Background: The latest 2015 Dietary Guidelines Advisory Committee Report has recommended healthy dietary patterns as an easier way for the public to understand and act upon. Despite the latest evidence supporting the association of the adherence to diet quality and lower mortality risk, few studies have evaluated changes in diet quality over time in relation to mortality risk. Therefore, we examined changes in diet quality and subsequent risk of total and cause-specific mortality in two large cohort studies.
Objective: To evaluate the association between 12-y changes (1986-1998) in three diet quality indices assessed by the Alternative Healthy Eating Index (AHEI), the Alternate Mediterranean Diet (AMED), and the Dietary Approach to Stop Hypertension (DASH)) with total and cause-specific mortality in the Nurses’ Health Study (NHS) and Health Professionals Follow-up Study (HPFS) from 1998-2010.
Methods: We followed 44,501 women in the NHS and 23,100 men in the HPFS, both from 1986 to 2010. The AHEI, AMED and DASH were defined from validated food frequency questionnaires and updated every 4 years. Cox proportional hazards models were used to calculate hazard ratios (HR) with adjustment for potential confounders (both at baseline and changes over time). Results across cohorts were pooled by an inverse variance-weighted, random-effect meta-analysis.
Results: During 758,683 person-years of follow-up, we documented 9,772 deaths, including 2,292 CVD deaths and 3,314 cancer deaths. The pooled HR comparing participants with the greatest improvement in diet quality (14%-33%) vs. participants whose diet quality remained relatively stable (no change, 0-3%) in the 12-year period was 0.89 (95% confidence interval [CI], 0.83 to 0.95) for AHEI; 0.83 (95 CI%, 0.65 to 1.05) for AMED; and 0.88 (95% CI 0.83 to 0.94) for DASH. In contrast, a decrease in diet quality was significantly associated with increased total mortality. In continuous analyses, a 20th-percentile increase in the three diet quality scores was associated with a 9%-20% lower total mortality (AHEI, 20% [15% to 24%]; AMED, 9% [6% to 12%]; DASH, 13% [9% to17%]). The results were largely similar when evaluated risk of death from CVD and cancer as outcomes. Notably, maintaining a higher vs lower adherence to any of the three dietary patterns during the 12 years was significantly associated with a 23-24% lower total mortality, a 19-27% lower risk of CVD deaths, and a 13-20% lower risk of cancer death.
Conclusions: In two large, independent cohorts of U.S. women and men we found consistent associations between increasing diet quality over 12 years and decreased total, CVD, and cancer mortality. These results underscore the importance of the strategies to promote and sustain a healthy diet in improving longevity among middle-aged and older adults.