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Associations of weight, weight change and body mass with breast cancer risk in Hispanic and non-Hispanic white women

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Associations of weight, weight change and body mass with breast cancer risk in Hispanic and non-Hispanic white women

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Content ASSOCIATIONS OF WEIGHT, WEIGHT CHANGE AND BODY MASS WITH
BREAST CANCER RISK IN HISPANIC AND NON-HISPANIC WHITE WOMEN
by
Made Rai Wenten
A Thesis Presented to the
FACULTY OF THE GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
MASTER OF SCIENCE
(APPLIED BIOMETRY AND EPIDEMIOLOGY)
December 2000
Copyright 2000 Made Rai Wenten
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UMI Number: 1407931
___ ®
UMI
UMI Microform 1407931
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UNIVERSITY O F SO U T H E R N CALIFORNIA
THE GRADUATE SCHOOL
UNIVERSITY PARK
LOS ANGELES. CALIFORNIA 9 0 0 0 7
This thesis, written by
I UADB
under the direction of hJ.5.....Thesis Committee,
and approved by all its members, has been pre
sented to and accepted by the Dean of The
Graduate School, in partial fulfillment of the
requirements for the degree of
D ta*
Date. Decemb e r 18, 2000
THESIS COMMITTEE
Chairman
/
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DEDICATION
For Darleen
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ACKNOWLEDGEMENT
I would like to extend my utmost gratitude to my committee chair and mentor, Dr.
Frank Gilliland, for his guidance and support. This manuscript would not have been
possible were it not for his vision and commitment. I would also like to thank Dr. Leslie
Bernstein and Dr. Jennifer Unger for their insightful comments. It has been an honor to
work with such dedicated teachers and researchers.
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TABLE OF CONTENTS
Dedication Page ii
Acknowledgement Page iii
List of Tables Page v
Abstract Page vi
Introduction Page 1
Methods Page 2
Results Page 6
Discussion Page 19
References Page 26
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LIST OF TABLES
Table 1.
Table 2.
Table 3.
Table 4.
Table 5.
Table 6.
Table 7.
Characteristics of selected covariates of breast cancer
cases and controls by ethnicity
Adjusted odds ratios and 95% confidence intervals for
risk of breast cancer among Hispanic white women
Adjusted odds ratios and 95% confidence intervals for
risk of breast cancer among non-Hispanic white women
Adjusted odds ratios and 95% confidence intervals for
risk of breast cancer among Hispanic and non-Hispanic
white women stratified by menopausal status
Adjusted odds ratios and 95% confidence intervals for
risk of breast cancer among Hispanic and non-Hispanic
white women stratified by BMI (kg/m2 ) at 18 years of age
Adjusted odds ratios and 95% confidence intervals for
risk of breast cancer among Hispanic and non-Hispanic
white women stratified by ER/PR status
Adjusted odds ratios and 95% confidence intervals for
risk of breast cancer among postmenopausal Hispanic
and non-Hispanic white women stratified by estrogen use
Page 8
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v i
ABSTRACT
To investigate weight and weight change as risk factors for breast cancer risk in Hispanic
and non-Hispanic white women, a population-based case-control study of Hispanic and
non-Hispanic white New Mexican women with incident breast cancer was conducted
from January 1, 1992 to December 31, 1994. Conditional logistic regression models
were fit to estimate relative risk of breast cancer for levels of weight, weight change and
usual body mass index (BMI) and to assess differences in the effects by ethnicity,
menopausal status, early life BMI, ER/PR expression in tumors, and hormone
replacement therapy (HRT). Weight change was associated with an increased risk for
breast cancer in pre and post-menopausal Hispanic and post-menopausal non-Hispanic
white women with ER+ /PR+ tumors. Because the prevalence of adult obesity continues to
rise among Hispanic women, adult weight gain may be an important modifiable risk
factor for breast cancer prevention among Hispanic populations.
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1
INTRODUCTION
Breast cancer occurrence varies between Hispanic and non-Hispanic populations
in the US. Both incidence and mortality rates are lower in Hispanic compared to non-
Hispanic white women; however, both rates are on the rise in Hispanic women (Eidson et
ah, 1994; Trapido et al., 1994). Among New Mexico Hispanic women, incidence rates
for breast cancer increased by 56 percent, from 36.8 per 100,000 in the early 1970’s to
57.5 per 100,000 in the late 1980’s. Mortality rates nearly doubled over a 30-year period,
from 10.2 per 100,000 to 18.6 per 100,000 (Eidson et al., 1994).
The explanation for the ethnic difference in rates and temporal trends in breast
cancer occurrence are not well understood. The contribution of risk factors other than
reproductive (Buchanan et al., 1985; Gilliland et al., 1998; Romieu et al., 1990; Romieu
et al., 1996; Romieu et al., 1989) and family history of breast cancer (Bondy et al., 1992;
Buchanan et al., 1985; Calle et al., 1993; Mayberry & Branch, 1994) has yet to be
determined in Hispanic women. Examining the relationships of adult weight, adult
weight gain and obesity with breast cancer occurrence is of interest due to the high and
rising prevalence of obesity in the US Hispanic population (Mokdad et al., 1999).
