Isotemporal substitution of inactive time with physical activity and time in bed: cross-sectional associations with cardiometabolic health in the PREDIMED-Plus study
Authors: Galmes-Panades Aina M. , Varela-Mato Veronica , Konieczna Jadwiga , Wärnberg Julia , Martínez-González Miguel Ángel , Salas-Salvadó Jordi , Corella Dolores , Schröder Helmut , Vioque Jesús , Alonso-Gómez Ángel M. , Martínez J. Alfredo , Serra-Majem Luís , Estruch Ramon , Tinahones Francisco J. , Lapetra José , Pintó Xavier , Tur Josep A. , Garcia-Rios Antonio , Riquelme-Gallego Blanca , Gaforio José Juan , Matía-Martín Pilar , Daimiel Lidia , Micó Pérez Rafael Manuel , Vidal Josep , Vázquez Clotilde , Ros Emilio , Garcia-Arellano Ana , Díaz-López Andrés , Asensio Eva M. , Castañer Olga , Fiol Francisca , Mira-Castejón Luis Alfredo , Moreno Rodríguez Anai , Benavente- Marín Juan Carlos , Abete Itziar , Tomaino Laura , Casas Rosa , Barón López F. Javier , Fernández-García José Carlos , Santos-Lozano José Manuel , Galera Ana , Mascaró Catalina M. , Razquin Cristina , Papandreou Christopher , Portoles Olga , Pérez-Vega Karla Alejandra , Fiol Miguel , Compañ-Gabucio Laura , Vaquero-Luna Jessica , Ruiz-Canela Miguel , Becerra-Tomás Nerea , Fitó Montserrat , Romaguera Dora 
Published: December 2019

Abstract
Background
This study explored the association between inactive time and measures of adiposity, clinical parameters, obesity, type 2 diabetes and metabolic syndrome components. It further examined the impact of reallocating inactive time to time in bed, light physical activity (LPA) or moderate-to-vigorous physical activity (MVPA) on cardio-metabolic risk factors, including measures of adiposity and body composition, biochemical parameters and blood pressure in older adults.

Methods
This is a cross-sectional analysis of baseline data from 2189 Caucasian men and women (age 55–75 years, BMI 27–40 Kg/m2) from the PREDIMED-Plus study (http://www.predimedplus.com/). All participants had ≥3 components of the metabolic syndrome. Inactive time, physical activity and time in bed were objectively determined using triaxial accelerometers GENEActiv during 7 days (ActivInsights Ltd., Kimbolton, United Kingdom). Multiple adjusted linear and logistic regression models were used. Isotemporal substitution regression modelling was performed to assess the relationship of replacing the amount of time spent in one activity for another, on each outcome, including measures of adiposity and body composition, biochemical parameters and blood pressure in older adults.

Results
Inactive time was associated with indicators of obesity and the metabolic syndrome. Reallocating 30 min per day of inactive time to 30 min per day of time in bed was associated with lower BMI, waist circumference and glycated hemoglobin (HbA1c) (all p-values < 0.05). Reallocating 30 min per day of inactive time with 30 min per day of LPA or MVPA was associated with lower BMI, waist circumference, total fat, visceral adipose tissue, HbA1c, glucose, triglycerides, and higher body muscle mass and HDL cholesterol (all p-values < 0.05).

Conclusions
Inactive time was associated with a poor cardio-metabolic profile. Isotemporal substitution of inactive time with MVPA and LPA or time in bed could have beneficial impact on cardio-metabolic health.

Trial registration
The trial was registered at the International Standard Randomized Controlled Trial (ISRCTN: http://www.isrctn.com/ISRCTN89898870) with number 89898870 and registration date of 24 July 2014, retrospectively registered.