Sleep and Vascular Health Study (SAVHS)

Habitual short sleep duration (< 7 hours/night) increases the risk of cardiovascular disease (CVD) and all-cause mortality. Yet most adults, especially emerging adults (i.e., 18-25 years) do not achieve the National Sleep Foundation recommendation of 7-9 hours of sleep each night. Additionally, the American Heart Association recently included sleep duration in the "Life's Essential 8". This recent development emphasizes the importance of sleep and the need to advance our understanding of how sleep impacts cardiometabolic health (CMH), particularly in emerging adults, a population whose CVD risk trajectory is malleable. Specifically, emerging adulthood is a critical age window when age-related loss of CMH accelerates. Based on my previous work and others, both self-reported and objective measures of poor sleep (e.g., duration, variability) are linked to early signs of elevated CVD risk in emerging adults, such as microvascular dysfunction and elevated central blood pressure (BP), which precede the development of hypertension.

The investigators aim to address the knowledge gap on whether sleep extension is a viable strategy to improve CMH in emerging adults with habitual short sleep duration. A prior study demonstrated the feasibility of sleep extension to improve BP and perceived sleepiness in predominantly normotensive emerging adults (18-23 years). Even without hypertension, reductions in BP are generally beneficial for CMH. The research hypothesis is that sleep extension (one extra hour in bed per night) will improve CMH and health behaviors in emerging adults who self-report < 7 hours of sleep per night. The primary aim is to determine if sleep extension is effective in improving BP. Investigators will assess CMH after habitual sleep (2 weeks) followed by a 2-week sleep extension intervention in 60 emerging adults (~30 female).

Participants will serve as their own controls. Due to the nature of the intervention (extending time in bed by 1 hour) all participants will be measured in their habitual sleep state followed by their extended sleep state.

The investigators will measure blood pressure using photoplethysmography at the finger during rest and handgrip exercise.

Passive leg movement will be used assessed blood flow responses to movement. The investigators will usie continuous measures of femoral artery diameter and velocity via duplex Doppler ultrasound (Hitachi Arietta 70) to calculate blood flow at rest and with the passive lelg movement. The femoral artery will be imaged in the longitudinal plane distal to the inguinal crease using a high-frequency (10-12 MHz) linear-array probe. Participants will be in a seated, reclined position with the lower leg free hanging. The ultrasound probe will be positioned by a lab member and the image will be recorded throughout triplicate 60-s measurements. Another lab member will independently move the lower leg through 90º range of motion at a rate of 1 Hz.

Researchers will assess circulating markers intercellular adhesion molecule 1 (ICAM-1) using ELISA; samples will be run in triplicate and with quality controls.

Philips actiwatch spectrum will be used to quantify sleep duration. Participants will wear the watch units for 14 days. The investigators will assess sleep duration and cross-check actigraphy wear times with a sleep diary.

Philips actiwatch spectrum will be used to quantify % of time in bed actually spent sleeping to calculate sleep efficiency.

The investigators will use the Pittsburgh Sleep Quality Index to asses sleep duration reflective of the one month period leading into the study.

The investigators will use the Pittsburgh Sleep Quality Index to assess perceived sleep quality reflective of the one month period leading into the study. The global score scale is 0 to 21.

The investigators will administer the Epworth Sleepiness Scale (ESS). The scale is scored as 0-10 (normal sleepiness), 11- 14 (mild sleepiness), 15-17 (moderate sleepiness), and 18 -24 (severe sleepiness).

The investigators will use the SphygmoCor XCEL system to assess pulse wave analysis (PWA) The sampling site is the brachial artery (upper alarm instrumented with a cuff for oscillometric sphygmomanometer). PWA will be expressed as % (calculated as augmentation pressure divided by the pulse pressure).

The investigators will use the SphygmoCor XCEL system to assess pulse wave velocity (PWV) The sampling site is the carotid artery (tonometry) and femoral artery (upper leg instrumented with a cuff for oscillometric sphygmomanometer). PWW will be expressed as meters per second.

The investigators will use indirect calorimetry to measure the participant's maximal oxygen consumption (VO2max) during incremental exercise on a treadmill. The investigators will use a Parvo TrueOne metabolic cart and Woodway treadmill.

The investigators will administer the Liebowitz Social Anxiety Scale. The scale starts at 0 (none) and ends at 3 (severe) for 24 questions related to anxiety and avoidance, and a cumulative score is calculated.

Appetite assessment via a visual analog scale (0 not feeling hungry/thirsty to 150 hungry/thirsty) and an ad libitum breakfast to measure food intake will take place during each of the experimental visits.

Researchers will analyze 24-hour urine samples for electrolyte (Na, K, Cl) content using the SmartLyte Electrolyte Analyzer. The Na, K, Cl will be expressed as milliequivalents (mEq).

Inclusion Criteria: 18 - 25 years old self-report sleeping less than 7 hours a night on average free from metabolic disease free from liver disease free from pulmonary disease free from cardiovascular disease Exclusion Criteria: blood pressure higher than 140/80 mmHg BMI greater than 35 kg/m2 use of blood thinners history of sleeping disorders no severe food allergies or eating disorders

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