Although a wealth of studies examining the association between breast cancer and
body size are available, few have included information on risk from weight, weight
change and obesity among Hispanic women (Mayberry & Branch, 1994). The paucity of
data on modifiable aspects of body size and breast cancer risk among Hispanic women is
an important gap in the knowledge base needed to prioritize primary prevention efforts.
The New Mexico Women’s Health Study offered an opportunity to further investigate the
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2
effect of body size on breast cancer risk among Hispanic women. We examined breast
cancer risks associated with weight, height, obesity, and adult weight gain, assessing
differences in effects by ethnicity, menopausal status, estrogen/progesterone receptor
status and use of hormone replacement therapy (HRT), utilizing data from this statewide
population-based case-control study among Hispanic and non-Hispanic white women.
METHODS
The New Mexico Women's Health Study is a statewide population-based case-
control study of breast cancer in Hispanic and non-Hispanic white women. Female
residents of the State (30-74 years) who were newly diagnosed with an invasive or in situ
breast carcinoma during the period of January 1, 1992 through December 31, 1994 were
eligible for participation in the study.
Identification of Case Subjects
Women with newly diagnosed primary breast cancer were ascertained by the New
Mexico Tumor Registry (NMTR), a population-based tumor registry and member of the
Surveillance, Epidemiology and End Results Program of the National Cancer Institute.
All Hispanic cases were eligible for the study. Because the overall expected number of
breast cancer cases for the study period was approximately three times higher for non-
Hispanic whites than for Hispanics, we randomly selected a sample of approximately 33
percent of non-Hispanic white cases. To maximize our power to examine ethnic
differences in effects with the available sample size, all Hispanic cases were included.
The sampling strata for non-Hispanic white cases were age group (30-39, 40-64, 65-74
years) and geographic region, defined by seven state health-planning districts. The
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sampling fraction for non-Hispanic whites in each of these 21 strata was chosen to
provide a distribution similar to the age and geographic distribution of Hispanic cases
determined by the NMTR in the three-year period 1988 through 1990. A total of 491
eligible Hispanic breast cancer ca,ses were obtained. The stratified random selection of
on-Hispanic white women resulted in the compilation of 493 cases. O f the eligible cases,
332 Hispanics (68%) and 380 non-Hispanic whites (77%) completed in-person
interviews. Reasons for non-participation have been reported elsewhere (Gilliland et al.,
1998). Tumor estrogen and progesterone receptor status was gathered by NMTR for
medical-records documentation.
Identification of Controls
Controls were acquired using random-digit dialing with frequency matching on
ethnicity, the three age groups and the seven health planning districts. We used a
modified approach to the Waksberg random digit dialing method described previously
(Gilliland et al., 1998). A total of 1039 eligible controls attained from approximately
3400 respondents completed the telephone-screening interview, including 511 Hispanic
and 528 non-Hispanic white women. O f those eligible, 844 (81.2%) were successfully
interviewed. Participation rates were 75.9 percent for Hispanics and 86.4 percent for
non-Hispanic whites.
Data Collection
In-person interviews were conducted at a location selected by the participant.
Written informed consent was obtained at the onset of the interview. All questionnaires
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were translated into Spanish so that interviews may be conducted in either Spanish or
English, according to the subject’s preference.
Weight at 18 years of age, usual weight and height were self-reported. Weight at
18 years of age, weight change (weight usual - weight at 18) and percent weight change
([weight usual - weight at 18] / weight at 18 x 100) were categorized into quartiles using
the distributions for all controls. Body mass index (BMI) was categorized using the
WHO (1997) criteria for overweight and obesity (BMI at 18 years of age: <18.5, 18.5-
<21.0, 21.0 - <25.0, >=25.0; BMI usual: <22.0, 22.0 - <25.0, 25.0 - <30.0, >=30.0).
Parity was defined as the number of pregnancies lasting six months or longer with
outcomes of either a single birth, multiple births, or a stillbirth. Age at first full-term
birth was defined as the age of the woman at the end o f her first pregnancy lasting six
months or longer, regardless of the outcome of the pregnancy. Duration of lactation was
the cumulative number of months of breastfeeding for all children.
Self-reported categories of non-occupational physical activity were assessed
during the in-person interview. Weekly MET-hours were calculated using hours per
week of participation in non-occupational physical activities and assigning MET values
to each activity (Ainsworth et al., 1998). MET-hours for all activities were categorized
as less than 20, 21-40 MET-hours, 41-60 MET-hours and >60 MET-hours.
Menopausal status was classified as either premenopause, natural post
menopause, surgical post menopause, or unknown based on self-report of menstrual
