Apolipoproteins and carotid artery atherosclerosis in an elderly
multiethnic population: the Northern Manhattan stroke study
Jiann-Shing Jeng a, Ralph L. Sacco a,b, Douglas E. Kargman a, Bernadette Boden-
Albala a,b, Myunghee C. Paik b, Jeffrey Jones c, Lars Berglund c,
a Departments of Neurology, Columbia University, New York, NY, USA
b School of Public Health, Columbia University, New York, NY, USA
c Department of Medicine, Columbia University, New York, NY, USA
Received 20 December 2001; received in revised form 2 April 2002; accepted 10 June 2002
The association of apolipoproteins A-I and B (apo A-I and apo B) with cardiovascular disease has been studied in younger
populations, but there is sparse information in the elderly. We determined whether apo A-I and apo B were associated with carotidartery atherosclerosis (CAA) in 507 stroke-free elderly community residents (mean age 70.19/11.7 years, 60% women, 41%Hispanics, 30% African American, 28% Caucasian). CAA severity was normal (no plaque or carotid stenosis) in 39%, mild(maximum plaque thickness 0/1.8 mm or carotid stenosis B/40%) in 25%, and moderate/severe (maximum plaque thickness /1.8mm or carotid stenosis E/40%) in 36%. CAA severity increased with age in all race/ethnic groups (P B/0.01). CAA was similaramong African Americans and Caucasians, but less in Hispanics (age adjusted OR: 0.5, CI: 0.4 Á/0.8). apo A-I B/1.2 g/l (OR: 2.0, CI:1.0 Á/3.3) and apo B E/1.4 g/l (OR: 2.0, CI: 1.1 Á/3.6) were associated with moderate Á/severe CAA. An apo B/apo A-I ratio E/1 wasassociated with moderate Á/severe CAA (OR: 2.4, CI: 1.3 Á/4.4), and the association varied by race (Hispanics OR: 4.3, CI: 1.8 Á/10;non-Hispanics, OR: 1.4, CI: 0.6 Á/3.2). Total cholesterol, triglycerides and low density lipoprotein cholesterol were not associatedwith moderate Á/severe CAA, while high density lipoprotein cholesterol was protective (OR: 0.4, CI: 0.2 Á/0.8). Thus, in an elderlypopulation, apo A-I and B were determinants of moderate Á/severe CAA, and the degree of association varied by race/ethnicity# 2002 Elsevier Science Ireland Ltd. All rights reserved.
Keywords: Apolipoprotein; Atherosclerosis; Carotid arteries; Racial differences; Risk factors
progressively attenuated with age, the absolute riskattributable to blood lipids is greater among the elderly
Extracranial carotid artery atherosclerosis (CAA) is a
Further, intervention studies have shown that
major cause of cerebral infarction and transient ischemic
lowering of low density lipoprotein (LDL) cholesterol
attacks, a disease primarily of the elderly. In population-
levels results in similar benefits in older and younger
based epidemiological studies, atherosclerotic risk fac-
subjects, as well as in a reduction in cerebrovascular
tors such as age, hypertension, systolic blood pressure,
events The lack of a consistent association between
diabetes mellitus, and smoking, but not lipids and
lipids and CAA is therefore puzzling. In addition, most
lipoproteins, have been consistently associated with
population-based studies of carotid atherosclerosis have
CAA It is notable that for coronary artery
so far been performed among Caucasians and in a few
disease, although the magnitude of the association is
cases African Americans, but there is little informationavailable for Hispanics. We recently demonstrated thatHispanics had significantly less carotid plaque than
* Corresponding author. Present address: Department of Medicine,
Caucasians or African Americans, and found a signifi-
University of California, Davis UCD Medical Center, 4150 V Street,
cant relationship between race/ethnicity, carotid plaque
Sacramento, CA 95817, USA. Tel.: '/1-916-734-7504; fax: '/1-916-
and LDL cholesterol, suggesting that the impact of lipid
0021-9150/02/$ - see front matter # 2002 Elsevier Science Ireland Ltd. All rights reserved. PII: S 0 0 2 1 - 9 1 5 0 ( 0 2 ) 0 0 2 4 6 - 0
J.-S. Jeng et al. / Atherosclerosis 165 (2002) 317 Á/325
Apolipoproteins A-I and B (apo A-I and B) are the
major protein constituents of the high density lipopro-tein (HDL) and LDL fractions, respectively. Previous
Race/ethnicity was categorized based on self-report,
studies addressing the association of apo A-I and apo B
following definitions used in the US census of 1990, as
with cardiovascular disease have yielded mixed results.
