Study design: Participants and exclusions
Latinos currently make up 17.8%, or 57.5 million, of the U.S. population, and this group is expected to double within the next 4 decades, the investigators wrote. A few prior studies on the roles of sleep disorders in the cardiometabolic health of Latinos, though suggestive, were limited by cross-sectional designs, relatively small samples, and underrepresentation of various Latino heritage groups.
The investigators on this new study worked with data from the federal Hispanic Community Health Study/Study of Latinos (HCHS/SOL) in which more than 16,000 people participated.
This multiyear federal study drew people who self-identified with different heritage groups, including Cuban, Dominican, Mexican, Central American, South American, and Puerto Rican. Participants initially aged 18-74 years underwent a first round of exams and assessments between 2008 and 2011 to determine what risk factors they had at the start of the study. In the second phase, which took place from 2013 to 2018, participants had a second set of exams. The National Heart, Lung, and Blood Institute and the National Institute of Diabetes and Digestive and Kidney Diseases funded the HCHS/SOL.
The investigators initially had a potential data pool of 11,623 participants in the HCHS/SOL. About 1 of 8 in this group, or 1,424 participants (12.3%), did not undergo a sleep study or did not have sufficient sleep data for analyses. Another 93 (0.8%) participants were excluded for missing data on covariates.
For incident hypertension analyses, participants who had prevalent hypertension at the first screening in the HCHS/SOL (n = 3,139) or had missing data on hypertension (n = 2) were excluded. That resulted in an analytic sample of 6,965 for hypertension questions.
For incident diabetes analyses, participants who had prevalent diabetes at the first screening (n = 2,062) or had missing data on diabetes (n = 21) were excluded, yielding an analytic sample of 8,023.
Incident hypertension was defined as participants not having hypertension at baseline and having hypertension, defined as a systolic blood pressure 140 mm Hg or greater, diastolic blood pressure 90 mm Hg or greater, or receiving antihypertensive medication within 4 weeks, at the second round of screening.
Cardiometabolic disease definitions
The researchers did not discriminate between type 1 and type 2 diabetes. They used the American Diabetes Association definition as a fasting plasma glucose 126 mg/dL or greater, 2-hour, postload plasma glucose 200 mg/dL or greater, or hemoglobin A1c 6.5% or greater, with an additional criterion on self-reported use of antidiabetic medication within 4 weeks before the visit.
In line with previous research, the investigators controlled for potential confounders measured at baseline including sociodemographic factors, health behaviors, and adiposity, which are considered important risk factors for both sleep disorders and incident metabolic diseases. These factors include education level, age, gender, and body mass index and whether participants had ever been smokers or users of alcohol.
Study limitations
Limitations of the study include use of a home sleep apnea test device that did not allow evaluation of arousal or sleep architecture. The researchers said this may have led to an underestimation of disease severity both due to overestimation of sleep time and underrecognition of hypopneas unassociated with desaturation. In addition, prior research has suggested that minority populations might underreport sleep disturbances, possibly “due to social desirability (a tendency not to encode a negative event), stress, stereotype threat, acculturation, attitudes, etc.” The participants were recruited mostly from urban areas, and the results might not be generalized to rural populations. In addition, 41% of study participants were of Mexican heritage, compared with 63% of the Hispanic population being of Mexican heritage in the United States.
Another researcher in the field of health disparities, Julia Roncoroni, PhD, assistant professor of psychology at the University of Denver, also noted this slight underrepresentation of Hispanics of Mexican origin and an overrepresentation of urban individuals in the HCHS/SOL.
“However, using data from HCHS/SOL, which is the largest multicenter epidemiological study of cardiovascular risk factors and sleep traits in U.S. Hispanics/Latinx, allows researchers to answer a high-impact question that would otherwise be prohibitively expensive and time consuming,” wrote Dr. Roncoroni.
Conclusions
The study offers “the first prospective evidence on the associations between SDB and insomnia with incident hypertension and diabetes in US Hispanics/Latinos.” The investigators concluded: “Given the fact that sleep disorders are largely undiagnosed and undertreated, they might represent modifiable targets for disease prevention and reduction among US Hispanics/Latinos. Culturally informed interventions focusing on detecting and treating sleep disorders might improve cardiometabolic health among US Hispanics/Latinos.”
Dr. Redline was partially supported by NIH grant R35 HL135818. This study drew from the Hispanic Community Health Study/Study of Latinos, which has been supported by contracts from the National Heart, Lung, and Blood Institute.
SOURCE: Li X et al. Am J Respir Crit Care Med. 2020 Aug 6. doi: 10.1164/rccm.201912-2330OC.