Long Sleep Duration and Vascular Function

Central aortic pulse pressure was measured one night during the week of 8 hours in bed, then again one night during the week of 11 hours in bed. Blood pressure was measured using an Oscar2 ambulatory blood pressure device. The device started recordings one hour prior to sleep and was programmed to take measurements once every 30 minutes during sleep until 10:00pm then every 45 minutes after 10:00pm until participants arose from bed. The change in central aortic pulse pressure from being awake to being asleep was compared between 8 and 11 hours in bed conditions.

Blood flow measured in the middle cerebral artery during hypercapnia was measured after one week of 8 hours in bed, then again after one week of 11 hours in bed. Cerebral blood flow was measured using transcranial Doppler during 3 minutes of transient hypercapnia induced by rebreathing. Cerebral vascular reactivity was considered as the percent increase in cerebral blood flow at the end of 3 minutes of rebreathing relative to the Torr change in end-tidal carbon dioxide (percent change/Torr).

Peak forearm blood flow was measured after one week of 8 hours in bed, then again after one week of 11 hours in bed. Peak reactive hyperemia in the forearm (ml/100ml/min) was measured using venous occlusion plethysmography after 10 minutes of forearm ischemia resulting from blood pressure cuff inflation at the upper-arm. Peak blood flow was considered the highest blood flow measurement after the blood pressure cuff was deflated.

Arterial stiffness was measured after one week of 8 hours in bed, then again after one week of 11 hours in bed. Carotid-femoral pulse wave velocity was used as the measure of arterial stiffness. Radial arterial tonometry was used to derive a central aortic blood pressure wave. Wave separation analysis of the aortic pressure wave was then used to calculate pulse wave velocity from transit time and carotid-femoral path length.

Score from a Manikin test of spatial orientation that participants took using a computer with automated software (Automated Neuropsychological Assessment Metrics, known as ANAM). Scores reflect "throughput scores" which is a continuous variable that is the ratio of correct answers per minute during the Manikin test. Higher throughput scores mean better outcome, in this case, better spatial orientation ability. Participants took the Manikin test after one week of 8 and 11 hours in bed (i.e., baseline) then the morning after one day of aerobic exercise. Exercise consisted of three sessions of 10 minutes brisk walking at a heart rate considered to be moderate intensity (50-70% of age-predicted maximal heart rate). Results reported reflect the change in throughput scores after exercise (morning after exercise minus baseline).

Executive function was assessed using a Stroop color-word test that participants took using a computer with automated software (Automated Neuropsychological Assessment Metrics, known as ANAM). Score reported are number of correct answers. A higher score means a better outcome, in this case, better executive functioning. Participants took the Stoop color-word test after one week of 8 and 11 hours in bed (i.e., baseline) then the morning after one day of aerobic exercise. Exercise consisted of three sessions of 10 minutes brisk walking at a heart rate considered to be moderate intensity (50-70% of age-predicted maximal heart rate). Results reported reflect the change in score after exercise (morning after exercise minus baseline).

Mental flexibility was assessed using a Switching task that participants took on a computer with automated software (Automated Neuropsychological Assessment Metrics, known as ANAM). Scores reflect "throughput scores" which is a continuous variable that is the ratio of correct answers per minute during the Manikin test. Higher throughput scores mean better outcome, in this case, better mental flexibility. Participants took the Switching task after one week of 8 and 11 hours in bed (i.e., baseline) then the morning after one day of aerobic exercise. Exercise consisted of three sessions of 10 minutes brisk walking at a heart rate considered to be moderate intensity (50-70% of age-predicted maximal heart rate). Results reported reflect the change in throughput scores after exercise (morning after exercise minus baseline).