Hispanic, Black but not of Hispanic heritage, non-
In some studies, although not universally found, apo B
Hispanic White, or others. Standardized questionnaires
was reported to give better information than lipid levels,
regarding sociodemographic characteristics, stroke risk
while in general, apo A-I levels have not been found to
factors and comorbid atherosclerotic diseases were
be independently predictive . However, most of
adapted from the Behavioral Risk Factor Surveillance
these studies were performed in younger and middle-
System by the Centers for Disease Control and Preven-
aged populations. Among the elderly, although total
tion Hypertension was defined as a systolic blood
cholesterol levels tend to decline, the HDL fraction of
pressure recording E/160 mmHg or a diastolic blood
plasma cholesterol (HDL-C), and its ratio with total
pressure recording E/95 mmHg based on the mean of
cholesterol (THR) remain important protective factors
two blood pressure measurements, a patient’s self-report
against CHD among the elderly . Under the new
of a history of hypertension, or use of antihypertensive
National Cholesterol Education Program guidelines, a
therapy. Diabetes mellitus was defined by a patient’s
high proportion of the elderly are candidates for
self-report of a history of diabetes mellitus, insulin use,
additional evaluation and possibly lipid-lowering inter-
oral hypoglycemic use, or fasting blood glucose E/126
ventions aimed at the primary or secondary prevention
mg/dl ( E/7.0 mmol/l). Body mass index was calculated
of coronary heart disease . However, few studies
as weight (kilograms) divided by height (meters)
have characterized the distributions of lipids and
squared, and obesity was defined as body mass index
apolipoproteins in elderly populations, particularly
E/27.8 for men, and E/27.3 for women. Leisure Á/time/
among minority groups, and even fewer have studied
recreation physical activity was assessed by a question-
the association of these parameters with measurements
naire adapted from the National Health Interview
of atherosclerosis in this context. The aim of this study
Survey of the National Center for Health Statistics
was therefore to investigate the association of apolipo-
. The questionnaire records the frequency and
proteins and lipids with carotid atherosclerosis in a
duration of 14 different recreational activities during
multiethnic population-based sample of stroke-free
the 2-week period before the interview. Leisure Á/time
physical inactivity was defined as subjects with noleisure Á/time recreational physical activity. Cigarettesmoking was characterized by amount (packs per day)
and duration (number of years smoked). Smoking wascategorized as no to mild smoking (none or any smoking
for B/20 years, or smoking B/1 pack per day for 20 Á/39years), and heavy smoking (any smoking E/40 years, or
The Northern Manhattan Stroke Study (NOMASS),
smoking at least 1 pack per day for 20 Á/39 years).
recruiting stroke subjects and controls, is a prospective
Alcohol use was collected as drinks per day, week, or
community-based study designed to determine incidence
month. Comorbid conditions included coronary artery
rates, risk factors and outcome of stroke The
disease (myocardial infarction, angina) and peripheral
cohort for the present study was derived from the
stroke-free subjects enrolled in NOMASS. Stroke-freesubjects E/40 years were randomly selected and re-cruited into this study through random digit dialingtechniques After informed consent was obtained,
2.3. Measurement of serum lipids, lipoproteins and
sociodemographic characteristics, stroke risk factors,
other medical conditions, diet, and functional statuswere evaluated, an electrocardiogram was obtained and
Plasma levels of cholesterol and triglycerides were
an echocardiography was performed. Fasting blood
specimens for glucose, lipids, lipoproteins and apolipo-
(Boehringer Mannheim, Germany). HDL cholesterol
proteins were drawn. A neurological examination was
levels were measured after precipitation of plasma apo
completed. Approximately two thirds of the recruited
B-containing lipoproteins with phosphotungstic acid
stroke-free subjects were randomly selected to undergo
and LDL cholesterol levels were calculated by the
carotid duplex ultrasonographic studies. In all, 507
Friedewald formula. Serum levels of apo A-I and B
stroke-free subjects, who had completed enrollment,
were determined by commercially available immunone-
including duplex ultrasonography and blood drawing,
phelometric procedures. The interassay coefficients of
variation for these measurements were 3 Á/5%
J.-S. Jeng et al. / Atherosclerosis 165 (2002) 317 Á/325
2.4. Category of CAA by duplex ultrasonography
models were developed by separately adding lipidparameters to a model containing other sociodemo-
CAA was assessed by a Siemens Quantum 2000
graphic and risk factors variables. Statistical interac-
duplex ultrasound system with 7.5-MHz scanning fre-
tions were evaluated in the final models.
