Circadian Mechanisms Underlying Non-Dipping Blood Pressure in Blacks

Study Overview
=================
Brief Summary
-----------------
This study seeks to examine central and peripheral circadian mechanisms in Blacks with appropriately dipping systolic blood pressure (blood pressure that dips by at least 10%) compared with non-dipping systolic blood pressure (blood pressure that dips by less than 10%) using a constant routine protocol. Constant routine protocols are commonly used in the field of circadian biology to examine rhythms in biological processes while controlling the entraining effects of light, activity, and diet.

Detailed Description
-----------------
This study will enroll a total of 40 participants (n=20 non-dippers; n=20 dippers) to complete a 30-hour constant routine protocol. Participants will undergo baseline testing that includes anthropometric measurements, clinic blood pressure measurements, completion of self-report questionnaires on sleep and mood, be fitted with an ambulatory blood pressure monitor and actigraphy watch, and be provided with home sleep testing (HST) equipment. Following completion of baseline assessment, eligible participants will be scheduled for the 30-hour constant routine protocol. The 30-hour constant routine protocol will allow for the hourly collection of saliva, collection of buccal cells every 4 hours, and constant monitoring of core body temperature, all of which are primary outcomes in the assessment of central and peripheral circadian clock markers. Amplitude and phase of these outcomes will be assessed in non-dippers versus dippers.

Official Title
-----------------
Central and Peripheral Circadian Mechanisms Underlying Non-Dipping Blood Pressure in Blacks

Conditions
-----------------
Circadian Rhythm, Blood Pressure

Intervention / Treatment
-----------------
* Other: Constant Routine Protocol


Participation Criteria
=================
Eligibility Criteria
-----------------
Inclusion Criteria: Black or African American race Age 18 years or older Exclusion Criteria: Work alternating or night shifts Pregnant or nursing Current illicit drug use History of severe mental illness Medical conditions that would be contraindicated for a constant routine protocol Take anti-hypertensive medications or beta-blockers Severe obstructive sleep apnea

Ages Eligible for Study
-----------------
Minimum Age: 18 Years

Sexes Eligible for Study
-----------------
All

Accepts Healthy Volunteers
-----------------
Accepts Healthy Volunteers

Study Plan
=================
How is the study designed?
-----------------

Design Details

Primary Purpose: Basic Science
Intervention Model: Single Group Assignment
Interventional Model Description: Constant routine protocol in Blacks with dipping and non-dipping blood pressure
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Constant Routine Protocol<br>Participants will be kept in constant conditions for 30 hours to observe circadian physiology in the absence of light, physical activity, and meals. | Other: Constant Routine Protocol<br>* Constant routine protocols are used in circadian research to examine underlying circadian rhythms in the absence of light, activity, and meals<br>|

What is the study measuring?
-----------------
Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Melatonin phase | Circadian phase of melatonin obtained from saliva | Melatonin phase during a 30-hour constant routine protocol | 
| Melatonin amplitude | Circadian amplitude of melatonin obtained from saliva | Melatonin amplitude during a 30-hour constant routine protocol | 
| Core body temperature phase | Circadian phase of core body temperature recorded and transmitted wirelessly | Core body temperature phase during a 30-hour constant routine protocol | 
| Core body temperature amplitude | Circadian amplitude of core body temperature recorded and transmitted wirelessly | Core body temperature amplitude during a 30-hour constant routine protocol | 
| Buccal cell mRNA expression | Expression of Bmal1 and Period 3 obtained from buccal cell mRNA | Expression of Bmal1 and Period 3 during a 30-hour constant routine protocol | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Cortisol phase | Circadian phase of cortisol obtained rom saliva | Cortisol phase during a 30-hour constant routine protocol | 
| Cortisol amplitude | Circadian amplitude of cortisol obtained rom saliva | Cortisol amplitude during a 30-hour constant routine protocol |