Role Of Social Jetlag On Glucose Tolerance And Vascular Function In Morning And Intermediate Chronotypes

Sleep debt promotes social jetlag and elevates cardiovascular disease (CVD) risk via circadian misalignment. Evening chronotypes are at risk for sleep debt during the workweek compared to morning chronotypes (MC). However, it is unclear if intermediate chronotypes (IC) differ from MC in social jetlag as it relates to glucose tolerance or vascular function. PURPOSE: To examine the role of acute social jetlag on metabolic and vascular function in MC and IC. METHODS: Adults were classified as either MC (15F, 58 ± 9y, BMI: 36 ± 6 kg/m2, VO2max: 24.5 ± 4.7 ml/kg/min) or IC (15F, 57 ± 8y, BMI: 33 ± 5 kg/m2, VO2max: 23.0 ± 3.6 ml/kg/min) via the Morningness-Eveningness Questionnaire (MEQ). Habitual sleep duration was calculated from the Pittsburgh Sleep Questionnaire Index. Time-to-bed and wake time were also self-reported prior to clinical testing. Social jetlag was then calculated as the difference in habitual versus clinical test sleep. Fasting pulse wave analysis (applanation tonometry) was used to depict central hemodynamics while brachial artery diameter (ultrasound) determined flow-mediated constriction (during occlusion) as well as dilation (post-occlusion). A 180 min 75-g oral glucose tolerance test was conducted to assess glucose tolerance. RESULTS: MC and IC did not differ in BMI, VO2max, or glucose tolerance. MC had earlier wake times prior clinical testing compared to IC (5:43 ± 0:24 vs.6:30 ± 0:45 am, P < 0.001), though sleep duration (6.64 ± 1:21 vs. 7.10 ± 1.47 h, P = 0.31) and social jetlag (0.11 ± 0.33 vs. 0.21 ± 0.41 h, P = 0.35) did not differ. MC had elevated brachial (P = 0.02) and central (P = 0.02) systolic blood pressure as well as a larger diameter during occlusion (P = 0.04). CONCLUSION: MC and IC did not differ in social jetlag prior to clinical tests, although MC did wake earlier. MC also showed vascular dysfunction compared with IC, suggesting chronotype-specific differences. Additional mechanistic work is needed in chronotypes to tailor exercise prescription for combating CVD risk. Supported by NIH RO1-HL130296 NIH RO1-HL130296