risk for developing cancer, fostered by access to venues and supports for substituting healthful for less healthful behaviors.
The wisdom of targeting midlife for prevention of cancer during older adulthood depends on evidence that changes in behavior during midlife can in fact modify risk for cancer later in life. Evidence from studies of immigrants who change from one lifestyle to another or populations experiencing industrialization reveal large changes in cancer risk, although such studies do not reveal when in life these behaviors or exposures occurred.
calculate relatively rapid drops in cancer incidence (i.e., from 2 to 20 years) after a number of behavior changes and interventions (e.g., folate intake and risk for colorectal cancer) as evidence that cancer can indeed be prevented. Studies such as that of Coombs and colleagues
find that when hormone replacement therapy use fell from 25% to 11.3% between 2000 and 2005, breast cancer incidence among women aged 40–79 years decreased by 8.8% suggests that breast cancer incidence can indeed be modified through health behavior change during midlife.
The Determinants of Cancer Risk During Midlife and Other Phases of Development
Although the work of the 2011 and 2012 CDC expert panels contributes markedly to our understanding of cancer risk and cancer prevention across the life cycle, little is known about how age, cancer risk, and cancer prevention operate among members of racial and ethnic minority groups and lower-SES populations to affect cancer risk. Yet, acquiring this information is essential to successively advancing the expert panel’s agenda for cancer prevention.
Efforts have been made in recent years to understand the determinants of cancer by recognizing that they occur at multiple interacting levels of influence, and that reducing cancer requires devising interventions that target more than one of those levels. Expert panel members’ investigations span levels of analysis. They range from the investigation of individual risk factors such as alcohol consumption
Importantly, panel members expanded from the prevailing focus on individual risk factors such tobacco, diet, physical activity, and obesity to include highly prevalent factors such as social and physical context and policies.
A first step in integrating the work of the expert panel is organizing these investigations into a multilevel model. Previous multilevel models portray factors from the microbiologic to the societal and make clear that they interact with one another in complex ways. One example is a 2008 framework developed by Hiatt and Breen
developed a six-level model of cancer disparities (biological/genetic pathways, individual risk factors, social relationships, social/physical context, institutions, and social conditions and policies). In this model race, age, and SES are included at the individual risk factors level, along with health behaviors such as tobacco use and diet, in order to capture their effects on behavior.
In addition, factors that might differentially expose racial/ethnic groups to cancer and thus help to explain increased mortality among racial/ethnic minority groups, such as segregation, discrimination, and racism, are included at other levels of the model. Segregation, for example, is included at the social/physical context level.
Situating Cancer Risk Along the Developmental Continuum
Although the multilevel models described above help to contextualize cancer risk and include chronologic age as an individual risk factor, none to date has considered how interactions among multiple levels of influence might vary across the developmental continuum. Figure 1 portrays multilevel determinants of cancer risk as proposed by Warnecke and colleagues
Considering developmental phase in a multilevel model of cancer risk seems prudent for at least two major reasons. First, meaningful factors may vary by race/ethnicity. A number of factors at the biological/genetic pathways level, for example, are known to vary by race/ethnicity. The onset of puberty, a risk factor for breast cancer, is significantly earlier for African-American than for white girls.
also found the age at menarche, one marker of the puberty transition, to occur considerably earlier in African-American than white and Mexican-American girls. Others have posited that social factors to some extent shape biological pathways to produce these differences.
The second way in which multilevel models might vary by race is that certain levels of analysis are likely to be more salient during certain phases of development than others, which might alter the way in which factors at these levels interact with factors at other levels. The theory of developmental plasticity, for example, tells us that puberty is a period of high sensitivity to chemical exposures and other environmental stressors.
found that high estrogenic fetal environments silence BRCA1 in daughters through methylation, resulting in less BRCA1 to defend cells from becoming cancerous. Also, decreases in physical activity and insomnia are known to be more pronounced in midlife and older adulthood,
which would negatively affect biology (biological/genetics pathway level) and perhaps increase the use of health care (institutions level). Zonderman et al.
suggests that it also might present unique challenges to adults with serious mental illness.
Transdisciplinary Research in Cancer Prevention During Midlife
Considering all of the risk factors for cancer increases the complexity of resultant investigations, and embedding them in a racial and socioeconomic context increases it still further. Extending this complexity across the developmental continuum represents an even greater challenge. Widening our lens to increase the range of factors that influence cancer risk challenges long-held modes of collaboration among scientists in which investigators operate largely within their own disciplines, and are rewarded for doing so. In the traditional multidisciplinary mode of collaboration, although investigators might come together to solve a research problem, each discipline historically has approached it through a separate lens. They might, for example, gather at the beginning of a research project with separate but related research questions, collect and analyze data independently, form independent conclusions based on their separate research questions, and then come together at the end of the project to try to make sense of it all. These investigators leave the collaboration with neither discernible change in their approach nor a record of bold new insights and discoveries. Likewise, they rarely bring new investigators into the team as new research questions emerge from their joint investigations. This mode of collaboration has failed to provide a comprehensive picture of risk factors and exposures for cancer during older adulthood that takes into account race/ethnicity and SES across the developmental continuum.
As has been argued previously by this and other authors, the growing awareness that cancer risks and exposures at multiple levels of influence interact in complex ways has made clear the need for new modes of collaboration that optimize the input of scholars from diverse backgrounds.
The most promising of these is transdisciplinary research, in which biological, behavioral, social, and clinical investigators transcend and operate outside their own boundaries and cultures to achieve synergy, inform one another’s work, and create new intellectual spaces in which no one discipline dominates and no way of knowing is privileged over other ways.