quency in B-mode and 5.0-MHz frequency in pulsedDoppler mode as described in detail elsewhere . Briefly, with the subject lying in a supine position, the
extracranial carotid arteries (including the common,internal, and external carotid arteries and the carotid
The mean age of the study group was 70.19/11.7 years
bulb area) were imaged in the longitudinal and trans-
(median age 71 years; range 40 Á/99 years); 40% were men
verse planes. The presence, morphology and thickness of
and 60% were women. The race-ethnic distribution was
carotid plaques, defined as an area of focal hyperechoic
41% Hispanic (n 0/206), 28% non-Hispanic whites (n 0/
wall thickening, and the extent of internal carotid artery
141), 30% non-Hispanic blacks (n 0/153) and 1% others
stenosis were recorded. Based on maximum carotid
(n 0/7). Of the subjects, 196 (39%) had no detectable
plaque thickness and extent of internal carotid artery
CAA, while 128 subjects (25%) had mild CAA (max-
stenosis bilaterally, CAA was categorized as normal (no
imum carotid plaque thickness 0/1.8 mm or maximum
carotid plaque or internal carotid artery stenosis), mild
internal carotid artery stenosis B/40%), and 183 subjects
(maximum carotid plaque thickness E/1.8 mm or
(36%) showed signs of moderate Á/severe CAA (max-
maximum internal carotid artery stenosis B/40%) and
imum carotid plaque thickness /1.8 mm or maximum
moderate Á/severe (maximum carotid plaque thickness
internal carotid artery stenosis E/40%). Sociodemo-
/1.8 mm or maximum internal carotid artery stenosis
graphics, atherosclerotic risk factors and comorbid
E/40%). The use of a carotid plaque thickness of 1.8 mm
atherosclerotic diseases for each of the CAA categories
to define the above groups was based on the CAA
distribution in 1050 stroke-free subjects where the mean
mellitus, hypertension, heavy smoking and presence of
maximum plaque thickness was 1.31 mm (SD:1.32) and
coronary artery disease or peripheral vascular disease
the 66.6% percentile was 1.8 mm . Internal carotid
was greater in the group with moderate Á/severe CAA
artery stenosis E/40% was defined by standard criteria
compared to no CAA. The group with mild CAA had
requiring a ratio of internal carotid artery: carotid artery
intermediate frequencies of these parameters between
velocities greater than 2, or peak internal carotid artery
the other two groups. Among the race/ethnicity groups,
systolic flow velocity of E/110 cm/s. In previous studies
the proportion of African Americans and Caucasians
at our center, the interrater reliability of the estimation
were higher among moderate Á/severe CAA compared to
of plaque morphology based on duplex Doppler sono-
no CAA, while the relative frequency of Hispanics
graphy had a k value of 0.05 for plaque surface
structure, well below the value of 0.40 suggested for
For all subjects, CAA severity increased with age.
Thus, while any form of CAA was present in only 14%of the subjects between 40 Á/54 years, this proportion
increased to 80% of the subjects E/75 years of age (datanot shown). This increase was most prominent among
Distribution of mild and moderate Á/severe CAA was
subjects with moderate Á/severe CAA, which increased
evaluated and stratified by different age ranges. AN-
from 3% of the youngest cohort to 51% of the oldest
OVA was used to compare mean age in the different
cohort. Concomitantly, the proportion of subjects with
groups of CAA in all and among each race-ethnic
no detectable CAA decreased sequentially from 86% of
subgroup. The association of sociodemographic para-
the subjects between 40 and 54 years to 20% of subjects
meters, risk factors and comorbid conditions with mild
E/75 years. When dichotomizing age at 65 years, there
CAA and moderate Á/severe CAA were compared sepa-
was a significant association with presence of CAA, with
rately using those with absent CAA as a reference. The
OR of 3.7 for mild CAA and 6.0 for moderate Á/severe
odds ratios (OR), 95% confidence intervals (CI) and
CAA (When analyzing the three race/ethnicity
significance were judged based on the x2 test for
groups separately, CAA severity increased with age in
categorical variables. Multivariate analyses were per-
all groups (P B/0.001) (data not shown).
