Dose a family history of coronary heart disease modify the relationship between physical activity and blood pressure in young adults?

Background: The purpose of this study was to examine the relationships between physical activity, a family history (FH) of coronary heart disease (CHD), and blood pressure (BP) in young adults. We were specifically interested in determining whether the relationship between moderate-to-vigorous physical activity and BP was modified by a FH of CHD. Methods: Subjects were 230 (103 males, 127 females) university students, Family history was self-reported and habitual physical activity was assessed with a 3-day activity diary. Indicators of habitual physical activity included estimated daily energy expenditure (EE) and EE in moderate-to-vigorous physical activity (MVPA) [median metabolic equivalent (MET) ≥ 4.8] and inactivity (IA) (MET < 2.8). Blood pressure was measured by an automated device according to standard procedures. Results: A large proportion of the sample (63% of males and 68% of females) reported a FH of CHD. In general, correlations between physical activity and BP were low (r < 0.30), but in the expected direction (i.e., positive for IA and negative for MVPA and EE). In males IA was significantly related to BP (r=0.25-0.29), but MVPA was not significantly related to BP (r= -0.01 to -0.16). In females diastolic BP was significantly related to IA (r= -0.21) and total EE (r= -0.18). Total EE was significantly correlated to DBP (r= -0.22) in males and to mean arterial pressure (r= -0.18) in females. No significant differences in BP were found between subjects with or without a FH of CHD. Slightly stronger correlations emerged between MVPA and BP for subjects with a negative FH of CHD compared to those with a positive FH of CHD. Conclusion: These data show a significant association between sedentary behavior and blood pressure in young adults. It is suggestive that the magnitude of the relationship between MVPA and BP may be modified by a FH of CHD. Thus, individuals with a FH of CHD may not be as responsive to increased levels of MVPA compared to those without a FH of CHD.