The third leading risk factor for disability-adjusted life years and the first leading risk factor for death in the United States is poor diet. The Health Eating Index (HEI), created by the Department of Agriculture and the National Cancer Institute, measures diet quality in accordance with the Dietary Guidelines for Americans. In recent years, this index has been utilized as an exposure variable in prospective cohort analyses. This index has received high marks for its ability to examine the intricacies of the human diet. Because the 2015-2020 Guidelines for Americans have been modified, the HEI has been updated to include defined restrictions for added sugars and saturated fats. Also, in the interval between the original Dietary Guidelines and the release of the new recommendations, deaths among participants in the Women Health’s Initiative (WHI) cohort have doubled due to aging.
The Neuhouser Group, from the Division of Public Health Sciences, examined the associations between the HEI-2015 and all-cause and cause-specific (cancer, cardiovascular disease (CVD), Alzheimer’s Disease, and dementia not otherwise specified (NOS)) mortality. The researchers also evaluated effect modification by income to determine if underlying risks are associated with causes of mortality. This study was published in the American Journal of Epidemiology.
WHI recruited >93,000 postmenopausal women 50-79 years old between 1993-1998 for the observational study (OS). Participants from WHI-OS participated in continued follow-up and extension studies from 2005-2010 and 2010-2020. The study’s sample consisted of 59,388 women. The participants’ medical conditions, demographics, and health behaviors were examined at baseline in self-administered, standardized questionnaires. At baseline, a food frequency questionnaire (FFQ), geared towards multi-ethnic and geographically diverse populations, was utilized to assess diet. The HEI-2015 scored a total of 100 points, including 9 adequacy components and 4 moderation components. One specific component - the empty calories component - was reestablished as added sugars and saturated fats. In order to determine the vital status of participants, data were utilized from WHI’s annual follow-up with participants and the National Death Index.
Multivariable Cox regression models were utilized to examine the association between HEI-2015 and risk of mortality, as well as effect modification by income. During the 18.2 years of follow-up, there were a total of 9,679 deaths: 3,303 cancer deaths, 2,362 CVD deaths, and 488 Alzheimer’s Disease or dementia NOS deaths. Women with the highest HEI scores, indicative of healthy diet, had an 18% lower risk of all-cause mortality (HR:0.82; 95% CI: 0.76-0.87), a 21% lower risk of cancer mortality (HR:0.79; 95% CI: 0.70-0.88), and no significant difference in risk of CVD mortality (HR:0.94; 95% CI: 0.82-1.08) compared to those with the lowest scores. There was no association between HEI-15 and Alzheimer’s Disease or dementia NOS (HR:1.09; 95%CI:0.81-1.48). Also, no effect modification was found by income status.
These findings are consistent with previous analyses in this cohort which examined the HEI-2010 and risk of death overall or death from cancer. Dr. Neuhouser summarized the findings, “An important take-away from this study is that the findings reinforce the importance of a healthy dietary pattern to decrease the chance from dying from cancer as well as overall mortality. Healthy eating that follows the Healthy Eating Index should be a part of the overall cancer treatment toolbox for patients.” The Neuhouser group plans to further their research by objectively measuring the participants’ food intake. Dr. Neuhouser explains, “Despite these promising findings, we know that dietary self-report is fraught with measurement error, so the results may not be considered definitive. We are currently doing work with blood and urine biomarkers of diet. We have constructed a biomarker score for these same healthy dietary patterns that is very promising. We anticipate that the biomarker score may be a very robust way to confirm and complement these results.”
Fred Hutch/UW Cancer Consortium members Marian Neuhouser contributed to this work.
George SM, Reedy J, Cespedes Feliciano EM, Aragaki A, Caan BJ, Kahle L, Manson JE, Rohan TE, Snetselaar LG, Tinker LF, Van Horn L. Alignment of dietary patterns with the Dietary Guidelines for Americans 2015-2020 and risk of all-cause and cause-specific mortality in the Women’s Health Initiative Observational Study. American Journal of Epidemiology. 2020 Dec 16. https://doi.org/10.1093/aje/kwaa268