formed using a logistic regression model to identify
We next analyzed univariate associations for socio-
independent factors. Variables were selected for entry if
demographic factors, atherosclerotic risk factors and
probability value was less than 0.10 after univariate
comorbid atherosclerotic diseases with the presence of
testing. Modeling was done using the selected variables
CAA. As seen in , mild CAA was less common
as the independent variables and CAA as the dependent
among African Americans than Caucasians and both
variable. Odds ratios and 95% CI were calculated.
mild and moderate Á/severe CAA was seen less frequently
Because of the co-linearity of various lipid parameters,
among Hispanics compared to Caucasians. No differ-
J.-S. Jeng et al. / Atherosclerosis 165 (2002) 317 Á/325
Table 1Frequencies of sociodemographics, atherosclerotic risk factors and comorbid atherosclerotic diseases in cohort
Comorbid conditionsCoronary artery disease
ence was seen in sociodemographic factors other than
which increased significantly with increasing severity of
age and race/ethnicity (gender, education and Medicaid
CAA. Of the ethnic groups, Hispanics had the highest
status) for subjects with and without CAA. Other
apo B/apo A-I ratio, resulting from slightly higher mean
variables, such as obesity, physical inactivity and
apo B and slightly lower mean apo A-I levels compared
alcohol drinking were not associated with the presence
to Caucasians, while African Americans had the lowest
of CAA. Among atherosclerotic risk factors, there was
ratio, largely due to the higher apo A-I levels.
no significant difference between subjects with mild
Categorical univariate analysis of lipids, lipoproteins
CAA compared to subjects without CAA, except for
and apolipoproteins for subjects with moderate Á/severe
heavy smoking. More prominent differences were found
for subjects with moderate Á/severe CAA, where hyper-
The levels for dichotomization were chosen to represent
tension, diabetes mellitus, and heavy smoking were
clinically relevant cut-off levels. As seen in the table, a
significantly associated with presence of CAA (
total cholesterol/HDL-C ratio E/5, apo A-I levels B/1.2
Further, history of coronary artery disease or
g/l and apo B/apo A-I ratio E/1 were significantly
peripheral vascular disease was significantly associated
associated with moderate Á/severe CAA levels. In con-
trast, no association with moderate Á/severe CAA was
The frequency distribution of apo A-I, apo B and the
found for total cholesterol levels E/5.92 mmol/l ( E/240
apo B/apo A-I ratio in the study cohort is shown in
mg/dl), triglyceride levels E/2.03 mmol/l ( E/200 mg/dl)
As seen in the figure, the apo A-I distribution was
and LDL cholesterol levels E/3.95 mmol/l ( E/160 mg/
somewhat skewed with a tail towards higher levels, while
dl). In univariate analysis, apo B levels E/1.4 g/l showed
the apo B distribution had a more Gaussian pattern.
a borderline association with moderate Á/severe CAA.
Levels of apo A-I were higher among women than men,
As gender and race/ethnicity influenced apolipopro-
and higher among African Americans than Caucasians
tein levels, a multiple logistic regression model was used
or Hispanics in agreement with previous population
to assess which apolipoprotein and lipid variables were
studies (). No differences in apo B levels were
independently associated with CAA. As seen in
found between these groups. Further, apo B levels
low apo A-I levels ( B/1.2 g/l), and an apo B/apo A-I
increased gradually with increasing CAA, while a
ratio E/1 remained significantly associated with mod-
decreasing trend was seen for apo A-I levels. These
erate Á/severe CAA after adjustment for age, hyperten-
differences were reflected in the apo B/apo A-I ratio,
sion, diabetes mellitus, heavy smoking and race-
J.-S. Jeng et al. / Atherosclerosis 165 (2002) 317 Á/325
logistic regression model. An apo B/apo A-I ratio E/1
Univariate odds ratio and 95% CI For variables associated with mild
significantly predicted mild carotid atherosclerosis (OR:
3.2, CI: 1.04 Á/10.0). Also age E/65 years (OR: 3.3, CI:1.9 Á/5.6) and heavy smoking (OR: 1.6, CI: 1.0 Á/2.7) were
predictors of mild CAA, while Hispanics were less
prevalent than non-Hispanics (OR: 0.6, CI: 0.3 Á/0.9).
