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Ten Years of Life
Is It a Matter of Choice?
Gary E. Fraser, MB, ChB, PhD;
David J. Shavlik, MSPH
Arch Intern Med. 2001;161:1645-1652.
ABSTRACT
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Background Relative risk estimates suggest that effective implementation of behaviors
commonly advocated in preventive medicine should increase life expectancy,
although there is little direct evidence.
Objective To test the hypothesis that choices regarding diet, exercise, and smoking
influence life expectancy.
Methods A total of 34 192 California Seventh-Day Adventists (75% of those
eligible) were enrolled in a cohort and followed up from 1976 to 1988. A mailed
questionnaire provided dietary and other exposure information at study baseline.
Mortality for all subjects was ascertained by matching to state death tapes
and the National Death Index.
Results California Adventists have higher life expectancies at the age of 30
years than other white Californians by 7.28 years (95% confidence interval,
6.59-7.97 years) in men and by 4.42 years (95% confidence interval, 3.96-4.88
years) in women, giving them perhaps the highest life expectancy of any formally
described population. Commonly observed combinations of diet, exercise, body
mass index, past smoking habits, and hormone replacement therapy (in women)
can account for differences of up to 10 years of life expectancy among Adventists.
A comparison of life expectancy when these factors take high-risk compared
with low-risk values shows independent effects that vary between 1.06 and
2.74 years for different variables. The effect of each variable is assessed
with all others at either medium- or high-risk levels.
Conclusions Choices regarding diet, exercise, cigarette smoking, body weight, and
hormone replacement therapy, in combination, appear to change life expectancy
by many years. The longevity experience of Adventists probably demonstrates
the beneficial effects of more optimal behaviors.
INTRODUCTION
AN UNDERLYING goal of therapeutic and preventive medicine is to increase
the number of productive and satisfying years of life experienced by the population.
Achieving this by prevention has the advantage of reduced morbidity when disease
does not develop or is delayed, and avoids the use of medications that are
costly and will cause adverse effects in a proportion of patients. However,
there is little direct evidence that life is extended by preventive strategies.
The implication that this is so has been strong, as many of these strategies
are associated with lower relative risks of mortality, and many of these associations
are reasonably assumed to be causal. Unfortunately, the mathematical relationship
between a lower relative risk and extra years of life is complex. It is not
easy to predict the number of years of life gained from a particular reduction
in relative risk for all-cause mortality.1
Relative risks are an appropriate means of reporting results for research
purposes. However, the general public and probably nonepidemiologic medical
practitioners may find results expressed as predicted extra years of life,
or delay in age at onset of a specific disease,2-3
equally, if not more, useful.
A statistical method that we recently described4
is applied to the Adventist Health Study cohort to predict the expected length
of life in subjects who subscribe to different behaviors. If associations
with mortality are causal, then the differences in expected age at death result
from individual choices. An advantage of the Seventh-Day Adventist population
is that there is a wide range of dietary and other health habits, enabling
us to evaluate strong contrasts. The cohort had no upper age limit, and person-years
of experience were obtained up to the age of 104 years.
SUBJECTS AND METHODS
The Adventist Health Study cohort was defined
in 1976 as non-Hispanic white subjects, at least aged 30 years, who lived
in California Adventist households and completed 2 mailed demographic and
lifestyle questionnaires. The study enrolled 34 192 men and women who
met these criteria and followed their cases until 1988. Further details of
the study design have been published previously.5
Briefly, subjects were initially contacted from names and addresses
in church directories. Of those then formally identified by a brief census
questionnaire, 75.1% completed an extensive lifestyle questionnaire that included
sections on demographics, medical history, diet, physical activity, and a
few psychosocial variables. Having been enrolled in the cohort, subjects were
contacted each year thereafter by mail to provide the name of any hospital
where they had been hospitalized during that year. Study field staff visited
these hospitals to photocopy data providing evidence of new myocardial infarctions
(international diagnostic criteria6) or cancers
(histological features required). Deaths during follow-up were found as further
described.
The height and weight used to calculate body mass index were self-reported.
The validity of body weight data was supported in a substudy7
in which the correlation between self-reported and measured weight was 0.95.
The dietary portion of the questionnaire was a food frequency instrument that
included questions for each of 55 foods or food groups, plus 10 qualitative
dietary questions. Most dietary questions had 8 frequency categories, ranging
from "never consume" to "more than once each day."8
The meat index was determined from responses to 6 questionnaire items
on the frequency of consumption of the following specific meats: beef (hamburger,
steak, other beef, or veal), pork, poultry, and fish. Vegetarians are defined as those eating meats never or less than once per month;
and semivegetarians as those eating meats more often
than vegetarians, but less than once per week. All others are nonvegetarians.
