Validation of recall of body weight over a 26-year period in cohort members
of the Adventist Health Study 2
Namgyal L. Kyulo MD, MPHa, Synnove F. Knutsen MD, PhDa, Serena Tonstad MD, PhDb,
Gary E. Fraser MD, PhDa, Pramil N. Singh DrPHa,c,d,*
aDepartment of Epidemiology and Biostatistics, Loma Linda University, Loma Linda, CA
bDepartment of Health Promotion and Education, Loma Linda University, Loma Linda, CA
cDepartment of Global Health, Loma Linda University, Loma Linda, CA
dCenter for Health Research, School of Public Health, Loma Linda University, Loma Linda, CA
a r t i c l e i n f o
Received 25 May 2012
Accepted 29 June 2012
Body mass index
a b s t r a c t
Purpose: The validity of recall of past body weight has been measured and tends to be high; however, the
paucity of validation data for recall in older age is noteworthy given the need for accounting for age and
disease-related weight change in prospective studies.
Methods: The Adventist Health Study-2 (AHS-2) is a prospective, questionnaire-based study (n ¼ 96,710)
that enrolled a cohort from 2002 through 2007 to investigate the role of lifestyle exposures (diet,
physical activity, anthropometrics) and health on outcomes such as cancer and mortality.
Results: The mean difference between current weight reported 26 years earlier in AHS-1 and recall of past
body weight in AHS-2 was only 0.67 kg, indicating underestimation in the recall of past body weight
from ages 30 to 70 years.
Conclusions: Misclassification is differential across both age and adiposity, and this tendency needs to be
incorporated into the interpretation of weight history and health outcome literature.
? 2012 Elsevier Inc. All rights reserved.
The validity of recall of past body weight has been measured in
several studies [1e8], and tends to be high (R > 0.8) in young and
middle-aged adults. In elderly subjects (>65 years), recall of past
body weight has been reported in one study of Canadian men .
The paucity of validation data for recall in older age is noteworthy
given the need for accounting for age and disease-related weight
change in prospective studies.
In the present study, our objective was to assess the validity of
26-year recall of past body weight in a sample of 2727 cohort
members (mean age of 70 years at time of recall) of the Adventist
Health Study-2 (AHS-2). AHS-2 represents the most recent
prospective cohort study (n ¼ 96,710) of U.S. and Canadian
Adventists enrolled from2002 to 2007. Adventists have, for the past
50 years, been enrolled in National Institutes of Health-funded
prospective studies to investigate how healthful lifestyle patterns
(i.e., diet, low body mass index [BMI], physical activity, avoidance of
tobacco) contribute to lower rates of noncommunicable disease .
Thus, validation of the AHS-2 data on recall of past body weight will
allow investigations of lifestyle and health outcomes that account
for weight variability owing to age, disease, and lifestyle factors.
Materials and methods
The AHS-2, a prospective study (n ¼ 96,710), enrolled a cohort
from 2002 to 2007 to investigate the role of lifestyle exposures
(diet, physical activity, anthropometrics) and health on outcomes
such as cancer and mortality. The design of this study has
been described elsewhere . The questionnaire is divided into
sections on medical history, diet, supplement use, physical activity,
anthropometrics (current, adulthood), and female reproductive
history. For anthropometrics, subjects reported their current
weight and height and additionally reported their weight at ages
20, 30, 40, 50, 60, and 70 years.
The AHS-1 study design has been described in extensive detail
elsewhere [9,11]. A total of 34,198 returned the AHS-1 lifestyle
questionnaire that includes self-reported height and weight.
Among non-Hispanic whites, the response rate to the lifestyle
questionnaire was in excess of 75%.
Of 96,710 AHS-2 cohort members, 5649 participated in the AHS-
1 conducted earlier. The mean of time elapsed between report of
body weight in AHS-1 (1977e1982) and report in AHS-2 was 26.1
years (95% confidence interval, 26.06e26.14). Of the 5649 AHS-2
This study was supported by grant #5-RO1 CA 094594 from the National Cancer
Institute (PI: Dr. Gary E. Fraser).
* Corresponding author. Center for Health Research, Nichol Hall 1710, School of
Public Health, Loma Linda University, Loma Linda, CA 92350. Tel.: 909-558-4590;
E-mail address: email@example.com (P.N. Singh).
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Annals of Epidemiology xxx (2012) 1e3
Please cite this article in press as: Kyulo NL, et al., Validation of recall of body weight over a 26-year period in cohort members of the Adventist
Health Study 2, Annals of Epidemiology (2012), http://dx.doi.org/10.1016/j.annepidem.2012.06.106
cohort members, we selected 2727 cohort members who reported
their current body weight during the following age ranges in AHS-
1: 28 to 32, 38 to 42, 48 to 52, 58 to 62, and 68 to 72 years old. Thus,
in this sample a comparison could be made to the recall of past
body weight at age 30, 40, 50, 60, and 70 years in AHS-2.