SociodemographicsAge ( E 65 years vs B 65 years)
A number of studies, including our own, have shown
that the prevalence of CAA and atherosclerotic risk
factors as well as the mortality rates of cardiovascular
diseases differ significantly among Hispanics, non-
Although stroke incidence rates were higher among
Hispanics than among Caucasians in NOMASS, the
severity of CAA was less in stroke-free Hispanics than
Caucasians and African Americans The race Á/
ethnic differences in CAA became more prominent in
advanced (moderate Á/severe) atherosclerosis. Our pre-
vious study also showed the age-adjusted maximal
plaque thickness was less in Hispanics than Caucasians
and African Americans These findings are con-
cordant with The Insulin Resistance Atherosclerosis
Study which revealed that Hispanics have significantly
less CCA intima-media thickness than Caucasians after
adjustment for conventional cardiovascular risk factors
Values are OR (95% CI). *P B 0.005; **P B 0.05 subjects with CAA
and insulin sensitivity . Other population-based
studies of racial differences in CAA, especially theCardiovascular Health Study and Atherosclerotic Risk
ethnicity (Hispanics versus non-Hispanics). In addition,
in Communities study , have mainly focused on
apo B levels E/1.4 g/l were associated with moderate Á/
African Americans and Caucasians and rarely on
severe CAA. In contrast, higher total cholesterol,
Hispanics. According to the findings from the Third
triglyceride and LDL cholesterol levels were not asso-
National Health and Nutrition Examination Survey, the
ciated with moderate Á/severe CAA, while a higher HDL
prevalences of cardiovascular risk factors, including
cholesterol level was protective (OR: 0.4, CI: 0.2 Á/0.8).
systolic blood pressure, body-mass-index, physical in-
In addition, a total/HDL cholesterol ratio E/5 was
activity and diabetes, are greater in Hispanic and
associated with moderate Á/severe CAA. This ratio
African American women than in Caucasian women
correlated significantly with the apo B/apo A-I ratio
. However, the United States vital statistics analysis
(r 0/0.56, P 0/0.02). Of note, the association between the
showed the mortality rates of coronary artery disease
apo B/apo A-I ratio and moderate Á/severe carotid
and stroke were lower among Hispanics than among
atherosclerosis remained significant also when the
Caucasians . Heterogeneity in Hispanic populations
total/HDL cholesterol ratio was included in the multiple
could explain some of these differences, and genetic and
regression model (OR 2.1, CI: 1.3 Á/4.4). A significant
other environmental risk factors not measured in this
interaction was detected between the apo B/apo A-I
study could also contribute to these race-ethnic dispa-
ratio and Hispanic race-ethnicity, but not among
African Americans and Caucasians (Hispanics, OR:4.3, CI:1.8 Á/10; non-Hispanics, OR:1.4, CI:0.6 Á/3.2).
4.2. Relation of apo B and apo A-I to CAA
No interaction between HDL cholesterol and Hispanicrace-ethnicity was detected.
The total apo B plasma concentration comprise the
Of the lipid or apolipoprotein parameters, only the
total amount of apo B in triglyceride-rich lipoproteins
apo B/apo A-I ratio differed significantly between the
(including very-low-density lipoproteins (VLDL) and
groups with mild CAA versus no CAA using a multiple
intermediate-density lipoproteins (IDL)) as well as in
J.-S. Jeng et al. / Atherosclerosis 165 (2002) 317 Á/325
Fig. 1. Relative frequency of apo A-I levels (top), apo B levels (middle) and the apo A-I/apo B ratio (bottom) in the studied population (n 0/507). Results for apo A-I and apo B are given as g/l.
cholesterol-rich particles (mainly LDLs) Recent
within the LDL spectrum there is particle heterogeneity,
studies have disclosed that triglyceride-rich apo B-
and smaller, dense LDL particles with a high apo
containing lipoproteins, primarily VLDL remnants
B:cholesterol ratio have been suggested to be particu-
and IDL are significantly related to ischemic heart
larly atherogenic . Studies have shown that hyper-
disease Lately, it has been hypothesized that
apobetalipoproteinemia is an important risk factor for
preferentially smaller particles within the triglyceride-
patients with ischemic heart disease as well as for
rich lipoprotein range, with a higher apo B: lipid ratio,
young adults with a parental history of premature
may be associated with cardiovascular disease Also
coronary heart disease So far, only a few studies
J.-S. Jeng et al. / Atherosclerosis 165 (2002) 317 Á/325
tion between apo B levels and carotid atherosclerosis is
Mean apolipoprotein levels (9SD) by age, gender, race-ethnicity and
not limited to elderly subjects, as apo B was found to be
a significant indicator of CAA also in middle-aged menand women in the Bruneck Ischemic Heart Disease and
Stroke Prevention Study Interestingly, we found aninteraction among apolipoproteins, Hispanic (versus
non-Hispanic) race-ethnicity, and CAA, as the associa-
tion between apolipoprotein levels and CAA was
particularly pronounced among Hispanics. It is note-
worthy that a high apo B level is a characteristic of the
metabolic syndrome, present in a comparatively high
frequency in Hispanics. Our previous study showed an
interaction among Hispanic (versus non-Hispanic) race-
ethnicity, LDL cholesterol and maximal ICA plaque
thickness However, in the present analysis, LDL
cholesterol was not associated with CAA and there was
no interaction between LDL cholesterol and race-
ethnicity. Although the methods of estimating CAA
applied to these two studies were not identical, it is
suggested that apo B may be more powerful than LDL-C in determination of CAA for Hispanics.