Few Adventist vegetarians are vegan. Nut consumption was included in these
analyses because of previously published evidence9-10
showing protective associations between nut consumption and deaths due to
coronary heart disease. This variable was divided into consumption categories
of 1 time per week (low), 1 to 4 times per week (medium), and 5 or more times
per week (high).
A dietary validity study11 enabled a
comparison of food frequency results with the average of 5 unannounced 24-hour
telephone recalls. Correlations between measurements of meat and nut consumption
by the food frequency instrument and the 24-hour recalls are 0.83 and 0.46,
respectively, when corrected for attenuation12
in the recall data.
Physical activity was categorized as low, medium, or high, based on
a cross-classification of 2 questions regarding occupational and leisure activities
that incorporated intensity and duration. The first question provided a list
of vigorous leisure activities that the subject must have undertaken at least
3 times each week for 15 minutes on each occasion. The second question asked
for the frequency of vigorous activities during performance of "usual daily
work or responsibilities." High exercise reflects
a positive response to either or both of the vigorous occupational or leisure
activity questions; and low exercise, low leisure
and low occupational activities. Others scored at a medium level of exercise.
There were virtually no current cigarette smokers in this population,
and past cigarette smoking was estimated by a simple question with 3 possible
choices: (1) "yes, currently smoking some"; (2) "yes, smoked in the past but
not now"; and (3) "no, never smoked cigarettes." The questions on hypertension
and diabetes required that these be indicated only when diagnosed by a physician.
The few (<1%) Adventist current smokers, being atypical, and non-Adventists
living in Adventist households are excluded from these analyses.
Follow-up to ascertain all deaths was completed for the years 1976 to
1988. Computer matching to California state death tapes13
was augmented by similar matching to the National Death Index when this became
available in 1979. These sources were supplemented by the use of church records
and short mailed annual surveys between 1976 and 1983.
To compare survival (after the age of 30 years) between California Adventists
and other Californians, data were used from the California non-Hispanic white
population projections, and mortality statistics, for 1985.14-15
This is approximately the midpoint of the Adventist Health Study follow-up,
and these are the first California population data that accurately identify
non-Hispanics. California State and other census data were known to overrepresent
the number of subjects 95 years and older.16
Corrected data became available in 1989, so we used 1989 hazards for these
oldest ages only in non-Adventist Californians.
It is expected that during the early years of follow-up of a volunteer
cohort an increasing proportion of subjects who were initially healthy will
develop health problems, and the cohort will finally approximate the overall
health status of the parent population. In the following analyses, the years
from 1976 to 1979 of the Adventist Health Study were eliminated to avoid a
healthy volunteer effect that was previously shown to disappear by follow-up
year 4.17 It was not possible to remove Adventists
from the California data, as religion was not recorded. However, because Adventists
constitute less than 1% of the California population, the conservative bias
will be minimal.
A multivariate current life table method4
used nonparametric estimates of age-specific baseline hazard rates. The method
uses proportional hazards modeling to produce maximum likelihood estimates
for the exposure coefficients, where the time variable is attained age. As
the method is multivariate, the effects of particular variables are independent
of others in the model. A product term with age accommodated differences in
effects by age, where such coefficients were statistically significant. These
were necessary for vegetarian status, exercise level, and nut consumption.
Then the hazards, which are conditional on exposure values, are used to calculate
age-specific probabilities for a life table.18
Estimators of the variance, confidence intervals, and tests of significance
for differences in the expected age at death have been described.4 The expected age at death as used in this report is
always conditional on survival to the age of 30 years.
Thus, the method produces estimates of life expectancy that depend on
the values of exposure variables. In a similar way that a proportional hazard
regression, for instance, produces relative risks, the method used herein
produces life expectancies comparing exposed with unexposed status. Compared
with the Kaplan-Meier method of survival analysis, the method used herein
is multivariate, and hence allows control of confounding by covariates.
