The Separate and Combined Associations of Physical Activity and Diet Quality and Their Changes over Time with Mortality: Findings from the EPIC-Norfolk Prospective Cohort Study ^†

Abstract

Background and Objectives: Both physical activity and diet quality are associated with longevity, but less is known about their combined associations, especially in consideration of their changes over time. We aimed to examine the separate and combined associations of physical activity and adherence to a Mediterranean-type diet and their changes over time with mortality outcomes. Methods: The participants included 9349 adults aged 40 to 79 years old from the European Prospective Investigation into Cancer in Norfolk (EPIC-Norfolk) cohort, with repeated questionnaire-based measurements of physical activity and diet from 1993 to 2004. From the questionnaire responses, we derived physical activity energy expenditure (PAEE) and adherence to the Mediterranean Diet Score (MDS) and calculated their average within-person changes (∆PAEE and ∆MDS, respectively). A multivariable-adjusted Cox regression was fitted to examine associations between PAEE and MDS at baseline, ∆PAEE, and ∆MDS and their combination with all-cause mortality, cardiovascular disease mortality, and cancer mortality up to March 2022. Results: For over 149,681 person-years of follow-up, there were 3534 deaths in the cohort. In the models mutually adjusted for potential time varying and static cofounders, for each 1-SD difference in baseline PAEE (4.64 kJ/kg/day), ∆PAEE (0.65 kJ/kg/day per year), baseline MDS (1.30 points), and ∆MDS (0.32 points per year), the hazard ratios (95% CI) for all-cause mortality were 0.90 (0.86 to 0.94), 0.89 (0.85 to 0.93), 0.95 (0.91 to 0.99), and 0.93 (0.90 to 0.97), respectively. Similar results were observed for cardiovascular disease mortality and cancer mortality. Among participants recording low PAEE (<5 kJ/kg/day) and low MDS (<8.5 points) at baseline, all-cause mortality was lower by 40% (18% to 56%) for those who improved both behaviours over time (recording high PAEE and high MDS), compared to those who remained to be low for both behaviours. During the follow-up, 461 potential deaths were prevented by adherence to high diet quality and high physical activity levels over the repeated assessments. Discussion: these findings suggest that improvements in physical activity levels and diet quality over time could lower mortality in middle-aged adults, and public health benefits could be realised by encouraging active living and healthy eating throughout adulthood.