Additional Study Information: The purpose of this clinical trial is to study the relationship of stress, salt excretion, and nighttime blood pressure. Blood pressure normally has a diurnal pattern: it is highest during the day and dips during the night. The effects of psychological stress can interfere with this normal pattern and cause elevated nighttime blood pressure or reduced blood pressure dipping. It is predicted that, in some individuals, psychological stress can interfere with the diurnal pattern of sodium excretion which, like blood pressure, is highest during the day and lowest at night. The purpose of this study is to examine stress-induced disruptions of sodium excretion as a possible cause of elevated nighttime blood pressure and reduced blood pressure dipping. After a thirty-minute enrollment visit and the overnight use of a sleep apnea device to confirm eligibility, participants will consume provided meals and snacks for three days. Then, stress will be induced at a laboratory visit, and urine and blood will be collected. Finally, blood pressure, environmental stress, and electrolyte concentrations in urine will be measured for 24 hours following the laboratory visit.