Abstract
BACKGROUND: Sitting time (ST) constitutes a significant aspect of sedentary behavior, and its worldwide escalation raises concerns regarding public health. International guidelines recommend limiting sedentary time and replacing it with physical activity (PA) to reduce the risk of diseases and mortality. This study examines the impact of replacing ST with PA on all-cause, cardiovascular disease (CVD), and cancer mortality in a representative cohort of the population of Spain. METHODS: We included 30 955 participants aged 15-69 years from two National Health Surveys performed in 2011 and 2017. Data were linked to mortality records as of December 2022. Data on ST, light PA (LPA), and moderate-vigorous PA (MVPA) were collected as part of the International Physical Activity Questionnaire at baseline. Isotemporal substitution analysis from Poisson regression models was used to estimate the relative risk ratio (RR) of replacing ST with LPA or MVPA. RESULTS: During a median follow-up of 5.7 years, 957 deaths were reported. The replacement of 1 h per week of ST with 1 h per week of MVPA was significantly associated with a lower risk of all-cause (3.3%), CVD (6.7%), and cancer mortality (3.1%). Similarly, replacing 1 h per week of ST with 1 h per week of LPA was significantly associated with a lower risk of all-cause (1.6%) and cancer mortality (2.1%). Finally, substituting 1 h per week of LPA with 1 h per week of MVPA was significantly associated with a 7.6% lower risk of CVD mortality. CONCLUSIONS: Substituting one hour per week of ST with an equivalent amount of PA was associated with a lower risk of all-cause, CVD, and cancer mortality.