ImportanceAdolescent sleep problems are prevalent, particularly among racial and ethnic minority groups, and can increase morbidity. Despite the numerous strengths of their racial and ethnic group, urban American Indian and Alaska Native adolescents face significant health disparities but are rarely included in health research. Understanding how sleep problems are associated with health outcomes among American Indian and Alaska Native adolescents may elucidate novel targets for interventions to promote health equity.ObjectiveTo assess whether baseline sleep problems are associated with changes in behavioral and cardiometabolic health outcomes among urban American Indian and Alaska Native adolescents 2 years later.Design, Setting, and ParticipantsAmerican Indian and Alaska Native adolescents were recruited via flyers and community events for an observational cohort study in California. Baseline assessments were conducted among 142 adolescents from March 1, 2018, to March 31, 2020, and follow-ups were conducted among 114 adolescents from December 1, 2020, to June 30, 2022.ExposuresBaseline actigraphy-assessed sleep duration and efficiency and self-reported sleep disturbances and social jet lag (absolute value of the difference in sleep midpoint on weekends vs weekdays; indicator of circadian misalignment).Main Outcomes and MeasuresMain outcome measures included self-reported depression (measured using the Patient Health Questionnaire), anxiety (measured using the Generalized Anxiety Disorder 7-item scale), past year alcohol and cannabis use, body mass index, systolic blood pressure (SBP) and diastolic blood pressure (DBP), waist circumference, and glycosylated hemoglobin (HbA1c). Analyses examined whether baseline sleep was associated with health outcomes at follow-up, controlling for age, sex, and baseline outcome measures.ResultsThe baseline sample included 142 urban American Indian and Alaska Native adolescents (mean [SD] age, 14.0 [1.4] years; 84 girls [59%]), 80% of whom (n = 114; mean [SD] age, 14.1 [1.3] years; 71 girls [62%]) completed follow-ups. Linear or logistic regressions showed significant negative associations between shorter sleep duration and depression (β = −1.21 [95% CI, −2.19 to −0.24]), anxiety (β = −0.89 [95% CI, −1.76 to −0.03]), DBP (β = −2.03 [95% CI, −3.79 to −0.28]), and HbA1c level (β = −0.15 [95% CI, −0.26 to −0.04]) and likelihood of alcohol (odds ratio [OR], 0.57 [95% CI, 0.36-0.91]) and cannabis use (full week: OR, 0.59 [95% CI, 0.35-0.99]) at follow-up. Greater social jet lag was associated with significantly higher SBP (β = 0.06 [95% CI, 0.01-0.11]) at follow-up.Conclusions and RelevanceThis cohort study found significant associations between poor sleep and adverse changes in health outcomes. Findings highlight the importance of developing culturally responsive interventions that target sleep as a key modifiable risk factor to improve the health of American Indian and Alaska Native adolescents.