history, history of hysterectomy with or without oophorectomy, and use of estrogen
replacement therapy as previously described (Gilliland et al., 1998). Age at menopause
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was the age at last natural menstrual cycle followed by one year of amenorrhea, after one
year of hormone replacement therapy, or at the date of bilateral oophorectomy. For
stratified analyses, we used categories of premenopausal and postmenopausal that
included both natural and surgical menopausal groups. Women with unknown
menopausal status were excluded from the stratified analyses.
Cumulative oral contraceptive use and lifetime HRT use were categorized into
quartiles and tertiles, respectively, based on the distribution for all cases and controls.
Family history of breast cancer was defined as having a first-degree relative (mother,
sister or daughter) diagnosed with breast cancer.
Statistical Analyses
Conditional logistic regression models were fit to calculate odds ratios and 95
percent confidence intervals (95% Cl) that estimated the relative risks o f breast cancer.
Models that included all participants were conditioned on three age groups, ethnicity and
the seven geographic districts. Analyses that were stratified by ethnicity were conditioned
on three age groups and the seven geographic districts. Selection of potential
confounders to include in the models was based on a review of the literature and change
in effect estimates of at least 10% in multivariate analyses. Based on the above criteria,
the following variables were selected as potential confounders: age; family history of
breast cancer; total MET-hours; parity; years of oral contraception use; months of
breastfeeding; age at first live birth; years of HRT use (in postmenopausal women only);
and menopausal status. Because the age groups were broad, additional terms for age were
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included in the models. Tests of trend were conducted using categories of mean scores
(Greenland, 1995a; Greenland, 1995b; Greenland et al., 1999).
To assess effects of weight at 18, weight gain, BMI at 18 and usual BMI on breast
cancer risk within ethnic and menopausal groups, analyses were stratified according to
ethnicity and menopausal status. Stratified analyses were also conducted to assess
whether the effects of weight gain differed for lean (BMI at 18 <22) versus non-lean
women (BMI at 18 >22). To determine if the effect of weight gain differed by tumor
hormone receptor status, analyses were conducted for cases with estrogen receptor
positive/progesterone receptor positive tumors [ER+ /PR+ ] tumors and cases with estrogen
receptor negative/progesterone receptor negative tumors [ER'/PR‘], Those women whose
tumors exhibited discordant expression patterns (ER+ /PR' and ER'/PR+ tumors) were
excluded from the analyses restricted by hormone receptor status. To ascertain whether
the effect of weight gain on breast cancer risk differed by hormone replacement therapy,
the analyses were stratified by HRT use (user, non-user). Differences in effects between
groups were assessed by creating categories of interaction terms in nested models and
utilizing the difference in likelihood ratio estimates to establish statistical significance (2-
sided, a=0.05). All analyses were conducted using Statistical Analyses System software
(SAS v6.12) (SAS Institute, 1997).
RESULTS
Hispanic and non-Hispanic white cases and controls showed differences in breast
cancer risk factors (table 1). Hispanic white women (38%) had more than three full-term
births compared to non-Hispanic white women (18%). In general, Hispanic women were
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7
younger than non-Hispanics at the time of their first child. An ethnic difference in HRT
use also exists such that 62% of Hispanics versus 51% of non-Hispanic whites never used
estrogen. Furthermore, 27% of non-Hispanic whites have used estrogen for longer than
48 months compared to only 17% of Hispanics who have used estrogen for as long a
period. Anthropometric measures also varied by ethnicity. Hispanic women were shorter
and had higher BMI than their non-Hispanic counterparts. More Hispanic women were
overweight or obese (BMI >25) (41%) compared to non-Hispanic white women (22%).
Non-occupational physical activity as measured by total MET was found to be a
significant confounder and not a mediator in the weight change, breast cancer pathway.
Usual BMI and weight change from age 18 to usual adult weight was associated
with increased risk of breast cancer among Hispanic but not non-Hispanic white women
(table 1). Height, weight at age 18 and BMI at age 18 were not associated with risk in
either ethnic group. After adjustment for reproductive and non-reproductive covariates,
obesity (BMI >30), adult weight gain greater than 14 kg and percent or relative weight
gain in the second and fourth quartile were associated with an increase in breast cancer
risk among Hispanic women with no substantial variation by menopausal status (table 2).
BMI at 18 and weight at 18 were not important risk factors for breast cancer in Hispanic
women. Weight change and relative weight gain were also risk factors for non-
Hispanics, but only in postmenopausal women, while BMI at 18, usual BMI and weight
at 18 were not significantly associated with breast cancer risk in non-Hispanic white
women (table 3). The effects o f BMI at 18, obesity and weight gain were not statistically
