Prospective associations of diet quality and device-measured physical activity with midlife cognitive function: evidence from the 1970 British cohort study.

BACKGROUND: Physical activity (PA) is a widely recognised modifiable risk factor for cognitive health. The role of diet and their combined associations on cognition in midlife remains unclear. We assessed the additive and interactive associations of moderate-to-vigorous PA (MVPA) and diet quality on cognition in midlife. METHODS: At age 46, participants from the 1970 British Cohort Study wore activPAL accelerometers for 1 week and completed the Oxford WebQ dietary questionnaire, from which the Pyramid-Based Mediterranean Diet Score (PyrMDS) was derived. Global cognitive z-scores were derived from standardised tests of processing speed, verbal memory and fluency at age 46 and 51. Multivariate linear regression examined independent and mutually adjusted associations between MVPA and PyrMDS at age 46 with cognitive z-scores at both timepoints. Combined MVPA-PyrMDS tertiles and interaction terms were also tested. RESULTS: In a sample of n=3028 (55% female), mean MVPA was 52±25 min/day and mean PyrMDS was 6.31±1.65. In mutually adjusted models at age 51, only PyrMDS was associated with global cognitive z-scores after covariate adjustment (per hour MVPA: β=0.228, 95% CI -0.026 to 0.481; per point PyrMDS: β=0.045, 95% CI 0.025 to 0.065). In combined analyses, PyrMDS was associated with better age 51 global cognitive z-scores irrespective of MVPA (high-PyrMDS:low-MVPA vs low-PyrMDS:low-MVPA: β=0.185, 95% CI 0.046 to 0.325). No interactions were observed. CONCLUSION: Diet quality demonstrated prospective associations with better cognition independently of MVPA, with associations remaining more consistent than for PA after adjustment of confounders. Diet quality may represent an under-recognised lifestyle target for cognitive health.