Abstract
Few studies have evaluated the relationship between changes in diet quality over time and the risk of death. We used Cox proportional-hazards models to calculate adjusted hazard ratios for total and cause-specific mortality among 47,994 women in the Nurses’ Health Study and 25,745 men in the Health Professionals Follow-up Study from 1998 through 2010. Changes in diet quality over the preceding 12 years (1986–1998) were assessed with the use of the Alternate Healthy Eating Index-2010 score, the Alternate Mediterranean Diet score, and the Dietary Approaches to Stop Hypertension (DASH) diet score. The pooled hazard ratios for all-cause mortality among participants who had the greatest improvement in diet quality (13 to 33% improvement), as compared with those who had a relatively stable diet quality (0 to 3% improvement), in the 12-year period were the following: 0.91 (95% confidence interval [CI], 0.85 to 0.97) according to changes in the Alternate Healthy Eating Index score, 0.84 (95 CI%, 0.78 to 0.91) according to changes in the Alternate Mediterranean Diet score, and 0.89 (95% CI, 0.84 to 0.95) according to changes in the DASH score. A 20-percentile increase in diet scores (indicating an improved quality of diet) was significantly associated with a reduction in total mortality of 8 to 17% with the use of the three diet indexes and a 7 to 15% reduction in the risk of death from cardiovascular disease with the use of the Alternate Healthy Eating Index and Alternate Mediterranean Diet. Among participants who maintained a high-quality diet over a 12-year period, the risk of death from any cause was significantly lower — by 14% (95% CI, 8 to 19) when assessed with the Alternate Healthy Eating Index score, 11% (95% CI, 5 to 18) when assessed with the Alternate Mediterranean Diet score, and 9% (95% CI, 2 to 15) when assessed with the DASH score — than the risk among participants with consistently low diet scores over time. Improved diet quality over 12 years was consistently associated with a decreased risk of death. (Funded by the National Institutes of Health.)
Generated Summary
This study, published in the New England Journal of Medicine, used a prospective cohort study design to investigate the relationship between changes in diet quality and the risk of total and cause-specific mortality. The research followed 47,994 women from the Nurses’ Health Study and 25,745 men from the Health Professionals Follow-up Study, analyzing data from 1998 to 2010. The study assessed diet quality changes over the preceding 12 years (1986–1998) using the Alternate Healthy Eating Index-2010 score, the Alternate Mediterranean Diet score, and the Dietary Approaches to Stop Hypertension (DASH) diet score. The primary objective was to determine if improvements in diet quality, as measured by these scores, correlated with a reduced risk of death from any cause, cardiovascular disease, and cancer.
Key Findings & Statistics
The study documented the following statistics related to diet quality and mortality:
- The pooled hazard ratios for all-cause mortality among participants who had the greatest improvement in diet quality (13 to 33% improvement) were:
- 0.91 (95% CI, 0.85 to 0.97) for the Alternate Healthy Eating Index score.
- 0.84 (95% CI, 0.78 to 0.91) for the Alternate Mediterranean Diet score.
- 0.89 (95% CI, 0.84 to 0.95) for the DASH score.
- A 20-percentile increase in diet scores (indicating an improved quality of diet) was significantly associated with:
- A reduction in total mortality of 8 to 17% with the use of the three diet indexes.
- A 7 to 15% reduction in the risk of death from cardiovascular disease with the use of the Alternate Healthy Eating Index and Alternate Mediterranean Diet.
- Among participants who maintained a high-quality diet over a 12-year period, the risk of death from any cause was significantly lower:
- By 14% (95% CI, 8 to 19) when assessed with the Alternate Healthy Eating Index score.
- By 11% (95% CI, 5 to 18) when assessed with the Alternate Mediterranean Diet score.
- By 9% (95% CI, 2 to 15) when assessed with the DASH score than the risk among participants with consistently low diet scores over time.
- In the Nurses’ Health Study, 5967 deaths were documented, including 1115 deaths from cardiovascular disease and 2089 deaths from cancer over 544,973 person-years of follow-up.
- In the Health Professionals Follow-up Study, 3979 deaths were documented, including 1226 deaths from cardiovascular disease and 1192 deaths from cancer during 286,402 person-years of follow-up.
- The multivariable analyses showed a significant inverse association across quintiles of change over 12 years between each of the three diet-quality scores and total mortality (P<0.05 for trend).
- A 20-percentile increase in any of the three diet scores was significantly associated with a reduced risk of death from any cause.
- A 20-percentile increase during the first 8, 12, and 16 years in any of the three diet scores was significantly associated with a reduced risk of death from any cause (Fig. 2).
- A 20-percentile increase over 16 years in any of the three diet scores was significantly associated with a decreased risk of death from cardiovascular disease (Table S10 and Fig. S2A in the Supplementary Appendix).
Other Important Findings
- Participants with a greater increase in diet quality were younger, engaged in more physical activity, and consumed less alcohol.
- Increased consumption of whole grains, vegetables, and n-3 fatty acids, and decreased sodium intake were reported with a greater increase in diet quality.
- Participants with consistently high diet quality at baseline and 12 years later were older and less likely to be current smokers.
- In continuous analyses, a 20-percentile increase in diet-quality scores was associated with a reduction of 8 to 17% in the risk of death from any cause.
- A 20-percentile increase in the Alternate Healthy Eating Index and Alternate Mediterranean Diet scores, but not the DASH score, was associated with a significantly reduced risk of death from cardiovascular disease.
- A significant inverse association between diet quality and the risk of death from cancer was seen only when the DASH score was used.
- Those with the poorest score at baseline but the largest improvements 12 years later had a lower risk of death from any cause when diet quality was assessed with the Alternate Healthy Eating Index score, the Alternate Mediterranean Diet score, and the DASH score.
Limitations Noted in the Document
- The study’s limitations included the use of self-reported dietary data, which is subject to measurement errors.
- Residual and unmeasured confounding could not be entirely ruled out, despite adjustments for numerous potential confounders.
- The study did not examine the association of each component of the diet scores and mortality, focusing instead on overall diet quality.
- Generalizability may be limited due to the study population primarily consisting of white health professionals.
Conclusion
The study’s findings strongly support the relationship between improved diet quality and reduced mortality risk. The consistent inverse associations between changes in the Alternate Healthy Eating Index, Alternate Mediterranean Diet, and DASH scores and a decreased risk of death highlight the significant impact of dietary choices. The research emphasized that moderate improvements in diet quality over time could meaningfully decrease mortality risk, and that a shift in dietary patterns could have significant health benefits. The study reinforced the recommendations of the 2015 Dietary Guidelines Advisory Committee, suggesting that adhering to various healthy eating patterns, not necessarily a single diet plan, can lead to positive health outcomes. The emphasis on whole grains, vegetables, fruits, and fish or n-3 fatty acids as key components of a healthy diet provides actionable insights for individuals looking to improve their dietary habits. The study’s conclusions suggest that by making incremental changes in diet quality over the course of a few years, individuals can significantly reduce their risk of death. The study emphasizes the importance of making informed dietary choices to enhance long-term health and well-being. Key takeaways include that a 20-percentile increase in any diet score, is associated with a 8-17% reduction in mortality.