Interaction between physical activity and television time on blood pressure level : Cross-sectional data from 45 000 individuals

Objectives: The aim was to investigate if there is an interaction between sitting time and leisure time physical activity on blood pressure and if there are age differences and sex differences in this respect. Methods: Linear regression analysis on cross-sectional data was performed in more than 45 000 men and women from two Swedish cohort studies, EpiHealth (45-75 years) and LifeGene (18-45 years). Self-reported leisure time physical activity was given in five levels from low (level 1) to vigorous physical activity (level 5) and television time was used as a proxy measure of sitting time. Results: High physical activity was associated with lower DBP (P = 0.001), but not SBP. Active middle-aged men had lower DBP (-1.1 mmHg; 95% CI -1.7 to -0.4) compared with inactive participants. Prolonged television time was associated with higher SBP (P < 0.001) and DBP (P = 0.011) in both sexes and in most age groups. Watching 3 h instead of 1 h television per day was associated with higher SBP in middle-aged women (SBP: 1.1 mmHg; 95% CI 0.7-1.4) and men (SBP: 1.2 mmHg; 95% CI 0.8-1.6). Only in young men, a high physical activity (level 4 instead of level 1) could compensate for a prolonged television time (3 h per day) in terms of DBP. Conclusion: Prolonged television time was associated with higher SBP and DBP in both sexes and at most ages, whereas an increased physical activity was mainly associated with a lower DBP. Only in young men, a high physical activity could compensate for prolonged television time regarding DBP