This allows the emergence of new scientific ideas, questions, methods, and analyses that would otherwise not have emerged had investigators worked in more traditional and siloed ways. If transdisciplinarity were to be achieved, the outcome could be a new multifaceted, broadly analytical understanding of risk factors and exposures for cancer that occur during midlife that could inform solutions and undergird a well-integrated plan for their dissemination to stakeholders.
defines as “research in which exchanging information, altering discipline-specific approaches, sharing resources, and integrating disciplines achieves a common scientific goal”) achieves the highest degree of collaboration of any collaborative mode.
It relies on early agreement on research questions, methods, goals, and timelines, and it may entail the development of multifaceted, broadly analytical models for investigating problems. Hall et al.
identify four phases of transdisciplinary research, namely development, conceptualization, integration, and translation, each of which requires resources and support from outside the team.
Rather than being intuitive, achieving and sustaining transdisciplinarity requires learning and support. Yet training in transdisciplinary collaboration has been slow to appear.
For the most part, scholars continue to be trained in the language and methods of their own disciplines, and few existing training programs have been systematically integrated into formal curricula at any level of education. This hinders the transfer of knowledge across disciplines and makes it difficult to develop broader analytical perspectives on inherently complex human problems.
Increasing collaboration to the level of transdisciplinarity requires structural changes within institutions, agencies, and universities. Needed are structures that foster interactions and training across disciplines and that prevent one discipline or group of disciplines from being favored over others. Favoring one way of knowing over others breeds the mistrust, conflict, misunderstanding, and lack of appreciation for the expertise of others that impede the free flow of ideas between disciplines. Mechanisms for avoiding these pitfalls include creating shared instructional and work space across disciplines, cross-training opportunities for pre- and post-doctoral fellows, and setting up one central administrator to oversee research awards so that the work of one department, division, or school is not privileged over others.
In addition to providing training, institutions must recognize and reward investigators who choose to work transdisciplinarily. Teams of investigators working across departments, divisions, and schools of universities remain the exception rather than the rule, primarily because of the nature of institutional incentives, and universities continue to recognize and reward work by individuals when it comes to tenure and promotion. At the present time, tenure and promotion committees largely pose an impediment to transdisciplinary research, especially for junior faculty members. This is because they fail to recognize the time required for establishing teams and have traditionally favored single-authored publications over multiauthored, collaboratively generated publications when evaluating faculty members for advancement.
Translation
In order for knowledge generated by transdisciplinary teams to result in decreased rates of cancer, its successful translation into communities is required. This entails making the boundaries of research teams sufficiently permeable to allow knowledge sharing from basic science to clinical science to program implementation and policy change. In addition, new mechanisms are needed to foster communication between these stakeholder groups (e.g., university investigators and policymakers), because they operate in a variety of settings and geographic areas, impeding opportunities for information-sharing and collaboration.
Community stakeholder input is essential to successful translation. For sustainable reductions in cancer incidence rates to occur, research findings must be used in a way that takes into account the context, value system, and needs of each affected community, whether the population is defined by race or ethnicity, SES, phase of development, or other factors (e.g., serious mental illness). Community-based participatory research involves engaging community stakeholders at each stage of the research process, thus enhancing the relevance and effectiveness of interventions by producing research findings that are meaningful to community members and tailored to their needs.
This engagement increases the likelihood that interventions like primary cancer prevention will be implemented and sustained. The hypothesis testing suggested by the work of Keum and colleagues
on the 2012 CDC expert panel would benefit from input from community stakeholders.
Effective translation also involves integrating primary prevention messages across specific risk factors. Investigators usually disseminate the knowledge that they produce within their own disciplines and arenas (e.g., alcohol consumption, physical activity,
or to the public. The result is that research-based recommendations are seldom coordinated and, in fact, one set of recommendations may differ from another even when both sets are based on similar evidence. The consequence of this practice is a failure to adequately inform healthcare providers, the public, and policymakers about our work in a way that can be understood and used to reduce risk for cancer.
Conclusion
The number of middle- and older-age people at risk for developing some type of cancer during their lifetimes is increasing as the Baby Boomer generation ages. Efforts by the CDC to bring together investigators from a range of disciplines involved in research on midlife exposure to risk hold promise for turning knowledge about midlife risk factors into interventions for preventing cancer during older adulthood. Yet capturing intersections of age, cancer risk, and cancer prevention, with consideration for how they might vary by race/ethnicity, SES, and other key factors, requires a new approach to collaboration within the sciences. Successful translation of the knowledge generated by these new collaborations depends on communication along the continuum from basic science to clinical science to program implementation and policy change. It also requires accounting for the context, value system, and needs of affected communities, which can best be achieved through working in partnership with community stakeholders.
A number of structural changes are needed to sufficiently capture the complexity of cancer risk during midlife to allow for the development of interventions to reduce rates of cancer during older adulthood. Universities and other research institutions need to develop and implement curricula on transdisciplinary research as early in the educational process as possible and to institute mechanisms for rewarding transdisciplinary collaboration. Only when investigators can integrate their work, with input from stakeholders, can we begin to create multifaceted solutions to reduce cancer incidence rates during older adulthood. Likewise we must disseminate the solutions in a consistent and integrated way so that they are less confusing for stakeholders and have a greater chance of improving the nation’s health.
Acknowledgments
Publication of this article was supported by grants NCI U54-153460, NCI U54-155496, and UL1 TR000448.
The publication of this supplement was made possible through the CDC and the Association for Prevention Teaching and Research (APTR) Cooperative Agreement No. 1 U360E000005-01. The findings and conclusions in this report are those of the author and do not necessarily represent the official position of the CDC or the APTR.
No financial disclosures were reported by the author of this paper.
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