Daily movement behaviours and cognition in mid-life: A cross-sectional compositional analysis of the 1970 British Cohort Study.

IMPORTANCEMovement behaviours (e.g. sedentary behaviour (SB), moderate and vigorous physical activity (MVPA), light intensity physical activity (LIPA) and sleep) are linked to cognition, yet the relative importance of each component is unclear, and not yet explored with compositional methodologies. OBJECTIVETo examine how time spent in one behaviour (e.g. SB, MVPA, LIPA, sleep) relative to all others is associated with overall cognition, including executive function and memory. DESIGN, SETTING, AND PARTICIPANTSThe 1970 British Cohort Study (BCS70) is an ongoing prospective birth cohort study of adults born in England, Scotland and Wales in a single week. At age 46, participants wore an accelerometer device and completed cognitive screening. Linear regression was used to examine cross-sectional associations between movement behaviours and cognitive scores, using a compositional approach. Isotemporal substitution was performed to model the effect of reallocating time between components of daily movement on cognition. EXPOSURESA thigh-mounted activPAL accelerometer device was worn without removal for one week. Daily time in SB, MVPA, LIPA and sleep were derived using a validated processing algorithm. MAIN OUTCOMES AND MEASURESStandardised scores of executive function (letter cancellation and verbal fluency), memory (immediate and delayed wordlist recall) and a composite score were derived from computer administered cognitive tasks. RESULTSThe sample comprised 4,481 participants (52% female). Time in MVPA relative to SB, LIPA and sleep was positively associated with cognition after adjustments for education and occupational physical activity, but additional adjustment for health status attenuated associations. SB relative to all other movements was robustly positively associated with cognition. Modelling time reallocation between components revealed a higher cognition percentile after MVPA theoretically replaced just 9 minutes of SB (+1.31; 95% CI: 0.09, 2.50), 7 minutes of LIPA (+1.27; 0.07, 2.46) or 7 minutes of sleep (+1.20; 0.01, 2.39). CONCLUSIONS AND RELEVANCERelative to time spent in other behaviours, more time spent in MVPA and SB was associated with higher cognitive scores. Displacement of MVPA time, given its smaller relative amount, appear most deleterious. Efforts should be made to preserve MVPA time, or reinforce it with time taken from other behaviours.