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Some epidemiologic studies of nutrition focus on dietary patterns rather than single nutrients or foods to evaluate the association between diet and health outcomes.1 Accumulated evidence supports an association between healthy dietary patterns and a decreased risk of death.2–11 Results from recent studies suggest that improved diet quality, as assessed by means of the Alternate Healthy Eating Index–2010 score,12 the Alternate Mediterranean Diet score,10,13 and the Dietary Approaches to Stop Hypertension (DASH) diet score,14 was associated with reductions of 8% to 22% in the risk of death from any cause15,16 and reductions of 19% to 28% in the risk of death from cardiovascular disease and 11% to 23% in the risk of death from cancer.2–4,17
Given such consistent evidence, the 2015 Dietary Guidelines for Americans recommended the Alternate Healthy Eating Index, the Alternate Mediterranean Diet, and DASH as practical, understandable, and actionable diet plans for the public.18 Such guidelines are important in the United States and globally because unhealthy diets have been ranked as a major factor contributing to death and health complications.19 Evaluation of changes in diet quality over time in relation to the subsequent risk of death would be important. Here, we evaluated the association between 12-year changes (from 1986 through 1998) in the three diet-quality scores noted above and the subsequent risk of total and cause-specific death from 1998 through 2010 among participants in the Nurses’ Health Study and the Health Professionals Follow-up Study. We also examined short-term changes (baseline to 8-year follow-up, 1986–1994) and long-term changes (baseline to 16-year follow-up, 1986–2002) in diet quality in relation to total and cause-specific mortality.
Methods
Study Population and Design
The Nurses’ Health Study, a prospective study that was initiated in 1976, enrolled 121,700 registered nurses who were 30 to 55 years of age. The Health Professionals Follow-up Study, a prospective study that was initiated in 1986, enrolled 51,529 U.S. health professionals who were 40 to 75 years of age. Baseline and follow-up questionnaires were sent to participants every 2 years to update medical and lifestyle information over the follow-up period.20,21 In both studies, follow-up rates exceeded 90% in both cohorts.22
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