Description of the Pooling Project and Component Studies
The Pooling Project of Prospective Studies of Diet and Cancer (Pooling
Project) is an international consortium of cohort studies with the goal
of analyzing diet and cancer associations using standardized criteria
across studies. This project is an example of a meta-analysis of individual
data as opposed to a meta-analysis of the published literature. The studies
in the Pooling Project were initiated independently and have either completed
follow-up of their participants or are ongoing.
The purposes of the Pooling Project are multi-fold. We evaluate whether
diet and cancer associations are consistent across cohort studies comprised
of different populations with different dietary habits. For each association,
we generate summary estimates which have greater precision than any of
the individual studies due to the larger sample size. We also examine
whether associations differ for specific population subgroups (ex: between
men and women; among never, past and current smokers; between lean and
overweight individuals) or for different histologic types or subsites
of specific cancers.
To maximize the quality and comparability of the studies in the Pooling
Project, we formulated several inclusion criteria a priori. Each study
is a published cohort study which 1) used a comprehensive dietary assessment
method to measure usual diet, 2) assessed the validity of their dietary
assessment instrument or a closely related instrument, and 3) included
a minimum number of cases of the specific cancer being examined. Additional
inclusion criteria also have been made for specific cancers. Currently,
28 studies are included in the Pooling Project. However, as we become
aware of new studies meeting the inclusion criteria, those studies are
invited to join the Pooling Project.
A brief description of each cohort study included in the Pooling Project
is given below.
The Adventist Health Study, AHS
The Adventist Health Study was assembled in 1976 when 13,857 male and
20,341 female California Seventh-day Adventists aged 25 years and older
completed a detailed lifestyle questionnaire. The participants for this
cohort were identified from a census questionnaire that was mailed to
all Seventh-day Adventist households in California in 1974. Participants
in the study were followed for cancer incidence though 1982.
Beta-Carotene Prevention Study, ATBC
The Alpha-Tocopherol Beta-Carotene Prevention Study is a randomized, double-blind,
placebo-controlled clinical trial that was designed to evaluate whether
daily supplements of alpha-tocopherol and/or beta-carotene would reduce
the risk of lung cancer and other types of cancer. The study consists
of 29,133 male smokers who resided in southwestern Finland and were 50-69
years at enrollment in 1985-1988.
NIH-AARP Diet and Health Study, AARP
The NIH-AARP Diet and Health Study was initiated in 1995 to study relationships
between diet and cancer. The study population consisted of 340,148 men
and 227,021 women, who were members of the American Association of Retired
Persons in 6 states and 2 metropolitan areas in the U.S., and were aged
50 to 71 years at the begiinning of the study. Participants completed
a mailed questionnaire that included the diet history, demographic characteristics
and other potential cancer risk factors.
and Retinol Efficacy Trial, CARET
The Beta-Carotene and Retinol Efficacy Trial was a multicenter randomized,
double-blind placebo controlled chemoprevention trial that tested whether
daily supplementation with 30 mg beta-carotene plus 25,000 IU retinyl
palmitate would reduce lung cancer incidence in a high risk population.
The trial was conducted among 18,314 heavy smokers, former heavy smokers
and persons with occupational exposure to asbestos. All participants completed
a food frequency questionnaire at baseline and every two years thereafter.
The Black Women's
Health Study, BWHS
The Black Women's Health Study is the largest medical study of
African-American women to date. This ongoing study was designed to
examine risk factors for cancer and other serious illnesses in
African-American women. The cohort was established in 1995 when 59,000
black women between the ages of 21 and 69 years completed mailed
questionnaires. The baseline questionnaire collected information on
demographic factors, medical and reproductive history, use of oral
contraceptives and other medications, physical activity, smoking,
alcohol, diet, and other factors.
Breast Cancer Detection Demonstration Project Follow-up Cohort,
The Breast Cancer Detection Demonstration Project Follow-up Cohort consists
of a subset of participants (n = 64182) who had participated in a national
mammography screening program conducted from 1973-1981 at 29 U.S. centers
(total number who participated in the screening program was 283,222).
The dietary component of the study began in 1987-1989 when 54,442 participants
completed a self-administered food frequency questionnaire. Follow-up
for cancer incidence is ongoing.
