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PURPOSE: Emerging evidence suggests that short sleep duration and delayed sleep timing may be independently related to insulin resistance (IR), although findings are mixed. Our aim was to investigate associations between sleep duration and timing with insulin resistance among adolescents. METHODS: The analytic sample included 384 Mexican adolescents from a birth cohort study who took part in a follow-up study beginning in 2015. Insulin and glucose were measured in fasting serum, and Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) was calculated (marker of insulin resistance; [insulin x glucose]/22.5). Sleep duration and midpoint were measured by actigraphy for 7 days after the visit and for analysis were separated by weekdays and weekends. In full and sex-stratified regression analysis, sleep duration and midpoint were exposures, and the log HOMA-IR was the outcome, adjusting for age. RESULTS: The mean age of the sample was 13.8 ± 1.93 with 51% female. Shorter sleep duration on weekdays was associated with higher log HOMA-IR (ß = -.049, 95% confidence interval [CI] -.097 to -.0009). Later midpoints on weekdays and the weekend were independently associated with higher log HOMA-IR (ß = .0408, 95% CI -.0049 to .087, and ß = .0486, 95% CI .0042 to .093, respectively). Girls showed stronger associations than boys for both sleep duration and timing with HOMA-IR. CONCLUSIONS: Sleep duration and sleep timing were independently associated with insulin resistance, and associations were more pronounced among girls.
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Resistência à Insulina , Adolescente , Glicemia , Estudos de Coortes , Estudos Transversais , Feminino , Seguimentos , Humanos , Insulina , Masculino , México , SonoRESUMO
INTRODUCTION: Hypertension affects up to 5% of children worldwide and predicts later cardiovascular morbidity. Associations of short sleep and hypertension have been frequently reported in adults but less consistently in children. This study aims to examine the role of late bedtimes, a marker of short sleep duration, and potentially misaligned circadian rhythms, on incident elevated blood pressure (BP) in a large cohort of Mexican children. METHODS: Participants included 2,033 adolescents recruited from public schools in Morelos, Mexico, free from elevated BP (<90th sex, age, and height-standardized percentile). Fourteen months later, all adolescents had a second BP assessment. We abstracted baseline habitual bedtimes from questionnaires to evaluate the association between bedtime and elevated BP incidence (≥90th percentile). Risk ratios and 95% confidence intervals were estimated with discrete-time mixed survival models, adjusting for potential confounders and accounting for clustering by school. RESULTS: Participants were 12.5 (SDâ =â 0.6) years old at baseline. At the follow-up visit 10% of adolescents had developed elevated BP. Compared to participants with a habitual weekday bedtime between 9 and 10 pm, those with a weekday bedtime 11 pm or later had a 1.87 times higher risk of developing elevated BP over the follow-up period (95% CI = 1.09, 2.21), after accounting for confounders. Participants with earlier weekday bedtimes also had a higher risk of elevated BP (RRâ =â 1.96; 95% CI = 1.27, 3.01). The associations persisted after accounting for wake time. CONCLUSION: These data showed a U-shaped association between weekday bedtime and elevated/high BP risk among Mexican adolescents.
Assuntos
Comportamento do Adolescente , Pressão Sanguínea , Comportamento Infantil , Hipertensão/fisiopatologia , Sono , Adolescente , Fatores Etários , Criança , Ritmo Circadiano , Feminino , Hábitos , Humanos , Hipertensão/diagnóstico , Hipertensão/epidemiologia , Incidência , Estudos Longitudinais , Masculino , México/epidemiologia , Fatores de TempoRESUMO
STUDY OBJECTIVES: Lead exposure has been linked to adverse cognitive outcomes among children, and sleep disturbances could potentially mediate these relationships. As a first step, whether childhood lead levels are linked to sleep disturbances must be ascertained. Prior studies of lead and sleep are scarce and rely on parent-reported sleep data. METHODS: The study population included 395 participants from the Early Life Exposure in Mexico to Environmental Toxicants project, a group of sequentially enrolled birth cohorts from Mexico City. Blood lead levels measured from ages 1 to 4 years were used to calculate a cumulative measure of early childhood lead levels. Average sleep duration, sleep fragmentation, and movement index were assessed once between the ages of 9 and 18 years with wrist actigraphs worn for a continuous 7-day interval. Linear regression models were fit with average sleep duration, fragmentation, or movement as the outcome and cumulative lead levels divided into quartiles as the exposure, adjusted for age, sex, and maternal education. RESULTS: Mean (standard deviation) age at follow-up was 13.8 (1.9) years, and 48% of participants were boys. Median (interquartile range) cumulative childhood lead level was 13.7 (10.8, 18.0) µg/dL. Patients in the highest quartile of the cumulative childhood lead group had on average 23 minutes less sleep than those in the first quartile in adolescence (95% confidence interval [7, 39]; P, trend = .02). Higher cumulative lead level was associated with higher sleep fragmentation in younger adolescents (younger than 14 years) only (P, interaction = .02). CONCLUSIONS: Shorter sleep duration may represent an as-yet unrecognized adverse consequence of lead exposure in youth.
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Chumbo/sangue , Privação do Sono/sangue , Actigrafia , Adolescente , Criança , Pré-Escolar , Estudos de Coortes , Feminino , Seguimentos , Humanos , Lactente , Chumbo/efeitos adversos , Estudos Longitudinais , Masculino , México , Privação do Sono/induzido quimicamente , Privação do Sono/fisiopatologia , Fatores de TempoRESUMO
OBJECTIVE: To assess whether adiposity measures differed according to joint categories of sleep duration and sleep variability in a sample of Mexican adolescents. STUDY DESIGN: A sample of 528 Mexico City adolescents aged 9-17 years wore wrist actigraphs for 6-7 days. Average sleep duration was categorized as age-specific sufficient or insufficient. Sleep variability, the standard deviation of sleep duration, was split at the median into stable versus variable. Adiposity measures-body mass index (BMI)-for-age Z score (BMIz), triceps skinfolds, waist circumference, and percent body fat-were collected by trained assistants. We regressed adiposity measures on combined sleep duration and variability categories. Log binomial models were used to estimate prevalence ratios and 95% CI for obesity (>2 BMIz) by joint categories of sleep duration and variability, adjusting for sex, age, and maternal education. RESULTS: Approximately 40% of the adolescents had insufficient sleep and 13% were obese. Relative to sufficient-stable sleepers, adolescents with insufficient-stable sleep had higher adiposity across all 4 measures (eg, adjusted difference in BMIz was 0.68; 95% CI, 0.35-1.00) and higher obesity prevalence (prevalence ratio, 2.54; 95% CI, 1.36-4.75). Insufficient-variable sleepers had slightly higher BMIz than sufficient-stable sleepers (adjusted difference, 0.30; 95% CI, 0.00-0.59). CONCLUSIONS: Adolescents with consistently insufficient sleep could be at greater risk for obesity. The finding that insufficient-variable sleepers had only slightly higher adiposity suggests that opportunities for "catch-up" sleep may be protective.