Stress, Salt Excretion, and Nighttime Blood Pressure (SABRE)

The study will examine urinary sodium excretion induced by psychological stress and its diurnal pattern as a novel biological mechanism that may underlie an abnormal diurnal pattern of blood pressure. The study will test the hypotheses that lower stress-induced sodium excretion is associated with an abnormal diurnal pattern of sodium excretion, and that an abnormal diurnal pattern of sodium excretion is associated with an abnormal diurnal pattern of blood pressure. Primary Aim 1: To examine the association between urinary sodium excretion after provoked psychological stress and the diurnal pattern of sodium excretion. Primary Aim 2: To examine the association between the diurnal pattern of sodium excretion and the diurnal pattern of BP. Secondary Aim: To examine whether the association between urinary sodium excretion after provoked stress and the diurnal pattern of sodium excretion is modified by ecological momentary levels of perceived stress, experienced during the daytime period. Exploratory Aim: To determine the socio-demographic, behavioral, and psychological traits, chronic stress, and biological stress-related factors that are associated with lower stress-induced sodium excretion. Identification of these factors will help determine who is at risk for having a differential sodium excretion response to psychological stress.

Blood pressure (BP) has a diurnal rhythm; it is normally highest during the daytime period and lowest during the nighttime period (BP dipping). The diurnal pattern of BP over a 24-hour period can be assessed using ambulatory BP monitoring (ABPM). Evidence indicates that an abnormal diurnal pattern of BP on ABPM, defined by reduced BP dipping or elevated nighttime BP, is associated with an increased risk of cardiovascular disease (CVD) events. Psychological stress occurs when an individual perceives that the environmental demands exceed his/her adaptive capacity. An individual's response to events that are representative of this overload, such as perceived stress and negative affect including anger, hostility, depression, vital exhaustion, and symptoms of posttraumatic stress disorder, are associated with reduced BP dipping and/or higher nighttime BP. Exposure to environmental factors which tax an individual's ability to cope, including lower socioeconomic status, job strain, and perceived racism, are also associated with reduced BP dipping and/or higher nighttime BP. This study will examine the disruption of the normal diurnal pattern of sodium excretion by psychological stress as a novel biological mechanism underlying an abnormal diurnal pattern of BP. The study will be conducted both in the laboratory and in the naturalistic environment with a multi-ethnic sample of 211 adult community participants from upper Manhattan who do not have a history of CVD, diabetes, chronic kidney disease, or another major medical condition and are not taking antihypertensive medication. During a laboratory visit, urinary sodium excretion in response to mental stress tasks will be examined.

All participants will receive the same intervention. All associated groups will be aware of the intervention protocol and the single-arm study model.

All participants will undergo stress-inducing tasks (psychological stress intervention) using cognitive research tools.

Participant will be shown a series of words for five minutes and a research coordinator will ask him/her to name the color of each (Stroop Color-Word Conflict Task). Then, for another five minutes, the participant will be asked to count backwards out loud by sevens starting from 1,000 (Mental Arithmetic Task). The research assistant will ask the participant to work as quickly and accurately as possible for both tasks.

This is to measure the ecological stress level for the awake period during which the participants' sodium excretion is monitored.

Inclusion Criteria: Age 21 years or older Screening mean blood pressure less than or equal to 160/105 mm Hg Exclusion Criteria: History of overt cardiovascular disease (coronary heart disease, stroke, peripheral arterial disease, heart failure, permanent or recurring arrhythmia) History of secondary hypertension History of other major medical condition (cancer, rheumatologic diseases, immunologic diseases, etc.) Taking anti-hypertensive medications or other medications that are known to substantially affect blood pressure (e.g. steroids, chronic anti-inflammatory medications, etc.) Non-English speaking