The exercise variable was handled differently from others to take into
account the fact that low exercise is not always a choice. Individuals in
the low exercise category can be grouped as follows: (1) those with known
physical disabilities that may preclude the choice to exercise more vigorously;
and (2) all others, who, as far as we know, chose to avoid exercise. The likelihood
function contains 2 indicator variables for low exercisers, the first for
those who indicated previous heart disease, stroke, rheumatoid arthritis,
other arthritis, or rheumatism, at study baseline, and the second for other
low exercisers. Because we wanted to focus on the effects of a choice not
to exercise, the life table analyses used the coefficient for the second dummy
variable to model the effects of low exercise. This was a conservative choice,
because low exercisers with the nominated disorders at study baseline had
a higher mortality on follow-up, no doubt due to their prevalent disease and
the low physical activity.
RESULTS
The number of deaths at particular ages and the person-years available
for analysis are shown for men and women in Table 1. Of the 5193 observed deaths, 1373 (26.4%) were ascribed
to coronary heart disease, 1074 (20.7%) to cancer, and 531 (10.2%) to stroke.
Risk factor values (Table 2) show
that 28% to 31% of the subjects are vegetarian (they eat meat less often than
monthly), that 23% eat nuts at least 5 times per week, and that about 40%
exercise vigorously for 15 minutes at least 3 times per week. More men than
women are past smokers (before joining the Adventist church), and 53% of postmenopausal
women have ever used hormone replacement therapy (HRT). Values of the last
4 variables and body mass index are usually shifted further toward the "more
healthful" direction in vegetarians.
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Table 1. Number of Deaths and Person-years of Observation, 1976 to
1988: The Adventist Health Study*
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Table 2. Values of Risk Factors in All Adventists and in Vegetarian
Adventists*
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The curves depicted in Figure 1
and Figure 2 compare California
Adventists with other Californians, and show that Adventists have increased
survival. The expected ages at death (95% confidence intervals) in Adventist
men and women, given survival to the age of 30 years, are 81.2 (80.5-81.8)
and 83.9 (83.5-84.4) years, respectively. This corresponds to an extra 7.3
(6.6-8.0) years of life expectancy for Adventist men and an extra 4.4 (4.0-4.9)
years for Adventist women, when compared with other Californians. The lower
curves in each figure demonstrate that at the age of 81 years, 28% more Adventist
men survive, and at the age of 86 years, 19% more Adventist women survive.
Vegetarian Adventist men and women have expected ages at death (95% confidence
intervals) of 83.3 (82.4-84.3) and 85.7 (84.9-86.4) years, respectively.
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Figure 1. Survival of California Adventist
men (1980-1988) and other California men (1985) beyond the age of 30 years.
The difference between the 2 groups was significant (P<.001).
These were non-Hispanic white subjects. Hazards for 1989 are used for non-Adventist
Californians older than 94 years (see the "Subjects and Methods" section of
the text). AHS indicates Adventist Health Study; CI, confidence interval.
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Figure 2. Survival of California Adventist
women (1980-1988) and other California women (1985) beyond the age of 30 years.
The difference between the 2 groups was significant (P<.001).
These were non-Hispanic white subjects. Hazards for 1989 are used for non-Adventist
Californians older than 94 years (see the "Subjects and Methods" section of
the text). AHS indicates Adventist Health Study; CI, confidence interval.
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The effect on life expectancy of changing a single variable will potentially
differ according to the values of the other variables in the model. Thus,
to estimate the effects of individual variables, we have first kept all covariates
at intermediate values, and changed only the variable of interest.
Contrasts in life expectancy between high- and low-risk values of a
particular exposure variable for covariates at medium risk (Table 3) range between 1.1 and 2.7 years, and in no case does the
95% confidence interval include zero. High physical activity, frequent consumption
of nuts, vegetarian status, and medium body mass index each result in an approximate
1.5- to 2.5-years gain in life expectancy compared with the corresponding
high-risk values. The sum of these independent effects (9.7 years in men and
10.4 years in women) is similar to those predicted in subjects who have contrasting
values for all variables simultaneously. Results are not shown in the table,
but hypertension accounts for the loss of 4.2 and 3.2 years and diabetes for
the loss of 4.6 and 8.6 years in men and women, respectively, when behavioral
covariates take medium-risk values. The effect of current cigarette smoking
cannot be evaluated in this population as there are virtually no current smokers.
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Table 3. Multivariate Estimates of the Effects of High- vs Low-Risk
Values of Individual Behavioral Risk Factors*
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Setting covariates at values labeled medium in an Adventist population
may not form a useful reference for many non-Adventists. In an effort to find
results that may be more generally applicable, we set covariate values at
the higher-risk values (lower part of Table
3). The effects seen are quite similar to those in the upper part
of the table and are, thus, not strongly dependent on whether high- or low-risk
covariate values are used.