different in premenopausal compared to postmenopausal non-Hispanic white women.
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TABLE 1. Characteristics o f selected covariates o f breast cancer cases and controls by ethnicity, New M exico’s W om en’s Health Study, 1992-1994*.
Risk Factors HisDanic
Cases (%) Controls (%) Crude OR (95% Cl)
Non-HisDanic
Cases (%) Controls (%) Crude OR (95% Cl)
Age (years)
30-39 42(13) 54 (14) 1.00 3 2 (9 ) 67(16) 1.00
40-64 213 (68) 249 (66) 0.98 (0.95-1.01) 270 (72) 275 (62) 1.05(1.02-1.07)
65-74 60(19) 76 (20) 1.27(1.11-1.46) 70(19) 99 (22) 0.99 (0.89-1.10)
Age at FLB (years)
Nulliparous 37(12) 29 (8) 1.62 (0.89-2.95) 61 (17) 72(16) 1.21 (0.70-2.07)
<=18 66(21) 88 (23) 1.00 4 2(11) 60(14) 1.00
19-20 65 (21) 92 (24) 1.01 (0.64-1.61) 60(16) 75 (17) 1.07 (0.63-1.82)
21-22 48(15) 61 (16) 1.11 (0.67-1.84) 58(16) 65 (15) 1.15 (0.67-1.98)
23-26 62(19) 66(17) 1.24 (0.76-2.02) 79(21) 84(19) 1.34 (0.80-2.24)
>26 37(12) 43 (12) 1.20 (0.69-2.10) 72 (19) 85 (19) 1.31 (0.78-2.20)
Parity
Nulliparous 36(11) 29 (8) 1.00 60(16) 70(16) 1.00
1 27 (9) 35 (9) 0.65 (0.32-1.34) 61 (16) 55(13) 1.42 (0.84-2.39)
2 64 (20) 94 (25) 0.56(0.31-1.02) 125 (34) 134(30) 1.15 (0.74-1.78)
3 76 (24) 71 (19) 0.97 (0.53-1.78) 63 (17) 98 (22) 0.69 (0.42-1.13)
>3 112(36) 150 (39) 0.70 (0.39-1.25) 63 (17) 84(19) 0.76 (0.46-1.25)
Breast feeding (months)
0 161 (51) 171 (45) 1.00 168 (45) 190(43) 1.00
1-12 104 (33) 126 (34) 0.91 (0.64-1.29) 165 (44) 153 (35) 1.25 (0.92-1.71)
>12 50(16) 79 (21) 0.70 (0.45-1.08) 39(11) 96 (22) 0.49 (0.32-0.77)
oo
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TABLE 1 (continued). Characteristics o f selected covariates o f breast cancer cases and controls by ethnicity, New M exico’s W omen’s Health Study, 1992-1994*.
Risk Factors Hispanic
Cases (%) Controls (%) Crude OR (95% Cl)
Non-Hispanic
Cases (%) Controls (%) Crude OR (95% Cl)
Family History (1st deg)
Yes 40(13) 36(10) 1.35 (0.83-2.21) 60(16) 53 (12) 1.40 (0.92-2.09)
No 275 (87) 343 (90) 1.00 312(84) 388 (88) 1.00
Estrogen use (months)
0 209 (66) 220 (58) 1.36 (0.91-2.03 175 (47) 238 (54) 1.03 (0.70-1.50)
1-48 61 (20) 86 (23) 1.00 87 (23) 97 (22) 1.00
>48 45 (14) 73 (19) 0.90 (0.54-1.50) 110(30) 106 (24) 1.10(0.73-1.65)
OC use (years)
0 136(43) 142 (37) 1.27 (0.82-1.97 144 (39) 154 (35) 0.76 (0.49-1.19
1 57(18) 79 (21) 1.00 78 (21) 67(15) 1.00
2-5 54(17) 75 (20) 0.83 (0.51-1.37) 65 (18) 109 (25) 0.58 (0.37-0.93)
>5 65 (22) 82 (22) 0.94(0.58-1.52) 81 (22) 110(25) 0.68 (0.44-1.06)
Menopausal status
Premenopausal 114(45) 145 (46) 1.00 107 (34) 169(44) 1.00
Post menopausal 138 (55) 172 (54) 1.04 (0.70-1.56) 211 (66) 219(56) 0.89 (0.59-1.33)
Total MET
0-20 84 (27) 56(15) 1.00 83 (22) 76(17) 1.00
21-40 59(19) 51 (13) 0.82 (0.49-1.37) 85 (23) 102 (23) 0.78(0.51-1.21)
41-60 89 (28) 118(31) 0.53 (0.34-0.82) 81 (22) 97 (22) 0.78 (0.50-1.21)
>60 83 (26) 154 (41) 0.37 (0.24-0.57) 121 (33) 165 (38) 0.69 (0.46-1.02)
Height (cm)
<=157.4 93 (30) 136(36) 1.00 31(8) 40 (9) 1.00
157.5-162.5 117(37) 122 (32) 1.39 (0.95-2.03) 73 (20) 103 (23) 0.96 (0.54-1.69)
162.6-167.6 67 (21) 86 (23) 1.04(0.68-1.60) 128 (34) 130 (30) 1.38 (0.80-2.37)
>167.6 38 (12) 35(9) 1.51 (0.88-2.61) 140 (38) 168 (38) 1.09 (0.64-1.87)
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TABLE 1 (continued). Characteristics o f selected covariates o f breast cancer cases and controls by ethnicity, New M exico’s W omen’s Health Study, 1992-1994*.
Risk Factors HisDanic
Cases (%) Controls (%) Crude OR (95% Cl)
Non-Hisr>anic
Cases (%) Controls (%) Crude OR (95% Cl)
BMI at 18 (kg/m2 )
<18.5 63 (20) 75 (20) 1.00 86 (23) 117(27) 1.00
18.5 -<21 127 (40) 166(44) 0.91 (0.60-1.37) 178 (48) 171 (39) 1.36(0.95-1.94)
21 -<25 108 (34) 115 (30) 1.13 (0.73-1.74) 94 (25) 125 (28) 1.06 (0.71-1.58)
>=25 17 (5) 23 (6) 0.90 (0.43-1.86) 14 (4) 28 (6) 0.70 (0.34-1.46)
BMI usual (kg/m2)
<22 64 (20) 102 (27) 1.00 187 (50) 198 (45) 1.00
22 - <25 109 (35) 133 (35) 1.33 (0.89-2.00) 107 (29) 146 (33) 0.74(0.53-1.03)
25 - <30 92 (29) 104 (27) 1.45 (0.94-2.24) 57 (15) 69 (16) 0.81 (0.53-1.24)
>=30 50 (16) 40 (11) 2.11 (1.23-3.63) 21 (6) 28 (6) 0.78 (0.42-1.45)
Weight at 18 (kg)
<=48 87 (28) 111 (29) 1.00 46 (12) 71(16) 1.00
49-53 89 (28) 121 (32) 0.91 (0.61-1.36) 115(31) 111 (25) 1.50 (0.94-2.38)
54-57 62 (20) 61 (16) 1.29 (0.81-2.05) 96 (26) 98 (22) 1.40 (0.87-2.26)
>57 77 (24) 86 (23) 1.14(0.74-1.77) 115(31) 161 (37) 1.09 (0.69-1.73)
Weight change (usual-18) (kg)
<=3 40(13) 78 (20) 1.00 116(31) 143 (32) 1.00
4-7 71 (23) 82 (22) 1.66 (1.00-2.77) 90 (24) 114(26) 0.94 (0.65-1.38)
8-14 67 (21) 101 (27) 1.30(0.79-2.14) 86 (23) 85(19) 1.10 (0.74-1.64)
>14 137 (43) 118(31) 2.27 (1.42-3.64) 80 (22) 99 (23) 0.91 (0.62-1.35)
% weight change^
<5.9 36(12) 69(18) 1.00 115 (31) 133 (30) 1.00
>5.9-14.3 77 (24) 90 (24) 1.71 (1.02-2.87) 94 (25) 127 (29) 0.81 (0.56-1.18)
>14.3-26.1 75 (24) 106 (28) 1.29 (0.77-2.16) 87 (23) 93 (21) 0.98 (0.66-1.46)
>26.1 127(40) 114 (30) 2.23 (1.36-3.67) (76 (21) 88 (20) 0.90 (0.60-1.36)
* Adjusted for age
f [(weight usual - weight at 18)/weight at 18] * 100.
o
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TABLE 2. Adjusted odds ratios and 95% confidence intervals for risk o f breast cancer among Hispanic white women, New Mexico W omen’s Health Study, 1992-1994.
Risk Factor
BMI at 18 (kg/m2)
<18.5
18.5 -<21
21 -< 25
>=25
Premenopausal*
OR 95% Cl
Postmenopausal*
OR 95% Cl
m ! !
OR 95% Cl
1.00
1.66
1.57
1.34
0.76-3.63
0.67-3.66
0.38-4.70
1.00
0.54
1.17
0.47
0.25-1.17
0.54-2.55
