"Association of Changes in Diet Quality
with Total and Cause-Specific Mortality"
N Engl J Med 
 
N Engl J Med 2017;377:143-53.
DOI: 10.1056/NEJMoa1613502
 
Mercedes Sotos-Prieto, Ph.D., Shilpa N. Bhupathiraju, Ph.D.,
Josiemer Mattei, Ph.D., M.P.H., Teresa T. Fung, Sc.D., Yanping Li, Ph.D.,
An Pan, Ph.D., Walter C. Willett, M.D., Dr.P.H., Eric B. Rimm, Sc.D.,
and Frank B. Hu, M.D., Ph.D.
 
N Engl J Med 
ABSTRACT
 
BACKGROUND
Few studies have evaluated the relationship between changes in diet quality over
time and the risk of death.
 
METHODS
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.
 
RESULTS
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.
 
CONCLUSIONS
Improved diet quality over 12 years was consistently associated with a decreased
risk of death. Funded by the National Institutes of Health.
 
FROM THE ARTICLE
BACKGROUND
 
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 shortterm
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
 
For the present study, the initial cycle was set
at 1986, baseline was set at 1998 (changes in diet
quality were calculated from 1986 through 1998),
and the end of follow-up was 2010. We excluded
participants who had a history of cardiovascular
disease or cancer at or before baseline in 1998,
missing information regarding diet and lifestyle
covariates, or very low or high caloric intake
(<800 kcal or >4200 kcal per day in men and
<500 or >3500 kcal per day in women). We also
excluded participants who died before 1998.
The final analysis included 47,994 women and
25,745 men.
 
CONCLUSION
In the present study, we found consistent associations
between improved diet quality over 12
years as assessed by the Alternate Healthy Eating
Index, Alternate Mediterranean Diet, and DASH
scores and a reduced risk of death in the subsequent
12 years. A 20-percentile increase in dietquality
scores was associated with an 8 to 17%
reduction in mortality.
 
In contrast, worsening
diet quality over 12 years was associated with an
increase in mortality of 6 to 12%. The risk of
death from any cause was significantly lower (by
9 to 14%) among participants who maintained a
high-quality diet than among those who had
consistently low diet scores over time.
 
Our results are consistent with those of recent
meta-analyses showing that higher dietquality
scores measured with the Alternate
Healthy Eating Index, Alternate Mediterranean
Diet, DASH, and the Healthy Eating Index–2010
were associated with a 17 to 26% reduction in
the risk of death from any cause.15,16  We found a
dose-dependent relationship between changes in
diet quality over 12 years and total mortality.
 
These results underscore the concept that moderate
improvements in diet quality over time
could meaningfully decrease the risk of death,
and conversely, worsening diet quality may increase
the risk.
 
The change in the risk of death
was more pronounced when longer-term (16
years) rather than shorter-term (8 years) changes
in diet quality were considered.
 
Taken together, our findings provide support
for the recommendations of the 2015 Dietary
Guidelines Advisory Committee that it is not necessary
to conform to a single diet plan to achieve
healthy eating patterns.18  These three dietary
patterns, although different in description and
composition, capture the essential elements of a
healthy diet. Common food groups in each score
that contributed most to improvements were
whole grains, vegetables, fruits, and fish or n− 3
fatty acids.
 
To improve our comparison of associations
between the three scores that differ in scoring
criteria and range, we evaluated the association
with mortality using a 20-percentile increase in
each score as a common unit for improving diet.
For example, if we assume a causal relationship,
a person with an increase of 22 of 110 points in
the Alternate Healthy Eating Index score over a
12-year period could reduce his or her risk of
death by nearly 20% in the subsequent 12 years.
An increase in consumption of nuts and legumes
from no servings to 1 serving per day and a reduction
in consumption of red and processed meats
from 1.5 servings per day to little consumption
will result in an improvement of 20 points in the
score. These findings are broadly consistent with
those of previous meta-analyses of the association
between consumption of nuts30  and red
meat31  and mortality.
 
In line with other studies, stronger associations
were seen when overall deaths and deaths
from cardiovascular causes were analyzed, and
null or weaker associations were observed for
death from cancer.2,3,8,12,32  Our results with respect
to improvement in the Alternate Healthy Eating
Index and a reduction in the risk of death from
cardiovascular disease were expected, given that
the Alternate Healthy Eating Index is based on
current knowledge of dietary factors contributing
to cardiovascular disease.12  Evidence supports
the inverse association between higher scores in
the Alternate Healthy Eating Index2-4,6,8,16  or the
Mediterranean-style diet10,11,13,32-34  and a lower risk
of death from cardiovascular disease in various
populations. We did not find significant associations
between changes in the DASH score and
death from cardiovascular causes. Although the
DASH score shares some food and nutrient components
with the two other scores, it does not
include fish or specific fatty acids, which have
been consistently associated with a reduced risk
of cardiovascular disease.21,33  In addition, previous
findings have shown that moderate alcohol intake
is associated with a reduction in the risk of
death from cardiovascular disease,21,35  and this
component is not included in the DASH score.
Although some studies have shown a significantly
reduced risk of death from cancer with
good adherence to some dietary patterns,4-6  other
studies have not shown such associations.2,8,32
 
Our study did not provide consistent evidence
that improving diet quality had a substantial effect
on overall mortality from cancer.
 
The strengths of our study include the prospective
design, large sample sizes, high rates of
follow-up, repeated assessment of diet and lifestyle,
and use of multiple diet-quality scores.
 
However, the study has certain limitations. Because
dietary data were reported by the participants,
measurement errors were inevitable. However,
our food frequency questionnaires were
extensively validated against diet records and
biomarkers. Although we were able to adjust for
many potential confounders, residual and unmeasured
confounding could not be completely
ruled out. We did not examine the association
of each component of the scores and mortality
because we considered that a high diet quality is
a combination of multiple components that act
synergistically. Finally, generalizability may be
limited because participants were mostly white
health professionals and we only included one
third of the initial population because of our
study design. However, our findings are broadly
consistent with those from other populations.
 
In conclusion, among U.S. adults, we observed
consistent associations between increasing diet
quality over 12 years and a reduced risk of death.
 
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