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Value of data from Nurses’ Health Study ‘cannot be underestimated’
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In a perspective paper published earlier this year in Public Health Research & Practice, Graham A. Colditz, MD, DrPH, highlighted the impact of 40 years’ worth of data generated by the Nurses' Health Study.
The study — established in 1976 to assess the association between oral contraceptive use and breast cancer risk — has evolved and expanded to address other emerging public health issues, such as exposure to air pollution or silicone implants.
The findings have greatly improved scientific understanding of health and disease in women, according to Colditz, the study’s principal investigator from 2000 to 2006.
“The study has guided recommendations from the U.S. Surgeon General in areas such as the adverse health effects of smoking, and resulted in changes to regulation, such as in the area of transfat and its effect on heart disease and diabetes,” Colditz, chief of the division of public health sciences and professor of surgery at Washington University School of Medicine in St. Louis, said in a press release. “The study is now working with a third generation of American women. Much has changed in the field of epidemiology in the past 40 years, and we have had to adapt to respond to emerging public health issues.”
Colditz spoke with HemOnc Today about how the Nurses’ Health Study has evolved over the past 4 decades and what areas researchers are exploring today to glean new insights.
Question: Can you describe the value of the Nurses ’ Health Study?
Answer: The study has made some major, seminal contributions to understanding women’s health in regard to cancer, heart disease, diabetes and stroke. It has set the standard for modern, epidemiologic, prospective studies of health, integrating lifestyle, biomarkers, genomics and so forth. It is contributing to the methods of conducting these studies and, more importantly, contributing to our insights of disease etiology. These results have been translated into practice at the policy, clinical and individual behavioral levels.
Q : What insights have the data yielded specific to cancer?
A: One of the clearest contributions has been with smoking-related cancers and colorectal cancer. These findings, along with findings from other studies, led to the U.S. Surgeon General concluding that smoking is a cause of colon cancer and pancreatic cancer. Other findings include the combination of estrogen plus progesterone and the longer use of hormonal therapy increasing the risk for breast cancer. The study identified multiple effects of oral contraceptives, one of which showed a significant decrease in risk for ovarian cancer. This is a powerful finding that has held up in other studies around the world. Further, researchers found there are benefits of physical activity for reducing colon cancer and breast cancer. With regard to diet, they have found that higher intake of fruit, vegetables and whole grains lowers the risk for breast cancer. The data also have been a rich source to combine with other cohorts in reanalysis.
Q: In what ways has this study laid a foundation for subsequent research?
A: This is emblematic of some of the combined analyses of diet in cancer and the work on endogenous hormone levels of blood samples collected from more than 30,000 participants showing a direct relation to breast cancer that is stronger for receptor-positive breast cancers. This gave us better insight into the risk related to one subtype of breast cancer or all breast cancers. A similar effect came from the results that showed intake of fruit, vegetables and whole grains are associated with lower risk for breast cancer. The other piece is how researchers collected the data from the beginning back in 1976. It certainly fits with the ‘paving the way for other research’ theme in that other researchers were able to use the same methods going forward.
Q: How could the study be used moving forward?
A: The Nurses’ Health Study can contribute to studies of obesity, pancreatic cancer and other malignancies that may not be as common as breast, colon or lung cancer. The next level out from this may be that researchers will put the overall evidence together instead of looking at one risk factor at a time. Then we can get a good idea of the importance of lifestyle factors in determining risk for various cancers and other chronic diseases.
Q: How has the study evolved since its inception?
A: The technology has changed — in 1976, we barely had computers on university campuses — and the potential to do genomic analyses has changed. The study has evolved to refine and repeat the measurement of physical activity and diet. It has moved to the integration of risk factors and models to predict disease and understand how much of the disease is driven by lifestyle. One of the classic examples of responding to public health issues was with the launch of a study that evaluated the possible health effects of silicone breast implants. It is interesting to see that, even though the cohort is ongoing, it has been able to respond, add questions and yield new outcomes. There has been definite strength in the evolution of the study during the past 40 years.
Q: Have the findings specific to cancer changed practice?
A: One study on its own is unlikely to change practice. However, the findings and contribution of the Nurses’ Health Study have clearly shifted the dial. At one time, there were not much data on the health effects of smoking in women. Now, we have really demonstrated that — just like men — women who smoke have more cardiovascular disease. This can be taken into other areas of disease, as well. The early findings from a study that showed physical activity after breast cancer diagnosis has the potential to reduce risk for recurrence and death has shifted the focus to energy, balance and activity after breast cancer and other cancers, too. In addition, findings that explored the association between longer use of hormonal therapy and increased risk for breast cancer can be coupled with findings of the Women’s Health Initiative Study, which led to the recommendation for shorter use of hormones. Findings that suggested alcohol intake increases risk for breast cancer are clearly now incorporated into American Cancer Society guidelines.
Q: What areas are investigators examining now?
A: There is a lot of work in the area of breast cancer subtypes and molecular markers that may give insight into the pathways of causation and the potential for prevention. For example, there are markers in colon cancer that predict outcomes after treatment. There are a range of issues that truly reflect the changing emphasis of where the science is and could be.
Q: Is there anything else that you would like to mention ?
A: The value of the study, with repeated measures and extended follow-up, really cannot be underestimated. Some of the findings on diet and breast cancer were not there during the early days. With long-term follow-up and the ability to really be able to look at women who have had higher intake of fruits, vegetables and whole grains — and to separate them from women who have not had high intake — these associations become most clear. The 40-year follow-up and the multiple measures really help us disentangle the importance of diet, energy balance, and the use of hormones and contraceptives on cancer risk. – by Jennifer Southall
Reference:
Colditz GA. Public Health Res Pract. 2016;doi:10.17061/phrp2631628.
For more information:
Graham A. Colditz, MD , DrPH, can be reached at Washington University School of Medicine, Campus Box 8100, 600 S. Taylor Ave., St Louis, MO 63110; email: colditzg@wudosis.wustl.edu.
Disclosure: Colditz reports no relevant financial disclosures.