Sedentary Behavior Is Associated With Impaired Nocturnal Blood Pressure Dipping

Blood pressure (BP) exhibits a circadian rhythm, normally decreasing or “dipping” by 10-20% at night compared to waking hours. Individuals vary in the degree of nocturnal dipping and those characterized as “non-dippers” have poor cardiovascular prognosis. Prior research indicates that moderate-vigorous intensity physical activity (PA) is associated with lower risk of non-dipping. However, the impact of high sedentary behavior (SB) or other dimensions of daily PA on nocturnal BP dipping remains unclear. PURPOSE: To examine the association between SB, daily PA, and nocturnal BP dipping. METHODS: This study was a cross-sectional analysis of baseline data from the RESET BP study. RESET BP recruited desk workers with resting systolic BP 120-159 mmHg or resting diastolic BP 80-99 mmHg who were not taking antihypertensive medication and who self-reported not meeting the current PA guidelines. Non-dipping was defined as <10% reduction in nighttime compared to daytime average systolic BP on 24-Hr ambulatory BP monitoring. A thigh-worn activPAL measured daily durations of SB (total and accumulated in bouts of ≥30 minutes, SB30, and ≥60 minutes, SB60), standing, stepping, sit-stand transitions, and steps per day. Logistic regression estimated the odds of being classified as a non-dipper per unit increase in SB, SB30, SB60, standing, stepping, sit-stand transitions, and daily steps after adjustment for age, sex, resting BP, and body mass index. RESULTS: Among 258 participants who were 59% female and had mean age 45±12 years and mean BMI 30.8±6.5 kg/m 2, 41 (16%) were classified as non-dippers. Each additional hour of SB was associated with greater odds of being a non-dipper as follows: total SB OR, 1.23 (p=0.070), SB30 OR, 1.23 (p=0.016), and SB60 OR, 1.23; p=0.019. Each additional hour of stepping (OR, 0.48, p=0.049) and 10 sit-to-stand transitions (OR, 0.73, p=0.047) were associated with lower odds of being a non-dipper. Standing and steps per day were not associated with the odds of being a non-dipper (p>0.10). CONCLUSIONS: An activity pattern with lower time spent in SB, especially in longer bouts, higher time spent stepping, and more sit-stand transitions is associated with nocturnal BP dipping and the latter may represent an additional mechanism through which daytime PA promotes cardiovascular health. RESET BP: Funded by National Institutes of Health R01 HL134809 and UL1TR001857