Results for apo A-I and apo B levels are given as g/l.
Both apo A-I and HDL cholesterol were similarly and
have addressed the important role of apo B on CAA,
significantly negatively associated with moderate Á/severe
and there is virtually no information in elderly .
CAA in the present study. We have previously demon-strated that HDL cholesterol has significantly protective
Our study clearly showed that an apo B concentration
properties in ischemic stroke . In the Physicians’
E/1.4 g/l and an apo B/apo A-I ratio E/1 were
Health Study, there was little predictive value of apo A-I
significantly related to moderate Á/severe CAA, even
for myocardial infarction after considering conventional
after controlling for traditional risk factors. These result
risk factors including HDL cholesterol and the total/
suggest that the plasma concentration of apo B, broadly
HDL cholesterol ratio . Our study results revealed
mirroring the number of potentially atherogenic parti-
that apo A-I and HDL cholesterol had similar protective
cles, was a better determinant of CAA than total
effects for CAA among the elderly. Further, the ratio of
cholesterol and LDL cholesterol in our elderly popula-
apo B to apo A-I was a significant determinant of
tion. This concept is supported by previous findings,
moderate Á/severe CAA, underscoring that analysis of
such as the Systolic Hypertension in the Elderly
these apolipoprotein levels may provide important
Program study, where a high apo B concentration was
information in risk prevention among elderly. Notably,
significantly related to carotid stenosis The associa-
the apo B/apo A-I ratio remained significantly asso-
Table 4Association of lipids and lipoproteins with moderate Á/severe CAA in univariate and multivariate models
In the multivariate model, adjustments were made for age, hypertension, diabetes mellitus, heavy smoking and race-ethnicity (Hispanics versus
J.-S. Jeng et al. / Atherosclerosis 165 (2002) 317 Á/325
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[8] Krumholz HM, Seeman TE, Merrill SS, Mendes de Leon CF,
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and other Caribbean islands and differ in several aspects
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from Mexican Americans. On the other hand, the setting
Cholesterol-lowering therapy in women and elderly patients with
of the study also had offered important strengths.
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helping to insure that the sample was population based
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[10] Sacco RL, Roberts JK, Boden-Albala B, Gu Q, Lin IF, Kargman
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than blacks and whites from the Northern Manhattan
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[12] Sharett AR, Patsch W, Sorlie PD, Heiss G, Bond MG, Davis CE.
B levels were independently related to moderate Á/severe
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CAA. Apolipoproteins, in particular the apo B/apo A-I
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This study was supported by grants NS 9993, HL
[14] Wilson PW, Anderson KM, Harris T, Kannel WB, Castelli WP.
62705, RR 00645 from the NIH. J.S.J. is a recipient of a
Determinants of change in total cholesterol and HDL-C with age:
research fellowship from the Department of Neurology,
the Framingham Study. J Gerontol 1994;49:M252 Á/7.
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Safety of Celecoxib vs Other Nonsteroidal Dohme for rofecoxib and of the advisory board of Pfizer/Searle for celecoxib. Dr Anti-inflammatory Drugs Ko¨hler and Dr Kuipers have received travel grants from MSD Sharp & Dohme andfrom Pfizer/Searle. 1. Silverstein FE, Faich G, Goldstein JL, et al. Gastrointestinal toxicity with celecoxib To the Editor: The results of the Celecoxib Long-
Generative Migration of Agents F.M.T. Brazier; B.J. Overeinder; M. van Steen; N.J.E. WijngaardsDepartment of Computer Science, Faculty of Sciences, Vrije Universiteit Amsterdam;de Boelelaan 1081a, 1081 HV Amsterdam, The Netherlands Abstract Agents, and in particular mobile agents, offer a means for application developers to build distributed applications. Incurrent agent systems, mobility