0.11-1.95
1.00
0.94
1.16
0.86
0.60-1.45
0.73-1.82
0.39-1.87
p-trend
BMI usual (kg/m2)*
<22
22 - <25
25 - <30
>=30
0.73
1.00
1.86
1.60
1.65
0.92-3.75
0.73-3.49
0.59-4.66
0.51
1.00
1.58
1.71
1.49
0.70-3.59
0.73-3.99
0.56-3.96
0.56
1.00
1.43
1.56
1.94
0.93-2.20
0.98-2.48
1.09-3.44
p-trend
W eight at 18 (kg)
<49
49-53
54-57
>57
0.47
1.00
1.53
1.77
1.35
0.75-3.13
0.73-4.28
0.64-2.87
0.42
1.00
1.12
1.33
1.55
0.53-2.36
0.56-3.17
0.64-3.75
0.03
1.00
0.92
1.36
1.24
0.60-1.40
0.83-2.22
0.79-1.96
-trend 0.47 0.30 0.13
Weight change usual-18 (kg)
<4 1.00
4-7 1.66
8-14 1.23
>14 1.81
0.73-3.74
0.53-2.85
0.81-4.05
1.00
2.21
1.85
2.10
0.81-6.10
0.67-5.09
0.86-5.10
1.00
1.74
1.35
2.19
1.02-2.98
0.79-2.30
1.33-3.62
p-trend 0.36 0.28 0.02
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TABLE 2 (continued). Adjusted odds ratios and 95% confidence intervals for risk o f breast cancer among Hispanic white women, New Mexico W omen’s Health Study,
1992-1994.
Risk Factor Premenonausaf
OR 95% Cl
Postmenonausaf
OR 95% Cl
All§ 1
OR 95% Cl
% weight change*
<5.9 1.00 1.00 1.00
>5.9-14.3 1.61 0.71-3.68 2.63 0.92-7.52 1.82 1.05-3.14
>14.3-26.1 1.14 0.47-2.73 2.09 0.74-5.87 1.29 0.75-2.23
>26.1 1.80 0.78-4.14 1.96 0.76-5.03 2.08 1.23-3.51
p-trend 0.43 0.55 0.07
Significant interaction between all Hispanic and all non-Hispanic women (p=0.04).
* * Significant interaction between all Hispanic and all non-Hispanic women (p=0.03).
t adjusted for age, family history o f breast cancer (1st degree relative), total METS, parity, oral contraceptive use, months o f breast feeding and age at first full-term birth.
* adjusted for age, family history o f breast cancer (1st degree relative), total METS, parity, oral contraceptive use, months o f breast feeding, age at first full-term birth and
estrogen use.
~ adjusted for age, family history o f breast cancer (1st degree relative), total METS, parity, oral contraceptive use, months o f breast feeding, age at first full-term birth,
estrogen use and menopausal status.
1 includes premenopause, post natural menopause, post surgical menopause and post surgical or surgical unknown.
# [(weight usual - weight at 18)/weight at 18] * 100.
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TABLE 3. Adjusted odds ratios and 95% confidence intervals for risk o f breast cancer among non-Hispanic white women, New Mexico W omen’s Health Study,
1992-1994.
Risk Factor Premenopausal*
OR 95% Cl
PostmenoDausaf
OR 95% Cl
All*§
OR 95% Cl
BMI at 18 (kg/m2)
<18.5 1.00 1.00 1.00
18.5 -<21 1.10 0.58-2.08 1.29 0.67-2.50 1.30 0.90-1.89
21 -< 25 0.84 0.41-1.73 0.84 0.41-1.72 1.01 0.67-1.53
>=25 1.48 0.37-5.95 0.51 0.15-1.76 0.62 0.30-1.31
p-trend 0.80 0.15 0.20
BMI usual (kg/m2)
<22 1.00 1.00 1.00
22 - <25 0.83 0.44-1.58 0.95 0.54-1.67 0.80 0.57-1.12
25 - <30 0.62 0.26-1.51 1.07 0.52-2.19 0.85 0.55-1.31
>=30 0.74 0.21-2.64 2.48 0.79-7.81 0.74 0.39-1.41
p-trend 0.32 0.24 0.33
Weight at 18 (kg)
<49 1.00 1.00 1.00
49-53 0.60 0.25-1.45 1.76 0.77-3.99 1.46 0.90-2.37
54-57 1.15 0.48-2.76 1.19 0.52-2.71 1.37 0.84-2.25
>57 0.59 0.25-1.37 1.02 0.46-2.26 0.95 0.59-1.53
p-trend 0.70 0.43 0.34
W eight change usual-18 (kg)
<4 1.00 1.00 1.00
4-7 0.86 0.44-1.66 1.32 0.66-2.66 0.96 0.65-1.41
8-14 1.28 0.63-2.60 1.29 0.64-2.60 1.17 0.78-1.77
>14 0.72 0.33-1.60 2.33 1.14-4.77 1.00 0.66-1.51
p-trend 0.86 0.04 0.69
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TABLE 3 (continued). Adjusted odds ratios and 95% confidence intervals for risk o f breast cancer among non-Hispanic white women, New Mexico W omen’s Health
Study, 1992-1994.
Risk Factor PremenoDausal*
OR 95% Cl
Postmenonausaf
OR 95% Cl
All* 8
OR 95% Cl
% weight change^1
<5.9 1.00 1.00 1.00
>5.9-14.3 0.55 0.28-1.09 1.16 0.59-2.30 0.79 0.54-1.17
>14.3-26.1 1.08 0.53-2.19 0.93 0.46-1.86 0.98 0.65-1.48
>26.1 0.60 0.25-1.46 2.49 1.18-5.24 1.00 0.65-1.53
p-trend 0.85 0.07 0.69
* adjusted for age, family history o f breast cancer (1st degree relative), total METS, parity, oral contraceptive use, months o f breast feeding, age at first full-term birth
and estrogen use.
* adjusted for age, family history o f breast cancer (1st degree relative), total METS, parity, oral contraceptive use, months o f breast feeding, age at first full-term birth,
estrogen use and menopausal status.
8 includes pre-menopause, post natural menopause, post surgical menopause and post surgical or surgical unknown.
1 1 [(weight usual - weight at 18)/weight at 18] * 100.
15
The effect of usual BMI and weight change were significantly larger among Hispanic
than non-Hispanic women (p=0.04 and p=0.03, respectively).
Further adjustment for weight at age 18 did not substantially alter the association
between weight change and breast cancer risk in each ethnic group (table 4). Hispanic
women who gained more than 14 kilograms had a greater than two-fold increase in risk
compared to women who gained less than 4 kilograms. Stratified odds ratios were larger
in postmenopausal women than premenopausal women but were not statistically
significantly different. In non-Hispanic white women, the more than two-fold increase in
risk in postmenopausal women was apparent after adjustment for weight at 18. In
Hispanic women, the effects of usual BMI on breast cancer risk were slightly reduced
after adjustment for weight at age 18 (OR: 1.89, 95% Cl: 1.02, 3.50).
To investigate the effects of weight gain on lean and non-lean women, we
performed stratified analysis defining lean as having a BMI at 18 less than 22 (table 5).
