Identifying Factors Behind Race- and Gender-Based Inequalities in Obesity and Cancer

A Profile of Whitney Robinson, PhD, MSPH, Health & Society Scholar, 2008–2010

    • May 1, 2013

The problem. Some groups of people are at higher risk for obesity and cancer and have worse outcomes than other groups. Studies show, for example, that Black women are at much greater risk for obesity than Black men. For most cancers, Black people have the highest death and shortest survival rates of any racial or ethnic group in the United States. Designing effective interventions to reduce obesity and cancer in these high-risk groups requires a deeper understanding of the causes of these conditions and which risk factors can be changed.

Scholar perspective. Whitney Robinson, PhD, MSPH, loved solving puzzles, so epidemiology was a natural career choice for her. "Epidemiology lets me look at data to find underlying trends," she said. "When you find the right way to analyze the data you can make powerful insights."

After graduating cum laude with a degree in biochemical sciences from Harvard University in 2001, Robinson pursued her MSPH and PhD degrees in epidemiology from the University of North Carolina at Chapel Hill, completing her PhD in 2008. Her doctoral dissertation—"Under the same roof: Understanding gender differences in obesity prevalence among U.S. Black and White young adults"—reflected her research interests in gaining insights into obesity and cancer.

Robinson wanted to focus her research on identifying and quantifying factors in childhood that underlie race- and gender-based inequalities in obesity and cancer. These factors, she anticipated, could be used to determine which interventions would be most effective in reducing racial disparities.

But Robinson knew that the methods of analyzing data that she was using were not good enough, and she wanted to develop better ways to use existing data and perhaps even new methods of data analysis. The Robert Wood Johnson Foundation Health & Society Scholars program enabled Robinson to gain the broader perspective she needed to do this. In 2008, she began the two-year interdisciplinary fellowship at the University of Michigan, one of the six universities participating in the Health & Society Scholars program. For more information on the program, read the Program Results.

"The program broadened my perspective and my research toolbox and connected me with like-minded scholars," she said. "I got to work with people who are interested in making changes in population health from different perspectives."

Discovering how methods impact study results. As a Health & Society scholar, Robinson began to study the causes of obesity in the United States through the complex lens of methodology. In one study, she and colleagues (co-authors were from Columbia University and the University of Utah) clarified methodologic issues in sociology and epidemiology in analyzing age, period, and cohort effects. By definition, age effects are the distribution of an outcome over a lifespan; period effects are trends in an outcome among all age groups; and cohort effects are the concentration of the outcome among individuals who were born in or around the same year, sometimes called generation effects. These analyses can help researchers study past population-level health trends, predict future health trends, and identify causes of individual-level susceptibility to health outcomes.

Sociologists often assume that cohorts have unique characteristics confounded by age and period effects, while epidemiologists often assume that period and age effects interact to produce cohort effects. Robinson and her colleagues used data from the National Health and Nutrition Examination Survey to illustrate the different definitions and statistical methods, as well as their implications for understanding obesity prevalence in the United States from 1975 to 2006.

Using three statistical methods to estimate age, period, and cohort effects, they found agreement about the age effect—the risk of obesity increased in childhood and early adulthood and stabilized by mid-adulthood. They also found agreement about the period effect—obesity prevalence increased across all ages beginning in the 1980s. But the results for the cohort effect differed; one method found a significant cohort effect where successively born cohorts had increased risk of obesity, but the other two methods did not find this. Robinson and her colleagues published their findings in Social Science & Medicine (Vol. 70(7), 2010).

"We showed that depending on the model you use, you can get different answers. It is not that any of them are necessarily wrong, but they are different ways of looking at the problem," said Robinson. Grants to Robinson's co-authors from the National Institute of Mental Health, National Institute on Aging, and National Institute on Alcohol Abuse and Alcoholism supported this research.

Under a competitive research grant from the Health & Society Scholars program, Robinson also studied whether childbearing makes Black women more likely to be obese than White women. In February 2013, she was still analyzing the data, but her preliminary results indicate that childbearing does not contribute to racial disparities in obesity.

Continuing interdisciplinary work in obesity and cancer. After completing her RWJF fellowship in 2010, Robinson joined the University of North Carolina Gillings School of Public Health faculty as an assistant professor of epidemiology. "Students wanted to learn about population health and social epidemiology. The Health & Society program gave me a skill set to talk about this," she said. "It helped me get a great job."

Robinson is also a fellow at the university's Carolina Population Center, a community of scholars and professionals who collaborate on interdisciplinary research and methods on population issues. She is also a member of the UNC Lineberger Comprehensive Cancer Center, one of only 40 National Cancer Institute-designated comprehensive cancer centers.

Robinson has continued her research to use methodologic innovation to identify the causes of obesity in the United States and ways to prioritize efforts to reduce cancer disparities. In 2012, Robinson and colleagues published the results of two studies about trends in obesity in adults and cohort effects and abdominal obesity in the International Journal of Obesity (May 2012 and December 2012). Both studies used data from the National Health and Nutrition Examination Survey.

In the first study, Robinson and her colleagues estimated cohort effects for obesity prevalence among adults born in the 1980s, and found that they were more likely to be obese than people born in the late 1960s. These effects were especially pronounced in Black males and females but appeared absent in White males. In the second study, they found that the Silent Generation (born 1925–1945) and Generation X (born 1965–1980) had higher cohort-specific prevalence of abdominal obesity than the Baby Boomers (born 1946–1964). These effects were stronger in women than in men.

By increasing understanding of obesity prevalence, studies like these can contribute to reducing obesity, Robinson explained. "We found that the environment changed. The effects in the IJO [International Journal of Obesity] study reflect that young people growing up in the 1980s, in an environment that was obesogenic, may carry increased vulnerability to obesity over their whole lives. Even if obesity rates stabilize for adults from the Baby Boom Generation and Generation X, rates in the Millennials could continue to increase. We have to focus on environmental change."

Under a nearly $1.3 million National Cancer Institute grant, Robinson is addressing a central challenge in cancer prevention and control: prioritizing efforts to reduce cancer disparities. With the help of a multidisciplinary team of mentors from the fields of nutrition, economics, genetics, and oncology, she uses epidemiologic methods and data from the Carolina Breast Cancer Study to identify the mechanisms of disparities in breast cancer between Black and White women.

"We see the disparities in breast cancer burden in the data, but it's hard to identify the pathways of the disparities," said Robinson, who started the five-year project in 2012. "I'm learning methods that will help me unpack some causes of these disparities, which will help us know the best place to intervene to have maximum impact on reducing the disparities."

RWJF perspective. RWJF created the Health & Society Scholars program in 2001 to build the field of population health. "There is a growing recognition that health is the result of the interaction of multiple factors including socioeconomic and physical environmental factors and health behaviors," said Pamela G. Russo, MD, MPH, senior program officer. "The evidence shows that these types of factors play a much larger role in determining health at the population level than do the traditionally considered health care and biological determinants of health. The program seeks to integrate paradigms and knowledge from a variety of disciplines to develop an understanding of how these determinants affect the health of populations, and thereby to design interventions with greater power to reduce health disparities," said Russo.

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#HSS Whitney Robinson: research answers can differ based on question asked & approach used

Whitney Robinson, PhD, MSPH

Whitney Robinson, PhD, MSPH
Health & Society Scholar, 2008-2010