As the model is multivariate, the joint effects of contrasting values
of several variables on expected age at death are explored (Figure 3 and Figure 4).
The first bar shows life expectancy when all variables take medium-risk values.
Then passing from left to right through the figures, additional variables
are also set at either high- or low-risk values, those variables to the right
of a particular bar being still at medium-risk values. In the final contrast,
when all variables are at either low- or high-risk values, the differences
in the expected ages at death are 10.8 years (men) and 9.8 years (women).
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Figure 3. Expected ages at death (95% confidence
intervals) in men with jointly high- or low-risk values for the risk factor
in a particular column and those to its left (other variables at medium-risk
values). BMI indicates body mass index.
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Figure 4. Expected ages at death (95% confidence
intervals) in women with jointly high- or low-risk values for the risk factor
in a particular column and those to its left (other variables at medium-risk
values). BMI indicates body mass index; HRT, hormone replacement therapy.
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These variables are behavioral, and their values result from conscious
choices by study subjects. Adding the pathophysiologic variables of hypertension
and diabetes to the model markedly increases the contrasts to more than 20
years. Confidence intervals are generally narrow, and those for different
risk factor combinations almost immediately become nonoverlapping. Those who
subscribe to intermediate-risk behaviors for all variables (the first bar)
achieve most of the increase in expected age at death found in the behaviorally
more extreme low-risk groups.
The life expectancy of each subject in the Adventist cohort was then
calculated, conditional on their risk factor values, and then compared with
the life expectancy when all variables take low-risk values. The results indicate
that half of Adventist men and women are losing more than 4 years of life,
apparently due to their suboptimal behavioral choices (Table 4).
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Table 4. Proportion of the Adventist Study Population Who Lose the
Specified Number of Years of Life Expectancy Apparently Due to Their Choices*
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COMMENT
These results strongly suggest that behavioral choices influence the
expected age at death by several years, even as much as a decade. Recommendations
to improve diet, increase physical activity, stop smoking, and reduce body
weight are common themes of most preventive medicine practices. Evidence of
the benefits associated with these behaviors can be used to motivate change.
It seems likely that the effects of these particular variables on life
expectancy can be applied to Adventist and non-Adventist populations. There
is no reason to suspect that Adventists are biologically different in their
responses to environmental exposures. In support of this generalizability
is the observation (Table 3) that
changing covariates to high-risk values did not systematically change the
estimated effects of the variables of interest. Analyses (not shown) on only
the Adventist diabetic or the Adventist hypertensive subjects, both high-risk
groups, also found contrasts of roughly similar magnitude to those reported
for all subjects. All results, Adventist and non-Adventist, are for non-Hispanic
whites and hence may not apply to other ethnic groups.
California Adventist men had a greater expected age at death by 7.3
years, and women by 4.4 years, when compared with non-Adventist Californians,
but even this relatively long-lived population is probably losing more than
4 years of life on average, due to suboptimal choices. The extra years of
life predicted in these analyses are slightly greater than similar estimates
from California Adventist and non-Adventist data collected between 1960 and
196519 and quite similar to comparisons between
Adventists and others in Norway20 and the Netherlands.21 As expected, average California Adventists and non-Adventists
are apparently less different than the theoretical extreme contrasts among
Adventists. These latter contrasts are described by the right-hand bars of Figure 3 and Figure 4 and account for a 10-year difference in life expectancy.
Adventist vegetarian men and women have expected ages at death of 83.3
and 85.7 years, respectively. These are 9.5 and 6.1 years, respectively, greater
than those of the 1985 California population in a univariate analysis. When
vegetarians are forced to take medium-risk values for all other covariates
in the statistical model, the corresponding expected ages at death are 85.3
and 88.6 years, respectively (Figure 3
and Figure 4). That these values
are higher than those from the univariate vegetarian analyses indicates that
sporadic high-risk covariate values have a greater effect on decreasing life
expectancy than do sporadic low-risk values on increasing life expectancy,
and the combined effects in a univariate analysis do not correspond to medium
risk.
To our knowledge, the life expectancies of California Adventist men
and women are higher than those of any other well-described natural population.
Comparable data from several other populations around the same calendar period
are shown in Table 5 and support
this conclusion. Japanese individuals have often been described as the longest-lived
population,23 but they do not survive as long
as California Adventists.