To assess the validity of recalling weight at ages 30 to 70 years
during AHS-2, we calculated a mean value (and 95% confidence
1 baseline minus the corresponding recall of past body weight repor-
ted 26 years later at AHS-2. Validity was also assessed by computing
a correlation between recalled (AHS-2) and current (AHS-1) weight.
The average age of the sample (n ¼ 2727) of non-Hispanic white
AHS-2 cohort was 70 years (standard deviation, 10.5). The mean
difference between current weight reported 26 years prior in AHS 1
and recall of past body weight in AHS-2 was only 0.67 kg (95%
confidence interval, 0.42e0.91). This indicates an underestimation
in the recall of past body weight during ages 30 to 70 years.
InTable 1, we present the demographics of the study sample and
an evaluation of how the validity of recall of past body weight as
measured by a mean difference (current weight at AHS-1 minus
recall of past body weight at AHS-2) varies by sociodemographic
factors. We found that the underestimation that occurred in the
recall of past body weight is greater in older age subjects, in both
women and men, and in obese subjects. Interestingly, among
higher income subjects (>$100,000 annual household income), we
found nonsignificant differences between current weight at AHS-1
and recall of past body weight 26 years later in AHS-2.
specific body weight in AHS-2 and current AHS-1 weight at the
For recall of weight at age30, 40, 50, 60,and 70years,the significant
(P < .0001) validation correlations coefficients were, respectively,
0.87, 0.89, 0.90, 0.86, and 0.83.
Our findings from AHS-2 cohort members indicate that the
validity of 26-year recall of body weight during adulthood was very
high in an older sample (mean age, 70 years). Thus, these survey
measures have good potential for use in studies of weight vari-
ability in the AHS-2 cohort. The misclassification that was identified
tended to be in the direction of underestimation and was particu-
larly prominent in 26-year recalls given by the obese and the very
old (>90 years). The recall of past body weight for these subgroups
should, therefore, be interpreted with caution.
Similar findings have been reported in the Manitoba Follow-up
Study in Canada , and in an analysis of the older subjects of the
Charleston Heart Study in the United States . Specifically, a rela-
tion between cognitive function and error in the recall of body
weight was shown in the Charleston Heart Study, such that there
was an increase in correlation between recalled weight and the
reported weight afterexcludingelderlysubjects whowith cognitive
impairment assessed by tests of mental status and memory. In our
sample, the lower accuracy at older ages (i.e., recall of weight at 70
years) could be indicative of age-related memoryloss , although
other contributing factors may exist.
In the AHS-2 sample the underestimation of past body weight
among the obese could be evidence of a social desirability bias. Also
noteworthy was the greater underestimation of past weight byever
smokers compared with never smokers. Previous studies [13,14]
have indicated that weight gain after quitting smoking may
increase recall weight underestimation in such populations.
Implications for confounding by disease-related weight loss in
studies of BMI and health outcomes
Several recent studies have shown that some of the attenuation
in risk owing to overweight/obesity during older age may be owing
to confounding by disease-related weight loss [15,16]. At least some
of this bias could be corrected if there is accurate data on adult body
weight during the prebaseline period. The findings in this report
and from a few previous studies [1e8] do indicate good validity
correlations (r > 0.8) for recall of body weight 20 to 28 years before
the baseline survey in a cohort study.
The underestimation of recall weight among overweight/obese
subjects misclassifies BMI from higher to lower category, thus
attenuating risk of BMIemortality relation in elderly subjects.
Overall, the evidence that this misclassification is differential
across both age and adiposity needs to be incorporated into the
interpretation of weight history and health outcome literature.
These data could be used as a basis for regression calibration when
analyzing effects of past body weight on an outcome.
 Stevens J, Keil JE, Waid LR, Gazes PC. Accuracy of current, 4-year, and 28-year
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Demographics of the subsample of AHS-2 cohort members and relationwith validity
of recall of past body weight as assessed by mean weight difference of (n ¼ 2727)
N Mean weight
Age at AHS-2 (yrs)
Recall of weight at age (yrs)
BMI at AHS-2
Some high school
High school diploma
Trade school diploma
Some college or higher
Annual household income (US$)
AHS ¼ Adventist Health Study; BMI ¼ body mass index; LL ¼ lower limit; UL ¼ upper
* AHS-1 weight reported at specific age: AHS-2 recall of past body weight at that
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