The overall effects of weight gain were apparent in lean Hispanic women, but not in non-
Hispanic white women. When the analysis was restricted to postmenopausal women,
non-Hispanic white women in the lean group who gained greater than 14 kg, had an odds
ratio of 2.2 (95% Cl: 0.93, 5.30) and those in the non-lean group had an odds ratio of 4.5
(95% Cl: 0.80, 24.2).
To determine whether the effects of weight gain differed by the hormone receptor
status of the tumor, we performed stratified analyses by ER/PR status (table 6). Hispanic
women with ER+ /PR+ tumors had an increased risk of breast cancer with weight gain.
Among postmenopausal non-Hispanic white women with ER+ /PR+ tumors in the highest
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
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TABLE 4. Adjusted odds ratios and 95% confidence intervals for risk of breast cancer among Hispanic and non-Hispanic white
women stratified by menopausal status, New Mexico Women’s Health Study, 1992-1994.
Risk Factor Hispanic White Women
PremenoDausaf PostmenoDausaf A1I§ 1
OR 95% Cl OR 95% Cl OR 95% Cl
Weight change usual-18 (kg)*
<4 1.00 1.00 1.00
4-7 1.65 0.72-3.81 2.48 0.89-6.93 1.84 1.07-3.17
8-14 1.28 0.54-3.05 2.04 0.73-5.68 1.46 0.85-2.52
>14 1.87 0.82-4.24 2.46 0.98-6.17 2.41 1.45-4.03
p-trend 0.27 0.14 0.01
Non-HisDanic White Women
Weight change usual-18 (kg)
<4 1.00 1.00 1.00
4-7 0.85 0.43-1.67 1.34 0.66-2.74 0.91 0.61-1.36
8-14 1.17 0.56-2.43 1.33 0.63-2.77 1.14 0.74-1.73
>14 0.71 0.32-1.60 2.27 1.09-4.73 0.97 0.64-1.48
p-trend 0.72 0.04 0.80
Significant interaction between all Hispanic and all non-Hispanic women (p=0.02).
* adjusted for age, family history o f breast cancer (1st degree relative), total METS, parity, oral contraceptive use, months o f breast feeding, age at first full-term birth and
weight at age 18.
; adjusted for age, family history o f breast cancer (1st degree relative), total METS, parity, oral contraceptive use, months o f breast feeding, age at first full-term birth,
weight at age 18 and estrogen use.
8 adjusted for age, family history o f breast cancer (1st degree relative), total METS, parity, oral contraceptive use, months of breast feeding, age at first full-term birth,
weight at age 18, estrogen use and menopausal status.
1 includes pre-menopause, post natural menopause, post surgical menopause and post surgical or surgical unknown.
O n
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TABLE 5. Adjusted odds ratios and 95% confidence intervals for risk of breast cancer among Hispanic and non-Hispanic white women stratified by BMI
(kg/m2 ) at 18 years of age, New Mexico Women’s Health Study, 1992-1994*.
Risk Factor Hispanic
BMI < 22
OR 95% Cl
BMI >= 22
OR 95% Cl
Non-Hispanic
BMI < 22
OR 95% Cl
BMI >= 22
OR 95% Cl
Weight change— usual-18 (kg)
<4 1.00 1.00 1.00 1.00
4-7 2.00 1.01-3.94 1.23 0.41-3.66 0.95 0.61-1.49 0.90 0.25-3.20
8-14 1.69 0.86-3.34 0.82 0.24-2.84 1.16 0.73-1.84 0.40 0.09-1.73
>14 2.53 1.33-4.83 1.30 0.45-3.71 0.97 0.60-1.57 0.58 0.20-1.66
p-trend 0.03 0.82 0.81 0.21
* adjusted for age, family history of breast cancer (1st degree relative), total METS, parity, oral contraceptive use, months of breast feeding and age at first
full-term birth, estrogen use and menopausal status.
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TABLE 6. Adjusted odds ratios and 95% confidence intervals for risk o f breast cancer among Hispanic and
non-Hispanic white women stratified by ER/PR status, New Mexico Women’s Health Study, 1992-1994*.
Risk Factor Hispanic Non-Hispanic
ER+ /PR+ ER/PR’ e r + /p r + ER7PR"
OR 95% Cl OR 95% Cl OR 95% Cl OR 95% Cl
Weight change—usual-18 (kg)
<4 1.00 1.00 1.00 1.00
4-7 2.02 0.92-4.43 1.43 0.57-3.61 0.99 0.58-1.68 0.58 0.25-1.34
8-14 1.53 0.70-3.38 1.56 0.63-3.88 1.00 0.57-1.75 1.22 0.53-2.82
>14 3.04 1.47-6.26 1.73 0.71-4.25 1.05 0.60-1.84 0.93 0.42-2.05
p-trend 0.01 0.27 0.87 0.67
* adjusted for age, family history of breast cancer (1st degree relative), total METS, parity, oral contraceptive use, months of breast feeding,
age at first full-term birth, months of estrogen use, menopausal status and weight at 18 years of age.
oo
19
quartile compared to the lowest quartile of weight gain, there was nearly a three-fold risk
of breast cancer (OR: 2.97; 95% Cl: 1.13, 7.77).
To evaluate the effect of estrogen replacement therapy (ERT) on the relationship
between weight gain and breast cancer risk, stratified analysis by groups of users and
non-users was conducted (table 7). An increased risk of breast cancer was found with
weight gain in non-users. Due to insufficient numbers of Hispanic ERT users, we were
unable to examine the effect of ERT separately in Hispanic and non-Hispanic women.
DISCUSSION
Numerous studies have examined the relationship of body size and breast cancer
risk among predominantly non-Hispanic white populations and concluded that there is a
heightened risk of breast cancer associated with weight (van den Brandt et al., 2000),
weight change (Huang et al., 1997) and obesity (Ballard-Barbash et al., 1990; Bames-
Josiah et al., 1995; Cold et al., 1998; Hall et al., 1999; La Vecchia et al., 1997; Maehle &
Tretli, 1996; Swanson et al., 1989; van den Brandt et al., 2000). Early studies suggested
that overweight women experienced an increased risk of developing breast cancer.
However, this relationship appears to differ by menopausal status (van den Brandt et al.,
2000). Among predominantly white populations, premenopausal overweight or obese
