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.



Eligible Ages
Over 18 Years
Eligible Genders
Accepts Healthy Volunteers

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

Study Design

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

Arm Groups

ArmDescriptionAssigned Intervention
Constant Routine Protocol
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
    Constant routine protocols are used in circadian research to examine underlying circadian rhythms in the absence of light, activity, and meals

Recruiting Locations

University of Alabama at Birmingham
Birmingham, Alabama 35294-0017
Stephen J Thomas, PhD

More Details

University of Alabama at Birmingham

Study Contact

Stephen J Thomas, PhD

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.


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