Teachers Study, CTS
The California Teachers Study (CTS), started in 1995, is an ongoing prospective study of 133,479 current and former public school teachers
and other school professionals who participate in the California State
Teachers Retirement System (STRS). The baseline questionnaire focused
on potential breast cancer risk factors including a comprehensive assessment
of diet, alcohol use, use of hormone therapy and oral contraceptives,
physical activity, menstrual and reproductive factors, family history
of cancer and other diseases, exposure to electromagnetic fields, and
Against Cancer and Heart Disease, CLUE II
In 1989, the Campaign against Cancer and Stroke (CLUE II) was conducted
in Washington County, MD. Using mobile trailers, the study was designed
to collect blood samples from as many adults as possible to provide specimens
for a serum bank. A brief medical history and baseline questionnaire was
administered to 32,898 persons at the time of blood collection. About
one-third of the adult county population participated with additional
participants from surrounding communities. Participants were given a food
frequency questionnaire to complete at home and were asked to return it.
Canadian National Breast Screening Study, CNBSS
The Canadian National Breast Screening Study is an ongoing prospective
study of 56,837 women living in 12 Canadian cities who had participated
in a randomized controlled trial of mammography (n = 89,835 women) and
had returned a self-administered food frequency questionnaire. The women
were 40-59 years at enrollment between 1982 and 1987.
Prevention Study II Nutrition Cohort, CPS II Nutrition Cohort
The Cancer Prevention Study II Nutrition Cohort is an ongoing cohort study
comprised of a subset of participants in the Cancer Prevention Study II,
a cohort study of approximately 1.2 million men and women that began in
1982. The Cancer Prevention Study II Nutrition Cohort consists of 86,406
men and 97,788 women who completed a self-administered questionnaire on
diet, lifestyle factors, and medical history in 1992. Participants were
50-74 years old at the beginning of the study.
Cohort of Swedish Men, COSM
The Cohort of Swedish Men began in 1997 when 48,850 men residing in two
counties in central Sweden (Västmanland and Örebro) completed
a mailed questionnaire. The men were born between 1918 and 1952. They
completed a comprehensive questionnaire on lifestyle factors, diet, and
Professionals Follow-up Study, HPFS
The Health Professionals Follow-up Study is an ongoing cohort study that
was initiated in 1986 and consists of 51,529 male dentists, pharmacists,
optometrists, osteopaths, podiatrists, and veterinarians aged 40-75 years
at the beginning of the study.
Women’s Health Study, IWHS
The Iowa Women’s Health Study is an ongoing prospective study of
41,836 postmenopausal women who were 55-69 years at enrollment in 1986.
Participants in the study consist of women initially identified from the
1985 Iowa driver’s license list who completed a mailed self-administered
Public Health Center-Based Study Cohort, JPHC
The Japan Public Health Center-Based Study Cohort is an ongoing
cohort study that combined Cohort I and II, which began in 1990 and 1993,
respectively. The study consists of 45,452 men and 49,924 women who were
aged 40 to 69 years at enrollment, and were identified using residence
registries maintained by local governments in Japan. Each participant
returned self-administered questionnaires that included dietary habits,
previous medical history and other lifestyle factors.
Melbourne Collaborative Cohort Study, MCCS
The Melbourne Collaborative Cohort Study is an ongoing cohort study of
24,479 women and 17,049 men aged 27-75 years (99.3% aged 40-69) who resided
in Melbourne Australia between 1990 and 1994. Participants were recruited
from electoral rolls, advertisements, and community announcements with
oversampling of Italian and Greek migrants (30% of participants). Detailed
information on lifestyle factors as well as blood samples and direct physical
measurements was collected from all participants.
Multiethnic Cohort, MEC
The Multiethnic/Minority Cohort Study was established in Hawaii and Los
Angeles in 1993-1996 to explore the relationship of diet and other lifestyle
factors to cancer. The cohort is comprised of more than 215,000 men and
women primarily of African-American, Japanese, Latino, Native Hawaiian,
and Caucasian origin, and is unique among existing cohort studies in its
ethnic diversity and representation of minority populations. At entry
to the cohort study, each participant completed a 26-page mail questionnaire
that included an extensive quantitative diet history, as well as other
demographic, medical, and lifestyle information.
