Data Source
The National Health and Nutrition Examination Survey (NHANES) is a prominent survey conducted by the National Center for Health Statistics, evaluating the health and nutrition status of the U.S. population. The study received ethical approval from the NCHS Institutional Review Board (Protocol #2005-06, Continuation of Protocol #2005-06 and #2011-17) to ensure participant protection. Informed consent was obtained from all participants or their guardians, with written consent documenting their understanding of the study. The NHANES protocols underwent review and approval by the NCHS Research Ethics Review Board, ensuring adherence to ethical and regulatory standards.
Study Population
This research encompassed four cycles over the periods of 2005–2008 and 2015–2018, starting with an initial cohort of 39,722 individuals. Exclusion criteria were applied as follows: individuals under 20 years of age (17,520), those for whom LE8 scores could not be computed (7,409), those not diagnosable with OSA (1,841), and participants with incomplete covariate data (992). Ultimately, the final sample included 11,960 participants (Fig. 1).
Obstructive Sleep Apnea
OSA is diagnosed based on the following criteria (10, 11): (1) snoring on three or more nights per week; (2) having episodes of snoring, gasping, or cessation of breathing three or more nights per week; (3) experiencing excessive daytime sleepiness between 16 and 30 times per month; (4) displaying one or more of the symptoms aforementioned .
Measurement of LE8
The Life's Essential 8 (LE8) scoring system evaluates CVH through four health factors and four health behaviors. The health factors include blood glucose, blood pressure, body mass index (BMI), and non-high-density lipoprotein (non-HDL) cholesterol. The health behaviors consist of diet, physical activity, nicotine exposure, and sleep duration 7,8. Each metric is scored from 0 to 100, with the overall LE8 score being the average of these scores. Detailed definition and scoring approach for the LE8 can be found in Supplementary Table 1. Participants are classified into CVH levels: high (80–100), moderate (50–79), and low (0–49) 7.
Data collection involved several methods: dietary assessment was done using the Healthy Eating Index-2015 (HEI-2015) 9 from two 24-hour dietary recalls and the U.S. Department of Agriculture’s food pattern equivalence data; physical activity, tobacco exposure, sleep duration, diabetes history, and medication use were self-reported via questionnaires. Physical measurements included height, weight, and blood pressure, with BMI computed and blood pressure averaged from three readings. Laboratory analysis of blood samples determined non-HDL cholesterol, fasting blood glucose, and glycated hemoglobin (HbA1c).
Covariates
To investigate the relationship between the LE8 score and OSA, several demographic and health-related covariates were adjusted to ensure robust analysis. Demographic adjustments included gender (male, female), age groups (20–44, 45–64, and ≥ 65 years), race/ethnicity (Mexican American, non-Hispanic Black, non-Hispanic White, other Hispanic, and other race-including multiracial), education level (less than high school, high school graduate, and college or above), poverty income ratio (PIR) (< 1.3, 1.3–3.5, and ≥ 3.5), and marital status (married/living with partner, divorced/separated/widowed, and never married). Health-related adjustments included cardiovascular disease (CVD), defined by a doctor’s diagnosis of congestive heart failure, coronary heart disease, angina, heart attack, or stroke; chronic kidney disease (CKD), defined by an estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m² and/or a urine albumin/creatinine ratio (ACR) ≥ 30 mg/g, calculated using the CKD Epidemiology Collaboration creatinine Eq. 10; and cancer status, determined through self-reports of physician-diagnosed cancer. Detailed methodologies for these variables are available on the NHANES website, ensuring transparency and reproducibility.
Statistical analysis
In accordance with NHANES guidelines, appropriate sample weights were computed, and complex multi-stage survey design methodologies were incorporated into the analysis. Continuous variables are presented as survey-weighted means with 95% confidence intervals (CI), while categorical variables are displayed as survey-weighted percentages with 95% CI. To evaluate intergroup differences, the weighted variance test and weighted chi-squared test were applied. Participants were categorized into two groups based on the presence or absence of OSA, using the absence of OSA as the reference group. Multiple linear and logistic regression models were employed to examine the relationship between LE8 and OSA. Restricted cubic spline (RCS) plots were used to capture potential non-linear associations. To ensure robustness, multivariate stratified subgroup analyses were performed across age, gender, education, poverty-to-income ratio (PIR), and marital status. Interaction P-values were calculated to assess the heterogeneity of the LE8-OSA relationship across these subgroups. The combined effect of LE8 indicators on OSA risk was evaluated using weighted quantile sum (WQS) regression models, with weight ratio analyses identifying the most influential factors 11. In the sensitivity analysis, the E-value was employed to quantify the potential influence of unmeasured confounders on the observed associations, thereby testing the robustness of the primary outcome 12. The E-value represents the minimum strength of the relationship between unmeasured confounders with exposure and outcome variables. A higher E-value suggests that the observed association is less likely to be explained by unmeasured confounders, indicating a more stable main outcome. All statistical analyses were conducted using R version 4.4.1 (R Foundation for Statistical Computing, Vienna, Austria) and Empower Stats software (http://www.empowerstats.net/en/), with a two-sided P-value < 0.05 considered statistically significant.