The Sleep Heart Health Study is a multi-center cohort study that has been implemented by the National Heart,
Lung, and Blood Institute to determine cardiovascular and other consequences of sleep-disordered breathing. The study
was motivated by the increasing recognition of the frequent occurrence of sleep-disordered breathing in the general
population and mounting evidence that sleep-disordered breathing may increase risk for cardiovascular diseases,
including coronary artery disease and stroke, and for hypertension and may reduce quality of life generally. Many
clinical questions remain unanswered concerning sleep-disordered breathing as well: for example, we lack insight as to
the point in the natural history of the disorder when intervention is warranted; and, while effective treatments for
some forms of sleep-disordered breathing have been developed, information is still needed on who is at risk from
sleep-disordered breathing so that these treatments can be applied in a cost-effective manner. Such questions can
best be addressed by longitudinal epidemiologic investigations that are conducted in a population context. The Sleep
Heart Health Study, implemented to obtain these needed data, will test whether sleep-related breathing is associated
with an increased risk of coronary heart disease, stroke, all cause mortality, and hypertension.
The consequences of sleep-disordered breathing might best be addressed by enrolling a sufficiently large cohort of
early middle-aged men and women who have not yet experienced cardiovascular disease and then prospectively following
the cohort for cardiovascular and other events, having assessed risk factors and presence of sleep-disordered breathing
on enrollment. However, this approach would be costly and currently needed information on the consequences of
sleep-disordered breathing would not be available for many years. For efficiency and practicability, the Sleep Heart
Health Study draws on a resource of existing, well-characterized, and established epidemiologic cohorts. The design
adds assessment of sleep to data collection in ongoing cohort studies including the Atherosclerosis Risk in Communities
(ARIC) Study sites in Washington County, Maryland, and Minneapolis Minnesota; the Cardiovascular Health Study (CHS)
sites in Sacramento, California, Washington County, Maryland, and Pittsburgh, Pennsylvania; the Framingham Offspring
and Omni cohorts in Framingham, Massachusetts; the Health and Environment and Tucson Epidemiologic Study cohorts in
Tucson, Arizona; the Strong Heart Study sites in Arizona, Oklahoma, and South Dakota; and New York City populations
assessed in studies of hypertension. Each of these populations is already established; some information on risk factors
for cardiovascular disease has already been collected in each of the cohorts, and all but the Tucson and New York
studies include ongoing and standardized monitoring for the occurrence of cardiovascular events.
The Sleep Heart Health Study will add in-home polysomnography to the data collected in each of the parent studies.
Using the Compumedics PS polysomnograph, a single over-night polysomnogram was obtained at home for
approximately 6,400 persons; the montage includes oximetry, heart rate, chest wall and abdominal movement, nasal/oral
airflow, body position, EEG, EOG, and chin EMG. In-home monitoring can now be conducted feasibly, and this montage
provides data on the occurrence of sleep-disordered breathing and on arousals. The sleep data was collected during the
second and third years of the initial five-year funding of the Sleep Heart Health Study, and more sleep data will be
continuously collected in the seventh and eighth years.
Approximately 1,000 participants will be enrolled from the parent cohorts of each of the seven Investigative Centers.
Recruitment approaches will be tailored for the requirements of the specific Field Centers. All participants will be at
least 40 years of age and all minority members of each of the parent cohorts will be recruited. Individuals younger than
age 65 years will be selected with stratification by history of snoring, as assessed by a standardized questionnaire to
be administered to all members of the parent cohorts; the sampling fraction for snorers will be greater than for
non-snorers in order to increase the prevalence of sleep-disordered breathing. For persons older than age 65 years,
snoring history does not predict the presence of sleep-disordered breathing and participants will be selected without
reference to snoring history. There is no upper age limit for participants and the presence of prevalent cardiovascular
disease will not exclude potential participants. The projected sample size of about 6,400 participants will provide
sufficient power for some of the primary hypotheses by the end of Year 4, but further follow-up will be needed to have
sufficient power for all primary and secondary hypotheses, both overall and within subgroups of a priori interest.
The extent of information available on key cardiovascular risk factors varies among the parent cohorts. Based on
review by the Comparability Subcommittee, some additional data will be collected on covariates at enrollment into the
Sleep Heart Health Study. However, the parent studies will be the principal source of information on risk factors for
cardiovascular disease in the participants. The cardiovascular outcomes for all sites include hospitalized acute
myocardial infarction, nonfatal coronary heart disease, stroke, and death due to cardiovascular or cerebrovascular
disease. Additionally, change in blood pressure and diagnosis of hypertension will be considered and all participants
will complete a standardized instrument on quality of life. The cardiovascular outcomes will be adjudicated by methods
already in place for the ARIC, CHS, SHS, and Framingham Field Centers and by the CHS process for the New York and Tucson
Field Centers. Ancillary studies will address other outcomes, such as cognitive functioning, that cannot be considered
in the full Sleep Heart Health Study cohort.
Each participant in the parent studies will be asked to complete the Sleep Habits Questionnaire which covers usual
sleep pattern, snoring, and sleepiness. Combining these responses with the ongoing outcome assessment of the full parent
cohorts will permit the testing of hypotheses concerning the consequences of self-reported snoring and sleepiness in a
combined sample of approximately 20,000 persons.
Although the Sleep Heart Health Study is a prospective cohort study, the cross-sectional findings will provide new
information on patterns of sleep and sleep-disordered breathing in the general population. Consequently, initial
analyses will be descriptive and also address cross-sectional associations of sleep-disordered breathing with prevalent
cardiovascular disease and quality of life and with risk factors for cardiovascular disease. Longitudinal analyses will
address sleep-disordered breathing as a predictor of cardiovascular outcomes and change in blood pressure.
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Last Updated:
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12 Oct 2007
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