women have lower risk for breast cancer, while their postmenopausal counterparts have
an increased risk (Ballard-Barbash, 1994; Hall et al., 2000; La Vecchia et al., 1997;
London et al., 1989; Peacock et al., 1999; Stoll, 1998; Swanson et al., 1989; van den
Brandt et al., 2000; Vatten & Kvinnsland, 1992). Few studies have examined these
relationships among Hispanic women.
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TABLE 7. Adjusted odds ratios and 95% confidence intervals for risk of breast cancer among postmenopausal Hispanic
and non-Hispanic white women stratified by estrogen use, New Mexico Women’s Health Study, 1992-1994*.
Risk Factor Hispanic & non-Hispanic
ERT: No ERT: Yes
OR 95% Cl OR 95% Cl
Weight change [usual-18 (kg)]
<4 1.00 1.00
4-<8 2.62 1.04-6.59 1.59 0.74-3.38
8-14 1.26 0.49-3.27 1.65 0.76-3.58
>14 2.91 1.33-6.38 1.71 0.78-3.76
trend 0.05 0.26
* adjusted for age, family history of breast cancer (1s t degree relative), total METS, parity, oral contraception use, months of breast feeding,
age at first full-term birth and weight at 18 years of age.
to
o
21
We found that usual BMI was associated with increased risk for breast cancer in
Hispanic white women. A nearly two-fold risk of breast cancer was evident in obese
Hispanic women. In contrast to the present study, Mayberry et al. (1994) found no
increase in breast cancer risk with adult BMI in Hispanic women. We did not observe a
difference in the risks associated with obesity in pre or postmenopausal Hispanic women.
In contrast, our results for non-Hispanic white women are consistent with the majority
findings for non-Hispanic white populations, suggesting a lower risk among obese
premenopausal non-Hispanics and an increased risk among obese postmenopausal non-
Hispanic white women. The reasons for the apparent ethnic difference in patterns in pre
and postmenopausal women are uncertain, but may indicate distinct mechanisms for the
effects among premenopausal women.
Adult weight gain may be at least as important a determinant of breast cancer risk
as obesity. In a study composed mostly of white women, there was greater than a two
fold increase in breast cancer risk in women in the highest tertile of weight gain
compared to baseline, independent of adult body mass (Ballard-Barbash et al., 1990).
Ziegler et al. (1996), found that the recency of weight gain (between the current and
proceeding decades of life) was a strong predictor o f breast cancer risk. Our findings
indicate that adult weight gain is an important breast cancer risk factor for Hispanic
women. In non-Hispanic women, an increase risk with weight gain was apparent only
among postmenopausal women. Overall, Hispanic women maintain a substantial risk
due to weight gain that was statistically significantly larger than the risk among non-
Hispanic white women. We lack data to directly investigate the explanation for these
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22
ethnic differences, but suggest that the findings are consistent with a different mix of
causal pathways for the effects of weight gain on breast cancer risk in Hispanic and non-
Hispanic white women.
The association o f weight gain with breast cancer risk was stronger in Hispanic
women who were lean at age 18 compared to Hispanic women who were non-lean,
suggesting that new onset obesity may be an important aspect of the risk equation for
Hispanic women. No studies that address this point have been reported for Hispanics.
We found limited evidence for an effect of weight gain in both lean or non-lean
postmenopausal non-Hispanic white women. Studies among other predominately non-
Hispanic white populations report consistent increases in risk with weight gain,
independent of early life BMI. Ballard-Barbash et al. (1990), found an increase in breast
cancer risk with weight gain regardless of BMI stratification. In the Iowa Women’s
Health Study cohort, Bames-Josiah et al. (1995) found that an increase in weight gain
conferred increased risk for breast cancer independent of BMI at age 18.
Consistent with findings by Enger et al. (2000), we found an increase in breast
cancer risk with weight gain largely among Hispanic and postmenopausal non-Hispanic
women with ER+ /PR+ tumors. These findings provide further evidence for a hormonal
mechanism for the effect of weight gain on breast cancer risk (Hankinson et al., 1998;
Thomas et al., 1997). Future investigation of the ethnic and menopausal differences in
effects of weight gain among women with ER+/PR+ tumors may help clarify the role of
sex steroids and metabolic hormones such as IGF-1 in the development of breast cancer.
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23
We also found an increased risk of breast cancer among women who never used estrogen
and who gained the most weight. Our lack of sample size prevented us from stratifying
by ethnicity, but nonetheless, our findings are consistent with that of Huang et al. (1997)
who reported that the increased risk of breast cancer with weight gain appeared to be
reduced among HRT users. The lack o f association between weight gain and breast
cancer risk among HRT users may be related to the increase in exogenous estrogen from
HRT intake that exceeds the level of endogenous estrogens produced by adipose tissue
(Huang et al., 1997).
The mechanisms that result in higher risk with obesity and weight gain have yet to
be clarified. The effects of weight change and obesity may be mediated directly through
