Objective: To prospectively analyze the associations with coronary heart disease (CHD) risk of reallocating time from sedentary behavior to various physical activities using the isotemporal substitution model, particularly according to whether the participants meet the recommended physical activity level.
Methods: We included 455,298 UK Biobank participants free of CHD at baseline (March 13, 2006, to October 10, 2010). Sedentary behavior time was quantified by summing up the time spent on television watching, computer (not at work), and driving. Physical activities were categorized as daily-life activities (walking for pleasure, light do-it-yourself, and heavy do-it-yourself) and structured exercise (strenuous sports and other exercise).
Results: During a median follow-up of 11 years, 20,162 incident CHD cases were documented. Sedentary behavior time was significantly associated with a higher risk of CHD, independent of physical activity. Replacing 30 min/d of sedentary behavior with an equal time of various physical activities was associated with a 3% to 12% risk reduction of CHD. Replacing 1 h/d of sedentary behavior with different types of physical activities was associated with a 6% to 23% risk reduction of CHD. Sedentary behavior to strenuous sports reallocations showed the largest benefit. Reallocations of sedentary behavior to various physical activities showed particularly greater benefits among those who did not meet the physical activity recommendations.
Conclusions: Replacing sedentary behavior time with various daily-life activities or structured exercise is associated with significant reductions in CHD risk.
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