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Table 5. Expected Length of Life at Birth and at the Age of 65 Years:
California Adventists Compared With International Populations
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The difference of only 2.8 years in the expected age at death of Adventist
men and women is much less than that seen in most other populations. In lower-risk
Adventists, this difference shrinks to less than 2 years. Compared with non-Adventists,
the Adventist women gain fewer years than men. In other Californians, the
expected ages at death of men and women differ by 5.7 years. Adventist women
can anticipate fewer years of widowhood, assuming their husbands are also
Adventist.
The volunteer status of the Adventist subjects may theoretically bias
comparisons with all Californians if there was a tendency for Adventists with
life-threatening diseases to not participate in the study. Indeed, such a
healthy volunteer effect was previously documented in the cohort,17 but this had largely disappeared by 1980, the first
year that we allow data to contribute to the comparison with other Californians.
Removing person-years from the analysis before 1978, 1979, 1980, 1981, 1982,
1983, 1984, 1985, and 1986, in turn, resulted in estimated life expectancies
(men and women combined) of 83.27, 83.22, 83.13, 83.18, 83.28, 83.30, 83.36,
83.29, and 83.46 years, respectively. The results were similar when men and
women were analyzed separately. The all-cause mortality rate increased from
1977 to 1979, but from 1980 onward remained stable, and as can be seen, these
differences trivially influenced the estimated life expectancies. By 1980,
the population had apparently accumulated a stable proportion of unwell participants
who were initially underrepresented due to self-selection.
The results previously discussed show that Adventists live longer but
do not identify the factors that contribute to their increased longevity.
Non-Adventists are usually nonvegetarian, eat nuts much less frequently,24-25 exercise vigorously less frequently,26 and are more likely to be current (or past) cigarette
smokers than Adventists who for practical purposes do not smoke. Vegetarians
also have lower body mass index values.27-29
The magnitude of the longevity contrasts between California Adventists and
non-Adventists can be readily accounted for by the combined effects of commonly
seen differences in these behavioral variables. The analyses comparing Adventists
with others, and those within the Adventist population, are broadly consistent.
This suggests that we have been able to identify many of the important variables
accounting for their higher expected age at death.
The independent effects described are those associated with adhering
to the nominated behavioral patterns at all ages after the age of 30 years.
This is not an unrealistic premise, as the rankings within a population of
meat intake,30 exercise habits,31
and obesity status32-33 remain
reasonably stable for many individuals during adult life. However, diabetes
and hypertension are often first manifest in middle age. The effects on life
expectancies when these last disorders are modeled to begin at the age of
55 years, rather than the age of 30 years, compared with their lifelong absence
are reductions of 3.8 and 2.8 years in male and female hypertensive subjects
and of 4.2 and 7.0 years in male and female diabetic subjects (covariates
set at medium-risk values), respectively. These values are only modestly less
than the reductions observed when these disorders are modeled to begin at
the age of 30 years.
Substantial gains in life expectancy would only be worthwhile if they
were also accompanied by a longer period of good-quality life. Although our
data cannot directly address quality of life, it was previously shown34 that the vegetarian Adventists took less medication
and had fewer overnight hospital stays, surgical procedures, and x-ray examinations
during the previous year. Vegetarians also had a reduced prevalence of several
chronic diseases29 that may degrade the quality
of life. The recent work of Vita et al35 with
non-Adventists provides strong evidence that persons who choose lower-risk
health habits postpone disability.
If the associations that we have found with behavioral risk factors
are confirmed by others and considered causal, the implications for public
health are profound. It has been estimated that a gain in life expectancy
in US women of 5 years, starting from 1980 levels (within the follow-up period
of the Adventist cohort), will take until 2040, ie, 60 years.36
Yet, our data suggest that an additional increment of similar magnitude could
occur more rapidly if major shifts in dietary and exercise patterns could
be induced.
The 6 variables that we chose for these analyses were those that significantly
predicted mortality in this population when a multivariate analysis was used.
Other variables, such as intake of fruit and vegetables and psychosocial and
religious factors, may also be important, but they either were not measured
or, as measured, did not predict mortality independent of the 6 chosen factors.
Although the variables that we used may in part be surrogates for other
factors, it is worth recalling that it is quite uncommon to find strong estimated
effects due to confounding alone. The confounding factors would then need
to be powerful determinants of risk and to be closely linked to the nominated
variables.37 The variables that we chose were
strongly and significantly related to coronary heart disease and/or all-cause
mortality.38-39 Thus, it is likely
that they do have important unconfounded independent associations with mortality,
although our estimates of these effects may be modestly distorted by unknown
confounding. Important determinants of mortality that are not included herein
but are independent of the chosen variables will not have biased our results.