effects on ovarian and peptide hormone production, or indirectly through changes in
energy intake and adiposity, which also modulate lifetime exposure to steroid and peptide
hormones (Kirschner et al., 1990). The association of weight gain with breast cancer risk,
independent of BMI or weight at 18, and the effect with non-ERT users, is consistent
with this mechanism. Weight gain and obesity are also associated with insulin resistance,
which may produce metabolic syndromes such as hyperinsulinemia in susceptible groups
(Colditz et al., 1995; Jemstrom & Barrett-Connor, 1999). Based on these considerations,
weight gain and obesity results in higher cumulative lifetime exposure to estrogens as
well as other hormonal breast epithelial cell mitogens such as IGF-1 and insulin that
increases breast cancer risk (Hankinson et al., 1998; Kaaks, 1996; Kazer, 1995; Oh et al.,
1993; Osborne et al., 1978; Thomas et al., 1997). Synergism between sex steroids and
IGF-I has been shown to stimulate proliferative activity in mammary cells (Clarke et al.,
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24
1997; Daws et al., 1996; Stewart et al., 1990). The combined effects of increased insulin
and estrogen exposure may underlie the increased risk with obesity and weight gain.
Because Hispanics appear to be a susceptible group for obesity (Mokdad et al., 1999) and
have a high prevalence of insulin resistance, hyperinsulinemia and subsequent overt
diabetes mellitus (Haffner, 1998; Lindeman et al., 1998; Tucker et al., 2000), the effect of
weight gain on breast cancer risk may be particularly important in this ethnic group.
The ethnic differences in pre and postmenopausal patterns of breast cancer risk
from weight gain may also be related to the high prevalence of insulin resistance and
hyperinsulinemia among Hispanic populations. In premenopausal women, obesity has
been shown to decrease levels of estradiol and progesterone due to increased anovulation
(Key & Pike, 1988; Pike et al., 1993), which in turn lowers breast cancer risk. However,
increased insulin and IGF-1 levels, especially among highly susceptible Hispanic women,
may counterbalance the lower estrogen and progesterone levels in premenopausal obese
women.
A number of limitations affect interpretation of our results. Response rates were
reasonably high for both Hispanic and non-Hispanic subjects, indicating that the
opportunity for selection bias is likely to be small. Recall bias may arise as subjects were
asked to recall their weight at age 18 and “usual” weight. Several studies reported that
there is a tendency of white women to underestimate past weights and body size,
especially among obese women (Lichtman et al., 1992; McTieman, 2000; Munoz et al.,
1996; Perry et al., 1995). Further, it may be more culturally acceptable for Hispanic
women to be overweight and thus report accurately their weight (Felts et al., 1996).
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25
However, there is no information to suggest that recalled weight or height varies by case-
control status for either Hispanics or non-Hispanic white women. This pattern of non-
differential recall may explain a portion of the ethnic differences in risk by producing
greater attenuation of breast cancer risk for non-Hispanic white than Hispanic women;
when in reality, their risk may be comparable.
In summary, weight change and obesity are risk factors for breast cancer in pre-
and postmenopausal Hispanic and postmenopausal non-Hispanic white women. Recent
data indicate that approximately one quarter of Hispanic women in the U.S. are
considered obese (BMI >=30) compared to only 16 percent of non-Hispanic white
women (Mokdad et al., 1999). Furthermore, the prevalence of obesity in Hispanic
women has increased 80 percent from 1991 to 1998; this represents the largest increase
among all groups in the US (Mokdad et al., 1999). Because the prevalence of adult
obesity is high and continues to rise among Hispanic women, adult weight gain may be
an important modifiable target for the primary prevention of breast cancer among
Hispanic populations. Culturally tailored interventions are needed to halt the steady
increase in obesity among US women, thereby reducing the occurrence of breast cancer
and other obesity-related chronic diseases.
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26
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Creator Wenten, Made Rai (author)

Core Title Associations of weight, weight change and body mass with breast cancer risk in Hispanic and non-Hispanic white women

School Graduate School

Degree Master of Science

Degree Program Applied Biometry

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag biology, biostatistics,health sciences, oncology,health sciences, public health,OAI-PMH Harvest

Language English

Contributor Digitized by ProQuest (provenance)

Advisor Gilliland, Frank (committee chair), Bernstein, Leslie (committee member), Unger, Jennifer (committee member)

Permanent Link (DOI) https://doi.org/10.25549/usctheses-c16-40710

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Legacy Identifier 1407931.pdf

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Rights Wenten, Made Rai

Type texts

Source University of Southern California (contributing entity), University of Southern California Dissertations and Theses (collection)

Access Conditions The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the au...

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