The Netherlands Cohort Study, NLCS
The Netherlands Cohort Study on diet and cancer is an ongoing cohort study
that was initiated in 1986. The study consists of 58,279 men and 62,573
women who were 55-69 years old at the beginning of the study and were
identified from 204 Dutch computerized municipal population registries.
New York State Cohort, NYSC
The New York State Cohort is a prospective study of 32,689 men and 25,279
women that was assembled in 1980 by sending a letter of invitation and
questionnaire to all women and a sample of the men in New York State who
had the same New York State telephone number for at least 18 years. Participants
in this study were followed for cancer incidence though 1987.
New York University Women’s
Health Study, NYUWHS
The New York University Women’s Health Study was assembled between
1985 and 1991. It consists of 14,291 women who were 35-65 years at the
beginning of the study, attended a breast cancer screening clinic in Manhattan,
New York City, and had not used hormonal medications or been pregnant
during the previous six months. Follow-up of the participants is ongoing.
Nurses’ Health Study, NHS
The Nurses’ Health Study is an ongoing cohort study of 121,7000
U.S. female nurses who were residents in 11 large U.S. states and were
30-55 years old at enrollment in 1976. The nutritional component of the
Nurses’ Health Study began in 1980; 89,538 women form the diet cohort.
Nurses’ Health Study II, NHSII
The Nurses's Health Study II is an ongoing cohort study of 116,671 female
registered nurses who were aged 25 to 42 years and living in 14 U.S. states
at enrollment in 1989. The nutritional component of the Nurses' Health
Study began in 1990; 97,809 women form the diet cohort.
Prospective Study on Hormones, Diet and Breast Cancer, ORDET
ORDET is a prospective study of women who were living in Varese Province,
northern Italy and were 35-69 years at the beginning of the study. Participants
were recruited in 1987-1992 from the general population via radio, television
and newspaper advertising and from women attending breast cancer prevention
Cancer Prevention Trial, PCPT
The Prostate Cancer Prevention Trial is a Phase III, randomized, double-blind,
placebo-controlled trial of finasteride for the prevention
of prostate cancer. A total of 18,882 essentially healthy men, aged 55
and older, were enrolled between 1993 and 1996 at 219 centers in the
United States and Canada. The 9,598 men that were randomized to the
placebo arm are included in the Pooling Project.
Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial, PLCO
The Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial, or
PLCO, is a multicenter, two-armed randomized controlled trial that was
designed to evaluate whether PSA (men only), digital rectal exam (men
only), flexible sigmoidoscopy, chest X-ray, CA-125 blood test (women
only), transvaginal ultrasound (women only) screening tests reduce
deaths from prostate, lung, colorectal and ovarian cancer.
are to be followed for at least 13 years from randomization for cancer
and death ascertainment. The trial recruited 154,938 men and women age
55 to 74 years, from 1992-2001.
The Shanghai Women's Health Study, SWHS
The Shanghai Women's Health Study is an ongoing prospective cohort study
that was established in 1997-2000. This study consists of 74,942 women
who lived in 7 urban communities of Shanghai and completed the baseline
interviews at participants' homes.
Mammography Cohort, SMC
The Sweden Mammography Cohort is an ongoing study of 61,471 women living
in two counties in central Sweden who participated in a mammographic screening
program between 1987 and 1990. At enrollment, women were 30-74 years old.
Women’s Health Study, WHS
The Women’s Health Study is an ongoing randomized double-blind,
placebo controlled clinical trial of 39,876 female health professionals
age 45 years or older. The study, initiated in 1992-1995, used a 2x2x2
factorial design to randomize participants to aspirin or aspirin placebo,
vitamin E or vitamin E placebo, and beta-carotene or beta-carotene placebo
(this component was terminated in January 1996). Of the women in the trial,
39,345 completed a food frequency questionnaire during the run-in phase
prior to randomization.
Lifestyle and Health, WLHS
In 1991 approximately 50,000 women in Sweden aged 30-49 completed a mailed
questionnaire. Detailed information was collected on a wide range of lifestyle
factors with a focus on oral contraceptive use, diet, UV light exposure,
reproductive factors and familial occurrence of cancer.