The effects ascribed to "nonvegetarian status" in Table 3 are probably related to the greater intake of foods high
in saturated fat and the lower intake of foods higher in unsaturated fat,
fiber, antioxidant vitamins, and other phytochemicals in nonvegetarian Adventists.29 This may affect mortality due to cardiovascular causes
and cancer.40-41 Similarly, those
who consume more nuts have been shown to have 35% to 50% lower rates of coronary
events in 4 of the largest cohorts in nutritional epidemiologic studies.9, 42-44 This
is probably due in part to the blood cholesterol–lowering effects of
nuts,10 and perhaps to their unusually high
content of antioxidant vitamin E.42 Increased
physical activity is associated with important reductions in the relative
risks of coronary events, stroke, and cancers of the breast and colon.45-48 The
mechanisms are not entirely understood, but probably include effects on blood
lipid levels, sex hormones in women, blood insulin level, the immune system,
and obesity and on the reduced risk of diabetes and hypertension.
The effect of HRT on all-cause mortality in women is controversial.
The only large clinical trial49 reported so
far did not confirm observational work that had suggested that HRT protected
against coronary heart disease, although this emphasizes the need for more
research rather than disproving that HRT may be beneficial overall.50 A possible explanation is that those using HRT are
self-selected to be more health-conscious and seek medical attention earlier,
and it is this that accounts for their lower risk. If so, such a bias could
also be present in the Adventist data, but must depend on factors other than
those already included in the model.
Other investigators have predicted the effects of different physiologic
risk factors, such as hypercholesterolemia, hypertension, and diabetes, on
life expectancy. These effects are often in the range of 1 to 4 years, similar
to those we found for behavioral risk factors. Physiologic risk factors may
be more directly damaging, but behavioral risk factors can affect total mortality
by changing risks of several causes of mortality.
Tsevat et al51 used a rather complicated
combination of data from US Vital Statistics and the Framingham Heart Program
and some assumptions and approximations about effects for those older than
85 years to predict changes in life expectancy. These were increases of between
0.5 and 5.7 years by either quitting smoking or changing blood pressure, blood
cholesterol, or obesity status to optimal levels. Grover et al,52
using Lipid Research Clinic cohort data, forecasted the benefits of antihypertensive
therapy, or lipid-lowering medications, in these hyperlipidemic subjects as
being between 0.85 and 4.74 extra years when the subjects were examined at
the age of 40 years.
More recently, an analysis of 5 large cohorts53
used the coefficients of a multivariate proportional hazards analysis to compare
hypothetical low-risk individuals with others who did have 1 or more risk
factors. Different studies in this group estimated that the low-risk groups
had 5.8 to 9.5 more years of life expectancy, the largest values being where
the baseline ages were lowest, as expected. No account was taken of the possibly
quite different effects of individual risk factors at different ages.39
It was estimated that higher physical activity may extend life by at
least 2.1 years54 in a Finnish study. The College
Alumni Study group55 estimated an extra 2.51
years for more active 35- to 39-year-old men, before the age of 80 years.
The Established Populations for Epidemiologic Studies of the Elderly found
that nonsmokers with high physical activity had more than 5 years greater
life expectancy at the age of 65 years when compared with those with low physical
activity.56 These results from univariate or
bivariate analyses are similar to our multivariate findings.
In conclusion, California Adventists live longer than other Californians,
and indeed longer than most, if not all, other formally described populations.
This may be explained by common differences in behavioral risk factors between
Adventists and others. Although it has been suspected that well-informed choices,
particularly in combination, improve life expectancy, we have demonstrated
herein the relatively large magnitude of such effects.
AUTHOR INFORMATION
Accepted for publication December 4, 2000.
This study was supported by grant R01-AG08961 and senior fellowship
grant 1F33CA66287 from the National Institutes of Health, Bethesda, Md (Dr
Fraser).
Corresponding author and reprints: Gary E. Fraser, MB, ChB, PhD,
Center for Health Research, School of Public Health, Loma Linda University,
Nichol Hall, Room 2008, Loma Linda, CA 92350 (e-mail: gfraser{at}sph.llu.edu).
From the Center for Health Research, School of Public Health, Loma
Linda University, Loma Linda, Calif.
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ABSTRACT
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